Building my latest rig in 308 (an 18" barrel from Armalite that was an overrun for barrels they made for some SOF units...bought it maybe 5-7 years ago.

I believe it was optimized for M118 (175gr OTM) so not sure if it was 1:10 or 1:11.25, have to go look

Wondering what type of ranges I could expect to still be sub-MOA. I've shot 600 yards with a bolt gun and 24" barrel in the past with tight groups (I consider 6-9" tight at that range). Obviously the shorter barrel and semi-auto/gas system is not going to offer the same results.

Have you still had tight groups at say 300-350?


Also, debating what to put on it as far as glass (leaning heavily toward NightForce....but not sure on magnification.). Their 5.5-20 x 50 is excellent, but I'm thinking I may want lower power if I ever wanted to use it as a practical gun for hunting instead of target shooting. Sometimes 5x is too much in thick woods and up close shots. Maybe a 2.5-10 x 40


Thoughts?

I've shot my 20" 308 AR to 1000 with relative ease. The longer you go holding tight groups gets more complicated with changing winds and stuff like that gas guns suffer from not being able to run as hot as a bolt action, but they can still get pretty far out there.

I think the 16" vs 20" will be a major difference.


Barrel whip perhaps won't be as much a factor but the lockup time on the semi vs bolt may present an issue.

I was mostly curious however as I don't really see me taking this past 300 often. I rarely get an opportunity to shoot long distance anymore.

16" is good for well beyond 300

For casual plinking with a 3-9 or 3-10 a 16-incher will do very nicely with a good trigger and ammo.

I have a 16, 18, and 20-inch 10T.  If you're really roaming the woods the 16-incher is the most pleasant to carry, swing, and shoot off-hand.

My 16" 308 does good out to 600 with a razor 1-6. I don't know if I could go much farther with 6x, but the 1x is worth it to me.
I am picking up a 2.5-10 just because.

Testing that our department armorer did in the late 1990s showed that a 20" barrel was about optimal for the .308.  Anything shorter and we lost velocity and increased muzzle flash A LOT.  Anything longer added weight with no significant gain in accuracy or velocity. Tests were done using our Remington 700s. We did not test any semi-autos.

ETA: our typical engagement was 200 yards or less, but we did practice out to 750 yards.  Accuracy testing was done at 100 yards.

Barrel length has less than you would think to do with accuracy than so many other factors.  At that range your scope not level is much more crucial than barrel length.  Take for instance the LaRue OBR with a 16" barrel that rifle is able to reach out to 1K with ease.  Once you have the dope on your rifle reaching out to 1K is not hard if you know how to call wind and use a ballistic calculator.  The other big factor will be ammo this is where developing a load for your rifle will make it a subMOA rifle.

I have shot my SCAR 17 out to 800 no problem (after I put a G trigger in).

Not an AR10 but the we found that the M118 vs. the M852 was a better choice of ammo at 1000 yards. This was with issued National Match M14's and before the Federal red box 175 SMK and the later M118LR was being made. The 173 grain 118 bullet has a slightly higher BC and did not flip in flight like the 168 SMK bullet did.  Under 800 yards the M852 was a better performer for accuracy.  Some where between 800 and 1000 yards and under certain atmospheric conditions the 168 SMK lost enough energy to flip and where it landed after that was anyone's guess.  My point is ammo selection if very important if shooting long range in .308/7.62 NATO.  You can only get so much velocity and that effects down range performance.

Ive only shot out to 300 yards but never any issues.

In theory 1" MOA take that to 800-1000 yards and youre looking at 8-10" groups.

20 inchers are pretty much unnecessary for 308s, IMO. Even Kevin Boland, back when he was still with KAC (who sell both 16" and 20" 308s, mind you), openly said something exactly along those lines in the KAC industry forums here a while back.

You gain essentially nothing going from 16 to 20 inches in 308. Literally.

I've run my 16" LMT MWSE in a couple 1000 yard courses. 16" 308s reach a grand easily.

