AR 10 308 Load Recomendations?

[bignate]

I've been working on a load for my DPMS 308. It's a 16" 1:10 twist barrel. It was cold out today, 38deg at the range. I shoot off a good bench, lead sled, and breath properly. I have a Burris 4.5-14x44 scope on it. Broke in as per DPMS recommendations to 100 rounds.

The best load for the day was:
125gr Herters HP
45.0 gr IMR 4320
Fed small based sized once fired brass
Win Large Rifle Primer
5 shot 1.65" group at 100 yards

180gr Nosler Ballistic Tip
40gr Reloader 15
Fed small based sized once fired brass
Win Large Rifle Primer
5 shot 1.70" group at 100 yards

165 Hornady boat tail soft point Interlock
38.0 gr IMR4320
Fed small based sized once fired brass
Win Large Rifle Primer
5 shot 2.10" group at 100 yards

Factory Sheep Dog 168gr HP
New fed brass
5 shot 1.90" group at 100 yards

I normally reload for my bolt guns where I can get 3 or more to touch at 100 yards. The norm for my 243 is about a quarter(good day a dime) and my 30/06 is slightly larger than a quarter at 100 yards.

So my question is can I expect better groups if I keep tinkering? Under an inch?
Any tips on preventing light primer strikes? (had a couple of those today)
I am going to free float the barrel, how much(if any) will that help?
Any pet load I should try?


Thanks for the help in advance, nate

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[therifleman]

My partner and I shoot 5 different 308 rifles and found that 44gr varget 168 nosler custom competition federal 210m rem brass at sammi spec length shoots one hole groups at 100. Some are ragged hole but many are hard to tell there wasnt one shot. 178 amax 41.3 imr 4064 rem 91/2 rem brass works as well.

 

[Scott]

Yes you can get better groups. I have a DPMS and I average about 3/4" with factory loads. Just keep trying and you will get it. That weapon is a sub MOA gun so just keep changing and I have the best luck with Nosler. Good luck.

 

[therifleman]

Dont forget that just changing primers can make a big difference. Remember too that slower is usually more accurate.

 

[OFADAN]

bignate, we have the same rifle at the Academy only with the longer barrel. It shoots 1/2 to 3/4" MOA out to 600 yards if we/I do my part. Your rifle has the capacity to shoot very well if you line up all the human and physical components effectively.

Using someone else's pet load isn't necessarily going to help (although you could get lucky and it might) but with you shooting more effectively while at the same time matching it with the exact load your particular DPMS likes is the ninja secret.

Matching the load to the rifle is like a fingerprint. No two rifles are going shoot the same load exactly the same. So if sub-MOA accuracy is your expectation then you need to learn how to start developing a load for match accuracy instead of hunting accuracy. If developing match accuracy is your expectation then expect to start down a disciplined vigorous pain-in-the-neck process. The key is just about any one can get lucky once-in-awhile and develop a sub-MOA load. But keeping it consistent in the long run is the challenge. Too many variables that can change and without a good understanding of all the dynamics involved it can be (don't ask me how I know) a very frustrating journey at which no of us will ever truly master or perfect. Some few do, but darn few.

Free floating the barrel will help - it could tighten up your groups but YMMV, the key is you will start shooting more consistantly because the barrel harmonics will be consistant since there is no outward influancing (note variable) pressure being exerted on your barrel.

 

[Gunner3456]

Bignate, I recently helped a friend develop an "accurate" round for a DPMS .308 AR-10. What it was won't help you because every gun is different.

However, we discovered that the chamber is about 1/16" or .062 thousandths longer that spec - way out imho. The distance from the base to the shoulder is about 1/2 that much too long, or .030, m/l. I would have sent the rifle back stat but he was in a hurry to go hunting with it with a small mag of course.

We loaded up 100 rounds, simply using book medium power loads for the sole purpose of "fire forming" the brass. We used heavier bullets but I don't recall the exact weight.

Then we case length sized, leaving them a touch long, but identical to each other.

Next we went through the process of setting the seating die to leave the bullet .020 back from touching the lands in the barrel. The resultant OAL was way too long and I didn't like it.

Only then did we begin to experiment with powders and bullets, of which I happened to have a variety. Right off the bat we had reduced the 100 yd groups from 2" m/l to 1" and we were pretty happy about that. No matter what else we tried, we never got much better than that, but 1 moa m/l at 100 yards is a killing shot imho.

