My barrel is dead, right?

milktree

milktree

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I have a Bushmaster DCM/CMP AR with what I think is a roached barrel.

The following was shot off a bench off sandbags at 200 yards with a slight breeze. The trigger is a Giselle high speed two stage (quite nice). The rifle's barrel is tight on the upper, the upper tight on the lower, the free-float tube free floating, but firmly attached to the upper, the sights tight, the crown clean and undamaged... the gun appears to be in great function.

The ammo is the same stuff I've been using for years, PPU 5.56 NATO 55gr XM93, I bought a lot of it years ago and I'm still using it. It's probably not the best ammo, but it's a known quantity.

There's two "groups", five shots with the Susan Bs next to the holes, then another five with Sacajaweas next to them, after I moved the sight four clicks.


I know that generally the shooter is the weak link, but I *know* I'm not nearly this weak of a link. I've used this rifle to shoot EMRL since '08, averaging about 170 with a good day as high as 181 (I'm still wicked proud of that, even if it's only "meh" compared to people who really know what they're doing)

So, I'm pretty sure I know what sight alignment should look like, what trigger squeeze should feel like, etc, and therefore off a bench on bags I should be able to get all the holes within 4" pretty easily, and within 2" if I'm really careful. These 5" and 7" "groups" feel like someone is screwing with me.

Is there anything else besides a worn out barrel that could cause this? Are there any visual clues to what a worn out barrel looks like?



used-up-barrel-small.jpg


The followup question is, "what should I replace it with"? :)
 
I don't know much about AR's. Did this happen recently as opposed to slowly creeping up to? If you've been doing reasonably well and of a sudden this happens, it's either ammunition, gun or you. You say it's known ammunition and commercial at that. Ergo, gun or you. If it's a scope, try a different one. If it's irons, make sure they're tight? If sights are good to go, it's barrel and/or attachment. Any chance you've really douched out the barrel? I mean really went after fouling. It sounds like you haven't shot it in a while, so mayhaps it's been sneaking up on you and you just forgot? It's not like the barrel would suddenly mung up while in the safe. Last, it's you, especially with irons. For some strange reason, I shoot groups like that with any AR at 100. Before you say I can't shoot for s**t, the last two groups @200 that I shot with my M1A were 21/2". 3 shot groups yes, just adjusting my sights for different ammunition. Something to do with my eyes and AR irons. I can shoot an M-1 carbine better than an AR. Both with irons. So, have your eyes aged since last you shot this rifle? One last thing, should it be a scope. Check your parallax at 200.
Having blathered on for a bit, have someone else shoot the rifle. It need not be at 200. See, if a known decent shooter, has problems also. It doesn't even have to be a special trip. Most people won't mind shooting free ammunition. There might also be some things peculiar to AR's that could cause this, but I don't know enough about that to help, sorry.
 
What rate of fire? Heat can effect a barrel and open up a group, but I don't think it would open that much. How many round do you have through the barrel total lifetime?
 
Maybe its just me....but a 5 to 7" group could just be the 55 grain ammo your useing. Accuracy specifications is not high on "nato" m193.... I believe the Median accuracy of m193 can not exceed 4 moa. Also not sure if this changed but @ 25 meters a solder had to "group " 3 consecutive 3 shot groups under 2" CTC before they went on to zeroing their wepon. This is just a base of what the military sees as "accurate enough".
is the barrel shot out? Look in there best you can, how many rounds down the tube? I have about 3k through my rra A2 and has not shown any signs of loss of accuracy yet.....was it bright and sunny where you where shooting. I know for myself bright clear sky's play with my eyes. Especially if there is any glare off the front sight.

Does the dmc/cmp BM have a 1/8 or 1/7 twist barrel?
A 5-7" group at 200 is dancing all over the 10 ring? 10 ring on a SR is 6"
 
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I'm not going to pretend I know a lot about HP shooting, but when barrels start to wear out, don't they do it slowly? Have you tries letting another good HP shooter try it out?
 
Moderator said:
I'm not going to pretend I know a lot about HP shooting, but when barrels start to wear out, don't they do it slowly? Have you tries letting another good HP shooter try it out?
Click to expand...

this helps, I have a goto guy....... more times than I care to mention he has proven "aint nutn rong wit dat gun boy".
 
