I have a delema with a new barrel

[Eric Anderson]

I put together a new AR-15 over Christmas. I was horrified the first time I shot it with IMI M193 and federal XM193 it looked like a shotgun pattern. I reset the barrel and retorqued the barrel nut when I got home.
Went back and made some ladder loads with lots of different bullet/ powder combos. Also brought a mag of PPU .223 to warm up the barrel beforehand so everything is consistent.
What I learned today:
It wasn’t the barrel bedding or barrel nut. The PPU still looks like a shotgun shot the target. In fact, pretty sure a turkey choke throws a tighter group.

The barrel shoots ok with several of the Norma bullets I tried.

It really likes Barnes tsx 55 grain fun bullets on top of IMR 4895
It’s best groups I was stacking bullet holes. unless I was having random fliers that completely missed paper, pretty sure I dropped a few rounds perfectly into a previous hole.

Now my delema. Is it worth keeping this barrel? It is unusable with M193 or equivalent. It is marginal with Norma varmit bullets. The only thing it is MOA capable with is the most expensive bullet out there. AR-15’s are not exactly suited for low volume precision firing. I have other rifles much better suited.

Has anyone else faced a similar situation? Had a barrel that only worked with premium ammunition. What did you do? Keep it, or buy another barrel?

 

[CAustin]

WOW it sure sounds like the barrel.

 

[WAB]

I had a 6.5 Grendel barrel that I couldn’t get to shoot under 2” (not as bad as yours!). I swapped it out for a Ranier Arms polygonally rifled match barrel. It is now shooting 1/2” at 100 and I shot a 1 1/2” 5 shot group at 300 just before deer season. I’ll get back on it once deer season goes out. I don’t want the gunfire on the farm right now.

 

[Shootist43]

What is the twist rate? Rifles that shoot 55 Grs. accurately will not stabilize heavier bullets hence the shotgun pattern.

Apology: I didn't realize that M 193 does in fact use a 55 Gr. bullet. Please disregard my comment.

 

[DG Gunsmith]

Sounds like a bad barrel... Better off swapping it for better one... Although, it might be possible to remedy it... Generally the 2 things that affect Accuracy the most, are the Crown & Chamber... Is it possible that it has a defective Crown? This is sheer speculation, as I haven't examined it personally... But, I have had luck in the past, Re-Crowning Muzzles... Another line o' thought... Have you measured the Bore Diameter vs the Bullets that work & the ones that don't?

 

[mdwest]

What twist rate is the barrel?

Barness 55gr is longer than the M193 projectile.. It flies far more like a 62gr bullet than a 55gr..

Your barrel may prefer heavier/longer bullets..

Shoot some 62gr stuff through it and see what happens..

If its shooting MOA with Barnes... but open groups with other 55gr stuff.. I'd at least consider putting a box of 62 or 70gr stuff through it first before writing it off to being a "bad barrel"..

My primary 556 AR hates 55gr winchester, remington, and federal options.. at best it will hold about 2 - 2.5 MOA..

But it LOVES 62gr SSA (FBI load), 62gr Hornady Black FMJ, and 75gr Hornady Black Interlock.. shoots 1 - 1.5 MOA with any of those.. and its not a "precision" gun by any means.. its a DIY build with a variety of parts from different manufactuers..

 

[Ray B]

The only similar situation I'm familiar with is a friend that has a rifle that came with a muzzle break. It wasn't hit by the bullets but with certain loads the harmonics of the barrel caused the muzzle break to affect the exit of the bullet which led to some loads having patterns while others were accurate.

 

[shootist~]

I would clean the bore and then polish with J-B Bore Paste. And give it one more try with the Izzy M193.

 

[Bob Nelson 35Whelen]

I put together a new AR-15 over Christmas. I was horrified the first time I shot it with IMI M193 and federal XM193 it looked like a shotgun pattern. I reset the barrel and retorqued the barrel nut when I got home.
Went back and made some ladder loads with lots of different bullet/ powder combos. Also brought a mag of PPU .223 to warm up the barrel beforehand so everything is consistent.
What I learned today:
It wasn’t the barrel bedding or barrel nut. The PPU still looks like a shotgun shot the target. In fact, pretty sure a turkey choke throws a tighter group.

The barrel shoots ok with several of the Norma bullets I tried.

It really likes Barnes tsx 55 grain fun bullets on top of IMR 4895
It’s best groups I was stacking bullet holes. unless I was having random fliers that completely missed paper, pretty sure I dropped a few rounds perfectly into a previous hole.

Now my delema. Is it worth keeping this barrel? It is unusable with M193 or equivalent. It is marginal with Norma varmit bullets. The only thing it is MOA capable with is the most expensive bullet out there. AR-15’s are not exactly suited for low volume precision firing. I have other rifles much better suited.

Has anyone else faced a similar situation? Had a barrel that only worked with premium ammunition. What did you do? Keep it, or buy another barrel?

@Eric Anderson
Just my 2 cents.
If any of my barrels won't shoot less than an inch with any projectile I decide to grow down it it goes back to the manufacturer, but then again I only use custom competition barrels on my hunting rifles. For my fun guns I'm happy with 2 to 4 inches depending on the rifle.
Bob