.222/223 is the best caliber for bullet shooters on a budget!

[Scotchmo]

Scott, please forgive my post above, I did not mean to sound condescending.... Chalk it up to being tired.... You obviously have spent a fair amount of time working out a formula for horsepower based on port area, and the relationship to projectile weight.... We know from empirical data that the FPE is roughly proportional to the smallest port diameter (not area)…. but this should be applied at about 950 fps (ie constant velocity)…. If the velocity is constant, then the projectile weight must be proportional to the FPE, and at 950 fps, it would be 1/2 gr. per FPE.... Further, if the pressure, barrel length and caliber are all constant, then the average velocity, and hence the acceleration, must be virtually constant as well.... and since we are talking about a maximum power shot, the valve is open until the projectile leaves the barrel.... For simplicity, let us assume an infinite reservoir, so constant pressure at the valve seat....

You state that the horsepower is proportional to the port area, which is the square of the diameter.... If the air is accelerating a projectile whose weight is proportional to the port diameter, can you mathematically prove that the muzzle velocity should remain a constant?.... If you can do that, then we have our answer as to why the FPE is proportional to the port diameter, rather than the port area.... ie the math to back up the observations....

Bob

".... Further, if the pressure, barrel length and caliber are all constant, then the average velocity, and hence the acceleration, must be virtually constant as well...."

That is only true for instance A (full port). There will be a big difference between the acceleration profiles of instance A (full port) and instance B (0.11” port).

Instance A will have a fairly constant acceleration as the slug moves down the barrel. Instance B will have a higher initial acceleration, which will remain constant only up to the choke point, and then acceleration will start to fall and then continue to fall after that.

When using  the constant velocity of 950fpe, I don't know if there is a single/simple equation to show why the projectile energy (FPE) is ending up proportional to port diameter. My first guess why is because the air mass proportions are skewing it toward that result. I plan on adding a variable port restriction into my dump gun spreadsheet model and running some simulations.

The flow through the restriction (orifice) will be assumed (modeled) as a friction-less nozzle, where in practice it's not. There would need to be a flow coefficient in order to get closer to real world results. It's the difference between a transfer port that is a simple orifice and a transfer port with a perfectly tapering inlet and outlet.

A couple years back, Lloyd ran some experiments in trying to maximize the supersonic projectile velocity in a PCP airgun. My spreadsheet model seemed to match up fairly well with those results. Now that I'll be trying to maximize the projectile FPE, near sonic velocities, in a ported gun, the same choked flow constraints will apply. So I have a renewed interest.

[rsterne]

The average acceleration must be the same, if the barrel length and MV is the same, no? (eg. 950 fps over 24").... Yes, the profile might be different, although if the port is half the diameter and the pellet half the weight, even that might not be too different.... although I would still expect more acceleration initially and less towards the muzzle with the smaller port.... After all, initially there is very little mass flow, because the pellet is stationary or barely moving, so the pressure governs, and the lighter pellet would therefore see higher acceleration.... Choking may occur as the pellet approaches the muzzle, but as you know, it is almost impossible to predict or model.... Most attempts to include choking end up predicting too little force/acceleration and a lower than observed velocity/energy.... This is likely due to a lot of the latter stages of acceleration being the result of the expansion of the air in the barrel, rather than new air being added through the (restricted) port.... I am convinced that no choking occurs with bore-area porting and a dump shot (dwell greater than shot duration), with the MV being subsonic.... or even low supersonic, because of the elevated SoS at high pressures....

I'm sure the FPE being proportional to the port diameter is not 100% accurate.... but it does seem to be a fair estimate, even though I don't have the math to say why.... I wish you better luck.... Perhaps a new thread in the Workshop, rather than hijacking this one further?....

Bob

[UnderPressure]

1 in 7" twist 25" long .223 GM blank for $58:

http://www.gmriflebarrel.com/557-blank-5-56-mm-223-caliber-25-x-1-062-1-7-gunsmith-edition-raw-blank/

Fast enough twist to shoot this BBT:

[rkr]

1 in 7" twist 25" long .223 GM blank for $58:

http://www.gmriflebarrel.com/557-blank-5-56-mm-223-caliber-25-x-1-062-1-7-gunsmith-edition-raw-blank/

Fast enough twist to shoot this BBT:

When you stick that barrel to a gun with 2900 psi max fill pressure, how fast will that bullet go?

[UnderPressure]

1 in 7" twist 25" long .223 GM blank for $58:

http://www.gmriflebarrel.com/557-blank-5-56-mm-223-caliber-25-x-1-062-1-7-gunsmith-edition-raw-blank/

Fast enough twist to shoot this BBT:

When you stick that barrel to a gun with 2900 psi max fill pressure, how fast will that bullet go?

