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All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Big Bore AirGun Gate => Topic started by: fpjeepy on January 25, 2019, 01:21:29 PM

Title: 12ga Big Bore
Post by: fpjeepy on January 25, 2019, 01:21:29 PM
I think the Airforce Texan is the most popular air gun right now, imo based off youtube views. But personally, I would like a more compact gun.

I think a 73 Cal Bullpup rifle with a shroud would be ideal. I think by going from 45 caliber to 73 caliber you can get faster accelerations and use shorter barrels with equal weight bullets. Switching to non-expanding bullets should provide similar penetration to the smaller caliber expanding bullets. (i.e. copper, brass, steel, aluminum)

The goal is a very quiet gun under 40" that shoots a 300gr projectile at 1050 fps. And does it all with 3500psi of air. I know higher pressures and helium make this easier, but sticking with basics here.

Do you think this is feasible? Do you think there would be a market for a gun like this?
Title: Re: 12ga Big Bore
Post by: MJP on January 25, 2019, 01:37:49 PM
Well you can hunt with far less than 800fpe, what is the purpose of said gun?
Not that there is nothing wrong with power.

That is the length of the elusive hammer if I'm not mistaken, do you want to create that or something similar.

.73 and 30" barrel tou could get pretty close to your goal with that pressure but the bullet is very short. And its bc going to be low so not a long range gun.

My small projectiles are pretty short for 20mm caliber and they weigh around 1600gr
Cant imagine how short 300gr ~18.5mm would be.

Marko
Title: Re: 12ga Big Bore
Post by: T3PRanch on January 25, 2019, 02:04:51 PM
A very similar gun to the one you describe is already manufactured by XP-Airguns in Kansas. It is called the Quigley - Scorpion .72

https://www.xp-airguns.com/photo-gallery.html (https://www.xp-airguns.com/photo-gallery.html)

Taming the bark of a .72 will be the trick.

Title: Re: 12ga Big Bore
Post by: dmeguy on January 25, 2019, 02:37:59 PM
A very similar gun to the one you describe is already manufactured by XP-Airguns in Kansas. It is called the Quigley - Scorpion .72

https://www.xp-airguns.com/photo-gallery.html (https://www.xp-airguns.com/photo-gallery.html)

Taming the bark of a .72 will be the trick.


They even had a prototype bullpup version on their Facebook page.


But I have to agree, taming the bark of a .72 to something that could be considered "very quiet", is going to take a magic wand or some pixie dust!
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 25, 2019, 03:16:54 PM
Well you can hunt with far less than 800fpe, what is the purpose of said gun?
Not that there is nothing wrong with power.

That is the length of the elusive hammer if I'm not mistaken, do you want to create that or something similar.

.73 and 30" barrel tou could get pretty close to your goal with that pressure but the bullet is very short. And its bc going to be low so not a long range gun.

My small projectiles are pretty short for 20mm caliber and they weigh around 1600gr
Cant imagine how short 300gr ~18.5mm would be.

Marko

The intended purpose would be to hunt deer and hogs in the US at close range. But also to be used for backyard target shooting, ideally.

The BC would be terrible. But my logic is this... 1050fps is the max speed that you can push a bullet that you want to keep quiet. Maximum point blank range (MPBR) on a 4" target for a bullet with .1 BC at 1050fps is 92 yards. MPBR for .5 BC at 1050fps is 100 yards. Basically, at close range, BC doesn't have a ton of an effect.

My idea for a bullet is attached below. Just a rough model, but it's showing a steel disc that would weigh 264gr. (301gr in copper) The tan color is a plastic of some sort that is mechanically fastened to the bullet so it doesn't destroy the shroud. There to hopefully keep the bullet flying straight.


Title: Re: 12ga Big Bore
Post by: fpjeepy on January 25, 2019, 03:23:51 PM
A very similar gun to the one you describe is already manufactured by XP-Airguns in Kansas. It is called the Quigley - Scorpion .72

Taming the bark of a .72 will be the trick.

Yeah, XP one of the few making .72 cal guns. I think it would have to be a bullpup style, because like you said taming the bark is going to be difficult. I'm thinking the shroud might need to be at large as 3" around and 15-20" long. And adding that to a gun that is already 40" long makes it impractical for a lot of hunting styles.
Title: Re: 12ga Big Bore
Post by: rsterne on January 25, 2019, 04:05:43 PM
I presume you have already done the math, as a .73 cal lead roundball would weigh 583 gr.... and yet only have a BC(G1) of less than 0.1.... BC doesn't affect trajectory much, but it sure affects the downrange velocity and energy retention.... For simplicity I would go with a .58 cal, and shoot roundballs, which weigh 292 gr. and have a BC of about 0.08.... Keep the velocity at around 950 fps, the wind drift is less than it is at 1050, although admittedly the MPBR would be less for a 4" target, 84 yds. instead of 92 yds....  You should be able to get that velocity on 3000 psi, and you will find that reaching 950 is a lot quieter than 1050, unless you have a really long barrel.... If you have your heart set on 1050, that should be possible using 3500 psi.... With a MV of 950, that .58 cal roundball will arrive at 100 yds. with over 400 FPE of energy.... The size of valve you will need for a .58 cal will be much smaller, which means less hammer strike, easier to cock, less air used per shot, easier to quieten it down, etc.etc.etc…. Just a suggestion....

Bob
Title: Re: 12ga Big Bore
Post by: MJP on January 25, 2019, 04:13:26 PM
Bob has very good points there, taming down .73 is going to be down right impossible.
 The volume of air needed to push the projectile around 1050fps is quite substantial.

I have pretty good understanding of bigger end of the bigbore rifles and the air volumes involved.
Taming something so big to backyard friendly would require can the size of a bucket.

Marko

Title: Re: 12ga Big Bore
Post by: rkr on January 25, 2019, 04:26:47 PM
Having made 150 fpe .357 very quiet and 270 fpe .45 backyard friendly, I would say that you need one enormous can to make that powerful .73 very quiet. In general it takes more air to get more power and more can volume to quiet it down. A good .357 can is 2" in diameter and over 10" long back vented model.
Title: Re: 12ga Big Bore
Post by: rsterne on January 25, 2019, 05:26:45 PM
So would 0.2 CI per FPE be a good starting point for a "can" ?.... If so, then for 300 gr. @ 1050 fps, maybe 3" in diameter and 2 ft. long....  :o

Of course a .58 cal at the same FPE would need the same size....  ::)

Bob
Title: Re: 12ga Big Bore
Post by: Back_Roads on January 25, 2019, 08:06:58 PM
So would 0.2 CI per FPE be a good starting point for a "can" ?.... If so, then for 300 gr. @ 1050 fps, maybe 3" in diameter and 2 ft. long....  :o

Of course a .58 cal at the same FPE would need the same size....  ::)

Bob
So a basic straight flow high performance car muffler to quiet it down < back roads terms>  ;)
Title: Re: 12ga Big Bore
Post by: rkr on January 26, 2019, 06:58:10 AM
So would 0.2 CI per FPE be a good starting point for a "can" ?.... If so, then for 300 gr. @ 1050 fps, maybe 3" in diameter and 2 ft. long....  :o

Of course a .58 cal at the same FPE would need the same size....  ::)

Bob

Just for the fun I checked the volumes of different good cans I have and considered at which power level they were quiet etc (ranging 12-270 fpe). It seems that it takes very roughly about 4000mm3 (rounds up to around 0.25CI) volume for each fpe to make a gun "quiet". By quiet I mean you can hear the shot but it would be a quiet one, not disturbing neighbors - bullet flight noise is about the same level as the shot noise. No action only quietness, that would take 3-4 times more volume for each fpe. It is also worth noting that the bigger the caliber the more flight noise and efficiency varies etc. - still perhaps that is a useful guideline - at least for reality checks. As for the upper limit, my biggest can is 50mm in diameter and 440mm long reflex type. It makes a 270 fpe .45 gun about backyard friendly. Same can in a 230 fpe .357 I would call normal backyard friendly. 300mm version of that can in a 150 fpe .357 is very quiet and so on.
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 26, 2019, 11:48:20 AM
I'm assessing this more as a viable product for a company to produce than something to have built for myself.
I presume you have already done the math, as a .73 cal lead roundball would weigh 583 gr.... and yet only have a BC(G1) of less than 0.1.... BC doesn't affect trajectory much, but it sure affects the downrange velocity and energy retention.... For simplicity I would go with a .58 cal, and shoot roundballs, which weigh 292 gr. and have a BC of about 0.08.... Keep the velocity at around 950 fps, the wind drift is less than it is at 1050, although admittedly the MPBR would be less for a 4" target, 84 yds. instead of 92 yds....  You should be able to get that velocity on 3000 psi, and you will find that reaching 950 is a lot quieter than 1050, unless you have a really long barrel.... If you have your heart set on 1050, that should be possible using 3500 psi.... With a MV of 950, that .58 cal roundball will arrive at 100 yds. with over 400 FPE of energy.... The size of valve you will need for a .58 cal will be much smaller, which means less hammer strike, easier to cock, less air used per shot, easier to quieten it down, etc.etc.etc…. Just a suggestion....

Bob

That being said I think you are right that a .58 round ball might be the simplest way to get what I'm looking for, but it's not very exciting. When was the last time that any modern gun product was released that used round balls? Modern arms use pellets, bullets, sabots, and discs. A .58 at 400 fpe works great, but I don't think anyone would consider it the latest and the greatest. Daisy Red Rider and flintlock muzzleloaders are the only ones I can think that use a round ball.

