Gas checks on PC'd bullets

[DickelDawg]

Okay. Been reloading for more than 30 years and casting for a couple of years. Just getting into powder coating cast bullets. My sizing dies are all Lee. Sized some PC'd 357 bullets....no problem. Sized some PC'd 452 bullets and all but one of the GC's fell off out of about 50 rounds. Haven't had this problem with "regular" lubed bullets. Any ideas as to what happened?

[BILLYBOB44]

Why are you Gas Checking a .452" projectile??

With good Powder Coat you should be good for 1400-1500fps-Should be no need for gas check??..Bill.

[Don Fischer]

did some 309 bullets a couple days ago and gas checked after PC'ing. That's a hard deal. Have a few I did several weeks ago and I sized and gas checked before PC'ing and sized again after seating. From now on I'm gonna GC and size before PC and size again after.

[DickelDawg]

Thanks for the info. That helps a lot!

[Dragonheart]

I spray 250 GC bullets at a time. My tray is drilled so the gas check base sets in the tray and stays completely clean. The 30 caliber bullets got a partial cure, gas check, sized then a second clear coat to increase the thickness of the polymer jacket. The second coat also bonded the check where is just does not come off. They were push through sized again.

They were loaded and fired by a friend at a velocity of 3100 fps out of his browning 30/06 with no barrel leading. He reported outstanding short range accuracy, although accuracy wasn't our immediate goal.
Attachment 164937

[fingers284]

I spray 250 GC bullets at a time. My tray is drilled so the gas check base sets in the tray and stays completely clean. The 30 caliber bullets got a partial cure, gas check, sized then a second clear coat to increase the thickness of the polymer jacket. The second coat also bonded the check where is just does not come off. They were push through sized again.

They were loaded and fired by a friend at a velocity of 3100 fps out of his browning 30/06 with no barrel leading. He reported outstanding short range accuracy, although accuracy wasn't our immediate goal.
Attachment 164937

MMMm.... define "partial cure" pls. I envision heating until the wet look is achieved and then allowed to cool for/before clear-coating?

[OS OK]

I spray 250 GC bullets at a time. My tray is drilled so the gas check base sets in the tray and stays completely clean. The 30 caliber bullets got a partial cure, gas check, sized then a second clear coat to increase the thickness of the polymer jacket. The second coat also bonded the check where is just does not come off. They were push through sized again.

They were loaded and fired by a friend at a velocity of 3100 fps out of his browning 30/06 with no barrel leading. He reported outstanding short range accuracy, although accuracy wasn't our immediate goal.
Attachment 164937

Hey Bud! How's things down Katy way?
I'm starting an 8mm project in the Yugo M48…have, 'I thinks', all the details down except PCing the gas checked rounds. I thought about checking them in a clean lube sizer so they would seat flat and crimp (Hornady checks), then doing the tumble + ASBB's routine and lay them on one of those Microwave pads or just do them on parchment as I do all the pistol rounds, then size the final time in a Lee push through.

Do you think that will work for me? My primary intention is to develop that round at speeds/trajectories that will make the sights on the M48 dead on along with the best MOA achievable and the MOA is the bottom line regardless of the sights working 'as-built'?

I spent this past winter getting her in shape as she was one of those old models that were put away for decades before being sold.Attachment 164958Attachment 164959Attachment 164960 Yes, I know she ain't 'milsurp' with the mods but I wanted that totally enclosed barrel to vent heat.

What do you think?

OS OK

PS…DickleDawg…I apologize for this post…I didn't even think before chiming in here…I can't pull it down so you have 'my blessings' to 'delete me' or whatever you need to do…this was stupid…Dragonheart is a friend and I just acted before I 'thunk'…again I apologize….OS OK

[Dragonheart]

You got it.

When I first got into PC I a couple of years ago I knew about this casting site, but didn't there was information on PC bullets, so I spent a lot of time learning the PC process from those in the commercial business (not bullets). What I was told by the professionals was if you heat until the powder flows about 300 degrees then let it cool and then do a second coat, both coats bond together, giving a thicker coating.

I started PC for handguns and a single coating seems to work just fine at lower velocities. A Phd professor who specialized in polymer physics told me that for rifle velocities the polymer jacket would perform better if the thickness of the coating was .002+" thick from the surface to the substrate. Since the bullet is riding on the polymer jacket just like a copper jacket thicker is better.

Double coating I have been getting about .003" in thickness and it is working at tested velocities up to 3100 fps. That was plain base bullets without gas checks and bullets with gas checks, neither bullets had any leading the barrel and the short range accuracy was good with both. I just need to get serious about accuracy testing now that we know the bullets are stable at high velocity and do not lead the barrel.

