Knurled bbt 51g

[oneshot61]

Sounds to me like Mr. Bill is on to something. Forgive my lack of knowledge, but it seems a lot of variables at play for home casters with lead temp, mold temp, mold quality, lead/tin percentages. Swaging with knurling and lubing the bullet seems like it would overcome a lot of those variables. This might be another step forward in our industry. I would love a swaged bullet for my .25 but can't bring myself to place a custom size order not knowing if they are going to shoot at all. Samples would be nice in a new product.
I'm not sure of the leade in my barrel, I can't see or get to it. Not sure if they are choked as I can't push a pellet through the breech. I do know both the .25 and .35 will shoot both pellets and bullets accurately. 

[Hobbyman2007]

Last adventure I read BillG was working on was the partitioned .25 cal slug . That was a while back . Hope he chimes in with some of his latest developments .

[oneshot61]

I'm ordering a hyskore shooting rest that hopefully will be in by next weekend, since I don't have a rest at all. I may not get home for 2 weeks but ill try. Ill shoot 2 groups, weighed and sorted and a group weighed and sorted that has been knurled and post the difference. The shooting rest should remove a lot of my human error. Ill do the same with my 357 ace as I also have some bbt hp. Both will be done at 100 yards.

[KnifeMaker]

Knurling on bullets has been around for decades. Hornady also sold, and very well may still offer such bullets in .38 for reloaders.

In PB's is serves to hold lube. for us, it has a very different use.

For the original poster, Congrats!!!  I will state that you listed several sizes of bullets. Yet still miss the most important aspect of sizing for AG's.

The bore should be slugged and bullets sized accordingly. You tested bullets in one hundredths in size. However, for top accuracy, you should be testing in Thousandths, not hundreds.

You have happily and accidently skirted around a common mistake of sizing to hundredths by knurling. You see, while knurling does slightly increase dia. it also slightly decreases it as well. 

How you ask, well, simply put, it gives the bullet both peaks and valleys on the surface. The peaks are very thin and delicate, while the valley is firm. What this does, is artificially allow the bullet to act as if it is perfectly sized. As anywhere between the peak and the valley can be the size of the bullet as The rifling will find it's proper depth, very easily in a knurled bullet.  So it is a very "Happy Stance" of a Great Winn-Winn!

You have without even thinking about it, produced bullets that are capable of being several different sizes at once, that the barrel makes the decisions. With the added benefit of lesser friction, and in case such as my bullets, (Made for my use only) carry a bit of lube for the big bore.

You see, lube normally goes in the lube grooves, and requires both heat and high rotational forces to work in a PB. However, in our AG's, the heat is missing. Hence, much of the lube is never used in the shot cycle. To our chagrin. However, Knurling, such as you are using, will easily hold, and distribute the lube in an AG barrel very well. 
Sounds like you have found yourself a real winn-winn here Sir!  You have found the proper bullet diameter, without ever making the effort to do it properly, yet found great success in you application.  Kinda a Blind hog finds acorn kind of thing. Which can be a very happy and rewarding kind of thing, in a fun way!
Don't' ya just love it when a plan comes together!!!

Congrats!!!

Knife

 


 

[oneshot61]

Thanks Michael, that was well explained. I would love to slug my barrel, both the .25 and the 357. However, the way the breech is made and the fact that both barrels are sealed in their upper tubes, means I would have to slug from the barrel end. Not sure that's accurate? Especially if they are choked at all. So I'm having to improvise in the bullet department on both guns. But, yes.. I'm a happy man, both with the bbt and the improvised knurling. So if you see a blind happy hog in the alabama woods toting an ace .25, don't shoot.. its me  

[Hobbyman2007]

I sure wish BillG would chime in here , to share some of his findings . I'll be trying the backwoods knurling method ASAP.

[Bill G]

