.300 Blackout PCers--opinions please

Wondering if I can streamline my process, cuz I'm so lazy :wink:

Current process:
- Cast (Lee 312-155, a gas check mold.)
-Resize to add gas checks. Mostly because I hear that GC aids accuracy. And its a GC mold.
-Coat.
-Resize again. Ready to load.

Questions:

-In your opinion, do GC help accuracy? Should I try omitting them?
-IOW, if I just cast, coat, resize, no GC will that hurt accuracy?
-Can I cast, coat, then resize and GC after coating? Or will additional thickness of PC mean that GC won't go on properly? I'm betting that's the case.

Would love to hear your process, too.

I gas-check when I size and only after PC. I shake, bake, check/size and load.

Casting means able to do testing for what works best for you. Try them both ways. Later, you should have no problem adding gas checks after PC, but good chance you won't want or need to anymore. In fact, many now are removing/enlarging the gas check shank from that mold for even better results ($5 HF step drill bit and 5 minutes work)! It's not like it's a $100 mold, and at around $15 a great mold to experiment with. Still using the mold as is here, with no G/C and great results, but have the drill bit and it is on the to do list.

Remember if the shanks are too large for checks to go on after PC'ing you can use the 25-06 Lee FCD to reduce them to the proper diameter, works for 270, 7mm and 30 caliber, all have the same shank size.

Gas checks improve accuracy on every boolit I have applied them to. I have molds that cast with gas check shanks, and I have dies to make plain based checks for standard boolits. If the mold has a shank, it gets a check (I make my own) and if I plan on shooting over 1400 fps I apply a check on plain based boolits. For 9mm I can see a noticeable increase in accuracy with a plain based check. Having a solid base that resists the deformation of higher pressure and velocity dramatically improves accuracy. I have inspected plain based boolits fired with rifle powder at high pressures, with stick powders, you can see where the base was peened by the powder. Such deformation degrades accuracy. The gas check (even paper patching) helps protect the base.

As for your boolit and it's use in the 300 blk, I have some experience. The Lee 312-155 2R was the first boolit mold I bought for the 300 blk. I was already ESPC coating with a Harbor Freight gun, using HF Flat Black. My first loads worked well but I think that was because the HF Flat Black does not coat as thickly as other powders. When I switched to Prismatic Powders, I noticed my boolits were too fat to chamber in 2 300 blk (AR rifle and pistol) 2 .308 Win rifles (M1A, Sig 716) and 2 30-06 rifles (03-A3, Rem 700). I measured the boolit just forward of the driving band as cast and it was .3035 and almost .306 after ESPC.

i bought an NOE 309 150 SP, which as cast measured .298. After either ESPC or ASBBDT the boolit measured .300 and ended my chambering issues. If I cast the 312-155 2R and coat with 50/50 Alox/Mineral Spirits they chamber just fine. I prefer PCd boolits so I will use the NOE mold for the 300 blk, .308 Win, and the 30-06. Besides, the NOE is a 2.98 R boolit and a prettier profile. Yes, this too is a gas check design.

I also shoot the Lee 309-230 5R which is a plain base semi boat tail boolit. I ASBBDT coat these and shoot them as subsonic, so the pressure and deformation is not an issue. I did try seating a check on the base and it worked but I have not actually loaded any in that fashion. I know there are some folks shooting PCd plain base boolits with success, and possibly some who are shooting boolits that have check shanks PCd without checks, but I have not heard of anyone getting great accuracy by doing so.

Maybe I'll have to give the GC a try with this lee mold. Been somewhat happy with around sub 2" groups at 100 yards right from the first tests, and zero leading or issues at 1900fps. But not using the gas check might be keeping me from sub MOA groups, and had thought just needed load development with Ramshot Enforcer, as I'm just getting started with this combo. So the question is, what is good enough group for you, and how much effort or expense do you wish to lay out for maybe (probably) some improvement? This is also why I bulk dry tumble PC without ASBB and bake them in a pile, not laid out pretty. Gas check, powder coat guns, trays of spaced out boolits, etc. Or, toss 300 pre-warmed into plastic tub, shake with a little powder, dump into fry basket,, repeat with another 300, then bake 600 at once, shake-quench-dump out and separate any that stuck together, Lee push through sized, then load.

Used to use G/C with plain base in a troubled 9mm, gas check shanked 40S&W and 500 S&W. But after PC'd, accuracy is as good or better, and zero leading or issues like running out of lube in the 500 S&W that GC's never helped, as it still leaded up the last inch of barrel using Carnauba Red and G/C. PC was the cure, not GC..

