M&P 15 Sport II Ammo Detail Question

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HCC17

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Hi all, I recently got my M&P 15 Sport II & I'm looking at 5.56 ammo. The info for this ammo says it's ideal for use in M16A1 and other standard rifles with a 1:12" barrel twist yet the barrel of the M&P 15 Sport II is 1:9. Will this ammo be safe to use in it?
 
Is it 5.56x45 NATO ?
If it is , and your sport is chambered for 5.56 you should be ok, I shoot 5.56 x45 in mine all the time. It doesn’t say anything about the barrel twist when I’ve bought it thou


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I don't know the answer, but he is asking (I think) if the twist of his rig is different from that recommended by the ammo, will the ammo be a decent shooter in his S&W. I think if he said what grain bullet his ammo had, those more in the know here would be able to say if his 1 in 9 barrel will stabalize the bullets OK??
 
SW Gun Guy said:
I don't know the answer, but he is asking (I think) if the twist of his rig is different from that recommended by the ammo, will the ammo be a decent shooter in his S&W. I think if he said what grain bullet his ammo had, those more in the know here would be able to say if his 1 in 9 barrel will stabalize the bullets OK??
Click to expand...

I didn't shoot any paper targets today. We just went down on the river shooting targets of opportunity. It was hitting some pretty small targets.
 
The m&p's 1:9 barrel is well suited for 55gr. 5.56×45 ammo. I recently picked up a sport 2, and when setting up the 100 yard zero, the XM193 55 grain ammo was shooting really tight groups. Well I decided to run some 62 gr. M855 green tips to see what type of groups I could get. I only ran 10 of those through it, and 3 of them completely keyholed in 25 yards.

I also have a Colt LE6920 Socom with a 1:7 twist barrel, and it spins the 62 gr. Bullets like a laser.

I read where many people have good results with the sport 2 and heavy projectiles. Me, not so much. I will, however, run some more heavier ammo through it before I chalk it up as a 55gr and under gun.
 
1/9 should stabilize M855 fine. My old 1/9 Bushmaster sure does. Very accurate with the old IMI M855 green tip.

Where 1/9 falls short is the 77 grain stuff.
 
Univibe said:
1/9 should stabilize M855 fine. My old 1/9 Bushmaster sure does. Very accurate with the old IMI M855 green tip.

Where 1/9 falls short is the 77 grain stuff.
Click to expand...

I also had a Bushmaster M4A3 Patrolman with a 1:9 that shot the 62 gr. extremely well. My bushy also had a chrome lined bore, which is thicker than the nitride on the sport 2. That may be why it spins those green tips accurately.
 
Your question: Will this ammo be safe to use in my rifle?

The answer: Yes.

While avoiding too much technical discussion, it may not be the most accurate load for your rifle, but will be perfectly safe, should function fine, and will probably exhibit at least acceptable accuracy.
 
bloodlord77 said:
I also had a Bushmaster M4A3 Patrolman with a 1:9 that shot the 62 gr. extremely well. My bushy also had a chrome lined bore, which is thicker than the nitride on the sport 2. That may be why it spins those green tips accurately.
Click to expand...

Chrome lining has nothing to do with the spin of the projectile. The inner diameter of the bore should be the same, per spec.

1:9 should do fine with 62 gr, but each barrel is different. I would try different ammo though as there are other reasons that some M855 might keyhole, such as the steel penetrator core being off center. If it were the barrel and not the bullet, I would expect more to keyhole than 3 out of 10.
 
cyphertext said:
Chrome lining has nothing to do with the spin of the projectile. The inner diameter of the bore should be the same, per spec.

1:9 should do fine with 62 gr, but each barrel is different. I would try different ammo though as there are other reasons that some M855 might keyhole, such as the steel penetrator core being off center. If it were the barrel and not the bullet, I would expect more to keyhole than 3 out of 10.
Click to expand...

Thanks. And yeah, I plan to put the sport2 through its paces with some heavy .223 loads. Even if it ends up liking the lighter projectiles only, it still will never leave my stable. It's an excellent rifle IMO.
 
bloodlord77 said:
Thanks. And yeah, I plan to put the sport2 through its paces with some heavy .223 loads. Even if it ends up liking the lighter projectiles only, it still will never leave my stable. It's an excellent rifle IMO.
Click to expand...

When the Sport first came out, there was a member on here by the name of Oneyeopen... He found that his 1:8 twist was more accurate with 40 grain loads than anything else.

Several members have also reported that the American Eagle XM855 keyholed with 1:8 twist back in the day, so it could just be the ammo.
 
From the reviews I've seen from people that have actually fired heavier bullets it does very well with them. Some of them shoot under MOA.
 
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