How many groups did you shoot like this? Previous posters are quite right that 55gr mil ball isn't the most accurate thing in the world, there's no reason not to expect regular 4" groups at 200yds even with your rifle bolted down. How many rounds do you have thru that barrel?

I shoot the same style Bushmaster; they're deliberately not chrome plated and I keep second-guessing myself as to whether the accuracy is decreasing. It's probably got 5k on it, tho, so the answer is probably "yes".
 
A loss of accuracy in a barrel will show up first as random fliers at 600yds, then as it gets worse, 300yd groups will start to go to hell.
A "shot out" barrel (from a highpower shooted's perspective) will still hammer the piss out of a target at 200yds.

Bushmaster put quality 1-8 twist barrels on their DCM rifles. Maybe if it has 7500+ rounds through it I'd think it was no good anymore.

There are 3 possibilities:
1. Your ammo sucks
2. Your barrel sucks
3. You suck

Forgive me for #3. It made my list more poetic.
But seriously, benching or scoping a SR is fairly difficult to do well.

My $ is on #1, then work on #3.
 
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mac1911 said:
Maybe its just me....but a 5 to 7" group could just be the 55 grain ammo your useing. Accuracy specifications is not high on "nato" m193.... I believe the Median accuracy of m193 can not exceed 4 moa. Also not sure if this changed but @ 25 meters a solder had to "group " 3 consecutive 3 shot groups under 2" CTC before they went on to zeroing their wepon. This is just a base of what the military sees as "accurate enough".
is the barrel shot out? Look in there best you can, how many rounds down the tube? I have about 3k through my rra A2 and has not shown any signs of loss of accuracy yet.....was it bright and sunny where you where shooting. I know for myself bright clear sky's play with my eyes. Especially if there is any glare off the front sight.

Does the dmc/cmp BM have a 1/8 or 1/7 twist barrel?
A 5-7" group at 200 is dancing all over the 10 ring? 10 ring on a SR is 6"
Click to expand...

OP: This is not a personal attack on you, your shooting capability or your rifle but:
It is always amazing to me that NES shooters routinely pride themselves in buying and shooting the cheapest ammunition possible and them want to blame the rifle for poor accuracy. [hmmm] Since they obviously are excellent shooters and they are not going to splurge for more expensive ammo, it must be the rifle. [wink] Of course a new barrel will cost much more than better ammo but, but, but... Kind of like buying a 572 crate motor and feeding it 87 octane gas... [shocked] Those groups do not look bad for that ammo with open sights at 200 yards. As mac1911 notes, that group could be giving 10 ring accuracy... (offhand).
White Feather
 
collecting a bunch of answers:

To all who have been extra kind about attempting to not insult me: Don't worry about it. I have no allusions of being a high master, and generally assume that it's *not* the gun's fault (or the motorcycle's fault, or the the computer's fault, or the table saw's fault) but rather something about my technique.

But sometimes the saw blade *is* warped, or the suspension oil is shot, or there's a bug in the UI, or the barrel is roached. (or the ammo is cheap :)

I've put about 2k rounds though it, maybe as few as 1,800. But I bought it used, and I don't know its history before that.

I was shooting sloooowly and deliberately, heat might be an issue, but it seems unlikely, I was shooting maybe one a minute, with breaks to look through the scope and scratch my head and chat with the nice guy at the next bench. (and pull targets as necessary)

The barrel is a 1:7", non-chrome lined.

Yea, I know it's cheap ammo (that's why I bought it) but I think it used to shoot better with the same ammo, so either I've started to suck, or the gun has started to suck, or I've gotten better and now whatever was "good enough" isn't anymore. (my hope :)

I was under the impression that the PPU XM93 was at the better end of "inexpensive ammo", so should be capable of better than what I'm seeing.

My impression (and this is completely subjective since I don't have marked up targets along the way) is that it's been getting worse somewhat gradually and progressively. However, I don't shoot nearly often enough to be totally confident that it's not just variations in my skill. Yea, I know, bad data.

