My first experience loading 308 for an AR-10

[SWThomas]

So I have a GA Precision GAP-10 that I'm going to start reloading for. I've got plenty of Nosler brass, Mil brass, Black Hills brass, and some headstamped RP. I got some Sierra MK 175g HPBT bullets for punching paper and some Barnes 180g TSX bullets for hunting. I'll load the Barnes bullets later. For primers I got the CCI #34 military primers. I'm planning to use Varget for my loads but I also have some IMR 8208 XBR. I finally got all the gear I needed to load up some test rounds and here's how it went.

I decided to start with the batch of Black Hills brass (which bites be in the ass later). All of this brass has been fired in the GAP-10 so it's formed to its chamber.

- I used my bump gauge and set the sizing die on the Dillon to bump the shoulder back .003-.005. I did everything in accordance with the instructions and sized a batch of 50.

- Next I trimmed all of the brass to 2.005 and deburred/chamfered them. I also use a primer pocket cleaning tool and cleaned out all the pockets.

- While I tumbled the case-lube off, I figured out my seating depth.

- I used a comparator and sorted all the Sierras in groups within .005 of each other.

- I got the GAP-10 out and used a seating depth tool to get me on the lands. The measurement on the tool was 1.643 and the average bullet length on the batch I chose was 1.250. This meant that 2.893 OAL put the ojive of the bullets right on the lands.

- I assembled a dummy round. The neck tension is plenty tight so I did not crimp the bullet. I chambered that assembled dummy round with the force of the bolt and it chambered and extracted just fine. No change in OAL so it wasn't too long.

- Next I checked to ensure it would fit in the magazine, and low and behold, it did not. I was expecting this. I had to seat the bullet deeper to an OAL of 2.827 to get it to fit in the magazine. So the comparator sorting and seating tool were pretty much a waste of time. But they'll come in handy when I load something for a bolt rifle.

- Next I get the Dillon set up for large primers and get it loaded up with 50 of the CCI #34s. I got the Varget and the powder trickler ready and got the brass out of the tumbler.

Unfortunately, this is where I stopped. I found out the hard way that Black Hills crimps their 308 brass and I couldn't seat any primers. The Noslers and RP brass are not crimped but I ran out of time. I haven't gotten a tool to swage pockets yet so I couldn't go any further. But once I do I think I got it all figured out.

Is there anything you see here that I did wrong or have any advice for a beginner?

[R112mercer]

Go to Home Depot and get a Countersink for about $10. Get the one with the widest (most shallow cutting) blade. You can use this as a cheap fix to remove the crimp from the brass till your swage tool gets to you.

I bump the brass all the down (i.e.: the die touches the shell plate) to ensure reliable feeding, other than that it seems like you're off to a good start!

[Tcon260]

I don't prescribe to the die touching the shell plate to set the head space on a die. For a few dollars, buy a headspace gage and set the bumping properly. YMMV

[R112mercer]

I'm running a JP barrel and use a JP case gauge. According to the gauge I have to bump the shoulder down that far. And some brass *still* doesn't go in the gauge...

[deerassassin22]

You can use a RCBS Case Prep tool or any manufacture and you can get the crimp out no issues.

[SWThomas]

I ended up reaming out the crimps with my chamfer tool. Worked like a charm. I don't think I'll use the Black Hills brass again. The primer pockets are off center. The Nosler brass seems to be better quality.

[dlouie87]

Have you shot any ammo that you have loaded up yet? My gas gun has a sweet spot right around 42.7 of varget with the 175.

[SWThomas]

Not yet. I'm gonna try this weekend

[SWThomas]

I fired them off today. All 50 fed and fired perfectly. Accuracy was best between 42.5 and 44.5 grains. I'm gonna load up some more and see if I can narrow it down a little more.

[dauntedfuture]

If you're getting 1moa 10 rd groups and good sd and ES then I'd stop there and call it good. There is simply not that much else you need to do for a ln ar10 rifle. Some are more finicky about cycling properly but varget and 175s should be well within the proper pressure curve for the gun. Don't hot-rod in a .308 gas gun like you might in a bolt gun.