M&P Sport II and Accuracy

[Pisgah]

If I'm not mistaken, the 1:9 twist rate was picked by the military specifically to stabilize the 55 grain bullet.

The original twist rate, when all 5.56 ammo was 55 gr., was 1:14. When they went to heavier bullets, the twist was tightened, but it still works just fine for the lighter ones. If you intend to shoot heavier than the 60-65 gr. bullets, 1:7 is more likely to give best performance -- but 55's will still work just fine.

 

[Rick_A]

The Saint is probably the best thing going for a midlength AR. Ya did alright.

 

[Rastoff]

Hey, instead of figuring if a gun is sub MOA off a benchrest, why don't you do 10 push-ups and 10 burbees and then try to shoot off hand at a moving Target at 50 yards. Try that with pajamas on too.

What pains me is that you think you'll be calm and shoot from a rest right after you hear your windows crack open. Be realistic and train your body to react right under stress. I don't care but how well your gun is or how accurate, just wanna know if you'll hit the target.

You dredged up a two year old thread to post this drivel? Pushups and burpees?

Don't follow all the hubbub about sub MOA or all that. The rifle is only as effective as its operator.

No, there is value in determining if the gun is good. An AR that is working properly should shoot ~1.5MOA or better with reasonable ammo. If it's not doing that, there could be a problem. So, yeah, it's worth it to take the time to check the accuracy of your gun.

 

[WR Moore]

If I'm not mistaken, the 1:9 twist rate was picked by the military specifically to stabilize the 55 grain bullet.

Actually, the M16 series went from 1-14 to 1-12 to 1-7. The 1-7 was allegedly due to the "need" to stabilize the 5.56 x 45 mm tracer bullet. This argument made sense in the M249 SAW, is somewhat questionable in the rifle. But, Big Green is big on "commonality" even if it doesn't make sense.

The 1-9 twist may have been the initial plan for the 62 gr bullet, might have crept in from the USAMTU competition where they sought heavier bullets for 600 yard matches. The wind drift of the 55 gr bullet at 600 yards/meters is significant.

Depending upon length, bullets heavier than 60+ grains can be used quite well in a 1-9 barrel. The Horanaday 75 gr HPBT bullet being a good example. The 1-9 has superior accuracy over the 1-7 unless you want to shoot something like the 75 gr A-Max or the 77 gr SMK or something even heavier. 1-6.5 was getting some attention before I quit shooting long range matches.

As I've noted before, we had problems with expanding bullets coming apart with the 1-7 twist.