Gunsmithing Horrible accuracy with one of my AR-15's

[SmokeRolls]

One of my AR-15's with a 5R 16" barrel is getting horrible groups and it's enough to take some action to correct. I was thinking that it may be the crown and I took the flash surpressor off and found alot of crud like cast bronze on the end of the barrel. I have never seen this much depositing on the end, enough that it may be contacting or just touching the edge of the rifling (The crown ) I need to buy a tool to re-dress the crown..... Any recommendations on the best tool or method to clean up the end of the barrel and regain my accuracy.... Also, is this normal build-up or excessive. I bought this upper used but it looked imaculate including the rifling. I cannot see any signs of excessive wear but I do not have the gunsmithing experience nor tools to check throat erosion or ?.. Any help would be appreciated....
SmokeRolls

 

[keithtb1]

Re: Horrible accuracy with one of my AR-15's

Have you tried shooting it without the flash surpressor. Could be off and thats why your getting the shavings there. Just a thought.

 

[bohem]

Re: Horrible accuracy with one of my AR-15's

I'm pretty sure you should be able to remove the crown crud by just letting the barrel sit in powder solvent overnight, just stick the entire muzzle into a snifter of the solvent for a few hours and then pick at it with a bamboo skewer to break the loosened crud off.

THen I'd suggest trying to shoot it without the flash suppressor to see what the accuracy looks like before you do any cutting at all.

 

[SmokeRolls]

Re: Horrible accuracy with one of my AR-15's

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: keithtb1</div><div class="ubbcode-body">Have you tried shooting it without the flash surpressor. Could be off and thats why your getting the shavings there. Just a thought.</div></div>
Whats up brother! Hows that 300 WM? Are you light'n the fires and kickin the tires?
Hope everything is well for you.

I don't believe the supressor is the culpret but I could be wrong. Nothing is being deposited inside the flash supressor, it's all at the very end of the barrel ( On the flat side just past the edge of the crown. The appearance of the deposites looks like someone brazed crap on the end of the barrel but it's not that, it just has the appearance of that.. That kind of stuff I know alot about, I'm a professional welder,brazer, silver solder guru..... Either way, I want to re-do the end of the barrel with a really good chamfer tool.......Now I just need the experts to weigh in and give me some advice. The bullet is not hitting the flash supressor though which I believe would rule that out.... Open to ideas though... Thanks for your imput.
SmokeRolls

 

[PMPerformance]

Re: Horrible accuracy with one of my AR-15's

You could also give it a go with some fine lapping compound and a brass ball in a screw gun..

 

[SmokeRolls]

Re: Horrible accuracy with one of my AR-15's

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body">I'm pretty sure you should be able to remove the crown crud by just letting the barrel sit in powder solvent overnight, just stick the entire muzzle into a snifter of the solvent for a few hours and then pick at it with a bamboo skewer to break the loosened crud off.

THen I'd suggest trying to shoot it without the flash suppressor to see what the accuracy looks like before you do any cutting at all. </div></div>
Point taken.....What brand of solvent are you recommending? Hops? Break Free? other? I don't want to use an ammonia based cleaner for greater than 8 minutes.
Once deposits are removed then I will take both of your recommendations on getting a group with flash supressor removed
Thanks for the imput, keep it coming.....SmokeRolls

 

[keithtb1]

Re: Horrible accuracy with one of my AR-15's

Gun is great. Best deal I've gotten on the net so far. I seriously would shoot that without the flash as my immediate first remedy. sounds like what your seeing is shavings from the jacket. Costs you nothing to do it. Good luck brother.

 

[bohem]

Re: Horrible accuracy with one of my AR-15's

Smoke-

I keep Hoppes #9 on the shelf all the time, but for something like this I'd probably take the rifle out to the shop and stick it in some Ed's Red. I don't think you need an ammonia based solvent for this.

The other thing you could do is get some WipeOut , wrap a sandwhich bag around teh muzzle and overfill the bore with the foam so it fluffs out the muzzle and soaks the area.

Probably any decent solvent should take care of you if you let it sit for a few hours.