You might check that out.

You don't want my general impression of DPMS.

PS Remember that all other things being equal, a heavier bullet will be longer - will have a higher aspect ratio than a light bullet. If for no other reason, the longer bullet will have different flight characteristics than the shorter bullet and can affect accuracy one way or the other depending on the gun in hand.

There are lots of ways to find out if your chamber is to specs - clay, go no-go sets, depth mics... Anyway, having seen one that's way out, if you keep having problems I'd look into that.

Cliff

 

[therifleman]

Trigger pull is a lot of the problem with many ar style rifles too. I have a DPMS 6.8 spc that has a real rough trigger and so are the groups. Any one here know what to do to get rid of the creep and pull weight, short of a custom drop in?

 

[Jambi]

168gr rebated BTHP
42.5 grains Reloader 15
Winchester Brass
CCI Military Primer

Overall Length set to 2 100ths off the lands. The length (for this chamber) just barely fits in a magazine.

The CCI Military Primer will reduce your light primer strike concerns. This load has gotten me sub moa out of a standard AR10A4 rifle. 3" groups at 700m.

I have found that if I try and push anything over 180 grains up to 2400fps I'll start flattening and popping primers in the AR10. A popped primer fits perfectly in the bolt locking lugs and will bring your shooting to a sudden stop. 175 still performs adequately (in my opinion) out 800-900m and 168 is solid in light wind out to 600-700m.

 

[Gunner3456]

My understanding is that the military primers are actually thick/harder than the civilian primers and might increase light strike problems.

I don't know that for sure, but CCI makes both for the large rifle under two different part no.'s. I "think" the military primers are #34 and the civilians are #200. Don't take my word for it - google it for sure.

Some "real" military rifles might poke a hole in a #200 periodically while some civilian guns might light strike a #34 (if I have those numbers right.)

$.02

 

[bignate]

Thanks guys. I'm going to keep tinkering with it, and hopefully get it in a better group. Yes the trigger is bad. Saving to get it replaced. I got the cold crud that is going around so as soon as I feel like it, its off to the range again. I also am going to cast the chamber as soon as the stuff gets here to see whats going on there.

nate

 

[therifleman]

I have worked a lot with col on the 308 and have found that seating depth is not very important. It seems that they will shoot well at any length that will chamber up. I use the sammi spec 2.80 and have great results. Just make sure they arent jammed into the lands.

 

[Timprice]

I got the blues. Accuracy problems, yeah. DPMS AP4 inch and a half to three inches at a hundred yards. Seven different loads. I also noticed that my oal gauge told me that the throat is way too long. Sent it back to shop. Pray for me. I am a bench rest shooter so it's not good news for me. On their site, approx 20 shooters are shooting one hole with every configuration they build. I think I have a bad barrel. Hopefully, they will make this right.

 

[therifleman]

I havent got any one holers from my dpms rifles but they both shoot in under an inch from the wobbly bench I made up. My 6.8 spc is doing really well and I have only got less than a hundred rounds through it. Sorry to hear of the problems with the 308, will be intrested to hear what they say. Please keep us all posted on it.

 

[Timprice]

I got the blues. Accuracy problems, yeah. DPMS AP4 inch and a half to three inches at a hundred yards. Seven different loads. I also noticed that my oal gauge told me that the throat is way too long. Sent it back to shop. Pray for me. I am a bench rest shooter so it's not good news for me. On their site, approx 20 shooters are shooting one hole with every configuration they build. I think I have a bad barrel. Hopefully, they will make this right.

 

[bignate]

Well I found that it likes hotter loads. Mine were all toward the bottom of the range in powder load.


nate

 

[PfcSalt]

No need to spend a wad of cash to get a good trigger. Bill Springfield modifies AR triggers very inexpensively. I had him do the trigger work on both my AR-15 and DPMS .308. Money well spent. My groups were like yours prior to the trigger job. My .308 rifle is now sub-MOA with no other mods.
http://www.triggerwork.net/

For $35.00 he will give you a 4lb trigger pull without the creep you now experience. He will also hone the sear-trigger engagement to smooth it out nicely with a clean break and lighten the hammer for increased hammer speed. For $15.00 more, you can have the lighter springs to make it a 3 lb. trigger. That's only $50.00 for a match quality trigger!

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