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Posted: 7/16/2010 6:44:40 PM EDT
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i recently bought a cmmg stainless conversion kit. i tried it in my buddies ar-15 (BCM midlength 16" 1/7) for the first time and we experienced an unusual problem. we plugged it in and it ran like a top with zero malfunctions from the first to the last round of a brick of winchester 36grain high velocity ammo. i was pleased untill i went down range to see bullets key-holing. the only explanation i can come up with is that 1/7 is so so much overkill for a 36 grain bullet that the rifling just stripped off a layer of lead from the bullet. we had a blast but now my friend is having trouble getting the ass load of lead in his barrel. has anyone experienced this problem? what's the best way to get tons of lead out of a barrel? and will 40 grain bullets have the same problem in the same barrel? my carbine has a 1/9 twist so i'm not worried about the same problem for myself, i would however like to know how to share my kit if need be. thanks,
Colt T |
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I shoot my CMMG kit in my 1/7 CMMG upper, and I haven't had any leading problems. I try to shoot 5 or 10 rounds of .223 every 250 rounds or so of .22LR. I then clean the barrel with a patch soaked in Hoppe's #9.
I suppose a good scrubbing with a bronze bore brush and a good lead-removing slovent would take care of any lead in the barrel. |
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Aguila 60 gr SSS Rounds will help too if you can stand the smell of burning Camel Shit. They are very accurate
in a 1:7" twist. If you were using Lead 22's, you could use only copper washed bullets they make a lot less mess. Winchester 333's, 555's, CCI Mini's, Federal Bulk from WalMart are good starting points but are still 36-40 grain bullets. Many people shoot a few .223 / 5.56mm rounds after 500 to 1000, 22's. I haven't had a problem with leading. I shoot only copper washed bullets from conversions for the most part... The SSS is lead though. Good Luck, Dave |
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Same here. I only shoot copper washed. After about 300 rounds of .22 I run a Boresnake and fire 5 rounds of .5.56. When I get home I give the rifle a good cleaning. Have not had any problems.
Is the Winchester Copper Washed? I use the Winchester 333 and 555 bulk. Best bulk I've used in a while. Dave |
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Quoted:
I have never had leading issues with copper washed/plated .22LR ammunition like the Win 555/333 bulk rounds - which I agree is also very accurate and very reliable.
I agree, shadowcop. The Win 333 stuff shoots very nice in my Marlin 60, my CMMG kit, and my Ruger MKIII. I do run a .223 round through any .22LR converted AR's every 1000 rounds or so if I have not put any .223 through them in the interim, but it is more prevention than anything else as I have never had a plugged gas port. I do clean the barrells well after each .22LR shoot and before putting a .223 round through the barrel to avoid ironing in any lead fouling. –––– Most conversion kis advise against hyper velocity ammo, and the slower the twist the better. I get great accuracy with1/12 twist barrels, ok accuracy with 1/0 twist barrels, and comparatively poor accuracy with 1/7 twist when shooting .22 LR. –––– With a .223/5.56mm barrel, you have a bore designed for .223 rather than a .22 LR. WIth a .22 LR the bore wil have a bore diameter of .222 and a land diamter of .217 or .218 - in both cases about .002 tighter than a .223 bore. Also, in a .22LR conversion klt, the bullet is fired in the conversion unit and then travels an inch or so before entering the rifling. In essence, it enters with a significant amout of velocity and inertia and then has to begin spinning in rifling that is much faster than the 1/16 twist that is optimum for the average 40 gr .22 LR load, and the bore is .002 larger than optimum. The end result can be the bullet skidding into the rifling before it starts to spin. If you shoot one into a 5 gallon bucket of water, you can recover the bullet and examine it. Ideally you should see sharp, parallel rifling marks on the bullet that are ven in depth fore and aft and on all sides of the bullet. If the bullet is sliding into the bore for any significant distance you will notive the rifling marks are wider at the base of the bullet as the leading edge of the rifling will cut straight back on the bullet before it starts to spin and that mark will remain near the base of the bullet (the same thing can happen in rimfire and cetnerfire revolvers and is an indicator that a bullet was fired from a revolver rather than a pistol). Worst case, you may see lead smears and no distinct rifling, indicating the bullet is stripping in the bore before it spins. The rifling may also not be even all the way around the bullet or fore and aft in a rifling groove on the bullet. That suggests the round is not entering the barrel straight and that will have an adverse effect on accuracy. |
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