 
Bob has very good points there, taming down .73 is going to be downright impossible.

Marko

Marko, you are quick to say it is impossible, but from what I am hearing... a 3.6" x 18" can would suppress a 300gr 72 cal at 1050fps and 735fpe to be backyard friendly. I would say that is far from impossible. If you think a can that large is goofy. That is merely another problem to solve. A possible solution is not making the can round. See the example below.
Title: Re: 12ga Big Bore
Post by: rkr on January 26, 2019, 01:22:23 PM

Marko, you are quick to say it is impossible, but from what I am hearing... a 3.6" x 18" can would suppress a 300gr 72 cal at 1050fps and 735fpe to be backyard friendly. I would say that is far from impossible. If you think a can that large is goofy. That is merely another problem to solve. A possible solution is not making the can round. See the example below.


This is 50mm diameter 440mm long can, it's not too bad from practical point of view. Whether it looks goofy or not is then another thing.

(https://farm5.staticflickr.com/4241/35732914416_5d936a3a10_c.jpg) (https://flic.kr/p/WrAwxj)Eva-ldc_zpsmgm4kafa (https://flic.kr/p/WrAwxj) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 01:28:20 PM
fpjeepy, Yo're right, it is quicker to say than do.

(https://img.aijaa.com/b/00477/14662020.jpg)

You only need to tame this. Ok, it is bigger but you get the idea. It is not a steam engine, cold weather is condensing the most of air coming out from 20mm.

There are only laws of physics against you unless you invent something to close the door right after elvis left the building...

I'm not saying it is impossible but is it handy or practical? NO.
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 01:32:19 PM
Before someone says, it was wrong said. Compressed air burst is condensing the moisture of surraunding air to visible cloud...
Title: Re: 12ga Big Bore
Post by: MJP on January 26, 2019, 02:46:41 PM
Well if you have not shot one then i would recommend to try just to let you know what kind of air volume you are dealing with.
By all means build it and let me know how backyard friendly you can get it.

One thing I might add please don't try it a residential area, there are other safety factors to consider than just the sound.

Marko
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 26, 2019, 03:02:07 PM
fpjeepy, Yo're right, it is quicker to say than do.

You only need to tame this. Ok, it is bigger but you get the idea. It is not a steam engine, cold weather is condensing the most of air coming out from 20mm.

There are only laws of physics against you unless you invent something to close the door right after elvis left the building...

I'm not saying it is impossible but is it handy or practical? NO.

Is rkr's can practical? What if it was 75% larger in diameter? Do you disagree with 0.25 in^3/fpe?
Title: Re: 12ga Big Bore
Post by: Sbak on January 26, 2019, 03:31:16 PM
Why just cans? Have it vent back into a reasonable diameter shroud. A lot of free volume provided along the barrel length
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 03:42:06 PM
Is rkr's can practical? What if it was 75% larger in diameter? Do you disagree with 0.25 in^3/fpe?
What is rkr's caliber? Air quantity?

By all means try it, I am not resisting.
Title: Re: 12ga Big Bore
Post by: rkr on January 26, 2019, 04:00:21 PM
Is rkr's can practical? What if it was 75% larger in diameter? Do you disagree with 0.25 in^3/fpe?
What is rkr's caliber? Air quantity?

By all means try it, I am not resisting.

It's .45 and it is backvented. Barrel ends in the middle of the can. 270fpe shots or there abouts. About the same length as gun with a 32" barrel.
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 04:04:10 PM
In my XP .45 power level is about 600 fpe. Recommendations for backyard frendliness?
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 04:15:27 PM
Actually in my .338 is the same power, you have heard it barking I believe. It has a muzzle brake too. Sorry if I disturbed your shooting in any way.  ;D
Title: Re: 12ga Big Bore
Post by: T3PRanch on January 26, 2019, 04:16:39 PM
In my XP .45 power level is about 600 fpe. Recommendations for backyard frendliness?

Don't pull the trigger! ;D  lol
Title: Re: 12ga Big Bore
Post by: rkr on January 26, 2019, 04:22:09 PM
In my XP .45 power level is about 600 fpe. Recommendations for backyard frendliness?

Turn down the power  ;D IMO above 300 fpe the can sizes needed are getting not so practical. Of course it would be interesting to see what can be done at 600 fpe level. Let me know if you want to build a can and need some tips for internals design.
Title: Re: 12ga Big Bore
Post by: rkr on January 26, 2019, 04:23:54 PM
Actually in my .338 is the same power, you have heard it barking I believe. It has a muzzle brake too. Sorry if I disturbed your shooting in any way.  ;D

I remember the air blast. I had to listen to your regulator to know when I had a moment of piece to concentrate on a shot :)
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 04:26:34 PM
I'm sorry. Well, honestly I am not.  ;D

It is a shooting range you know.  8)
Title: Re: 12ga Big Bore
Post by: rkr on January 26, 2019, 04:33:48 PM
I'm sorry. Well, honestly I am not.  ;D

It is a shooting range you know.  8)

600 fpe .338 vs 45 fpe .25 is not a fair competition. I don't recall who shot better but that's the only time I've been distracted by shooting of others. It's that break and air blast that does the trick.
Title: Re: 12ga Big Bore
Post by: TPL on January 26, 2019, 04:39:17 PM
Yes, the point is that up to some level you can expect to silence the muzzle report but when we are talking about certain power levels and/or calibers it comes very demanding to say the least.

So that earlier was not just joking, I meant just this.

And I remember we were talking about .73 now.
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 27, 2019, 08:54:50 PM
I saw this pellet design... Thought it might be another way to get a lightweight large diameter pellet
Title: Re: 12ga Big Bore
Post by: rkr on January 28, 2019, 06:36:15 AM
I saw this pellet design... Thought it might be another way to get a lightweight large diameter pellet


You could just cast pellets from tin, I bet it would be cheaper and they would most likely be more accurate. Although I don't know if 73 cal pellet molds are available, .45 and .50 you can buy.
Title: Re: 12ga Big Bore
Post by: MJP on January 28, 2019, 06:57:17 AM
And where do you get tin so cheap?
I have not found pure tin so cheap that I would make bullets out of it.

Any special calibers, mold need to be made your self or have made by some one.

Marko
Title: Re: 12ga Big Bore
Post by: rkr on January 28, 2019, 07:21:41 AM
And where do you get tin so cheap?
I have not found pure tin so cheap that I would make bullets out of it.

Any special calibers, mold need to be made your self or have made by some one.

Marko

Define "so cheap". It is costly but those plastic sabot special thingies are usually even more expensive. Then there's the question why shoot pellets when you could shoot EPP/UGs or other light bullets. Actually the question could also be why go for a .73 cal in the first place if you want to shoot extra light bullets/pellets?
Title: Re: 12ga Big Bore
Post by: MJP on January 28, 2019, 10:09:34 AM
Well that is an interesting question indeed. Why choose .73 in the first place?

We have shot saboted rounds out of the 20mm and they have all been over 500gr and some 2000-2500fpe.
That could be a good reason but its not going to be back yard friendly by a long shot.

Marko
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 28, 2019, 04:39:32 PM
And where do you get tin so cheap?
I have not found pure tin so cheap that I would make bullets out of it.

Any special calibers, mold need to be made your self or have made by some one.

Marko

Define "so cheap". It is costly but those plastic sabot special thingies are usually even more expensive. Then there's the question why shoot pellets when you could shoot EPP/UGs or other light bullets. Actually the question could also be why go for a .73 cal in the first place if you want to shoot extra light bullets/pellets?

The reason for 73 cal is because it is 12ga and there are slug molds available. The reason for 73 cal bullets that are only 300gr is because they accelerate faster at the same pressure. Force = Pressure x Area. So since 73 cal has a 2.6x greater cross-sectional area it will accelerate a bullet to the same velocity in a barrel that is 2.6x shorter. Obviously, all things are not equal because the expansion rate of compressed air isn't infinite so the real-life numbers will be less, but the point is, more can be done in a shorter barrel if the diameter is larger.

@3500psi .45 needs 40"+ of barrel to hit 950fps @300gr. So at what caliber can you get 950fps @300gr in 18" If it can be done in a smaller diameter than .73 great! If it can't .84 is an 8 bore.   ;D
Title: Re: 12ga Big Bore
Post by: MJP on January 29, 2019, 03:13:25 AM
Well I have gotten 600fpe at 3600psi from 31" .457 shootin 290gr so no need for 40" barrel.
500fpe on 2900psi on same bullet and barrel.
Its all about the valve and porting to get the power.
Maybe a 12gauge could be fun to try.
But anyway give it a go and do post some pictures of the build, it is interesting.

Marko
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 29, 2019, 09:44:20 AM
Well I have gotten 600fpe at 3600psi from 31" .457 shootin 290gr so no need for 40" barrel.
500fpe on 2900psi on same bullet and barrel.
Its all about the valve and porting to get the power.
Maybe a 12gauge could be fun to try.
But anyway give it a go and do post some pictures of the build, it is interesting.