Just did a quick test to see how Hornady GC would apply after PC and they install and fit like normal using Lyman 4500 and .312 H&I die with GC installer. Lee push through sizer would not seat them fully, although I could not pull them back off. Plain base CG that I use for M1 30 Carbine (.309) and a different Lee mold also would not fit and are way too loose.

Thanks for the tips and thoughts and experience!

To experiment, I tried loading coated, no gas check. First 3, my chamfered cased neatly sliced the coating from the boolit! Maybe took some lead, too. Abandon that option.

Putting GC on coated boolits-- worked like a charm. 20 straight with a seeming perfect fit.

Now, to see how they shoot compared to GC then coated over the GC. If they compare, that will cut a step from my process. Not sure I can get shooting this weekend. If not, may be a while.

My accuracy goal: 4moa. That's what I get with PC over GC. I get 2 MOA with jacketed bullets. Maybe GC over PC will be better...

Attachment 139086I am using a 210 grain Lyman mold with a GC and HF flat black on a 10.5 inch barrel AR-15. The plain lead [NO PC] with GC cycles at 10.5 grains of 1680 but the same bullet PC needs 11 grains. Accuracy seems identical.

I just got NOE's group buy run of the C.E. Harris mold. I hope it feeds in my gun, since it has a tiny flat point that the Lee version doesn't have.

Thanks for the accuracy report, Rob. Duke, I hope that Harris mold works for you.

I DID get to shoot for 20 mins this weekend, only at 25 yards, under less than ideal circumstances. Looks like no difference in accuracy between PC over CG vs. GC over PC. I loaded another batch, and will try it at a more meaningful 100 yards in about 3 weeks.

Those of you who have used GC for a long time--haver you ever had evidence of the GC separating in flight? Just a paranoid thought I had, while wondering if PC over GC would reduce the risk of GC separating.

Quote:

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Originally Posted by DaveSpud

Thanks for the accuracy report, Rob. Duke, I hope that Harris mold works for you.

I DID get to shoot for 20 mins this weekend, only at 25 yards, under less than ideal circumstances. Looks like no difference in accuracy between PC over CG vs. GC over PC. I loaded another batch, and will try it at a more meaningful 100 yards in about 3 weeks.

Those of you who have used GC for a long time--haver you ever had evidence of the GC separating in flight? Just a paranoid thought I had, while wondering if PC over GC would reduce the risk of GC separating.

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Yes!
Ive shot a few thousand 30 cal cast over the years, mostly over sky screens and have found gas checks embedded in my start screens. Some struck flat and some on their side. I might add that this was only maybe less than 5 over 1000 rnds but it did occur. I don't think I will use them when using a Supressor.

Just my .02

Been shooting 308W PC over the GC for a couple years, they DON'T come off - unless you are pulling boolits, then they stay in the neck.

Hmmm, that would indicate that PC over GC might be more accurate/consistent than GC over PC, if the GC sometimes come off....

Rockitrob, I have heard that HF Flat Black is more abrasive that other types of PC. That might account for the larger powder charge to make it cycle.

I might have to polish my feed ramps. Most of the dummies seem to have fed well, but sometimes I get jams. We'll have to see how they do actually being fired.

What does concern me is that the noses are getting kinda banged up by the feed ramps, even on some pretty hard boolits. And if it fails to feed, it seems to be telescoping the boolit into the case neck a bit, so I'll have to be careful.

I'm going to crimp harder on the live rounds I load, because I'd hate to have it compress my powder during loading and give me an overpressure situation.

2wheel - check your neck tension. When I started with the 308W I'd get a jam & pushback once in a while but they didn't chamber. Same with the BO but after I worked out the mag problems it's OK. I FCD both & don't worry about it. Usual problem is 223 ramps in the extension - you can widen them.

OK, I got to the 100 yard range today to check accuracy on GC over PC vs. PC over GC. Conditions were not great. Side wind 5-10mph. Results....

I could see no difference in acccuracy. Best groups on both were about 3MOA. I shot some FMJ for comparison and got 2-3MOA, so not much difference.

So I'll stick with GC over PC for a while, to save that last step.

Only reason I did PC over GC was the other way sometimes PC'd shank was too large. Boolits need to be dry when cooking PC if GC are on, else steam will pop them off or make crooked.