Hey guys I'm not back solid yet be will work toward being a regular part.of the forum in the near future.  New position that required a lot of travel and now requires lots of overtime.  Things should be settling soon and I'll be back to making slugs and offering up some of the newer stuff I had in the works before life happened.  First off, thanks so much for the kind words and patience.  Before I did erred my attention to this rude interruption called work , I had been shooting those new partitioned nose slugs through my Marauder.  I'm gonna say no go on the choked barrel for these. Nothing group with this gun.  It could be the choked barrel or the fact that I changed the valve to an older WAR valve that Jim Gaska set me up with.  Jim and I  live in the same small town about 20min apart. I need to pay him a visit to see how things are going. He's so busy that I hate intruding.  Anyway, I never really tuned that valve to be as efficient as I should have.  Those last couple of months were hectic to say the least. Honestly, I think that I need to procure a TJ barrel before I spend any more time testing.  The choked barrel and these slugs just don't agree with each other.  The partitioned nose slug is nasty in soaked news paper rolled into 3" x 5" logs.  Imo, those test weren't real.since the range was only ~15yrds.  But... it was cool to see the effect.
Some technical finding that will likely help those of you who want to try this for your self.  First off, I'm a tool maker by trade and can make neat devices but they aren't necessary for small scale trials.  The file method is exactly how I did the first one.  It is difficult to track the file and get the consistency that was displayed by the original poster. You did a great job.  A pointer to those of you who will try this. To get best consistency,  only allow the file to travel the distance of the circumstances of the slug.  The band's should be ~1\16 wide and be at the tail and at the tangent  of the body and nose slightly behind actually.   For.those of you who can make a dedicated knurling device, you'll want to know your lan diameter for sure.  I found that I could control the depth of knurled fairly accurately but would max out in pure lead at .011ish on average.   At first I would creep up the size to match the bore diameter but quickly discovered, that with the .25cal, it was best to just go the whole .011". I'll try to explain why.  Typically the land diameter for a .25 is .243. Since we want some engagement, I swaged them .001over (.244).  The knurled diameter would be +.011 (.255). This averages .2495.  To me, what this means is that the break away friction is far less than with a typical cast or swaged slug.  To quantify this, it only required 15 to 17 lbs of force to break away and like 3lbs of dynamic force. Very close to a well fitting pellet.  As you all have noticed, this also has the added benefit of "filling the bore". This aids in true centering. Of course as always a proper chamber is most beneficial.   In short you can cast a bullet that measures slightly smaller for your bore but will effectively size it self with minimal effort, lower break away and very good seal. I forgot to mention sealing.  The knurled, as you all understand, is as deep as it is tall. As it conforms to your chamber and bore the peaks lay over creating sort of labyrinth seal if you will. The chambering effort is maybe more than a good fitting pellet.  That kind of sums it up. I couldn't be more excited for you guys who are having success with this process. Great job.  An idea that came to me after seeing Bob's bore riding BT design was to have a bore rider that was engaged by say .0015 to .002 with the lans. Now picture this. Where the rebate is, there is an undercut. This creates a skirt that is say .02 thick and .03 deep. From a profile it would appear as a BBT.  Once pressure is introduced, obtration occurs at the skirt thus fully engaging and sealing the bore. Knurling is time consuming which equates to expensive 2nd operation.   And so goes the pursuit of the evolution of the airgun slug.

I'll be seeing you here soon I hope.

[rsterne]

Nice to see you back, Bill.... hope you have the time to become a regular again....

Bob

[Bill G]

Mee too.
Hey does anyone hate the auto correct on these phone as badly as I do.  I just read.over my post.   Just for the record....I'm not slow, I'm just a slow learner.  Lol.

[rsterne]

With a quick phone, apparently.... *LOL*....

Bob

[Bill G]

Technology that only my children understand.. lol

[oneshot61]

Thank you Mr. Bill for your post. I really appreciate the tips and information, and I think we are all looking forward to you being able to continue your endeavors with the swaged, knurled slugs. As my luck would have it, Mr Bobs boat tails lent themselves almost a perfect 1/16-3/32 knurl just by their design. It knurled the rear band and the rear of the nose as can be seen in the picture. I only did one direction on the file and is not cross hatched by flipping the files on a second pass. Although I may try that also just to see what I get, as well as excluding the nose portion.  It is more work but to me if the end result is a more accurate bullet, I'm ok with that. I can do about 30 per minute. I hope others will jump in and give it a go and let's see what we get.

[KnifeMaker]

Thanks Michael, that was well explained. I would love to slug my barrel, both the .25 and the 357. However, the way the breech is made and the fact that both barrels are sealed in their upper tubes, means I would have to slug from the barrel end. Not sure that's accurate? Especially if they are choked at all. So I'm having to improvise in the bullet department on both guns. But, yes.. I'm a happy man, both with the bbt and the improvised knurling. So if you see a blind happy hog in the alabama woods toting an ace .25, don't shoot.. its me  

Texas has been my home for the last 40 years, but OH how I miss the Alabama Woods! I grew up in the farm and deep woods part of the north east of Ala. on the Mountain above FT. Payne. Beautiful!!!

Man, I miss  it!  (And the deer have a much better flavor there, as they have a LOT of good food available to them. Here, Not so much.

Knife

[KnifeMaker]

so good to see you here Bill!