[OS OK]

"Thanks …D…I think that I am 'on-track' now that I have received so much helpful info here on the forum. I hate to 'muddle' around when I know better!"

"Again…DickleDawg…I apologize for 'hijacking in' on your thread…I feel like a heel for doing so!"

OS OK

[Dragonheart]

Hey Bud! How's things down Katy way?
I'm starting an 8mm project in the Yugo M48…have, 'I thinks', all the details down except PCing the gas checked rounds. I thought about checking them in a clean lube sizer so they would seat flat and crimp (Hornady checks), then doing the tumble + ASBB's routine and lay them on one of those Microwave pads or just do them on parchment as I do all the pistol rounds, then size the final time in a Lee push through.

Do you think that will work for me? My primary intention is to develop that round at speeds/trajectories that will make the sights on the M48 dead on along with the best MOA achievable and the MOA is the bottom line regardless of the sights working 'as-built'?

I spent this past winter getting her in shape as she was one of those old models that were put away for decades before being sold.Attachment 164958Attachment 164959Attachment 164960 Yes, I know she ain't 'milsurp' with the mods but I wanted that totally enclosed barrel to vent heat.

What do you think?

OS OK

Hi OS,

Good looking rifle. It been a rainy week here, so I am getting lots of inside projects done.

I have been playing around with different PC methods for gas checks. One I tumbled the bullets, installed the checks then tumbled them again to get two coats, then sized again. I cooked them base down to maintain a flat base on the bullets. These worked fine and the checks were definitely bonded to the bullets.

I make my own checks https://youtu.be/R5sIuzphTEk and I didn't have a problem getting my checks to seat over the PC base, but I understand some have problems getting Hornady checks to seat. This may be caused by the thicker locking lip of the Hornady check not wanting to go over the coated base? Hornady makes a good gas check so checking first or spraying with the bullet base in a recess to keep the powder off the base would eliminate any problems getting the checks to seat.

We have found we get much better results out of the rifle if you double coat the bullets. The question now is do we really need gas checks at all? Our plain base double coated bullets seem to perform just the same as checked bullets at high velocity. The polymer jacket is doing the same thing that a metal jacket or gas check does.

[ryokox3]

I spray 250 GC bullets at a time. My tray is drilled so the gas check base sets in the tray and stays completely clean. The 30 caliber bullets got a partial cure, gas check, sized then a second clear coat to increase the thickness of the polymer jacket. The second coat also bonded the check where is just does not come off. They were push through sized again.

They were loaded and fired by a friend at a velocity of 3100 fps out of his browning 30/06 with no barrel leading. He reported outstanding short range accuracy, although accuracy wasn't our immediate goal.
Attachment 164937

So after you partial cure, how long do you have before doing the second coat? Necessary to do soon, or can it wait a while?

[OS OK]

I fully intend to get around the gas checks all together and get those velocities too. I purchased 'clear high gloss' from a local dealer/sprayer who advised that it would flow/coat better than any pigment PC. He was right.
I will load/test the checked and unchecked loads with the exact loads together side by side just to see if there are any perceptible differences at all and in any respect.
With this hi-end PC I am getting .0025-.005" thickness on the first coat depending on how hard I 'tap' those rounds to knock off all the extra PC that wants to hang on the nose of the round and cause irregularities in COAL measurements.
I saw your pic's of the check maker, whatta nice piece of work there…wish we were neighbors! I just hope that you don't get 'finger cramps' from 'flicking' that air valve too often…...

OS OK

[popper]

I am getting .0025-.005" thickness on the first coat Interesting. So you get 0.010 thick and shoot to 3100? Pretty much means the coating is taking all the pressure from the rifling.

[Hickok]

Annealing the gas checks has worked very well for me. Well worth the effort, they go on easier, size down easier, and bite better.

[OS OK]

I am getting .0025-.005" thickness on the first coat Interesting. So you get 0.010 thick and shoot to 3100? Pretty much means the coating is taking all the pressure from the rifling.

No…we are talking about OA, overall thickness added to the boolit…and Dragonheart has the results already…I'm just starting.
What is your point?

OS OK

[Dragonheart]

So after you partial cure, how long do you have before doing the second coat? Necessary to do soon, or can it wait a while?

Sometimes I wait a couple of days before doing a second coat because once I set up to spray I may do 1K or more bullets, so I will be spraying several batches and loading my trays for the first cook. Just looking the partial cure coating looks and feels hard. As long as you keep the bullets clean there doesn't seem to be a problem with coating later.

