Load workup for a new toy.

[Griz44]

I finally took the jump and went the EBR route. I had resisted doing this for a long time.
The right deal on the right gun came along, so I now own a Bushmaster AR-10 chambered for .308 WIN
This is the ORC model, and I have a 4X illuminated reticle scope sitting idle that will fit right on there.
The brass and bullets came in a few days ago, so I will start the process of getting some ammo made to feed it.

Who has one of these? What do you feed it? Any favorite loads for it? Any do's or don'ts when brewing ammo for an EBR? All my other stuff is Bolt guns, so this is a new foray for me.

Looking through the books and my shelves, seems Varget is a popular powder, and 150g bullets are the choice pill.
I bought a batch of Hornady 150G SP bullets, and a couple of bags of new PRIVI brass. I have never used PRIVI before, but it was all I could find on short notice.
My workups usually involve 10 rounds at each loading level
For a control group, I bought a box of Remington PSP 150G at Wally World

Hodgdon Varget:
44g (2773 fps)
45g
46g
47g (2937 fps)

Accurate 2520:
42g (2554 fps)
43g
44g
45g
46g -46.5 (2809 fps)

Hodgdon 4350:
44g (2364 fps)
45g
46g
47g (2504 fps)

[MoJo]

When I shot a .308 in high power rifle matches I used H4895 and 168 gr OTM bullets. Closest thing to an X ring seeking load I've ever shot.

[Houston1944]

Varget and Reloader 15 are good choices for the 308, especially since they both are not sensitive to temperature changes. This is why I have moved away from 748 and the IMR powders. It is nice to get work up a load in the summer and know the results will be the same in the winter.

[Griz44]

Varget and Accurate 2520 batches are loaded and ready to go to the range. Will probably be Wednesday or Thursday.

[Grungir79]

So how'd those loads turn out?

[Griz44]

Sorry, I should have followed up and posted. This will fix it!
I just wish I was as good as the gun! I am convinced it will do even better in the right hands.
The Gun- Bushmaster LR-308, 16" barrel, UTG 1" riser, Barska 4X 28mm scope.
This gun is new, and I broke it in last week with 300 rounds through it.
The Ammo- twice fired PRIVI brass, Wolf Large Rifle Primers, Hornady .308 150 grain SP Interlock #3031.
Powders - as described on each target. Targets all have a 2" center circle, and have been resized to be more bandwidth friendly.

Load 1-A - Accurate 2520 - 42.0 grains


Load 1-B - Accurate 2520 - 44.0 grains


Load 1-C - Accurate 2520 - 45.0 grains


Load 2-A-1 - Varget - 44.0 grains


Load 2-A-2 - Varget - 44.0 grains


Load 2-B - Varget - 45.0 grains


Load 2-C - Varget - 46.0 grains


Load 3-A - H4350 - 44.0 grains


Load 3-B - H4350 - 45.0 grains

[Grungir79]

So what was the difference between L2-A-1 and L2-A-2? Both seem to be winners, but I'd lean towards L2-A-2. I assume this was at 100yds? Very nice so far for initial load development, can't wait to see what you do with further fine-tuning!

[Griz44]

So what was the difference between L2-A-1 and L2-A-2? Both seem to be winners, but I'd lean towards L2-A-2.

The two are the same everything, except I was interupted by a friend that saw me there and wanted to chat for about 20 minutes, so the barrel cooled way down while we conversed.
Since everything else was done with a warm barrel, I wanted to see what difference there was starting out cold. There was not much difference.
Everything was at 100 yards and benched on the front handguards, with the stock on my shoulder, right elbow on the table. I tried to keep the rythum as close to the same all the way through, meaning 2 warmup shots, then 10 seconds apart for all the rest of the group. I let the gun cool about 10 minutes between each group. (With the exception of group L2-A which got split in two by 20 minutes.)
Spread staring to occur with barrel heat up. This I would expect. Since it is a semi-automatic with a large capacity magazine, it was designed to run hot so I wanted the load testing to reflect the actual designed usage. The range will no allow rapid fire, so that test will have to wait until I can get to the lease and set up some rapid fire exercises. Overall, I am very happy with the gun, it's smooth performace right out of the box and it's accuracy. I may try a batch of Hornady SST projectiles with it to see if they make any difference. They make a huge difference in my Remington 700 bolt gun. The downside is they cost more, and this Bushmaster sures like to eat a lot of ammunition!