PC issues w/ rifle

[cs86]

Trying to solve an issue here. I haven't Powder coated many rifle boolits is the past and I'm getting into them more. I started casting rifle boolits for a 308 about a year or 2 ago. I started with using wax lubes and alum gas check. Results were pretty good with no leading as long as I kept it at a reasonable velocity. I decided to run a few bullets with some PC and an alum gas check. I had only ran a few through my 308. If I remember right I thought there was a deposit with a specific look on the rifling at the muzzle end of the barrel. I wasn't sure if it was lead. I didn't run enough through the gun to get much build up. So I cleaned the gun and put it away for the next time. I haven't had a chance to get back to the 308 and PC, but ran into something similar with my 300blkout.

Recently I've put together an AR-15 300blkout. I've ran some tests with it for functionality. Different powders and different bullets. Jacketed seemed to function great. I then tried some wax lubed bullets, and PC bullets. At this point my primary concern is on the PC bullets. Yesterday I had took out some new NOE 150gr PCed bullets with Alum GC and ran some function tests along with some extras loaded just to shoot. I ended up getting buildup on my muzzle break that was lead. I then broke the gun down and looked it over. The barrel was clean about half way down then I'm assuming leading started and continued to the end of the barrel. This leading doesn't remind me of the normal leading I'm use to and I think it's because I don't use GCs on my pistols much. I think the GC is scrapping the leading from the previous bullet.

With the 300blkout I'm using an AAC 16" barrel pistol length gas system with a 1:7 twist. If I remember right I think the barrel is slugged right over .308. I coated the bullets using the ASBB method and sized to .310.

What confuses me is why would I be getting leading starting half way down the barrel? Is the powder coast not thick enough?

Could any of the deposit be aluminum scrapped off into the barrel? I never noticed this with wax lubes. I didn't clean the barrel or muzzle break yet and thought I'd try and take some pictures. Hopefully I can get to it.

Any thoughts?

[popper]

I run PC cast GC in my 308 AR, ESPCd, Cu GC. No leading and good accuracy. I do get a dusty 'lube' star in the muzzle & I thought some was lead, no just PC 'soot'. I run 145 gr PB DT in my 16" BO & get some leading muzzle end. I think the DT method (for me) isn't coating heavy enough for HV rifle. I ESPCd the bases after DT and get better results. Double DT makes the noses too large.

[cs86]

I had something else baffle me... For my functionality test I ran 2 loads of 1gr increments using lil'gun and H110 under the 150gr NOE boolits. First shot would determine cycling of the next round and the 2nd shot would be to see if the bolt locked back. During the process the lower powder charges worked better than the high charge. The higher charge would jamb the second round and the bolt wouldn't lock back on the last round.

[Smoke4320]

My first thought is the coating is not being cured all the way and what you see it PC residue..
Try cleaning the barrel with normal solvent for shotguns ( made to remove the wad fouling.. If it disappears its PC and not lead ..
Means either your oven is not reaching the proper temp or your not leaving them in long enough to get a full cure
just some ideas to try

[cs86]

Any specific indications of how to tell when not fully cured? Like failing a smash test or something prior to loading?

[Smoke4320]

Like failing a smash test would be one ..
PC scraping off when sizing is another
leading of any kind would be another Unless you are trying to shoot nearly pure at 1700-200 FPS
I have been able to get 50/50/2 up to 2100 FPS very accurately out of a 308 1-10 twist

several people have reports similar issues and adding curing time made their issues go away ..
we are all still new to this and everyone does something a little different so you have to modify to fit your circumstance
IE I sent some instructions to a fellow on how I shake and bake ..
Told him I use Chinese soup containers and Zip lock twist containers (Failed to mention the depth of those containers)
Said I put 3 teaspoons of powder in to start along with 50 to 100 bullets.. works great for me .. after about 200 to 300 bullets I add 1 more teaspoon of powder
Well he followed my instructions but was using approx 2" deep containers ( not 5 to 6" deep) he added 3 teaspoons of powder way way too much for such a shallow container
a simple detail left out lead to him having issues

[popper]

I'd guess at the pistol gas moving the BCG too fast, overgassed. You don't say what boolit & ~fps, sub or (I assume) super. First try just one in the mag, you should get LOE. If not, you have a bolt LB catch tension problem or gas is wrong. Second round jam is either over-run ( lower boolit slides forward when the first is loaded & hits the front of the mag) or the bolt doesn't go back far enough (typical of under gassed). Lil gun may be causing the bolt to unlock early, pressure is lost around the case so the bolt doesn't go back all the way. Third possibility with over gassed is that the spring/buffer/BCG bounce at the wrong time and the latch can't catch. Give us more info.

[cs86]

I'm just working with supers. I'm currently working with a 150gr NOE mold. I don't have a chrono so my fps would have to be estimated by the published data. I've been using the hornady manual for starting loads and working up. It is the only published data I can find. I'm new to the AR platform so I'll need some help with the info anyone needs and probably some help with terminology. I understand when the system is under gassed that it fails to strip the next round or lock back on the last round. The only thing I'm aware of when over gassed is higher recoil. I'd like to understand more how to determine when the system is over gassed. How do you correct an over-run?

Last night I started cleaning the barrel. It took some time and I don't think I have it completely clean yet. I used some chore boy to clean it. Hoppes wasn't getting a lot out and I don't have any other solvents. I took some pictures, but haven't had time to post them.

[popper]

Try the choreboy wrapped brush dipped in some acetone, kerosine & ATF - Ed's Red cleaner. The BCG (bolt & carrier)/ buffer weight & spring force have to be pushed back far enough to pick up a new round. Gas pressure in the tube unlocks the bolt -high pressure in supers with pistol gas system - plus the boolit is not out of the barrel yet (Lilgun is a fast powder) so chamber pressure pushes the case & BCG back - fast. The spring & buffer act like a slinky, bounce back and forth. That may trip the hold open latch. I'd get a side adjustable gas block as the block is under the hand guard. Over-run can be caused by rough rims on the brass or the mag. 223 mags have a ridge at the shoulder to hold the lower rounds back in the mag. It doesn't work for the BO as there is no shoulder at the rib. Most depend on the ogive of the boolit/rib to hold the case back. After loading the mag, slap the back on something hard to set all the cases to the rear of the mag. Clear an over-run jam by locking the bolt back, drop the mag & everything should fall out. Try sizing, 2 cycles of ASBBDT & final size. Hope that helps, not an expert by any means just what I've found works.