How to post-mortem a FUBAR AR Barrel?

nza

nza

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So, now that I have a new 14.5 going onto my upper, I'd like to see what went wrong with my old 14.5. If you recall, it was shooting consistent keyholes, exact lateral profiles were printing on paper with all variety of ammo. AFAIK, there are no burrs for FH Kiss.

Is it a shot out liner? is it a divot or pitting inside? is it a bent barrel? is there a pressure ring from shooting an obstructed barrel?

Short of taking it to a machine shop to slice lengthwise, how have you inspected your barrels to see what happened.
 
"...shooting consistent keyholes..." There are several causes of key holing. Undersized bullets, oversized barrel and not enough bullet velocity being a few and the most common.
Start by slugging the barrel as undersized bullets is unlikely. There shouldn't be a liner in a good barrel. Since it was consistent with all ammo, the velocity isn't likely either. I'd bet on an oversized barrel.
 
sunray said:
Start by slugging the barrel as undersized bullets is unlikely.
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+1. Before cutting anything, be sure to slug the bore and see what it measures at. Keyholing is caused by a lack of stabilization and an oversized bore sounds like a very likely culprit in your case, assuming the twist rate was reasonable for the bullet weights you were shooting.


Mark
 
I have the same problem with my 10.5" another thing is that EVERY SINGLE casing from it gets totally jammed in the die when I try to reload them??? Oversize chamber/barrel for me too?
 
"...jammed in the die when I..." Um, you lubing 'em? Sounds like you aren't. An oversized barrel means the diameter of the inside of the barrel is bigger than it should be. Nothing to do with the chamber.
I suppose 'slugging a barrel needs a how-to. You literally hammer a cast bullet or suitably sized lead fishing sinker, a .224" bullet in this case, through the barrel with a 3/16" brass rod and a plastic mallet then measure it with a micrometer. That'll give you the diameter of the barrel.
 
slugging the barrel... won't the slug just come out as the smallest size along the barrel? if its a worn out at the muzzle end, and I push it through the chamber end, it wills till come out chamber-sized...
 
nza said:
slugging the barrel... won't the slug just come out as the smallest size along the barrel? if its a worn out at the muzzle end, and I push it through the chamber end, it wills till come out chamber-sized...
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Yes, it will give you the smallest ID. You will also be able to feel any tight or loose spots. If the muzzle end is worn you should feel that along the way. A quick way to check your muzzle is to try and insert a bullet into it, ogive first. It should stop on the ogive before the full diameter portion of the bullet or the bore is significantly worn there.


Mark
 
Maybe see if someone has a bore scope you could use, don't those typically reveal details of bore quality that might otherwise not be seen?

I'd say hold off on destroying the barrel until you've tried a few nondestructive alternaties. Unless you just wanna smash the thing.
 
Ohhh. Probably a cheap wilson 5.56 marked barrel.
Remember willwagspal, he built it for me circo 2003. On avg 5000 rds a year for 10 yrs...

And I wasn't a safe queen. I ran that gun like a #####. So I think the barrel itself could of been damaged.
 
nza said:
Ohhh. Probably a cheap wilson 5.56 marked barrel.
Remember willwagspal, he built it for me circo 2003. On avg 5000 rds a year for 10 yrs...

And I wasn't a safe queen. I ran that gun like a #####. So I think the barrel itself could of been damaged.
Click to expand...

50 thousand rounds. Yeah that barrel is shot out.
 
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