S&W M&P15 Keyholing

[Gatehouse]

I mentioned on another thread about how my Norinco barrel (15K rounds) outlived my SW MP`15 barrel (9-10K rounds) presumably due tot he chrome lining.

https://www.canadiangunnutz.com/forum/showthread.php/1643512-S-amp-W-M-amp-P-15-Sport-II-or-Norinco-CQA


But I wasn't sure the barrel was shot out, so I decided to remove the flash hider and really clean the barrel and crown with copper remover and also JB paste. I was slightly hopeful as I took it to the range today to check it out, but no such luck, still keyholing!

Now the big question...Rebarrel? Or just buy a whole new one?

 

[Anpaul]

How many rounds do you have through the factory barrel?

 

[Smokinyotes]

What weight of bullet and what twist?

 

[enefgee]

Who made the ammo - there were reports a few years ago of Norinco 556 with undersized bullets.

 

[Gatehouse]

It's Federal .223 55gr FMJ. It's not an ammo issue.

 

[drill702]

If you put a bullet in the end of the barrel does it go in until it hits the case?

 

[Gatehouse]

If you put a bullet in the end of the barrel does it go in until it hits the case?

No, but that would be fun.

There is still rifling. I might try cleaning up the crown with a crowning tool, but I can't see anything wrong with the crown at this point.

 

[faizi]

If you put a bullet in the end of the barrel does it go in until it hits the case?

If it hits the case then is it worn off barrel??

 

[SuperCub]

Tagged

 

[saskcop]

There is no way that gun should be keyholing with 55 grain ammo. There has to be something going on here with the rifling.

 

[cr5]

Doesn't S&W have a lifetime warranty on their barrels as well? Just get them to replace it.

 

[-[Crosshair]-]

Doesn't S&W have a lifetime warranty on their barrels as well? Just get them to replace it.

I don't think they'll replace a barrel with 10,000 rounds through it just like GM wouldn't replace your front disk brakes after 100,000km. Looks like normal barrel wear to me, 10k rounds seems about right.

 

[Gatehouse]

They warranty defects, not wear and tear. It never had any defects, only maintenance I had to do was replace extractor/springs and clean it. I think they are very solid rifles for the price, but barrels will wear out.

 

[RifleDude]

If it keyholes with a variety of ammo, it's a worn barrel (almost certainly the case here). If it only does it with one type/brand of ammo, it's the ammo.

 

[cr5]

I would have expected closer to 20K for round count before the barrel is done but at least barrels are pretty cheap and it's easy to change.
Are these not chrome lined or nitrided?

 

[Gatehouse]

If it keyholes with a variety of ammo, it's a worn barrel (almost certainly the case here). If it only does it with one type/brand of ammo, it's the ammo.

I haven't tried other ammo, but it was shooting thousands of this Federal AE223 stuff with no problem until it started keyholing. And the other 2 M&P's and my Tavor don't have an issue with the ammo, so...

 

[Tenguns]

I’d just throw a new barrel from International Barrels on it.

 

[Horilka]

Barrel is nitrided and there are report of higher round counts for sport 2 so this is kind of strange.

 

[lone-wolf]

I haven't tried other ammo, but it was shooting thousands of this Federal AE223 stuff with no problem until it started keyholing. And the other 2 M&P's and my Tavor don't have an issue with the ammo, so...

Don't be sad, I'd be quite happy if I shot enough to wear out a barrel. How long did it take?

 

[Gatehouse]

Barrel is nitrided and there are report of higher round counts for sport 2 so this is kind of strange.

How much higher? I was a bit surprised...but not that surprised. It's seen lots of extended shooting and the barrel has been smoking hot on many occasions.

I'm open to ideas