Which plain-base mold for a .308 AR?

[theTastyCat]

Hey all - long story short, I'm about to start loading for my .308 DPMS AR. I'll be powdercoating them and eventually (when I'm darn sure there's no keyholing) I'd like to be shooting them through a suppressor.

I've had some bad experiences getting even j-words to load in a few of my ARs (for totally separate reasons than bullet shape, but I've still got PTSD and clumps of missing hair from the aggravation), so I'd wondering what boolit shape you all have had luck getting to load in ARs.

One final wrinkle - I would *really* like to be able to coat the bases just to be extra, extra sure than I'm keeping as much residue as possible out of my $1,000 suppressor, which when eventually filled with lead will become a crappy, slippery club. So - maybe possibly even a sort of flat nose? I imagine that a pointed nose would load best, but would also be the most difficult to coat the base of.

I've been looking at Accurate Molds; here's his 31-170T, which says for .308:



I'd ask him for one with no lube grooves since I'd be PCing. Might that have a snowball's chance in hell of loading reliably in an AR?

Again, many thanks to you all! I realize this is ridiculously complex......

[clodhopper]

I have not fired cast in a .308 AR, but any kind of flat nose sure made the M-1s reliability go down.

Powder coating the bases of pointed bullets might be accomplished by spraying the bullets in a solid tray drilled with holes to hold the bullets on end, then transferring the sprayed bullets to another tray with the holes drilled more shallow to bake.

Never tried it, just a wild idea.

[yondering]

You can get flat nose bullets to feed in the AR platform just fine. I shoot a lot of cast in several AR15 and AR10 rifles, some with 1/4" hollow point noses. With really big flat noses you may need to open the feed ramps a little, which doesn't seem to have any downsides for feeding pointed bullets.

You really don't want a plain base design in a gas operated action though, unless you're only running subsonic loads. Think about what happens to the bullet base as it passes the gas port; powder coating doesn't protect it from that kind of gas cutting. Even aluminum gas checks can suffer gas cutting in this situation. I've experimented with this quite a bit; scraping the accumulated lead and carbon out of the bolt carrier group isn't much fun. That gas cutting at one spot on the bullet base is terrible for accuracy too. I recommend a good crimp-on gas check design with copper checks to save yourself trouble down the road.

[winelover]

My Armalite will only feed, with 100% reliability, designs that are pointy spitzers. Believe me I have tried dozens of designs. I have a friend with over 30 different thirty caliber rifle moulds. The only other bullet it will feed, is Mi-Hec's 30 cal Silhouette, after fine tuning the magazine feed lips. No way will that Accurate 31-170T design, feed in my carbine.

I have shot thousands of cast though my AR but all are heat treated and copper checked. I have zero leading. Most loads are less than 1800 fps. Ten shot groups average, 2 MOA at 100 yards. Push them faster, and they start to open up real quick. Lubing on a Star, after first sizing and heat treating. I don't do PCing, so no help there.

Winelover

[theTastyCat]

Well heck. I've read over and over that gas checks and suppressors are bad, bad news, as a gas check that comes loose would basically run the can. So even if I coated the base, gas cutting would still ruin my day?

So I guess my question is simple: is there any way at all to cast for my 308 while being friendly to my suppressor, i.e. no buildup or baffle strikes from a renegade gas check? I figured powdercoating would save the day here...

[popper]

31-165C, remove GC shank should be close to 173gr. Works fine PCd in my 308W DPMS, 2400 fps. I can do OK with PB @ 2100 in BO, 145gr. Both are carbine gas & rifle lower. Your can may provide enough pressure to cycle @ 2100. Or if you go subs, single pull. I've shot a lot of uncoated base in the BO, gas system is clean - don't know about a can. I have an adjustable gas block and I notice it gets tough to adjust sometimes - I think just carbon fouling. His 31-170B looks interesting.

[theTastyCat]

Popper, this is hilarious! I've just been running some errands and was reading while I waited and, noticing that you are *the* guru of autoloader 308 casting, literally the first thing I was going to do when I sat down again was to PM you!! You beat me to it - awesome!

So sorry to be so dense, let me unpack your post a little bit - basically you're saying that in your DPMS (and also a 300BLK) you're running plain base with no gas check and not having any problems with gas cutting - am I hearing you right? That would be *exactly* what I needed to hear!

What powder are you using to get to 2100? I'd love for it to cycle, especially since cycling by hand is somewhat of a pain even with an extended latch since the scope is in the way. Finally, removing the GC shank would simply make it plain base, yes? And I'm sure something that Accurate would do for me. I too have an adjustable gas block - maybe that would help me get loads to cycle. Man, 2400 fps is basically a full-bore .308 load!! In cast...you really are a wizard. Can't wait to try to replicate that! I imagine my can may complicate things a bit, but I'm darn sure going to try. When your gas block gets tough to adjust, do you do anything to correct that, or does it just tend to ease over time?

One more question...sorry!! A member here kindly sent me some 168-gr. spitzers to try, and I got them all loaded up but they won't chamber, but they fall right into my chamber gauge. The boolit (PCed) is a consistent .311, so I figure they'd need to be sized down, but I figure that might mess up the gas check. Have you by chance slugged your DPMS? And/or what do you size to for reliable chambering?

MANY, many thanks!!!

[popper]

308w is GCd. 2400 in carbine, 2700 in rifle upper. BO is PB 2100 with H110. I tried running PB RD 170 in 30/30 with 2400 & Rx7, worked -2000 but accuracy was poor. My AR needs 310 sized. I did get a 150 PB to shoot good from 308mx, forget the fps, using 2400.

[theTastyCat]

Gotcha. So new plan is Hornady crimped-on gas checks. Are you using H110 also in 308 to get the 2400/2700 or a different powder?

Thanks again!

[popper]

4895 mostly.