It needs 3800 PSI minimum to get 950 FPS:

https://www.gatewaytoairguns.org/GTA/index.php?topic=156052.msg155724522#msg155724522

So if a 2900 PSI max fill gun is regulated at say 2500 PSI velocity will be much lower.

[rkr]

There are not that many guns that can take 3800 psi fills (especially reasonably priced ones) so that 75 grain bullet is not very practical. You can make 950 fps with 2800 psi, 24" barrel and 225420 47 grain bullets. I actually got 980 fps so 950 fps should be doable with bullets in the low/mid 50 grain weights. Add barrel length and even 60 grains starts getting useful.

[JayV21]

How about this idea as a .224 or .223 slug slinger...... a Seneca Recluse conversion?   It’s single shot so it could allow for longer bullets and if I recall correctly, it will allow for a longer  barrel without looking too awkward since it currently has a 24” barrel.  It’s a *(&^ if a rig and has the double tubes.   Any ideas?

[rkr]

Rebarreling a bigbore to smaller caliber is the easiest way to make a .224 or .257 bullet shooter. Recluse would work but the trigger is not the greatest. Evanix/Winchester .357 and .45 guns are good candidates with rather long magazines and enough power. Kral guns can be modded for power but magazine is short. Evanix AR6 would be a very nice candidate with long magazine if it wasn't for the trigger. With enough work most any gun can be made to shoot 40-50 grain .224 slugs, single shot ones being easiest to convert.

[KnifeMaker]

I hoe to be testing the .222 barrel in the Mini Raptor again as soon as the weather permits and I get the valve back to optimum.


It was at 75 fpe before I switched to the .257 barrel which gave 87 fpe.


After a little maintenance, the .257 barrel went 106 fpe with no increase in HS Or Reg Pressure.


It will be interesting to see where the .222 barrel is now with no other changes other than the barrel swap. 


Knife

[UnderPressure]

There are not that many guns that can take 3800 psi fills (especially reasonably priced ones) so that 75 grain bullet is not very practical. You can make 950 fps with 2800 psi, 24" barrel and 225420 47 grain bullets. I actually got 980 fps so 950 fps should be doable with bullets in the low/mid 50 grain weights. Add barrel length and even 60 grains starts getting useful.

Do you have a picture of your 225420 47 grain bullet?

[rkr]

There are not that many guns that can take 3800 psi fills (especially reasonably priced ones) so that 75 grain bullet is not very practical. You can make 950 fps with 2800 psi, 24" barrel and 225420 47 grain bullets. I actually got 980 fps so 950 fps should be doable with bullets in the low/mid 50 grain weights. Add barrel length and even 60 grains starts getting useful.

Do you have a picture of your 225420 47 grain bullet?

http://arsenalmolds.com/bullet-molds?product_id=165

[gabi.nechita]

I think I'm leaning towards this barrel mated to my .25 gauntlet.
Barrel Blank - Twist:12.6" | .222Rem/5,6x50Mag/5,6x50RMag | OD:.67" | L:26.18" | Cr-Moly Steel"
.219 bore
.224 groove
Is this twist going to be ok?

I've been using that twist succesfully with 47 grain 225420 bullets. 24" version is enough for 980 fps.

Hi RKR
Do you think that 12.6 twist and 47 grains is a better solution then 15 twist horney barrel and rws 41.5 grains?

[rkr]

I think I'm leaning towards this barrel mated to my .25 gauntlet.
Barrel Blank - Twist:12.6" | .222Rem/5,6x50Mag/5,6x50RMag | OD:.67" | L:26.18" | Cr-Moly Steel"
.219 bore
.224 groove
Is this twist going to be ok?

I've been using that twist succesfully with 47 grain 225420 bullets. 24" version is enough for 980 fps.

Hi RKR
Do you think that 12.6 twist and 47 grains is a better solution then 15 twist horney barrel and rws 41.5 grains?

It has better BC and thus it will have less wind drift at long distance which usually means smaller groups in real life shooting. It will also carry more energy assuming same velocity. The downside is that it will not fit in most magazines, I believe Evanix AR6 and long magazine .45/.357 Evanix/Winchester guns can be modded to use that bullet. JSAR Raptor and Sumatra are also likely candidates.

[KnifeMaker]

I just received an e mail that I should have this mold by Friday.
I have been testing bullets that are from the same mold, but decked to throw them at 29 grs for use in the PP 700 pcp pistol.