This.  Hence why my ECR went away for an APC.

I don't think you're getting what "sob moa" actually is.  If a gun is sub-moa, it is at ALL distances.  minute of angle is a measurement of a degree of an angle, NOT a particular grouping size.  It just works out to about an inch at 100 yards.  If you shoot a group that is under 6" in diameter at 600yds you are still moa, 10" at 1000yds, etc.  The angle remains the same.  What can change is wind, temp, ammo, projo condition, barrel fouling, and numerous other things that cause degradation of accuracy, but under the exact same conditions using loads designed for the rifle the accuracy will only change as the barrel wears, usually after thousands of rounds down the tube.

So, if your rifle is sub-moa, it's sub-moa.  Distance doesn't change that.  Now how sub it is determines group sizes at longer ranges.  My most accurate rifle is a .270WSM Remmy 700 that I had custom built.  At 100yds I can lay a dime over my best 5-shot groups and hide all the holes.  At 500yds it opens up to about 3" or so (which is probably more me than the rifle).  Both are about .5-.6 moa.  At 1000yds that should be somewhere about 6" of spread, unfortunately I haven't had opportunity to try it at those distances yet, but I know the rifle is capable.

You running 175 ski? Or what?

Powder?

Txl

Twist rate has more to do with .308 predictable hits at distance than barrel length, in addition to BC.

You want tight twist, and high BC, with a consistent load.

Todd Hodnett prefers a 16" bull barrel with at least a 1/9 or tighter twist with the .308 gas guns.  

Even his son was out-shooting 24" .308 bolt guns at a mile with the little 16" carbine with custom barrel, shooting 175gr SMK's IIRC.

When I was chasing this demon before I wised up and ditched .30 cals, I was pissing in the wind at 800yds even in practical competitions, because the wind just takes your low BC .30 cal pill, and washes it downstream wherever it wants, while you continue to miss target after target.

Within 700yds, a well-built .308 with the right barrel and load can do very nicely when the wind is low.  Once you get varying wind, it's time to know your limits.

Either way, go with a RLGS and a tight twist if you plan to shoot at those distances, and use either Black Hills or a great hand load.  Prepare to be frustrated.

I was using 155gr Scenars, which have a pretty good BC, but fly much faster than the 168s and 175s, so you are flatter, with the same or better wind drift.  I was using Lapua Doppler radar data, not theoretical drag models, so POI was dead on for elevation right out of the gate.  

i have since gone to .260 Remington and 6.5 Grendel for these purposes.  My 16" 6.5 Grendel has 1/7.5 twist, so it doesn't care about the transonic region, not that it gets near it within 1000yds anyway.

Factory Federal 175 grain Gold Medal Match in 308 (not 7.62 - they offer both).

Thanks for all the info in this thread.  I have a 16" LMT MWS and am shopping for glass.

I built my DPMS LR-308 with an 18'' SASS barrel with a 1:8 twist I believe and it's very accurate. You will still have great shot groups with a semi-auto.

I haven't done too much long distance shooting with it yet just to try out to 1,000 yards, but I did use that rifle this last month for deer "hunting"(it was really just shooting).

I shot two deer while they were full-out running across a pasture at 220yards with neck shots to save the meat.  

The third deer I shot at 430 yards through the aorta.  I ended up hitting the deer a couple of inches high of the heart, but it dropped within 10 ft.  I opted for a safe body shot on that deer because it was raining and I had low light as the sun was rising in my direction making the scope glare in the light.

I'd say the semi-auto is still pretty good at distance.

Is it chrome lined 11.25 or SS 10?

Take a look at the Nightforce 2.5-10x42 MIL-R

Have you ever fired and noticed an accuracy difference in the 7.62 labeled stuff?  From what I have gathered, both rounds are identical and the 7.62 are usually a couple bucks cheaper because they don't polish the cases.  That appears to be the only difference.

I bought both one day at Academy and could not tell a difference on paper between the two.  I buy the 7.62 when I can because it is cheaper.

SS