Burr from flash hole .DPMS 5.56 barrel

[hogginhank]

I am new to the AR platform scene and I have a couple questions. I recently put a new 20" DPMS 1:9 twist 5.56 on my bushmaster. Before I shot it I did the standard cleaning in the tube and felt the patches sticking. My buddy that is very familiar with AR's, assembled the gun for me and was with me when I was doing the initial barrel cleaning. I looked down from the muzzle(bolt out and unloaded ofcourse) and with my bore light shining from the chamber I could see a little burr where the flash hole was drilled. I asked him if he had ever seen this and he said that after owning multiple AR's and helping people build up AR's that he had never come across a burr from the flash hole. I ran a brush through the barrel a few times and the burr was gone. I finished cleaning it but could still feel a little bump when passing a patch. I got the barrel from midway and if I would have known their policy I wouldn't have shot it and just sent it back. Well I shot it and ran about 40 rounds of american eagle ammo through it and then started working up some loads. It seems really picky and I have tried a number of powders/bullet combinations and it just doesn't shoot as good as I would like. My problem is that the 55 gr noslers with H335 shot pretty well so I loaded up 30 of them for hunting. It will shoot that load very different on every trip to the 100 yard range. Let me explain so you can get an idea of the issues I am having.. I can shoot a 5 shot group and the first 3 are .7" and it will throw 4 and 5 up and inch and a half and over to the right an inch and a half. I shot this load last week and had a 1.5 inch group. I shot a couple days later, same conditions, and my groups were around .58"

I know this is a long post but bear with me. I'm trying to paint a picture for ya'll so you don't think I just started shooting and reloading last week.

Rings, delta ring and everything else was tight and nothing was found loose. At this point I have had a couple of shooting days with the gun and I am now on at least 200 rounds down the barrel so I would think it's probably broke in and the rough spot should be a tad bit smoother???. Yet everytime I clean the barrel I still feel a little bump when I pass a patch passed the flash hole..I even put a different leupold on it to rule out scope issues and had the same results.

I spoke with Mark at DPMS and he said that I could ship it to them and they would shoot 5 different factory ammos with 5 shot groups and if it didn't shoot to their spec then they would replace the barrel. Well I shot a few groups with 2 different Hornady ammo and Fed premiums all in 55 gr and I got 1.9" groups with 2 of them and a 1/2" group with the 3rd. I tried it again and I got .9"-ish groups with the ammo that shot at almost 2" groups and the stuff that shot 1/2" printed a 5 shot group at 1.3". I am very concerned that if they shoot this gun they will get lucky and print a couple groups that are in "Their" spec and I'm stuck with a barrel that will shoot good "Sometimes"?? Mark mentioned that if they shoot the first 2 brands of ammo and it is in spec than they stop their test and send it back..If not they shoot all 5 brands and then make their assessment.

Shouldn't they do something about the "Bump" at the flash hole regardless. This can't be good for accuracy???.. I am hesitant to even send it in because I always seem to have the worst luck with stuff like this. I asked about the burr and had a number of questions but he was still focused on letting me know that they don't condone reloaded ammo and their tests would be from factory ammo??? Custom loaded ammo from and experienced reloader should result in at least ONE load that a "Particular" barrel will like..Still scratching my head???

Has anyone ever had an issue with a burr from the flash hole affecting accuracy and specifically a DPMS barrel?

I'm not bashing DPMS because they were helpful on the phone and I haven't actually started dealing with them on this "Issue". I will shoot some more tomorrow and see what results I come up with and make a decision on sending in my upper for them to test.

Sorry for the crazy @$$ long post..It's just kind of hard to paint a picture by typing..I have reloaded for a long time and shot a good amount as well incase ya'll are wondering if I was just launching rounds down range with a red hot barrel or something stupid. I tested all the loads with common sense and tried to rule out everything I could and I'm leaning towards the flash hole??

Thanks in advance for anyone that actually FINISHES

reading this long post and has any input or advice..Hank

 

[madcratebuilder]

Re: Burr from flash hole .DPMS 5.56 barrel

Odds are good any 'burr' at the gas port well be gone after the first two or three rounds.

 

[RuLins05]

Re: Burr from flash hole .DPMS 5.56 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: madcratebuilder</div><div class="ubbcode-body">Odds are good any 'burr' at the gas port well be gone after the first two or three rounds. </div></div>

Yup, I've seen them before and after shooting I don't notice any hindrance compared to other barrels I've used. Are these groups being shot in prone or...More info on how the rifle is being shot would be helpful

 

[hogginhank]

Re: Burr from flash hole .DPMS 5.56 barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RuLins05</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: madcratebuilder</div><div class="ubbcode-body">Odds are good any 'burr' at the gas port well be gone after the first two or three rounds. </div></div>

Yup, I've seen them before and after shooting I don't notice any hindrance compared to other barrels I've used. Are these groups being shot in prone or...More info on how the rifle is being shot would be helpful

</div></div>

Well that makes me feel better.Can you "Feel" the flash hole when you clean your barrel? I guess this just freaks me out. I have been shooting for over 30 years and have been reloading and messing with guns for the last 25 but my experience is limited to bolt guns mostly so these black guns, though very simple in function, have got me scratching my head a little.

I am shooting off of a heavy wooden table that has it's 4"x4" legs cemented. I have an old bench rest tripod( I think it's a Lyman??) with a leather pad and my rear bag is an old leather bag I got from a bench rest guy in the late 80's.

