My first experience loading 308 for an AR-10

Discussion in 'Ammo & Reloading' started by SWThomas, Nov 30, 2013.

  1. SWThomas

    SWThomas The Gunny

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    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?
     
  2. mgardner

    mgardner New Member

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    Sounds good to me as long as the gun is made to be fired with 308 Winchester ammo and not 7.62 Nato. There are some minor differences in dimensions and the 308 runs at much higher pressures. I love the Barnes TSX bullets for killing elk and deer. You can push them to higher velocities because they ride on the rings only. My 30-06 and 300 win mag shoot them very well.
     

  3. Teddybear

    Teddybear Member

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    SW, I use mil spec 7.62 Nato brass in my M1A's and my AR10 all the time. Your rifle will fire the 7.62 Nato. The case however is thicker on the Nato than it is on the 308 Winchester. Reduce your powder charge by 10% on what ever load your loading when using the Nato case and work up, and you should be fine.
     
  4. mgardner

    mgardner New Member

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  5. SWThomas

    SWThomas The Gunny

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    I ended up reaming the crimps out with my chamfer tool. They're all loaded up in a ladder from 40.0g - 44.5g in .5g increments. I'll see what the rifle likes and cycles with and then hone in on tweaking down to the 1/10 of a grain for best accuracy. This sure is fun!