[popper]

OS OK, I may have mistakenly thought you were going to do 2 coats. As groove is usually 0.004-5", thick coating fills the groove, not alloy. If the 'thickness' is really added O.D., cut the numbers in half - probably OK. Several have tried thick with soft alloy - results were not particularly good.

[Dragonheart]

When I say coating thickness I mean the build up from the substrate to the surface of the polymer, so if your bullet diameter with the coating increases .008"overall then the thickness of the coating is half that or .004". At rifle velocities the polymer jacket has to withstand much more shear force, so according to the professor, this is the reason a thicker coating is needed. If you can get the thickness in a single application, whatever works. Here in the Gulf Coast I have to contend with unusually high humidity, so my process may vary somewhat with the day, but on rifle bullets I am double coating.

Typical rifling groove depth is .004", so yes the hard polymer jacket is conforming and riding on the rifling just like a metal jacket. What is more amazing is the toughness of the polymer and the bonding of the polymer to the alloy, yet there is enough flexibility in the polymer jacket to seal the base of the bullet like a gas check or metal jacket. Sizing the bullet actually increases the hardness of the polymer at the friction point. Coating the base of the bullet provides an insulator from the hot gases. When cooked base down the polymer tends to flow and fill the voids on the bullet's base, creating a flatter more even base and should enhance accuracy because a bullet is steared from it's base.

I still have a lot of questions regarding the polymer jacket, fortunately I have gotten a lot of help from some that are very knowledge in physics and the chemistry of polymers. A lot of the answers as far as polymer coating bullets is going to come from testing, since what we are doing is a relativity new field. One thing for sure the polymer jacket is not just a lube.

[OS OK]

OS OK, I may have mistakenly thought you were going to do 2 coats. As groove is usually 0.004-5", thick coating fills the groove, not alloy. If the 'thickness' is really added O.D., cut the numbers in half - probably OK. Several have tried thick with soft alloy - results were not particularly good.

I'm going to tamp a soft lead slug down the Yugo M48, 8mm, before I coat these Lee C324-175-1R boolits…that should tell me the overall thickness of the PC so that it is the depth of the grooves at least. Like Dragonheart explained about the actual hardness of the PC coating…I'm thinking this…If we keep putting an oversized boolit in a case neck that is expanded for a J-boolit…we are effectively swaging them back down to some extent. If we had an expander made that would open the neck up another =.001 or .002" and seat the lead into that then my question is this…will the neck area of the chamber be large enough in inside diameter to accept it into battery?
Therefore I want to try the thicker coating resembling the FMJ or TMJ and size it just as I would use for the J-boolits @ .323 on the O.D. of the drive bands.
The other concern is that I want the nose of the boolit to be coated thick enough to make it effectively a bore rider. Through my queries on this project, I have ben told that the Lee boolit is an excellent design for the 8mm and I hope that the weight is in line with the rifle twist. I really do want to make this a long range shooter and stay with the stock sight assembly…I like the inverted 'V' design…it really works with my old eyes and contact lenses.

OS OK

PS…I want your thoughts too on this crazy scheme…Dragonheart?

PPS…I'm going to start with a blend of soft lead + linotype mixed 3:1. I've batched it up already and it is @ 15.3 -16.6 BHN in the ingots and was air cooled. Tin is suppose to be @ 1.33% acording to the alloy calculator from this forum. I'm guessing from the start that this will be adequate…the tin content ought to fill out those boolits and make them look pretty dang good. I dunnoh yet? That is the starting point unless one of you suggest otherwise...

[Lloyd Smale]

same question. I thought coating took care of leading. Why would you want to waste the money on a gas check? So with using gas checks you have to run the bullet through your sizer to seat and crimp gas check, tumble, coat and bake twice, put them back through the lube sizer to size the bullet. I hate to be the pessimist on this subject all the time but it sure seems like a lot of work to fix a problem that doesn't exist. Even with gas checks I can put a check on and run a bullet through my star and I'm done. Sized, lubed and ready to shoot. I kind of saw the justification for tumble lubing with alox. You didn't size the bullet and it was fast and you didn't need to invest in any equipment. I guess I'm just a bullheaded dinosaur but is sure cant see switching to something that is more labor intensive when the only advantage is a little less smoke. Get away from the alox based lubes and use something like lars Cordoba or lbt blue and there isn't much more smoke then with a jacketed bullet. Don't get me wrong I watch this section of the forum about every day. I'm allways up for something that makes my life eaiser or is a big step up in performance and hope that one day I find it here.

Why are you Gas Checking a .452" projectile??

With good Powder Coat you should be good for 1400-1500fps-Should be no need for gas check??..Bill.