Marko

You are getting   965fps w/ 290gr @ 3600psi w/ 31"
Airforce texan is 800 fps w/ 310gr @ 3000psi w/ 36"

Either way .457" is not going to get 950fps+ w/ 300gr @3500 out of 18"
What will?
Title: Re: 12ga Big Bore
Post by: Brian W Cook on January 29, 2019, 11:33:37 AM
https://youtu.be/CNhRf_IrZpY
I’m kinda partial to .58’s since i built mine about 10 years ago.    It has a gold bead front sight and an old adjustable peep in the back .  Mounted low as possible.   At 920 FPS with rb it’s better than hedge ball accurate at 100 yards . 
And it just runs on 3100 psi
Title: Re: 12ga Big Bore
Post by: rsterne on January 29, 2019, 11:50:54 AM
You might get 600 FPE at 3500 psi using an 18" barrel with a .58 cal.... if you do everything right.... It will, of course be VERY noisy, because with that short a barrel the residual muzzle pressure will be very high....

Bob
Title: Re: 12ga Big Bore
Post by: TPL on January 29, 2019, 12:39:15 PM
Define "so cheap". It is costly but those plastic sabot special thingies are usually even more expensive.
Lead is quite cheap, tin is at least 10 times more expensive. Sabots cost something too but not that much if you 3D print them. It takes some experimenting to make it right, to make them work as they should and search right form, material and printing parameters. Once it is done it only takes some time and filament.

I remember we got 494 m/s with doppler trigging on LabRadar. Because of sabot it was necessary to move it forward and protect it from sabot parts separating bullet and I think trigging distance was something like 15-20 meters from muzzle. Bullet was .45 cal out of 20mm and energy quite precisely 3500J. Weight of the bullet must of being something like 445 grains. (28.8 g). That energy is for bullet only of course, sabot was long gone.

Just FYI.
Title: Re: 12ga Big Bore
Post by: TPL on January 29, 2019, 12:45:16 PM
Make, was it 3500 or 3600J? The max with sabots?

Well it doesn't matter much anyway.
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 29, 2019, 12:48:38 PM
You might get 600 FPE at 3500 psi using an 18" barrel with a .58 cal.... if you do everything right.... It will, of course be VERY noisy, because with that short a barrel the residual muzzle pressure will be very high....

Bob

All 300gr @ 950fps is 600fpe, not all 600 FPE is 300gr @ 950fps. I'm not interested in 600gr @ 680fps. If 58 cal can't do it how about 62 cal (20 gauge) ?

And the idea behind the short barrel is to make room for a large can...
Title: Re: 12ga Big Bore
Post by: TPL on January 29, 2019, 01:36:19 PM
I agree with Bob, you should be good to go with .58 IF you do everything right.

It shouldn't be even max limit but quite close to it anyway. With air I mean.
Title: Re: 12ga Big Bore
Post by: MJP on January 29, 2019, 01:38:42 PM
Nice .58 Brian!
Well you just need to build it and see what happens. And if it's not powerful enough, swap a bigger barrel. Just make the valve large enough from the start.
It was 3600J

Marko
Title: Re: 12ga Big Bore
Post by: Brian W Cook on January 29, 2019, 01:54:33 PM
Thanks Marko !
It’s probably my favorite airgun. I’ve killed a few deer with the round balls and one with the hollow point i shot in the video.   
Works great . 
Title: Re: 12ga Big Bore
Post by: MJP on January 29, 2019, 03:37:23 PM
Do you use balanced valve?
I have one .58 blackpowder in my safe, fun to shoot as well.

Marko
Title: Re: 12ga Big Bore
Post by: Brian W Cook on January 29, 2019, 04:21:44 PM
It’s a conventional poppet for now .   
Title: Re: 12ga Big Bore
Post by: rsterne on January 29, 2019, 04:28:30 PM
You asked about 300 gr. @ 950 fps, which is 600 FPE.... I didn't think it was necessary to repeat that, but yes you should be able to do that in .58 cal  with an 18" barrel at 3500 psi....

Bob
Title: Re: 12ga Big Bore
Post by: Doug Wall on January 29, 2019, 05:01:09 PM
Has anyone ever set up a .58 with a 500gr Minie ball? That might be interesting.
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 31, 2019, 08:58:11 AM
You asked about 300 gr. @ 950 fps, which is 600 FPE.... I didn't think it was necessary to repeat that, but yes you should be able to do that in .58 cal  with an 18" barrel at 3500 psi....

Bob

I apologize. I thought you were trying to better your argument by modifying things slightly.
Title: Re: 12ga Big Bore
Post by: rsterne on January 31, 2019, 12:48:49 PM
I am well aware that using a heavy bullet at low velocity is a good way to "inflate" FPE numbers.... My "lofty goal" predictions are always done with a bullet weight of 1/2 the FPE, so that is at 950 fps.... You're pretty new around here, so you wouldn't have known that....  ;) …. Oh, and welcome, BTW....  8)

I think the idea of a short barreled 12 ga. is a cool way to get lots of FPE.... I am just trying to show you it's not the only answer.... and realize that quieting a 600 FPE beast with a short barrel is going to be a TALL (or at least "long") order....  ???

Bob
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 31, 2019, 03:21:12 PM
I am well aware that using a heavy bullet at low velocity is a good way to "inflate" FPE numbers.... My "lofty goal" predictions are always done with a bullet weight of 1/2 the FPE, so that is at 950 fps.... You're pretty new around here, so you wouldn't have known that....  ;) …. Oh, and welcome, BTW....  8)

I think the idea of a short barreled 12 ga. is a cool way to get lots of FPE.... I am just trying to show you it's not the only answer.... and realize that quieting a 600 FPE beast with a short barrel is going to be a TALL (or at least "long") order....  ???

Bob

You've done a good job convincing me. I'm definitely thinking 12gauge might be a little overkill. 20ga at 62cal looks better. and might have an advantage over the 0.58 in that it might work even if everything isn't perfect. 
Title: Re: 12ga Big Bore
Post by: fpjeepy on January 31, 2019, 03:35:19 PM
Also, does anyone have any decibel readings for their big bores?

I'm seeing that the Maxim 50 suppressed muzzleloader is 140 dB. I think that is the quietest gun you can buy without a stamp and use for deer at the moment, as well as the .357 Bulldog (w/ pitbull mods - 94dB) and .45 Texan. Which are a little more marginal in my opinion.

I think the goal would be under 100 dB which might not be backyard friendly for a lot of people.
Title: Re: 12ga Big Bore
Post by: Jim Holmgren on January 31, 2019, 03:48:58 PM
A roundball in .73 weights around 500gr and have a bc about .10
If you have bullet in cal .73 that weights 300gr it would be way shorter then wide, maybe around .35 inch long :o.
It will of course work but you BC and long range performance will not be the best.

If you raise the pressure to 4500psi then you could even make you goal in .50cal for little better BC.

Accurate molds have mold close to 300gr in 20ga anything lighter would probably be needed to be custom made.
http://www.accuratemolds.com/bullet_detail.php?bullet=62-340S-D.png (http://www.accuratemolds.com/bullet_detail.php?bullet=62-340S-D.png)


Will this be a bullpup or a pistol? It will be awesome power in that compact of package! ;)

Has anyone ever set up a .58 with a 500gr Minie ball? That might be interesting.

What a great idea! convert a old reproduction muzzleloader to PCP ;D
Title: Re: 12ga Big Bore
Post by: MJP on January 31, 2019, 03:58:11 PM
Well i know one guy who did one very nice muzzleloader pcp.
Lets see if I can find a picture or if Timo has some pictures?

Marko
Title: Re: 12ga Big Bore
Post by: rsterne on January 31, 2019, 08:01:11 PM
I think the idea of a 20 ga. might be a great compromise....  8)

Bob
Title: Re: 12ga Big Bore
Post by: PikeP on January 31, 2019, 10:56:41 PM
Hey Fielding, originally from Maryland myself...you have some ambitious goals set but I think all can be met within reason and if necessary some compromise. Attached are some approximations I ran for a .58 cal with the parameters shown. Look forward to seeing if you commit to the build!

Title: Re: 12ga Big Bore
Post by: fpjeepy on January 31, 2019, 11:55:20 PM
A roundball in .73 weights around 500gr and have a bc about .10
If you have bullet in cal .73 that weights 300gr it would be way shorter then wide, maybe around .35 inch long :o.
It will of course work but you BC and long range performance will not be the best.

If you raise the pressure to 4500psi then you could even make you goal in .50cal for little better BC.

Accurate molds have mold close to 300gr in 20ga anything lighter would probably be needed to be custom made.

Will this be a bullpup or a pistol? It will be awesome power in that compact of package! ;)

Has anyone ever set up a .58 with a 500gr Minie ball? That might be interesting.

What a great idea! convert an old reproduction muzzleloader to PCP ;D

I was definitely thinking along the lines of custom bullets. With the 73 cal it would need to be a mix of metal and polymer to get something decent looking at 300gr.

At 62 cal I modeled a copper pellet at 320gr that looks decent. I would need to be custom turned and be expensive enough to warrant its use solely for hunting. But the link you posted above would be a good plinking round and preppers supply.

Bullpup with integrated suppression. And I would like to avoid 4500psi to be able to use standard equipment.



 
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 01, 2019, 12:00:29 AM
Hey Fielding, originally from Maryland myself...you have some ambitious goals set but I think all can be met within reason and if necessary some compromise. Attached are some approximations I ran for a .58 cal with the parameters shown. Look forward to seeing if you commit to the build!

Can you run the same for 0.62? I'd be curious. What is that software?

