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Discussion Starter · #1 ·
I purchased an S&W M&P15 Sport 2 back in 2016 and have been using the same ammo since the get go (Tula .223 62gr FMJ Steel Case), with the very occasional Wolf ammo that my son would buy. Approx. 2K rounds of Tula & <100 Wolf rounds.

Shot great right out of the box, 3” groups at 50 yards, open sight, standing with minimal adjustments. Weapon cleaned after every shoot.

About 6 months ago, I started to get some bullet tumbling action. When it started, it was about 1 in every 20 rounds. Would clean the heck out of barrel and bolt carrier group and tumbling seemed to stop for about 50 rounds.

Now, this past week, my daughter was shooting it, tumbling went to about 12 out of 20.

Same day, I used some ammo that I got from a friend, he didn’t know what the characteristics were, but I think they may have been 55gr FMJ 5.56 rounds. Placed 20 rounds with only 1 tumbler.

Rifle has a 1/9 twist, and Tula ammo gave me ZERO problems until recently, no misfires or ejection problems.

After every shoot, gun is cleaned and re-oiled. I am at the edge of the Mojave Desert and our temps can swing up to 110 in summer to the teens in the winter, but temp doesn’t appear to be the culprit.

Does anyone have any ideas/suggestions/solutions?
 

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I'm far from an expert, so take this with a grain of salt. AFAIK, there are only a few causes of bullet tumbling.
  • A bullet that is too heavy (or possibly too light) for the barrel twist. The1/9 twist of the M&P 15 should be OK for anything from 40-77 or so. So, that is not likely your problem.
  • A mal-formed bullet. One with a malformed base will cause tumbling.
  • Uneven or incomplete powder burns. This can conceivably unbalance the bullet and cause it to start tumbling as it exits the barrel.
Have you noticed whether your gun is dirtier than normal after shooting a high number of tumblers? That would point to the powder.
 

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Discussion Starter · #3 ·
I'm far from an expert, so take this with a grain of salt. AFAIK, there are only a few causes of bullet tumbling.
  • A bullet that is too heavy (or possibly too light) for the barrel twist. The1/9 twist of the M&P 15 should be OK for anything from 40-77 or so. So, that is not likely your problem.
  • A mal-formed bullet. One with a malformed base will cause tumbling.
  • Uneven or incomplete powder burns. This can conceivably unbalance the bullet and cause it to start tumbling as it exits the barrel.
Have you noticed whether your gun is dirtier than normal after shooting a high number of tumblers? That would point to the powder.
No more than usual. These are all factory loads with the exception of the few unknown loads (about 40 rounds).
 

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My only comment is, you are shooting CHEAP bargain basement rounds that you have no idea what the charge is or even how much or type, consequently the rounds are the prime suspect. I'd say bite the bullet (sic) and get some high quality rounds like Black Hills or some other name brand ammo (if you can find it) and report back.

Junk in is always junk out and what you are shooting is junk.

Only time I've ever had a tumbling issue was when I used too much propellant and exceeded the velocity the bullet was stable at and I got bold wipe and hard extraction as well. Backed the charge down and it vanished (and so did the other issues.).

If you have no idea what is inside the cartridge, then is's ALWAYS the prime suspect.
 

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Discussion Starter · #5 ·
My only comment is, you are shooting CHEAP bargain basement rounds that you have no idea what the charge is or even how much or type, consequently the rounds are the prime suspect. I'd say bite the bullet (sic) and get some high quality rounds like Black Hills or some other name brand ammo (if you can find it) and report back.

Junk in is always junk out and what you are shooting is junk.

Only time I've ever had a tumbling issue was when I used too much propellant and exceeded the velocity the bullet was stable at and I got bold wipe and hard extraction as well. Backed the charge down and it vanished (and so did the other issues.).

If you have no idea what is inside the cartridge, then is's ALWAYS the prime suspect.
Daryl - I've been using this ammo for 5 years, all factory. Problem just reared it's ugly head last year. But, to your point, I'll try to find some quality ammo and give it a run. Thanks
 

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Are you using a backer for paper targets or just shooting the paper itself? If just paper they may not be tumbling. The paper is probably tearing.
 
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