 

[USMCj]

Re: Horrible accuracy with one of my AR-15's

The crud you speak of is a common occurance with AR15's. Its just carbon buildup, scrape it off it a dental pick or similar. You dont need to redo the crown.

 

[pwc001]

Re: Horrible accuracy with one of my AR-15's

If that does not help, I have an AR-15 16" E.R. Shaw BBL that would not shoot and got some Tubbs Final Finish bullets and loaded them up and shot them, I don't know what they did but it went from a 2" group at 100 yards to 3/4" group at 100 yards. I have not shot that gun much since then but it might help yours.

 

[300WSM]

Re: Horrible accuracy with one of my AR-15's

just soak it overnight then use some scotchbrite

 

[SmokeRolls]

Re: Horrible accuracy with one of my AR-15's

Thanks guys.... Does this build-up ever cause horrible accuracy? I have used two different optics on this rifle on this rifle (Both atleast $1,000-$1500) and I am lucky if it's 3 MOA, very easy to average 4" MOA group @ 100. If this doesn't fix the accuracy I will check the crown, then the barrel nut then the chamber..... I havn't used handloads in this rifle but I have used Hornady Tap ammo, Federal HP, Wolf, various different rounds....All with terrible accuracy.
Thanks again........SmokeRolls

 

[USMCj]

Re: Horrible accuracy with one of my AR-15's

If the buildup is enough to cause it to have a false crown, yes, it will hurt accuracy. After I scraped mine off, I did notice tighter groups.

 

[cz777]

Re: Horrible accuracy with one of my AR-15's

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300WSM</div><div class="ubbcode-body">just soak it overnight then use some scotchbrite </div></div> i would use ballstol for 3 days a bath -this works well use of Barrett bore cleaner as well! next look head spacing too..

 

[308sako]

Re: Horrible accuracy with one of my AR-15's

Deleted in protest

 

[SmokeRolls]

Re: Horrible accuracy with one of my AR-15's

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308sako</div><div class="ubbcode-body">While the crown should be inspected after a through cleaning, it is but one of many possible sources of inaccuracy. I struggled for almost a year diagnosising a Colt that in the end simply had a loose upper reciever to barrel extension fit. 'Bout drove me crazier... LOL.

Does the gas tube enter the carrier without contact? Take the bolt out of the carrier and the charging handle out of the upper. Run the carrier up and down and see how she feels. Then with the bolt back in, but not the charging handle, do it again. How does the fired brass look? Is the gas tube binding against the barrel nut... check all the known suspects of inaccuracy.

Please report back. </div></div>
I'll check all this out soon..... Will respond back on this another day and let you all know what I find out.... Thanks for the imput..............SmokeRolls

 

[Skunkeye]

Re: Horrible accuracy with one of my AR-15's

What ammo are you shooting? What twist barrel?

The reason I ask is a friend was shooting 40 grain varmint loads through a 1 in 7 twist barrel and experiencing horrible accuracy, some of the bullets were coming apart before hitting the target. The muzzle brake had copper/gilding metal debris built up to the point it was almost touching exiting bullets.

A good clean, and and switch to 69-77 grain ammo and the thing was shooting like a champ.

 

[Clark]

Re: Horrible accuracy with one of my AR-15's

I help other shooters at the range as well as help myself with my scores of beater gun projects.

50% of the time, accuracy problems are loose screws fastening the scope mount to the receiver.

But the scope mount is part of the upper receiver in most new AR15s, so your problem is more subtle.

AR15 accuracy problems I have seen:
Lands cannot be reached with bullet seated at tip of case mouth.
Ammo gets bent feeding from magazine.
Copper fouling
Rifle is too light

 

[KYS]

Re: Horrible accuracy with one of my AR-15's

We need more info.

This will have a lot to do with your bullet to barrel twist ratio. AND the quality and type of ammo you are using. Wolf will often wield you poor results and bad fouling. I would also recommend you let someone else shoot your rifle for you and see if they get the same results.

The person who sold you this upper should be questioned as well. You could have some fire cracking in the barrel but unlikely, they would have had to done some serious mag dumps and sustained high rates of fire for a few hours.

Who is the barrel manufacturer? Have you checked your scope mounts? The scope price doesnt matter, maker of the scope does. What are you using?