And I'm not sure that I have the time or knowledge base to do the build myself. I would likely have to commission someone else to do the building.
Title: Re: 12ga Big Bore
Post by: MJP on February 01, 2019, 01:40:00 AM
If you are giving parameters to builder 18" and 600fpe I think it will remain a pipe dream.
Or at least it will be difficult to find a builder willing to take the chance of failure meeting the goals.

Not to put you down but it's not an easy task to accomplish.
Like Bob said, everything must be just right, and it will take time and money to hone all the details.

Good luck to your endeavor, will be interesting to folow how it comes together if you find the right builder.

Marko
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 02, 2019, 02:33:28 PM
20ga 309gr aluminum core copper jacket slug.
Title: Re: 12ga Big Bore
Post by: TPL on February 02, 2019, 03:46:05 PM
Nice picture. And you are trying to do what exactly?
Title: Re: 12ga Big Bore
Post by: rsterne on February 02, 2019, 10:03:22 PM
I agree, nice picture.... How would you make it, and at what cost?.... I'll take a guess at the BC at about 0.115, the same as the SD.... Virtually no expansion at airgun velocities.... A lead roundball in 20 ga. would weigh 349 gr. with BC(G1) of ~0.082... In cast linotype, a 20 ga. roundball would be about 318 gr. with BC(G1) of ~0.075...

Sighted at 50 yards, the 309 gr. boattail starting at 950 fps (619 FPE), PBR (4") = 84 yds, would be about 9.35" low at 100 yards, retained energy 478 FPE.... Using the same FPE of 619, same 50 yd. zero, the lead roundball would be going 894 fps at the muzzle, PBR(4") of 79 yards, and would be about 11.19" low at 100, retained energy 448 FPE.... while the linotype roundball would have a MV of 937, PBR (4") of 81 yds, and be about 10.39" low at 100 yards, retained energy 427 FPE.... I doubt the deer would know the difference between 427 FPE and 478....  ???

Just putting things in perspective.... cost and complication vs. available and cheap....  ;)

Bob
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 02, 2019, 10:44:42 PM
I agree, nice picture.... How would you make it, and at what cost?.... I'll take a guess at the BC at about 0.115, the same as the SD.... Virtually no expansion at airgun velocities.... A lead roundball in 20 ga. would weigh 349 gr. with BC(G1) of ~0.082... In cast linotype, a 20 ga. roundball would be about 318 gr. with BC(G1) of ~0.075...

Sighted at 50 yards, the 309 gr. boattail starting at 950 fps (619 FPE), PBR (4") = 84 yds, would be about 9.35" low at 100 yards, retained energy 478 FPE.... Using the same FPE of 619, same 50 yd. zero, the lead roundball would be going 894 fps at the muzzle, PBR(4") of 79 yards, and would be about 11.19" low at 100, retained energy 448 FPE.... while the linotype roundball would have a MV of 937, PBR (4") of 81 yds, and be about 10.39" low at 100 yards, retained energy 427 FPE.... I doubt the deer would know the difference between 427 FPE and 478....  ???

Just putting things in perspective.... cost and complication vs. available and cheap....  ;)

Bob

You make a great point. Maybe it is not worth all the work for an 11% fpe gain and maybe some added accuracy. But maybe it is for some people. I don't know. My thoughts follow this logic. 3500 psi compressed air is set. Making a gun that requires helium or 5000psi is not practical. If we want an ultra quiet gun that is a practical length that can still kill a deer, I think the best way to get there is a larger bore which allows the barrel short enough to allow for a significant can within the "practical length." So if barrel length, diameter, pressure, and propellant are set... there isn't a lot left to try to maximize the killing power. Increasing the BC of the bullet would help deliver more energy to the target. A heavier bullet would do that as well, but then calculating trajectory becomes more important. Not saying one is better than the other, and idealy the gun would be able to do both and leave that decision up to the shooter. But that was the logic that leads me to try to solve the question, "What 62cal 300gr bullet would be most effective at killing a deer at 100 yards?"
Title: Re: 12ga Big Bore
Post by: rsterne on February 02, 2019, 11:19:11 PM
Yep, you solved that.... My question would be is building that special bullet worth the cost and difficulty.... For me, no, for you, maybe it is....  ;) …. That's the cool thing about airguns…. If you can dream it, you can pretty much build it....  8)

Bob
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 02, 2019, 11:28:16 PM
Yep, you solved that.... My question would be is building that special bullet worth the cost and difficulty.... For me, no, for you, maybe it is....  ;) …. That's the cool thing about airguns…. If you can dream it, you can pretty much build it....  8)

Bob

I wouldn't say I solved it, but it's one possible solution.
Title: Re: 12ga Big Bore
Post by: dyotat100 on February 03, 2019, 01:16:05 AM
Copper doesn't work in airguns. Not enough power to get it going
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on February 03, 2019, 01:33:26 AM
Copper doesn't work in airguns. Not enough power to get it going
Can you imagine the force required to engrave the copper jacketed bullet into the rifling?  My thumb hurts just thinking about it, haha
Brainstorming: pre-engraved bullet you index into the rifling.  Or a bore size bullet with groove size forward and rear driving bands of lead like naval artillery shells.Or have a lever n fulcrum built into the rifle to force the bullet into the rifling, hehehaha

Or use tried and true lead which has been used for centurys.  Jacketed bullets revolutionized powder burning firearms but that's probably not going to be a simpler and more economical or even more accurate use in pneumatic guns.

Plus, expanding on what Doug said, the coefficient of friction of copper vs lead, ie the friction drag in the barrel as the bullet moves down the barrel is much greater for copper than lead (which is why lead {babbit alloy} was used as a bearing material for so long, lots less friction) and a lot of you potential energy in the compressed gas would be wasted overcoming the friction, resulting in lower velocities vs the same projectile in lead.
Title: Re: 12ga Big Bore
Post by: MJP on February 03, 2019, 03:35:15 AM
Jacketed bullet out of 600fpe gun will come out at about 50-75fps if I remember correctly.

Marko
Title: Re: 12ga Big Bore
Post by: TPL on February 03, 2019, 01:19:24 PM
Jacketed short bullet came out from my Corsair .308 about 150 fps. Normally it is about 230 fpe gun with lead. I didn't try another.  ;D

Bullet BC also depends much of the mass of it. I see no point to reduce it and also energy though the velocity would be somewhat higher. Lead speed is already in transonic area. Any improvement there would require high supersonic speed and that is not possible. And last but not least, momentum would suffer the most.
Title: Re: 12ga Big Bore
Post by: rsterne on February 03, 2019, 01:42:07 PM
While I agree that copper is likely a non-starter for an airgun bullet.... the OP stated his goal of a 300 gr. bullet at 1050 fps, so that already sets as a constant the velocity, energy, and momentum.... All that he is trying to do is package that 300 gr. in the least drag shape, while having a larger enough caliber to be able to achieve (a now reduced) 950 fps with an 18" barrel.... I completely understand the goal, and seeking to improve the BC of that 300 gr. bullet is admirable.... Some things suggested, such as a polymer front and back that he hopes to somehow get to stay attached to a cylindrical center section.... or a copper jacket.... may not work, but I admire his persistence and efforts nevertheless.... I would pursue a lightweight metal instead of lead, certainly tin would do the job and can be cast easily and is soft enough for airgun use.... and it would be a lot cheaper than some fabricated design.... There may be another alternative alloy that would be even less dense and could be cast or swaged, and result in a sleeker bullet than a cast tin one.... It never hurts to dream.... you just need to pinch yourself once in a while to wake up and check the reality of your ideas....  ;)

A thought to consider.... Pure Aluminum has a BHN of 15, compared to copper at 35.... Lyman #2 alloy is BHN 15, and COWW are BHN 12.... I have no idea if you could shoot an aluminum bullet at 1000 fps without it destroying your barrel or not.... Perhaps you could powder coat it using HTC.... If you could figure that out, the specific gravity of aluminum is only 2.7, compared to tin at 7.3 and lead at 11.4.... Imagine a 300 gr. aluminum bullet in 20 ga. that looks like this....

(http://noebulletmolds.com/photos/albums/308-154-FN-BT-/308-154-FN_-BT-_154_gr_Sketch.Jpg)

Bob
Title: Re: 12ga Big Bore
Post by: TPL on February 03, 2019, 02:09:07 PM
Well.. yes, I understand somehow. If it is decided the caliber will be 12ga, then maybe this plan is close to solution, just forget copper.

What I mean there are many ways to move 309 grain mass much more aerodynamically than this but who am I to disaggree...
Title: Re: 12ga Big Bore
Post by: rsterne on February 03, 2019, 02:32:30 PM
If you are wondering where I got that shape.... a 20ga. bore is virtually double a .308 one.... That means if you scale a bullet up, it will be 8X the weight.... So, that BBT as a 20 ga. bullet would weigh 8 x 155 = 1240 gr.... However, aluminum is only (2.7 / 11.4) = 24% of the density of lead.... and 1240 x 0.24 = 298 gr. for a pure aluminum bullet in 20 ga. (.62 cal).... Make the nose bore-riding, or nearly so, so that only the single driving band has to engage the rifling.... Size it 0.001-0.002" under the groove diameter, and make sure that the midbody clears the lands.... I think it could be made to work....  8)

Bob
Title: Re: 12ga Big Bore
Post by: MJP on February 03, 2019, 02:39:23 PM
Well alu is light for sure but try to tap one in to the barrel and see how it goes, the tensile strength of alu vs lead?
Lead is much more softer and malleable than aluminum, it just wont work any better than copper on airgun pressures in a rifled barrel.