What started me down this path is that I went out to practice and the spread on the paper seemed a lot worse than the spread I expected based on "calling my shots". I have in the past been pretty good about calling them, but I might be out of practice on that, too. Based on my poor performance I thought I'd test the rifle/ammo in such a way that took me out of the equation as much as possible. Hence the shooting off the sandbags.

The place I was shooting from was in shade, so there wasn't any glare off the front sight.


It sounds like I should try again, off the bench, with a scope (I have a 4-12x50 Nikon and a carry handle mount), and/or some handloads that I know are consistent.

So.... who wants to be a go-to guy for me? WSA or your club :)
 
Maybe try 100 yards and see what your groups look like. Sometimes you just have a bad day shooting. Also at 200 yards the wind may have been worse than you thought.
 
PPU / Prvi Partizan is terrible ammo if you're expecting reliability/accuracy/safety

In rifles you may get pie plate sized groups at 50 feet

In pistols it will jam constantly

Their hollow point ammo does NOT expand

They have been known to put the wrong primers in ammo (small rifle in a small pistol)

I know of a couple stories of guns blowing up / being seriously damaged from using PPU ammo

avoid PPU / Prvi Partizan, Made in Serbia
 
additionalmc said:
PPU / Prvi Partizan is terrible ammo if you're expecting reliability/accuracy/safety

In rifles you may get pie plate sized groups at 50 feet

In pistols it will jam constantly

Their hollow point ammo does NOT expand

They have been known to put the wrong primers in ammo (small rifle in a small pistol)

I know of a couple stories of guns blowing up / being seriously damaged from using PPU ammo

avoid PPU / Prvi Partizan, Made in Serbia
Click to expand...

......... Yeah .......

No offense to you but I've had amazing luck with there ammo and I know a bunch of people that have too . I mainly shoot the 54r.
 
additionalmc said:
PPU / Prvi Partizan is terrible ammo if you're expecting reliability/accuracy/safety

In rifles you may get pie plate sized groups at 50 feet

In pistols it will jam constantly

Their hollow point ammo does NOT expand

They have been known to put the wrong primers in ammo (small rifle in a small pistol)

I know of a couple stories of guns blowing up / being seriously damaged from using PPU ammo

avoid PPU / Prvi Partizan, Made in Serbia
Click to expand...


Um... My experience suggests otherwise.

out of 1,500 rounds (I think, roughly) I've had *one* fail to fire, and otherwise my only complaint might be accuracy, but it's certainly better than "pie plate at 50 feet" I wouldn't claim that PPU is super excellent, but it's not nearly as bad as you say.

At least it's all brass cased, boxer primed, and surprisingly consistent case weight.

- - - Updated - - -

white feather said:
There you go. [grin] Mount the scope, buy a box of decent ammo and compare the two. Start at 100 then go to 200. Where is WSA?
White Feather
Click to expand...

Woburn Sportsmens Association, but it's actually in Bedford, MA. (they moved about 60 years ago but kept the name)
 
white feather said:
OP: This is not a personal attack on you, your shooting capability or your rifle but:
It is always amazing to me that NES shooters routinely pride themselves in buying and shooting the cheapest ammunition possible and them want to blame the rifle for poor accuracy. [hmmm] Since they obviously are excellent shooters and they are not going to splurge for more expensive ammo, it must be the rifle. [wink] Of course a new barrel will cost much more than better ammo but, but, but... Kind of like buying a 572 crate motor and feeding it 87 octane gas... [shocked] Those groups do not look bad for that ammo with open sights at 200 yards. As mac1911 notes, that group could be giving 10 ring accuracy... (offhand).
White Feather
Click to expand...

Correct @ 200 yds the correct target to use for NRA match prone slow fire would be the MR 52 which has a 3.79" ten ring. I been spoiled as the club I shoot 200yd matches uses SR for all positions to keep things simple( i think thats how cmp does it also? )... I still put my money on the ammo. I have some ppu m855 stuff its 2 moa @ best @ 100 yards with my RRA A2 standard rifle from the led sled... You can load 100% better ammo at same or less cost than the best cheap stuff. most expensive bullet I have used is the sierra @ 20 cents each plus about 10 cents for powder and 3 cents for primer.
all of the better bullets are all over the 1moa area with my RRA NM from the rest @ 100 yards. Hornady 75gn match, nosler CCs, sierra match, ect ect.
My skill set cant deliver that so I use the cheapest of the 3 which right now is hornady match. I think even loading the hornady bulk 55 gn can deliver better accuracy than m193 or m855 ? I will try some of the PPU out of my NM rifle and see?

here is a group( labeled wrong on the target of 55gn hornady FMJ with W844 powder out of my flat top NM/varmint rifle
..... im a little doubtful the PPU "nato" i have will be this good ?
here also is PPU 69 grain match fired from the same gun same set up, forgot about that batch.
 
