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View Full Version : Rifle keyholing after using 22 conversion


Nate87
06-26-2011, 5:09 PM
Here's the situation; My rifle has been used quite a bit since I got it. It's a LWRC M6A2. Up until recently it has been nothing but great. Accuracy and reliability outstanding. No issues.

About two months ago I did some accuracy testing with the rifle and was able to pull off MOA groups with 77grain blackhills match ammo at 100. Well the past two outings have brought to my attention that the rifle has started to keyhole on the targets. I initially noticed something was off when I was shooting at about 200 meters and my impacts were sporadic and not consistant. I then decided to head to the range to shoot on paper and see what was going on. At 25 meters you can clearly see the round is tumbling and impacting sideways on the target.

The only thing that has been different from when I did the accuracy testing to now is the use of .22lr conversion in my rifle. After the testing I purchased the conversion kit, put it in and fired away. In all I shot about 3500 rounds of 22 through my upper. The majority of the rounds used were standard velocity lead rounds and a little bit of the copper high/hyper velocity rounds.

So after the first trip to the range when I saw the keyholes on paper I figured it had to have been becasue of 22 rounds i put through it. There was some nasty build up and fouling on the flash hider as well as the crown of the barrel. I figured it was due to the crud on the crown that was throwing off the round and also all the lead fouling inside the barrel. I took it home and cleaned it all out. Took off the flash hider cleaned up the crown and cleaned the crap out of the barrel. Took it back to the range hoping it would shoot straight. NOPE! Still keyholing. This time at 50 meters but still the same results.

So my question is if any other members here have had similar experiences. Or if the use of a 22 conversion will accelerate the wear on the barrel or if anyone has any ideas on what is causing the keyholing and how to fix it. One thing I will mention is that the rifle has around 20,000 rounds through it. I know that's quite a bit and is coming up on the time to rebarrel the rifle. But like I said, it was shooting great a few months ago and it was at about the 18-19,000 round mark. The only thing different was the use of the 22 kit from then to now.

Any help or ideas would be appreciated. I know everyone will say it's time for me to rebarrel the rifle after 20,000 rounds and that's probably what I will do but the main thing I want to focus on is the effect on the rifle thats caused by the 22 conversion.

Nate

missiontrails
06-26-2011, 5:20 PM
Maybe something to do with the lead......

Army
06-26-2011, 5:42 PM
The first eight or so inches of your barrel is totally leaded over from the .22's sliding before engaging the rifling. Basically, you have no rifling for the centerfire bullets.

Conversions are smoothbore until the end of the chamber insert. The .22 has too much speed to immediately engage and spin from the rifling, so it gets swaged down and strips lead. The lead fills the grooves, leaving no room for jacketed bullets.

Pressure does go up BTW, so always scrub the bore very well after conversion firing to remove the built up lead.

ZedOddSix
06-26-2011, 5:53 PM
Total shot in the dark here but missiontrails might be on to something. Does the depth of the rifling look normal? Could the lead from the .22's partially filled them in decreasing their bite?

ZedOddSix
06-26-2011, 5:54 PM
I just got out typed. Lol.

Nate87
06-26-2011, 5:58 PM
The first eight or so inches of your barrel is totally leaded over from the .22's sliding before engaging the rifling. Basically, you have no rifling for the centerfire bullets.

Conversions are smoothbore until the end of the chamber insert. The .22 has too much speed to immediately engage and spin from the rifling, so it gets swaged down and strips lead. The lead fills the grooves, leaving no room for jacketed bullets.

Pressure does go up BTW, so always scrub the bore very well after conversion firing to remove the built up lead.

Thats what I was thinking. That the softer lead filled in the rifling and smooted out the bore a little. I used some Bore Tech as well as Wipeout foam to clean things out. Scrubbed a little with the copper brush but I guess I'll give it another go and scrub some more.

r6raff
06-26-2011, 6:24 PM
20,000 rounds and you could still shoot MOA at 100meters? I say that is good and call it a day, retire that poor barrel of yours. Sounds like Army has hit it on the head. I have heard of similar things in the past and think that is why most people say to fire some .22 and finish the day burning down some 5.56 through the barrel to clear out the lead deposits. Looks like you may have figured out why those guys recommend that.

I have always been leery about using a conversion bolt to shoot .22 out of my ARs, I really want to, but haven't heard the best things, both regarding weapon consistency and bolt conversion functionality.

I must say, again, shooting MOA close to 20k rounds to me seems very impressive, I have over 8k rounds down my BCM and it still shoots MOA but I cant imagine putting 12k more rounds through it and still shooting the same. Maybe I am just under estimating the capabilities of the weapon.

Either way, I think its time to retire that *****, give that LWRC a shiny new barrel :p

Nate87
06-27-2011, 5:10 PM
Thanks for the info. I guess it's time for a shiny new barrel anyways. Just sucks that it seems the barrel life was cut shorter than what it could have been. I'll be sure not to use the 22 converstion in the next barrel and only in my dedicated 22 AR. But I will try and salvage it before getting it rebarreled to see if I can squeeze some more life out of it for a little longer.

r6raff
06-27-2011, 9:54 PM
Thanks for the info. I guess it's time for a shiny new barrel anyways. Just sucks that it seems the barrel life was cut shorter than what it could have been. I'll be sure not to use the 22 converstion in the next barrel and only in my dedicated 22 AR. But I will try and salvage it before getting it rebarreled to see if I can squeeze some more life out of it for a little longer.

What kind of groupings are you getting now? Sorry if I missed it in your previous posts. I'd say shoot it until you cant tell where its hitting LOL, seriously though, if you are a perfectionist then swap it, if you enjoy tagging 12" steel plates at 100-200 meters and its still good then your good to go. That or continue using it for .22 considering the loss of rifling in the early stages of the barrel may not effect the .22 as much as the 5.56...

I would keep shooting it to be honest, and see how many rounds I could get through it until it was completely worthless. But I almost exclusively shoot steel and only shoot paper ever thousand rounds to check my groupings. If I pull the trigger and it goes bang, then ping I am happy.

xxINKxx
06-27-2011, 10:00 PM
Your about 5k rounds past the average life of that barrel. I would be happy. 20k is damn good. At least barrels aren't too expensive.