Nothing wrong in dreaming, just some times you need to wake up.
Discarding sabots is the only logical answer if you want aerodynamic and light projectile.

Marko

 
Title: Re: 12ga Big Bore
Post by: rsterne on February 03, 2019, 02:52:09 PM
You could be right about the tensile strength of aluminum being too high, Marco.... or the shear strength, which is related to that.... Pure aluminum is a lot weaker than the alloys, but possibly still too strong to be able to engage the rifling....

Bob
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on February 03, 2019, 03:57:12 PM
I did experiment with lathed aluminium VLD profile .457 bullets shot in a 458 Weatherby and although I got extreamly high muzzle velocities there were a couple of problems, the velocity dropped off very fast and don't kid yourself, aluminium will foul the barrel and I had a hard time cleaning it well enough to go back to regular copper bullets and get accuracy back.  And yes, I could hit an 8" paper plate 5 out of 5 at a measured 1000 yards with that rifle and cast paper patched bullets. Not a stock barrel, it was a stainless bull, fluted, and the action was sleeved with it overlapping the barrel thru the chamber length.

In an air rifle a BBT with it's driving bands shortened some so it would not take so much engraving force might work though
Title: Re: 12ga Big Bore
Post by: MJP on February 03, 2019, 04:38:43 PM
And then there is the fact that aluminum oxidizes on the surface, its not thick by much but its hard as nails.
I would advise against puting aluminum bullets in any barrel that costs money.

If you could coat that aluminum bullet with thin lead then that might be worth trying.

Marko
Title: Re: 12ga Big Bore
Post by: rkr on February 03, 2019, 05:16:24 PM
Does it have to be a rifled barrel? There are many shotgun slugs available for smoothbores.
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on February 03, 2019, 05:23:16 PM
But with a smooth bore you lose the benefits of spin on the projectile you achieve through rifling.
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on February 03, 2019, 05:27:43 PM
And then there is the fact that aluminum oxidizes on the surface, its not thick by much but its hard as nails.
I would advise against puting aluminum bullets in any barrel that costs money.

If you could coat that aluminum bullet with thin lead then that might be worth trying.

Marko
I've been trying the powder coat on my cast bullets which might work covering an alminium bullet.
There's HiTek Super coat too which PBers are using instead of lube.
My interests changed and I quit firearms to go all pneumatic but if I were still shooting PB I would not hesitate to try those... Except that for long range Al just did not work
Title: Re: 12ga Big Bore
Post by: rkr on February 03, 2019, 05:40:00 PM
But with a smooth bore you lose the benefits of spin on the projectile you achieve through rifling.

There are "finned" slugs that are supposed to spin. I don't know if they work or not but perhaps worth investigation?
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 03, 2019, 07:39:27 PM
Aluminum oxidizes into aluminum oxide. The stuff on sandpaper. Some people recommended against it for that reason. Alloys or coatings could help this. But I also don't think the aluminum bullets would be heavy enough. Or if they were heavy enough they would require so much twist to stabilize that it would drastically reduce muzzle velocity.

I think like Bob suggested tin could work well. Or Pewter (92/8 Tin/Antimony) They would be expensive, but drastically reduced labor, but being able to just pour them.

I had another couple crazy ideas, maybe #9 shot lead mixed into a strong plastic polymer. Again, it would be easy to pour. And if the mold was set vertically the bullet would have most of the weight forward.

Or maybe a Pewter "Power belt" The plastic skirt would help reduce barrel friction and provide a good seal. And a ballistic tip would improve BC, and a hidden hollowpoint behind it would help reduce the weight. For that matter maybe a traditional copper jacketed lead bullet could be made light enough. Since "Power belt" has all the tech figured out, maybe they would do a limited quantity run of a couple thousand 0.62 bullets. Worse come to worse they could be used as 20ga slugs. I'm confident they would work in a can, because that is what the suppressed maxim 50 recommends for their guns.
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on February 03, 2019, 09:05:21 PM
I was lucky enough to score a box of these:
https://www.midwayusa.com/product/173073/inceptor-preferred-hunting-bullets-458-socom-458-diameter-200-grain-arx-frangible-lead-free (https://www.midwayusa.com/product/173073/inceptor-preferred-hunting-bullets-458-socom-458-diameter-200-grain-arx-frangible-lead-free)

I can't understand why the are discontinued, they shot GREAT in my Texan!!!

Metal dust infused polymer composite, did not foul the barrel in any way, accurate and good FPS/FPE
Title: Re: 12ga Big Bore
Post by: TPL on February 04, 2019, 04:09:10 PM
You don't need ballistic tip subsonic. Actually flathead works the best or even better than that, hollow point in ballistics.

Due to balance.
Title: Re: 12ga Big Bore
Post by: rsterne on February 04, 2019, 07:39:00 PM
I would agree, spending time on a ballistics tip for Subsonic work is not something I would do.... Certainly all the drag programs don't show any advantage to them at airgun velocities.... For deer I would use a medium depth hollowpoint to get good expansion with fragmentation.... You can get that if the hollowpoint is too deep....

Bob
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 04, 2019, 10:58:45 PM
You don't need ballistic tip subsonic. Actually flathead works the best or even better than that, hollow point in ballistics.

Due to balance.

G1 is the "best" we have these days. For long-range G7 is better, but the numbers are smaller and bullets with a higher BC sell better (whether G1 or G7) so G1 is usually the one cited. And neither were intended to be accurate predictions at subsonic speeds. So just because the math says so doesn't mean that its the case.

It goes against everything I know about aerodynamics that of these two bullets the hollowpoint has less aerodynamic drag. One is pushing a snow plow, the other is a dart.

Title: Re: 12ga Big Bore
Post by: fpjeepy on February 04, 2019, 11:07:28 PM
I would agree, spending time on a ballistics tip for Subsonic work is not something I would do.... Certainly all the drag programs don't show any advantage to them at airgun velocities.... For deer I would use a medium depth hollowpoint to get good expansion with fragmentation.... You can get that if the hollowpoint is too deep....

Bob

I personally, wouldn't be looking for expansion. A 0.62" hole would be good enough. (by comparison, I would guess more than 70% of deer have been killed by a bullet smaller than .308 in diameter with less than 2x expansion. [0.618"]) And if the bullet were to expand to 2 times its diameter I suspect it would not have enough energy at 300gr to get a pass through.
Title: Re: 12ga Big Bore
Post by: Brian W Cook on February 09, 2019, 08:05:24 PM
If a guy happened to have a 18” barreled 12 gauge side lever top end laying around rusting . What valve configuration would you run ?  Right now it has a .437 port going through the bolt .    Maybe run a balanced valve and run it in the upper 3000’s to get the bullet / round ball moving ?
Title: Re: 12ga Big Bore
Post by: rsterne on February 09, 2019, 10:52:40 PM
I would expect the two bullets you portrayed in Reply # 85 to have a significant difference in subsonic drag.... Comparing the upper one to an identical bullet with the plastic nose removed.... much less so.... If you made yet another design, with the caliber and LOA of the upper one, but a hollowpoint of about 50% of the caliber.... it could even have less drag....

Bob
Title: Re: 12ga Big Bore
Post by: TPL on February 12, 2019, 02:09:29 PM
G1 is the "best" we have these days. For long-range G7 is better, but the numbers are smaller and bullets with a higher BC sell better (whether G1 or G7) so G1 is usually the one cited. And neither were intended to be accurate predictions at subsonic speeds. So just because the math says so doesn't mean that its the case.

It goes against everything I know about aerodynamics that of these two bullets the hollowpoint has less aerodynamic drag. One is pushing a snow plow, the other is a dart.
G1, G7 and whatsoever are only mathematical ballistic models we use to estimate bullet fly. BC is a relative number comparing actual bullet drag to its speed against any chosen mathematical model. The model we use is not changing the bullet behavior. It only changes numbers. There is no the best model for short and long range. Only for bullet shape vs. speed. You are bind to subsonic, right?

Bullet model mostly used for subsonic is G1. For supersonic it is mostly G7. That doesn't change bullet properties in any way. None of those models are telling exatcly about your actual bullet unless you make a new mathematical model, Gfpjeepy12GA.  :D

What comes to real drag you could try for example this: http://www.geoffrey-kolbe.com/drag.htm (http://www.geoffrey-kolbe.com/drag.htm). It has found very good. Try with sharp nose vs. flat in subsonic area and see youreself. You'll see the difference also supersonic. Ballistics can surprise sometimes.

There is only one thing to remember with ballistic calculators, garbage in, garbage out. Oh, maybe two, not all of them are suitable for all uses.
Title: Re: 12ga Big Bore
Post by: MJP on February 13, 2019, 09:36:58 AM
If a guy happened to have a 18” barreled 12 gauge side lever top end laying around rusting . What valve configuration would you run ?  Right now it has a .437 port going through the bolt .    Maybe run a balanced valve and run it in the upper 3000’s to get the bullet / round ball moving ?

Full bore size porting, with as big of a valve you could possibly fit in your frame, and still have enough area to flow past it.
 Balenced of course, no point making it pain in the behind to cock it.