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Is there a chance the barrel is fouled with copper or lead? If the 55gr fmjbt is open in the back lead could be melting and fouling your rifling.

I just processed a 5000pc lot of PPU brass and found all kind of oddities from cases that stand off at a visible angle to very long and very short cases. Some of the primers were crimped in so heavily that the decap pin punctured the primer rather than push it out. Some primers practically fell out of the case even with a crimp. Some of the cases wouldn't fit in the shell holder on the press.
 
With that few rounds, I'd start with cleaning the barrel real well and then running some black hills 77gr, or some other match ammo above 69gr through it at 100yds, then 200yds.

Unless the previous owner was a pretty active shooter, I'd doubt the barrel is toasted. I just replaced a 1:7 chrome lined at 13k rounds of mixed ammo and it wasn't shooting groups that big. FYI, I replaced it with a Rainier Mountain Series and it shoots great. $320
 
OK, test #1 with not-PPU ammo:

100Y.jpg 100Y, ~ 1.1" 200Y-1.jpg 200Y #1, ~ 2.4"
200Y-2.jpg 200Y #2, ~ 3.1" 200Y-3.jpg 200Y #3, ~ 3.2"

This was done off a bench on sandbags, fully supported, with a Nikon 12x scope mounted to the carry handle.
There was no wind that I remember.

The ammo:
- 55gr Hornady FMJ-BT (If I remember correctly they get good reviews for being quite consistent)
- 24.0gr AA2460 (measured each load, I didn't use the 550's powder measure)
- CCI #400 Small Rifle primer
- once fired PMC brass, headstamp matched (and weighed, 'cuz I can) to +/- 1gr,
- no crimp
- 2.222" OAL
I would have measured their speed, but my chronograph had a dead battery. (check these things before you leave home!)

So, it's *at least* #1 (ammo sucks).

I'm a little concerned that the groups kept opening up as I shot, the 100Y is damn close to 1MOA (I'm totally happy with that!) but by the 4th five shot group it had opened up by 50%

I'd have shot more, but I only made 20 rounds.

I don't understand this part:

But seriously, benching or scoping a SR is fairly difficult to do well.
Click to expand...

It was mildly annoying to re-adjust the sandbags after each shot, but other than that it felt like I was breaking the trigger consistently, and the gun was rested such that there was very little force keeping it in place. I was able to hold the crosshairs on the "X" with no visible motion, while keeping my eye centered such that the chromatic aberration (that red/green halo you get with less than $2,500 scopes) was very small.

Is there an aspect I'm not considering? Iron sights are more annoying, but not significantly so.


The first group suggests it's *not* the barrel, it's the ammo and me.
 
additionalmc said:
PPU / Prvi Partizan is terrible ammo if you're expecting reliability/accuracy/safety

In rifles you may get pie plate sized groups at 50 feet

In pistols it will jam constantly

Their hollow point ammo does NOT expand

They have been known to put the wrong primers in ammo (small rifle in a small pistol)

I know of a couple stories of guns blowing up / being seriously damaged from using PPU ammo

avoid PPU / Prvi Partizan, Made in Serbia
Click to expand...

Back when I had my Colt 6520 I used shitloads of PPU 55 gr FMJ with 0 problems. My only "gripe" about it is the ammonia smell the ammo gives off, its like cracking open smelling salts with every 5 rounds.

None of this matters anyways because I never see PPU 55 bulk at non-retard prices anymore. Ever since the factory blew up a few years ago? its been hard to come by.

-Mike
 
milktree said:
OK, test #1 with not-PPU ammo:

View attachment 112865 100Y, ~ 1.1" View attachment 112866 200Y #1, ~ 2.4"
View attachment 112867 200Y #2, ~ 3.1" View attachment 112868 200Y #3, ~ 3.2"

This was done off a bench on sandbags, fully supported, with a Nikon 12x scope mounted to the carry handle.
There was no wind that I remember.