My scope is a Weaver Grand Slam 6x20x44 with AO and Tally rings. I have replaced my 11 1/2 lb trigger with a regular ols single stage trigger that I deburred and polished as well as put in the JP enterprise spring kit and it is pretty crisp and smooth at about 4.5 lbs.

My loads are done with serious OCD and I use an old bench rest powder measurer ( H.L. Culver) so it is a breeze to load up all my rounds with precise loads. All brass is trimmed to the same length, same primers on all bullets in my test groups and not even enough runout on the loaded ammo to see it on the runout guage. All groups are shot and I let the barrel cool. Heck, that fat barrel doesn't even seem to get very warm even after a few groups are shot.

I have never tried the prone shooting before and I don't have a bi-pod(yet) for this AR. I wish I could tell you more but I'm still kind of stumped.

My gunsmith asked me a few questions and I forgot to mention the "Test" he told me to try....He asked me what power I was shooting on and I told him 20X. He said that after shooting at that high power for a while that people sometimes are so focused on the target that they aren't really fucusing on the center of the crosshairs?? I am new to the hight X settings since the highest X I have ever used before was with my leupold 4x12. So I only had 6 bullets left of the load I had worked up that shot pretty good. I'm still not sure if this is my issue and I will have to shoot a few more down range to confirm it but the 5 shot group at 10X had shot 1,2 touching...#3 hit about 3/4" from the first 2 and shots 4 and 5 hit touching the first 2 shots?? Is this all "Me" or WTF??

My parralex is set correctly and with all the "Human" factors figured in I think I am shooting my groups pretty much the same way for all the shots fired. Granted everyone pulls a shot once in a while and I know when that happens and I note that on my pad at the bench as to which shot I think I pulled.

I forgot to mention the magnification "Test" I tried because I was hoping to get out this morning and shoot some more reloads and see if I could duplicate my findings and get smaller groups with a lesser power setting on the scope?? I guess I will try that on Tuesday and get back with ya'll. I hope I answered a few of your questions?? I know its hard to diagnose someone elses problems via the internet but with any luck one of ya'll have had a similar issue and you can shed some light on this or give me a few pointers on how to rule out a couple more things.. Thanks a ton for ya'lls time and input..Hank

 

[BCP]

Re: Burr from flash hole .DPMS 5.56 barrel

It sounds like your rifle is shooting fine and the problem is something you are doing technique wise combined with a little parallax error.

 

[hogginhank]

Re: Burr from flash hole .DPMS 5.56 barrel

I'm going to try a few more test groups at the lower power setting and do some at 20X to compare them. I have the scope dialed in where it is paralex free. Guess I will just have to put some more time in at the range..This gun give me a fricken headache

 

[Outsydlooknin75]

Re: Burr from flash hole .DPMS 5.56 barrel

complaining about 3/4 moa out of a FACTORY AR?

 

[stinkyDrunk]

Re: Burr from flash hole .DPMS 5.56 barrel

Blow 200 rounds of blasting ammo through it. Then forget about it and enjoy your new rifle. Life is too short to be OCD about everything, especially a DPMS barrel.

 

[hogginhank]

Re: Burr from flash hole .DPMS 5.56 barrel

The problem is that it shoots 3/8" , 5/8",3/4" and up to 1.5" groups with the same ammo with the same outdoor weather conditions and the same methods of shooting. And I didn't just start shooting last week so it's not like it's my first rodeo at the bench. I am at about 280 rounds down the tube so it should be broke in. Anyways, thanks to all that gave me some input. I appreciate it. Hank

 

[bowslngr]

Re: Burr from flash hole .DPMS 5.56 barrel

Sorry if this strikes a sore spot, but if the rifle will shoot half inch groups (especially more than once) then the problem is not with the rifle. More than likely it is due to inconsistancy on your part. You mentioned that you are new to the platform. Little differences in your pressure points (cheekweld, trigger pull, vertical handgrip) can have noticeable impacts.

 

[hogginhank]

Re: Burr from flash hole .DPMS 5.56 barrel

Thats some good info. I do recall holding the stock a little firmer against my shoulder on one of my best 5 shot groups that were fire a little faster than I normally fire so I guess I kept my form the same. I guess I will get back out to the bench and do some "Shooter" tests to see what I m doing different. I need to let my buddy shoot as well(he shoots the AR's a lot) and see how it shoots for him. Thanks for the ideas folks..Hank

 

[hogginhank]

Re: Burr from flash hole .DPMS 5.56 barrel

Well I went back and looked at a number of the groups I have logged in my binder for my AR and I noticed that when I shot 3 or 5 shot groups without changing my hold on the gun that my groups were .5" on average?? I compared the groups to the ones where I shot, marked the shot on my spiral, wrote down the chrony data and got back on the gun for follow up shots and my groups grew. I tested this again and shot 5 shot groups while keeping the same hold on the gun for each shot and not looking away. I was happily surprised at my .5" and less groups but at the same time scratching my head?? I guess I need a few pointers on shooting this AR. I have been shooting bolt guns for a number of years but I'm starting to figure out that I must be doing something different between shots with my hold if I can cut my group sizes in half, if not more, when I stay on the gun a fire the shots one after another without looking up or messing with stuff?? I guess I need a few tips on how some of you avid AR folks go about staying consistent when you shoot the crazy @$$ black guns. Thanks in advance for any input. Hank