Marko
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 13, 2019, 01:44:13 PM
I would expect the two bullets you portrayed in Reply # 85 to have a significant difference in subsonic drag.... Comparing the upper one to an identical bullet with the plastic nose removed.... much less so.... If you made yet another design, with the caliber and LOA of the upper one, but a hollowpoint of about 50% of the caliber.... it could even have less drag....

Bob

Why do you say that? I don't follow the logic
Title: Re: 12ga Big Bore
Post by: rsterne on February 13, 2019, 02:15:48 PM
It's not a matter of "logic", ballistics design is well known, and has been for decades.... Check out this Drag calculator, there is an explanation there of the program used....

http://www.geoffrey-kolbe.com/drag.htm (http://www.geoffrey-kolbe.com/drag.htm)

The "McDrag" program was developed by Robert McCoy at the Aberdeen Proving Grounds and tested against doppler radar and chronograph measurements, and is within 6% Subsonic (below Mach 0.8 ) and 11% Transonic (Mach 0.8-1.2) of real world results.... It is even better Supersonic (over Mach 1.2), at only a 3% margin of error....

Pointed bullets are vastly superior Supersonic, and the higher the velocity the narrower the angle of the conical nose shock wave.... so the narrower the nose must be to stay inside that cone (which at Mach 2 means within a 30 deg. angle).... Below Mach 1, and in particular below Mach 0.8 (900 fps) there are no shock waves to deal with, so a pointed nose makes little difference to the drag.... Elmer Keith was one of the first to demonstrate that, and his work with large Meplat bullets is legendary, particularly for pistol bullets, which for the most part are Subsonic.... A large Meplat (flat nose) transfers more of the energy of the impact to the quarry by making a larger diameter (but shallower) wound cavity, and hence is preferred for hunting, particularly with airguns, which traditionally are lower power than their PB counterparts.... There is a lot of similarity between our requirements and those of handgun (or blackpowder) hunters....

Cutting the nose off of (shortening) a spire point bullet to get a Meplat is not the same thing as leaving the bullet the same LOA and using a larger Ogive radius to create a Meplat within that LOA.... The former does increase the Subsonic drag, the latter may in fact reduce it.... Experimenting with the Kolbe Drag Calculator will give you a better idea of what affects bullet drag and what doesn't than your eyeball.... That same drag program is also used by JBM Ballistics and Lila.... and other than using sophisticated CFD computer programs to analyze the drag, I have never found anything better....

Bob
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 18, 2019, 01:13:06 PM

It's not a matter of "logic", ballistics design is well known, and has been for decades.... Check out this Drag calculator, there is an explanation there of the program used....

http://www.geoffrey-kolbe.com/drag.htm (http://www.geoffrey-kolbe.com/drag.htm)

The "McDrag" program was developed by Robert McCoy at the Aberdeen Proving Grounds and tested against doppler radar and chronograph measurements, and is within 6% Subsonic (below Mach 0.8 ) and 11% Transonic (Mach 0.8-1.2) of real world results.... It is even better Supersonic (over Mach 1.2), at only a 3% margin of error....

Pointed bullets are vastly superior Supersonic, and the higher the velocity the narrower the angle of the conical nose shock wave.... so the narrower the nose must be to stay inside that cone (which at Mach 2 means within a 30 deg. angle).... Below Mach 1, and in particular below Mach 0.8 (900 fps) there are no shock waves to deal with, so a pointed nose makes little difference to the drag.... Elmer Keith was one of the first to demonstrate that, and his work with large Meplat bullets is legendary, particularly for pistol bullets, which for the most part are Subsonic.... A large Meplat (flat nose) transfers more of the energy of the impact to the quarry by making a larger diameter (but shallower) wound cavity, and hence is preferred for hunting, particularly with airguns, which traditionally are lower power than their PB counterparts.... There is a lot of similarity between our requirements and those of handgun (or blackpowder) hunters....

Cutting the nose off of (shortening) a spire point bullet to get a Meplat is not the same thing as leaving the bullet the same LOA and using a larger Ogive radius to create a Meplat within that LOA.... The former does increase the Subsonic drag, the latter may in fact reduce it.... Experimenting with the Kolbe Drag Calculator will give you a better idea of what affects bullet drag and what doesn't than your eyeball.... That same drag program is also used by JBM Ballistics and Lila.... and other than using sophisticated CFD computer programs to analyze the drag, I have never found anything better....

Bob

I guess maybe I was a little confused. You said..

If you made yet another design, with the caliber and LOA of the upper one, but a hollowpoint of about 50% of the caliber.... it could even have less drag....

Bob

I took that as saying that a hollowpoint will have less drag than a pointed bullet. Which I believe is what TPL was saying.

You don't need ballistic tip subsonic. Actually flathead works the best or even better than that, hollow point in ballistics.


But what you describe above is making another bullet that has the same LOA with a flat point. This will make a heavier bullet and in turn a higher sectional density and in turn a theoretical lower drag. But in my opinion, that's not a fair comparison because higher sectional density bullets have a higher ballistic coefficient. Using the calculator I failed to ever make a bullet that had a higher B.C. with the same weight that was flat pointed vs the pointed at Mach 0.5 (They didn't list 0.8). And even at that, it is only guaranteed to be within 11% (for 0.8) which isn't great. I.e disregard if the gains are less than 12% . Hollowpoints will always be lighter than their parent flat point and therefore have higher drag. 

I would argue logic is important. I see no benefit in blindly following an 89% accurate formula. There is a reason rocketships, airplanes, and torpedos are pointed. If this wasn't true then I could be a millionaire by patenting the hollowpoint racing bike helmet, the hollow-tip airplane wing, and the flat-sided baseball.

I'm not arguing that flat pointed and hollowpoint don't have a place in airgun hunting. I think they are greatly suited for that. But not because they have less drag than their pointed counterpart. Rather, because they are great in terms of terminal ballistics.
Title: Re: 12ga Big Bore
Post by: rsterne on February 18, 2019, 01:44:52 PM
No, by varying the density (ie specifying a constant weight in the Kolbe Calculator, for instance your 300 gr. target), you can separate the effects of length and shape from that of the SD.... HPs don't have higher drag, they do, however have a lower SD, all other things being equal, and a different CG position....

I am not about to try and "guess" my way around a proven ballistics program by doing what I think looks right.... No program is perfect, and as you state, worst case for this one is "89% correct" (actually, at Mach 0.75, it is 94% correct, that 11% error is only between 900-1350 fps, being the least reliable at Mach 1).... In addition, nature seldom gets it wrong, and you don't see many birds or fish with flat skulls.... but on the other hand, not many of them fly/swim at Mach 0.8 either....

I wish you luck in your pursuit of a better ballistics approach.... I hope to do some real research in this regard once I get my LabRadar in 2 more years.... but until I have data to prove McCoy wrong, I won't be betting against him....

Bob
Title: Re: 12ga Big Bore
Post by: rsterne on February 18, 2019, 02:15:44 PM
Try these dimensions in the Kolbe Calculator....

Diam = 0.62"
Length = 1.00"
Nose Length = 0.50"
Meplat = 0.00"
Driving Band & Base = 0.62"
Weight = 300 gr.

You will get BC (M0.5) = 0.09 and BC (M1.0) = 0.06

Now change the Meplat to 0.31" (50%) and leave everything else the same (including the weight, to keep the SD constant)….

You will get BC (M0.5) = 0.09 and BC (M1.0) = 0.10 …. ie the same drag at Mach 0.5, but a lot less at Mach 1....

Want to see what happens between those two velocities?.... Look at the graph at the bottom of the page, at Mach 0.8.... Notice that the sudden increase in drag occurs at a HIGHER velocity for the bullet with a meplat…. Not only that, but the Drag Coefficient Cd is much less for the bullet with a Meplat, from that inflection point onwards.... peaking at only Cd=0.8 instead of Cd=1.1.... That is a lot more difference than 11%.... At Mach 0.8, the Cd of the pointed bullet is about 0.4, while that of the bullet with the Meplat is about 0.24 (40% less)…. At Mach 0.9, the pointed bullet Cd is about 0.6, while the one with the Meplat is about 0.35....  :o

In the transonic region in particular, it seems that "eyeball logic" does not necessarily apply.... IMO, based on the extensive work of Robert McCoy, and verified by the Aberdeen Proving Grounds....

Bob

Title: Re: 12ga Big Bore
Post by: fpjeepy on February 18, 2019, 02:37:24 PM
HPs don't have higher drag,

You have nothing to prove this. The calculator was developed for flat pointed bullets.

worst case for this one is "89% correct"

Actually, from the link you provided... "This showed that the typical standard deviation errors to be expected were about [...] 11% in the transonic region.."

"Standard deviation errors" means 68.2% (one standard deviation) for the bullets they tested fell within 11% of the value calculated. So the worst case scenario would be worse. 

In addition, nature seldom gets it wrong, and you don't see many birds or fish with flat skulls.... but on the other hand, not many of them fly/swim at Mach 0.8 either....

How about airplanes? Maybe McCoy should call up Boeing and let them know what they are missing.

I wish you luck in your pursuit of a better ballistics approach.... I hope to do some real research in this regard once I get my LabRadar in 2 more years.... but until I have data to prove McCoy wrong, I won't be betting against him....

I don't think you need any fancy equipment. Just buy some muzzleloader bullets, and pull the ballistic tips off half of them and show me that those shoot flatter at 950fps.

