Troubleshooting

slimjim · Posted: Sat Sep 15, 2012 8:15 pm Post subject: Troubleshooting

I'm making some progress on my new AR build in 6.8. Accuracy hasn't been the best so far. Got some groups under 2 MOA this third time out. A concern is the brass is forming with an indentation. Do you think this is an irregularity in the chamber wall? Should I be concerned? This is factory Hornady brass, once fired with 110 HPBT.

Elvis · Posted: Sat Sep 15, 2012 9:13 pm Post subject: Re: Troubleshooting

the dents are 45 degrees across case??see if you can bore scope the chamber to find the cause. it could be my eyes or the photo but those cases the top one and one 4th from left look as crooked as all heck eg not at right angles to the base??

DallanC · Site Admin Joined: Jan 18, 2005 Posts: 3572 Location: Utah

Its either a malformed chamber or a very dirty one. Try cleaning it first... with some *MILD* abrasive. If it still persists you might want to consider a chamber casting.

-DallanC

Elvis · Posted: Sun Sep 16, 2012 12:07 am Post subject: Re: Troubleshooting

looked again and got another set of eyes to look aswell. that 1st case looks like case mouth is not at right angles either. whats the story morning glory???

Ominivision1 · Posted: Sun Sep 16, 2012 1:32 am Post subject: Re: Troubleshooting

Those shells look exactly like the ones a shooting buddy bought over for me to look at. He was firing wolf steel cased ammo which has some kind of coating on them and he then fired some of his handloads which looked like yours.

Clean the chamber and barrel first.

slimjim · Posted: Sun Sep 16, 2012 3:51 am Post subject: Re: Troubleshooting

Elvis wrote:

it could be my eyes or the photo but those cases the top one and one 4th from left look as crooked as all heck eg not at right angles to the base??

Its the camera lens, Elvis. Your eyes are fine. Its an inexpensive digital camera I picked up on vacation. Get much off the center of the image and there is noticeable distortion. I had to adjust the angle of camera to get the light right and the cases ended up off center in the image.

slimjim · Posted: Sun Sep 16, 2012 3:52 am Post subject: Re: Troubleshooting

Ominivision1 wrote:

Clean the chamber and barrel first.

Ok, clean the chamber first. Maybe use some mild abrasive.

But for the sake of discussion, so what if it remains? Is it an issue? I had an M1 with a tooling mark in the chamber and it was affecting extraction. Extraction on this one is the best of any of my ARs. Its the accuracy that is concerning me. It started out at 3 MOA the first two times out. I've been measuring and inspecting every little thing I can find. This third time out (with about 60 rounds already through it) it seem to settle down and was shooting 1 1/2 to 2 MOA. With some more adjustments, there might be some light at the end of the tunnel.

Vince · Posted: Sun Sep 16, 2012 5:02 am Post subject: Re: Troubleshooting

Dallan hit it Slim...do a chamber cast. If there are any problems in the chamber this will highlight them.

I would be loathe to take an abrasive to the chamber for two reasons...#1 an abrasive takes of metal and unless done very carefully you could end up with worse problems, and #2, if the problem is a warranty issue, then they would not honour the warranty if they can see that you have had a go at fixing the problem yourself.

Cheers, Vince

MacD · Posted: Sun Sep 16, 2012 5:37 am Post subject: Re: Troubleshooting

My only suggestion is to mark a casing before firing with felt marker. Load the round with the mark at 12 oclock and then inspect the fired case to locate the deformation relative to the mark. This will identify the suspect surface area in the chamber. The chamber cast is the best tool. This will allow measurement of roundness, taper and that the axis is true. If it isn't dirt I suspect the boring or reaming was botched. The deformation looks like a twist.

TRBLSHTR · Posted: Sun Sep 16, 2012 9:32 am Post subject: Re: Troubleshooting

Hi SJ;I'm not an expert in ar's but have built several and done some tuning on them-so take this with a little salt.#1 less than 200 rounds thru an ar is hardly break-in time on the barrel and action,#2that dent looks like it could be an ejection mark-like maybe where the brass could be hitting the top of the ejection port on the way out?#3 one way to prove if it is the chamber is to remove the gas tube and plug the hole in the gas block(so you don't get blowback in your eyes,and you turn your ar into a bolt action-then you can manually load /shoot/eject and inspect cases.Hope this is some insight. Very Happy

Suzanne · Posted: Sun Sep 16, 2012 10:20 am Post subject: Re: Troubleshooting

Just what I was gonna say.....(no really) remove the gas so you can chamber one round and eliminate the ejection question. I don't actually see how it could hit at such an angle, but I wonder if you added anything to the original extractor (like stronger spring, or D-ring, O-ring or spring buffer) if so, you might have too much extraction? I dunno, just a guess. Personally I'd check the extraction issue first because I'd think you would be able to see a chamber deformity making a dent that obvious.

Suz

Ominivision1 · Posted: Sun Sep 16, 2012 11:52 am Post subject: Re: Troubleshooting

Boy my eyes must be getting bad because I took Slim's pic and enlarged it 500% and cannot see any indentation. If there is, definitely check your chamber and take pics using the macro mode and also be aware like Troubleshooter and Suz said that the brass might be hitting the deflector.

Here is an example of bad chambers on ar15's

slimjim · Posted: Sun Sep 16, 2012 12:11 pm Post subject: Re: Troubleshooting

I have a DPMS upper without a deflector. I should be able to mark the case as MacD suggested and not have to fool with the gas tube. I definitely will give a good cleaning and inspection before I go out again.

slimjim · Posted: Sun Sep 16, 2012 12:14 pm Post subject: Re: Troubleshooting

Ominivision1 wrote:

Boy my eyes must be getting bad because I took Slim's pic and enlarged it 500% and cannot see any indentation.

OV1, its there. I resized them and the indentation remained like a hook up near the shoulder. I should be able to take picture of my chamber like you suggested with my digital camera. I'll wait to see if it returns after a good cleaning.

Elvis · Posted: Sun Sep 16, 2012 11:33 pm Post subject: Re: Troubleshooting

slimjim wrote:

Elvis wrote:

it could be my eyes or the photo but those cases the top one and one 4th from left look as crooked as all heck eg not at right angles to the base??

Its the camera lens, Elvis. Your eyes are fine. Its an inexpensive digital camera I picked up on vacation. Get much off the center of the image and there is noticeable distortion. I had to adjust the angle of camera to get the light right and the cases ended up off center in the image.

phueew pleased about that Embarassed

I thought about ejection but those marks in my experience would be on case mouth, my buddy had a .223 that started out as a .222 and the chamber left marks on the cases where the chamber was recut, otherwise it was fine.
you will get it sorted it may just take a little time. Very Happy