I have a few checkering files, that i have a strong feeling will do an excellent job! They have very sharp points, rather than the typical lines a normal file has. So one pass will do away with a need to do the norman opposing angle pass. (I Think) LOL!!!

Knife

[oneshot61]

I run to Texas a lot, mostly Laredo, San Antonio to drop freight. Alabama is very beautiful, and a hunters paradise. The dear are regular patrons of the soybean and cornfields here, and it shows on them.
 Let us know how those files work. They may be better than the ones I'm using at the moment.

[K.O.]

Thanks Michael, that was well explained. I would love to slug my barrel, both the .25 and the 357. However, the way the breech is made and the fact that both barrels are sealed in their upper tubes, means I would have to slug from the barrel end. Not sure that's accurate? Especially if they are choked at all. So I'm having to improvise in the bullet department on both guns. But, yes.. I'm a happy man, both with the bbt and the improvised knurling. So if you see a blind happy hog in the alabama woods toting an ace .25, don't shoot.. its me  

next best to slugging... just chamber a round  take out the mag use an allen wrench to seat it as deep as you can and then push it back out the breech... then do a push thru from the muzzle to the breech(added benefit you will feel tight or rough spots) and then you will KNOW if it is choked or not...

as far as sizing you do not even need to measure... I am using the NOE system with 10$ changeable bushings... I picked up a .252 just to/in case I need to size in steps... I also picked up 2 .250 bushings both where just slightly under .25... an extra in case I go to far when opening it up for the barrel...but it looks like the Xl 725 barrels are on the heavy side of .250 so it may work for them.. I am guessing I need to open it to about .2506 or so...

so when I first sized to .250 I chambered a round and pushed it back out like described above...it had almost no rifling marks on the nose I mean even less than the round on the right in the below pic to be ( to be turned for Mrod)... so I took wet dry on a dowel and opened it up just a touch so that it ended up like the next pic...I feel it may be just a touch to loose so I may just open it up a touch more...

 I am sending them thru a stock .25 Green mountain barrel with its choke which on mine is only down to about .2485-2495 not .243...point is I want the nose to bore ride as much as possible but be stable in the barrel ...

right now they are 2 moa at 50 yards ( at 750-760 fps in one Mrod and 690-700 fps in the other) but that is pine tree standing side rested and with the stock leade which works for pellets  but I bet is hard edged because of how they feel when rounds are being chambered and the small bit of finning (on drive band)when sized just about right(2nd pic again)... I am pretty sure of moa and maybe sub moa when  all is sorted...

so yep  testing knurled against rounds that are sized just right for each barrel is on my list of thing to try with the choked barrel... and non choked barrels...

It also looks in the first pic that the XL 725 barrels need me to try casting at a lower temp and mold temp...or maybe use  some antimony in the alloy so they drop a touch larger for the XL 725 barrels... they where bought a couple years apart and I think the earlier barrel is just a touch tighter than the new one...

[oneshot61]

Thanks for the tip Mr. Kirby on the breech and choke, and thanks for posting those pictures. It gives me a better understanding of what is going on in the barrel. Ill give that a go tonight as I just pulled in off the road. Ill see what I come up with and post some pictures tomorrow. Its going to rain me out tomorrow so no shooting, but if I don't get called out then definitely Saturday. My new shooting rest will not be in till Wednesday and I will be long gone before then. So ill do my best without it, but continue to shoot when I can use the rest and maybe get a better feel for what this is all doing to accuracy.
  I hope to see more people trying this and posting their findings, either here or somewhere on the gta. The more the merrier I say. Especially in different calibers.
 That being said, I'm looking forward to Mr. Bill being able to start his swaging and knurling. I'm definitely in. I usually build up stock and then buy to shoot, so that in a pinch I've got a cache. I definitely don't want to roll 3-5k bullets

[K.O.]

 My pleasure Dan,  Kirby is my first name..

[oneshot61]

My pleasure Dan,  Kirby is my first name..

Yes sir, I understand. Its an old southern, old south habit. Calling people mr. or mrs. and their first name, if we didn't know their last name. Its common here and definitely a respect thing. I'd get the stink eye as a kid if I forgot. It stuck.

[customcutter]

My pleasure Dan,  Kirby is my first name..

Yes sir, I understand. Its an old southern, old south habit. Calling people mr. or mrs. and their first name, if we didn't know their last name. Its common here and definitely a respect thing. I'd get the stink eye as a kid if I forgot. It stuck.

Mr Kirby just learned one of our southern habits, Mr Daniel.  As a child we would have gotten a smack on the bottom as well.  LOL