I did't intend for this to become a ^*%$#@ match... You keep shooting hollowpoints and I'll wrongly keep shooting ballistic tips and everyone will be happy.
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 18, 2019, 02:50:15 PM
Try these dimensions in the Kolbe Calculator....

Diam = 0.62"
Length = 1.00"
Nose Length = 0.50"
Meplat = 0.00"
Driving Band & Base = 0.62"
Weight = 300 gr.

You will get BC (M0.5) = 0.09 and BC (M1.0) = 0.06

Now change the Meplat to 0.31" (50%) and leave everything else the same (including the weight, to keep the SD constant)….

You will get BC (M0.5) = 0.09 and BC (M1.0) = 0.10 …. ie the same drag at Mach 0.5, but a lot less at Mach 1....

Want to see what happens between those two velocities?.... Look at the graph at the bottom of the page, at Mach 0.8.... Notice that the sudden increase in drag occurs at a HIGHER velocity for the bullet with a meplat…. Not only that, but the Drag Coefficient Cd is much less for the bullet with a Meplat, from that inflection point onwards.... peaking at only Cd=0.8 instead of Cd=1.1.... That is a lot more difference than 11%.... At Mach 0.8, the Cd of the pointed bullet is about 0.4, while that of the bullet with the Meplat is about 0.24 (40% less)…. At Mach 0.9, the pointed bullet Cd is about 0.6, while the one with the Meplat is about 0.35....  :o

In the transonic region in particular, it seems that "eyeball logic" does not necessarily apply.... IMO, based on the extensive work of Robert McCoy, and verified by the Aberdeen Proving Grounds....

Bob

I did that and I got this message... "Warning: Nose length is less than one calibre. The calculated nose drag contributions for transonic and supersonic speeds are probably too high."

i.e this is not based on the extensive work of Robert McCoy, and verified by the Aberdeen Proving Grounds....

Additionally, the program doesn't allow you to lock the secant location. So all things are not the same. The area near the shoulder (the part with the largest surface area) is closer to tangent on the bullets with a larger meplate. I would imagine that if you could lock this at a set angle results would be different. Your flat point bullet looks closer to the ideal subsonic rocket nose shape than the pointed version the software draws and it is because of that sharp corner. 
Title: Re: 12ga Big Bore
Post by: rsterne on February 18, 2019, 04:17:45 PM
There is no shoulder unless you select a Secant Ogive.... the default is a Tangent Ogive.... If you notice on the dimensions I gave you, when you run the calculator the ogive radius is larger on the design with the Meplat…. THAT is part of the reason it has less drag, the angle of the ogive where it meets the Meplat (where a shockwave would form) is shallower.... On both versions, the nose is 0.5" long, so the parallel portion of the bullet is also 0.5" long.... The ogive starts at exactly the same point on both....

RE the warning about the nose drag, change the nose length to 0.65" to eliminate that.... The parallel portion will be shorter at 0.35".... You get the same 0.09 BCs at Mach 0.5, but a higher BC at Mach 1.0 in both cases (note the ogive is a larger radius with the longer nose).... The Cd graphs still show the same trends.... The bullet with Meplat has the start of the high drag transition at higher velocity, and the increase is shallower, and the Cd at Mach 1 is a lot less (0.45 vs 0.63)….

I see no point in continuing to argue with you.... You have decided your eyeball is better than McCoy's math, and it very may well be.... My eyeball tells me the same thing.... However, my eyeball is not calibrated for Transonic flow.... Interestingly, the Subsonic drag is virtually the same regardless of nose shape, so below 900 fps they should in theory be equal within 6%.... I'll bet you that you can't measure a string of 10 bullets and get a Cd within 6%....

As with all theories, one you prove it wrong, it's time for a new theory.... I'm perfectly willing to throw out McCoy's work when that data becomes available.... Until then, I'll continue to use it as a useful design tool.... YMMV....

Just to give you something to think about.... which do you think might have less drag (same mass, so same SD)….

(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Airflow%20Around%20Meplat_zpsqawtjb2g.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Airflow%20Around%20Meplat_zpsqawtjb2g.jpg.html)

the round nose pellet shown in red (Ogive 0.5 calibers).... or the black one with a 1.0 caliber Ogive radius and a Meplat…. I drew them different lengths for clarity, but you can assume they are the same LOA....

I have been told there is no such stagnation zone when you examine such a design with CFD.... However, the velocity of the air in that area is closer to the velocity of the pellet than the free stream velocity in that CFD anaylsis…. so what is that, if not a stagnation zone (air being dragged along with the pellet)….

Bob
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 18, 2019, 04:56:31 PM
There is no shoulder unless you select a Secant Ogive.... the default is a Tangent Ogive.... If you notice on the dimensions I gave you, when you run the calculator the ogive radius is larger on the design with the Meplat…. THAT is part of the reason it has less drag, the angle of the ogive where it meets the Meplat (where a shockwave would form) is shallower.... On both versions, the nose is 0.5" long, so the parallel portion of the bullet is also 0.5" long.... The ogive starts at exactly the same point on both....

RE the warning about the nose drag, change the nose length to 0.65" to eliminate that.... The parallel portion will be shorter at 0.35".... You get the same 0.09 BCs at Mach 0.5, but a higher BC at Mach 1.0 in both cases (note the ogive is a larger radius with the longer nose).... The Cd graphs still show the same trends.... The bullet with Meplat has the start of the high drag transition at higher velocity, and the increase is shallower, and the Cd at Mach 1 is a lot less (0.45 vs 0.63)….

I see no point in continuing to argue with you.... You have decided your eyeball is better than McCoy's math, and it very may well be.... My eyeball tells me the same thing.... However, my eyeball is not calibrated for Transonic flow.... Interestingly, the Subsonic drag is virtually the same regardless of nose shape, so below 900 fps they should in theory be equal within 6%.... I'll bet you that you can't measure a string of 10 bullets and get a Cd within 6%....

As with all theories, one you prove it wrong, it's time for a new theory.... I'm perfectly willing to throw out McCoy's work when that data becomes available.... Until then, I'll continue to use it as a useful design tool.... YMMV....

Just to give you something to think about.... which do you think might have less drag (same mass, so same SD)….

(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Airflow%20Around%20Meplat_zpsqawtjb2g.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Airflow%20Around%20Meplat_zpsqawtjb2g.jpg.html)

the round nose pellet shown in red (Ogive 0.5 calibers).... or the black one with a 1.0 caliber Ogive radius and a Meplat…. I drew them different lengths for clarity, but you can assume they are the same LOA....

I have been told there is no such stagnation zone when you examine such a design with CFD.... However, the velocity of the air in that area is closer to the velocity of the pellet than the free stream velocity in that CFD anaylsis…. so what is that, if not a stagnation zone (air being dragged along with the pellet)….

Bob

If the calculator gives you a warning as the nose gets shorter because it is not accurate, I would also assume that the least accurate area, is just inside the bounds of the cutoff. And you will notice that this flat point advantage diminishes as the nose gets longer.

I will agree that in your example the black outline would have less drag. But I would argue that if you left the blue "stagnation zone" on the bullet (even as a plastic ballistic tip) it would have even less drag.
Title: Re: 12ga Big Bore
Post by: rsterne on February 18, 2019, 05:12:13 PM
and be longer, and therefore require a faster twist rate.... I will agree that in general, longer bullets have less drag.... and so does McCoy....

That is one of the reasons I suggested you consider a bullet cast from Tin instead of Lead.... at the same weight, a Tin bullet will be longer and have a lower Form Factor, and hence less drag, even though the SD is the same.... We agree on most things.... and I agree with you that to the eye, a Meplat seems it should be greater drag than a round or pointed nose at the same LOA.... Unfortunately, that has not so far proven to be the case.... I don't understand why, any more than you do.... but I am willing to accept the calculations that are available, until they are proven wrong....

Bob
Title: Re: 12ga Big Bore
Post by: rsterne on February 18, 2019, 05:41:39 PM
I have been looking for this CFD output, perhaps it may be helpful in visualizing the flow around a pellet.... This calculation was done with a pellet velocity of 235 m/s (770 fps)…. It is "reversed", and shows the air velocity relative to the surrounding air, instead of relative to the pellet, as most of the CFD outputs show (pellet stationary, air moving is typically the way CFD is done)....

(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Air%20Moving%20With%20Pellet_zpsuw9r47ac.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Air%20Moving%20With%20Pellet_zpsuw9r47ac.jpg.html)

The darkest red air is moving with the pellet, being dragged along at that velocity.... It's pretty interesting how much of a teardrop shape results if you consider the air and pellet moving together through the surrounding air.... I know that's not a perfectly true description of what is happening.... but perhaps can give some credibility to the concept.... and why Meplats aren't really that bad after all....

Bob

Title: Re: 12ga Big Bore
Post by: fpjeepy on February 19, 2019, 01:34:08 PM
New idea... So the reason I haven't suggested a traditional sabot is that it would wipe out the baffles in the suppressor... But what if it was more like a pressure cone for a blow dart or the powerbelt muzzleloader bullets. It would still reduce the bullet size from 62cal to say 45cal, but it would be tapered so that it would fly straight through the baffles. Like below.
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 22, 2019, 10:37:47 AM
Well, I thought it was a good idea.
Title: Re: 12ga Big Bore
Post by: TPL on February 22, 2019, 11:10:16 AM
Well, the base is much more important in subsonic or transonic than the nose. I see your new idea likely the worst possible option. But hey, why not to try it?