The ammo:
- 55gr Hornady FMJ-BT (If I remember correctly they get good reviews for being quite consistent)
- 24.0gr AA2460 (measured each load, I didn't use the 550's powder measure)
- CCI #400 Small Rifle primer
- once fired PMC brass, headstamp matched (and weighed, 'cuz I can) to +/- 1gr,
- no crimp
- 2.222" OAL
I would have measured their speed, but my chronograph had a dead battery. (check these things before you leave home!)

So, it's *at least* #1 (ammo sucks).

I'm a little concerned that the groups kept opening up as I shot, the 100Y is damn close to 1MOA (I'm totally happy with that!) but by the 4th five shot group it had opened up by 50%

I'd have shot more, but I only made 20 rounds.

I don't understand this part:



It was mildly annoying to re-adjust the sandbags after each shot, but other than that it felt like I was breaking the trigger consistently, and the gun was rested such that there was very little force keeping it in place. I was able to hold the crosshairs on the "X" with no visible motion, while keeping my eye centered such that the chromatic aberration (that red/green halo you get with less than $2,500 scopes) was very small.

Is there an aspect I'm not considering? Iron sights are more annoying, but not significantly so.


The first group suggests it's *not* the barrel, it's the ammo and me.
Click to expand...

Your results with the hornady bulk is on par with my findings. I will say reloaded bulk 55gn hornady bullets have always out shot any m195/855 bulk ammo I have tried. @ 200 yards I would suspect the same. Your groups will open up as your gun gets hotter. Your 200 yd groups have more verticle dispersion than horizontal ..... from what I learned that's mostly breathing control?

Sand bags are ok but I found I get more consistant results with my led sled plus with 50lbs of weight on it.
I still need to readjust. If you want a rest that will return to close to zero you would need at least a ransom style machine rest......
Nice to see its not the barrel.
 
mac1911 said:
Your results with the hornady bulk is on par with my findings. I will say reloaded bulk 55gn hornady bullets have always out shot any m195/855 bulk ammo I have tried. @ 200 yards I would suspect the same. Your groups will open up as your gun gets hotter.
Click to expand...

I infer from the above that even with careful load refinement I'm not going to get much better than that from Hornady bulk 55gr bullets. Is that what you meant? Do ladder tests even make sense for a .223 heavy barrel? (more of a question for the reloading section perhaps)

What does "hotter" mean in this context? Anything above ambient, or uncomfortable to touch? The above was 20 rounds shot over about 40 minutes, which doesn't seem like it should generate enough heat to make much difference. Am I naïve about that?

Your 200 yd groups have more vertical dispersion than horizontal ..... from what I learned that's mostly breathing control?
Click to expand...

Off the bench on sandbags, the rifle wasn't moving at all before the shot. Or at least it wasn't moving to any degree I could see through a 12 power scope; so I doubt it's breath related. I can imagine variations in how the butt of the rifle was supported might change the shape of the group. Fixing that "problem" (not really a problem in the grand scheme) might be beyond my interest for this rifle. If I get a bench rest rifle, that might change :)
 
Coyote33 said:
What's with the weird coins? Out of quarters?
Click to expand...

Dollar coins are very nearly 1" in diameter, so it's easier to make a guestimate on the group size

Dollar coins are a little heavier, so they hold the paper flat more easily. (why I initially put them on at all)

Dollar coins are more fun.
 
How was the wind? Most of your groups have more horizontal than vertical. Did the scope have AO and did you set it correctly to dial out parallax (not just to 100 or 200)? Were all screws torqued to spec? How stable is a carrying handle mount? The 1:7 might have been happier with some heavier bullets. (69 Sierra Matchking?) In the summer, I have always been concerned when a round sits in a hot chamber longer than the previous rounds. I think it will cause some of the vertical stringing. Just because a rifle will shoot 1" at 100 does not necessarily mean that it will do 2" at 200 as minor variations tend to multiply not add... Those groups look pretty good compared to the earlier ones. Moving in the right direction. [thumbsup]
White Feather
 

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