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  #1  
Old 09-29-2020, 07:54 PM
HCC17 HCC17 is offline
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Default M&P 15 Sport II Ammo Detail Question

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?
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Old 09-29-2020, 08:08 PM
JT64 JT64 is offline
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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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Old 09-29-2020, 08:31 PM
Velle Velle is offline
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I shot 200 rounds of American Eagle 55 grain 5.56 through mine today.
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Old 09-29-2020, 08:39 PM
HCC17 HCC17 is offline
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It says 5.56 mm 55grain
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Old 09-29-2020, 08:43 PM
SW Gun Guy SW Gun Guy is offline
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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??
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Old 09-29-2020, 09:10 PM
jbtrucker jbtrucker is offline
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Twist rate chart
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File Type: jpg BW.jpg (81.5 KB, 209 views)
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Old 09-29-2020, 11:19 PM
MyDads38 MyDads38 is offline
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Quote:
Originally Posted by jbtrucker View Post
Twist rate chart
Thanks for the chart!
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Old 09-30-2020, 12:07 AM
Velle Velle is offline
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Quote:
Originally Posted by SW Gun Guy View Post
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??
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.
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Old 09-30-2020, 10:26 PM
bloodlord77 bloodlord77 is offline
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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.
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Old 10-01-2020, 12:37 AM
Univibe Univibe is offline
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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.
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Old 10-01-2020, 06:21 AM
bloodlord77 bloodlord77 is offline
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Quote:
Originally Posted by Univibe View Post
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.
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.
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Old 10-01-2020, 08:16 AM
Pisgah Pisgah is offline
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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.
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Old 10-01-2020, 07:24 PM
cyphertext cyphertext is offline
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Quote:
Originally Posted by bloodlord77 View Post
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.
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.
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Old 10-01-2020, 08:04 PM
bloodlord77 bloodlord77 is offline
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Quote:
Originally Posted by cyphertext View Post
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.
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.
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Old 10-01-2020, 08:14 PM
cyphertext cyphertext is offline
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Quote:
Originally Posted by bloodlord77 View Post
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.
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.
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  #16  
Old 10-01-2020, 09:25 PM
Velle Velle is offline
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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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  #17  
Old 10-03-2020, 04:54 PM
Moe Mentum Moe Mentum is offline
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Yes, shoot it.
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