Unless you mean the base part will get lost right after muzzle like sabot? Also then nothing would steer the bullet inside the barrel.
Title: Re: 12ga Big Bore
Post by: jackssmirkingrevenge on February 22, 2019, 02:53:42 PM
But what if it was more like a pressure cone for a blow dart or the powerbelt muzzleloader bullets.

That won't be stable in the barrel because the center of gravity is ahead of the contact area with the barrel.

There are a number of publicly accessible studies on sabot design like this one (https://apps.dtic.mil/dtic/tr/fulltext/u2/a056428.pdf) that go into a lot of detail as to what works and what doesn't.

What you can do to avoid baffle strikes is to put rods inside the tube like Salvo 12:

(https://i.imgur.com/8Vtxc3g.png)
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 23, 2019, 01:36:10 AM
But what if it was more like a pressure cone for a blow dart or the powerbelt muzzleloader bullets.

That won't be stable in the barrel because the center of gravity is ahead of the contact area with the barrel.

There are a number of publicly accessible studies on sabot design like this one (https://apps.dtic.mil/dtic/tr/fulltext/u2/a056428.pdf) that go into a lot of detail as to what works and what doesn't.

What you can do to avoid baffle strikes is to put rods inside the tube like Salvo 12:

(https://i.imgur.com/8Vtxc3g.png)

genius
 
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 26, 2019, 01:36:43 PM
Would that be messed up by the sabot spinning in a rifle (which isn't the case in a shotgun) And does anyone think accuracy would be affected?

What about a sabot with a thick wall that was intended to fall off the back rather than flare out like a shotgun wad?
Title: Re: 12ga Big Bore
Post by: Jim Holmgren on February 26, 2019, 02:43:03 PM
Would that be messed up by the sabot spinning in a rifle (which isn't the case in a shotgun) And does anyone think accuracy would be affected?

What about a sabot with a thick wall that was intended to fall off the back rather than flare out like a shotgun wad?


I would be hard to say but you could set up a test rig without baffles and only guiding rods and see what gives without danger of destroying the suppressor.

I have also seen a pipe full of holes to guide the wad which may be easier to machine? One could also mill a tube lengthwise for 6 or something groves, or do like some integrally suppressed firearms and use a barrel full of holes that bleed of to the baffles.
Title: Re: 12ga Big Bore
Post by: jackssmirkingrevenge on February 26, 2019, 09:10:41 PM
Would that be messed up by the sabot spinning in a rifle (which isn't the case in a shotgun) And does anyone think accuracy would be affected?

The Salvo 12 attaches to the choke tube thread on a shotgun barrel so is not intended for us with rifled bores, however if the rods are sufficiently densely placed I don't see that being an issue.

Quote
What about a sabot with a thick wall that was intended to fall off the back rather than flare out like a shotgun wad?

A one-piece sabot of that nature is unlikely to work well in terms of adequate separation, you'd need a separate pusher base and centering petals like tank APDS ammunition, which are not going to work well in a suppressor.  As Jim says a perforated tube might be your best bet if the guide rods don't work.
Title: Re: 12ga Big Bore
Post by: rsterne on February 26, 2019, 10:00:18 PM
Arrange the guide rods to match the twist rate of the barrel.... Hence relative to the rods, the sabot/wad would have no angular velocity.... A 24" twist in a .62 cal. would be an angle of only about 5 deg....

Bob
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on February 26, 2019, 10:26:06 PM
Or just EDM long spiral slots through the barrel wall, aligned with the barrel grooves, matching the twist

http://www.robrobertsgunworks.com/edm-porting (http://www.robrobertsgunworks.com/edm-porting)

I've seen long spiral EDM cuts before but the example I linked to is just 'compensator' ports in a shotgun barrel, the Magnaport is used on rifle barrels.

EDM can be used to machine complex shapestoo, not just ports though.
Title: Re: 12ga Big Bore
Post by: MJP on February 27, 2019, 02:34:35 PM
Would be interesting to see something built and not just dreaming about it.
I for one like to see some action.  ;)

Marko
Title: Re: 12ga Big Bore
Post by: Jim Holmgren on February 27, 2019, 03:20:18 PM
Would be interesting to see something built and not just dreaming about it.
I for one like to see some action.  ;)

Marko

Its is also easier to make a working concept with a prototype then trying to find out whats work in theory. ;)

Try to find a muzzle loader barrel in 20ga or a dom tube in 0.60" or 16mm id, (as you will use custom bullets/sabots the exact barrel groove dia is not to impotent)
Then test and see if you can reach you goal in a smooth bore and if you can you can buy a custom barrel blank or test to cut or button rifling you own.

For air you could make you own tube with a 1.1/4" 4130 tube 0.09 wall or use two cheap pcp bottles with 18x1.5 threads.
The valve could be mounted in a big air tube or in a lower receiver that you could machine out of a billet of aluminium.

For loading you could have a endless solution's, bolt, fallingblock, threaded artillery type, break action, sliding sleeve, muzzle loader, revolver, for say a few.

Triggers can you use from a exiting air rifle like the marauder or design you own.
You could even have a externally hammer if you wanted.   

And the stock could be anything from a simple skeleton to a nice laminate of you liking.

When you can fire bullets/sabots start to thinking with the suppressor and ammunition types.
Fun to throws some ideas ;D
Could you make a sketch of the rifle that you want to build and post it?
Title: Re: 12ga Big Bore
Post by: fpjeepy on February 28, 2019, 11:53:20 AM

Quote
What about a sabot with a thick wall that was intended to fall off the back rather than flare out like a shotgun wad?

A one-piece sabot of that nature is unlikely to work well in terms of adequate separation, you'd need a separate pusher base and centering petals like tank APDS ammunition, which are not going to work well in a suppressor.  As Jim says a perforated tube might be your best bet if the guide rods don't work.

Below is a 62cal/40cal sabot. I think with a 1:24-1:28 it might stabilize bullets up to 265gr like this http://www.accuratemolds.com/bullet_detail.php?bullet=40-265S-D.png (http://www.accuratemolds.com/bullet_detail.php?bullet=40-265S-D.png)

If it was made out of a stiff enough material, I'm hoping the bevels at the front would ease it through the baffles, and the flats around the base would pull it off the back of the bullet. 
Title: Re: 12ga Big Bore
Post by: MJP on March 01, 2019, 01:58:12 AM
You are going to have hard time separating the sabot if you bevel the end like that, we used a cone shape petals to open the sabot upon exiting the muzzle.
It's pretty consistent now, I can hit pistol size ram at 100m repeatedly shooting with saboted .257 bullets out of the .457
Muzzle velocity was around 400-450m/s if I remember correctly.

Marko
Title: Re: 12ga Big Bore
Post by: fpjeepy on March 02, 2019, 02:17:47 PM
You are going to have hard time separating the sabot if you bevel the end like that, we used a cone shape petals to open the sabot upon exiting the muzzle.
It's pretty consistent now, I can hit pistol size ram at 100m repeatedly shooting with saboted .257 bullets out of the .457
Muzzle velocity was around 400-450m/s if I remember correctly.

Marko

The goal would be for the petals not to open. If they open they will hit the baffles. The idea is that the flats at the base would provide enough resistance to pull the sabot off the back.

Another idea would be to have a zig zag thin skin of plastic connecting the petals so that it can open, but not more than a small amount. Enough for the bullet to slide out, but not enough to contact the baffles.

Sounds like it is getting expensive, but I think less than a couple of dollars a sabot would be acceptable. Me personally I would probably shoot the 350gr full bore hollow base cast lead 20ga slugs for everyday shooting and have 25 or so of the 270gr sabot bullets just for hunting.

Hypothetically, would the average Joe prefer to buy a $1000 American made gun or a $350 made in China gun?

Title: Re: 12ga Big Bore
Post by: MJP on March 02, 2019, 02:28:57 PM
Well make the gun and the sabots, shoot some and you'll see what opens and what won't separate.
We have tested many sabot designs for different calibers, and if you want to separate the sabot you need to get it open quickly.
Plink with something else that doesn't make noise and loose the can on your hunting setup.

Marko
Title: Re: 12ga Big Bore
Post by: Kinetic45^ on March 02, 2019, 03:19:52 PM
Not hitting baffles was why I suggested venting the end of a longer barrel into a surrounding 'LDC can' with EDM.  The ports would align with individual chambers.
This does work as I've built one like this - .410 barrel for a Texan which will shoot slugs or plastic shot cups.
Title: Re: 12ga Big Bore
Post by: fpjeepy on March 02, 2019, 05:56:34 PM
Not hitting baffles was why I suggested venting the end of a longer barrel into a surrounding 'LDC can' with EDM.  The ports would align with individual chambers.
This does work as I've built one like this - .410 barrel for a Texan which will shoot slugs or plastic shot cups.

I wasn't discrediting your suggestion. It just seemed like a lot of work for something that may not be as effective as a traditional can. It's my understanding that quieting a .62cal is not going to be easy.
Title: Re: 12ga Big Bore
Post by: sgtbunny on May 29, 2019, 01:43:23 PM
You guys make my brain hurt.
Title: Re: 12ga Big Bore
Post by: fpjeepy on June 11, 2019, 01:58:19 PM
You guys make my brain hurt.

I feel the opposite... Innovation is the only thing that turns my brain on. It hurts that I don't have the time or money to pursue this.