It is very accurate in the little pistol, adn quite accurate in the Mini Raptor as well.


It gets 1036 fps for 92.73 fpe in the Mini Raptor in its .257 version. I am anxious to see the results in the .222 as well. the .22 version decked to 29 grs hit 75 fpe in the .222.


I will order a second one for decking as I plan to use the mold at full size for the Mini.


Knife 

[JayV21]

Maybe in the future a .223 Raptor will be added to the heard.  From what it looks like, everyone and their grandmas are trying to unload their PCPs, most likely to collect enough bubble gum money for a Raptor.   Hence, the lower than expected resale value of ones’ beloved AGs.  Knife, have you tried the .224 Northamericanarms bullet in your .223 Raptor?   If you’d like, I’ll send you some from my pile for you to try out.  N/C.  Just curious to see how they would do.

I appreciate it!  I do have some on hand. If it will ever stop poring down rain, I will test them in this new barrel.

Hello Knife!  Was wondering if you had a chance to test the NAA 30 grainers in your Raptor? 

[KnifeMaker]

That Rifle looks good Ric!


Tofazfou and I discussed and played with the idea of a .224 years ago. He and i went in different directions. While both went with the .257, I still want to go .22. Tof. Went with the 172 HmAir, and man, what a shooter it is!


I've long been a proponent of the North American Arms black powder .22 bullets. It's a deal that can't be beat!


Knife

Sadly, in testing the NNA bulelts, I learned that they are VERY hard and do not shot nearly as well as any of my cast slugs.


I have found that the 1-20 twist out shots the 1-16 twist by a good margin. 1-16" gave me apx. 4-5 inch groups at 80 yards. The 1-20" is giving me 1" with the worst slug, and 1/2" with the best two. slugs.


The barrel JSAR sent for testing is a .250 with a 1-22 twist. Looking forward to the testing with quite an assortment of both swagged and cast slugs.


Just as soon as the new valve arrives, the test will begin. 


Mike/Knife


Knife

[KnifeMaker]

Maybe in the future a .223 Raptor will be added to the heard.  From what it looks like, everyone and their grandmas are trying to unload their PCPs, most likely to collect enough bubble gum money for a Raptor.   Hence, the lower than expected resale value of ones’ beloved AGs.  Knife, have you tried the .224 Northamericanarms bullet in your .223 Raptor?   If you’d like, I’ll send you some from my pile for you to try out.  N/C.  Just curious to see how they would do.

I appreciate it!  I do have some on hand. If it will ever stop poring down rain, I will test them in this new barrel.

Hello Knife!  Was wondering if you had a chance to test the NAA 30 grainers in your Raptor?

Yes I did. Very hard, shoots terrible! Even when properly sized.


I received the new arsenal mold and decked it to 31.8 grs. man it is a shooter. I had the reg set to 2700 (usually at 3000) and it hit 1010 fps for a very accurate combination!


I will be testing them full length as well shortly.


Mike

[rkr]

Maybe in the future a .223 Raptor will be added to the heard.  From what it looks like, everyone and their grandmas are trying to unload their PCPs, most likely to collect enough bubble gum money for a Raptor.   Hence, the lower than expected resale value of ones’ beloved AGs.  Knife, have you tried the .224 Northamericanarms bullet in your .223 Raptor?   If you’d like, I’ll send you some from my pile for you to try out.  N/C.  Just curious to see how they would do.

I appreciate it!  I do have some on hand. If it will ever stop poring down rain, I will test them in this new barrel.

Hello Knife!  Was wondering if you had a chance to test the NAA 30 grainers in your Raptor?

Yes I did. Very hard, shoots terrible! Even when properly sized.


I received the new arsenal mold and decked it to 31.8 grs. man it is a shooter. I had the reg set to 2700 (usually at 3000) and it hit 1010 fps for a very accurate combination!


I will be testing them full length as well shortly.


Mike

You're talking about 225420 mold? What barrel were you using? Looking forward for the results with full length bullets, they were fine in my 12.7" twist LW barrel at around 950 fps.

[KnifeMaker]

Ric, Y
Yes I will be testing the full length as I saved a few before decking the mold.


the longer full length like a fast twist. However, the shorter slugs that most are now shooting in typical AG's likes a much slower twist.


The New production JSAR  valve arrived today. Will be installing and testing over the weekend. 


Mike


Nice build you have there Ric!

[rkr]

People will start with short slugs but at some point they will start thinking about longer ones with better BC. Then it comes to things like practical fill pressure, barrel length and how long bullets the magazine will hold. I believe those 225420 bullets are pretty close to what they will end up with assuming magazines will gain some length.