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Posted: 6/6/2014 8:55:19 AM EDT
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Ok, I have had the bolt replaced once already and upon firing it again I am getting same results. So, here I am trying to see if anyone else has had these issues and what the solution was.
The gun is a 300 blackout pistol with a pistol length system so very short gas tube and short barrel. The ammo I am using to test with is Remington 220 grain subs, Remington 125 gr Match and Hornady 110 gr vmax. The first time I fired the gun the bolt looked almost the same only a lot heavier on rust/burnt looking residue on rear of bolt. Upon cleaning with some steel wool and Hopps cleaner it looked like melted copper was on the back of the bolt so I had the entire carrier/bolt replaced. I took pictures before shooting it, since it had been test fired from manufacturer and pictures after. It looked a little better but not much. Once again I cleaned with some fine steel wool and solvent cleaner to remove rust/burnt areas and was once left with what looks like melted copper on the rear of bolt. I am considering just replacing the bolt with a NIB bolt but don't want to be masking a problem if there is actually one. Is this simply the characteristic of a pistol length gas tube where I am guessing the temps are much higher that are being introduced onto the bolt versus a carbine length? Here are some pictures: Before shooting Before Pic 1 After Shooting After Shoot 1 After Shoot 2 After Shoot 3 After Cleaning, it even appears some copper is on the gas rings themselves. After Cleaning 1 After Cleaning 2 Any help would be appreciated. The gun fires all ammo fine and without a hitch. Ammo |
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Otis BONE Tool. Great little doohickey for cleaning bolt and carrier. What's the bore of the barrel look like? I just bought a barrel that had loose rust in it, probably from being stored in a humid warehouse where the metal shavings in it were able to rust quick. Good thing I cleaned the bajeebus out of it before I put anything down it. |
| I highly doubt what is encrusted on the bolt is copper, and don't throw away the original bolt because there is nothing wrong with it. what kind of lube are you using and how much do you apply? I suspect the short gas tube is getting a full load of fire and it is cooking your lube. try a shot or two with a dry bolt, see if it makes a difference. |
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It's not copper. It's rust from the iron you deposited on the carbon deposits by using steel wool.
Btw. For that reason and because steel wool is an abrasive, it's a huge no no for cleaning guns. Get proper tools. I mean shit man your basically cleaning the thing with sand paper from a functional standpoint. |
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Quoted:
It's not copper. It's rust from the iron you deposited on the carbon deposits by using steel wool. Btw. For that reason and because steel wool is an abrasive, it's a huge no no for cleaning guns. Get proper tools. I mean shit man your basically cleaning the thing with sand paper from a functional standpoint. Hate to tell you this... But wrong answer... It IS Copper. I work for an AR Manufacturer and I've been doing a LOT of testing short barreled 300 Blackout uppers as well as 16". It would appear that the fact that you have to enlarge the port on the barrel to get 300 Blackout to cycle is the root of the cause of this. That's the only conclusion I've been able to come to. I had an 8.1" barrel that had a port that was 0.125" and it threw massive amounts of copper on the back of the bolt. So much that it finally hindered the bolt enough to cause malfunctions. I've since found that even when the port is smaller, it's still larger than a 5.56mm port and the projectile is still engaging the bore with more surface area and going slower than 5.56mm so the problem has not gone away... Just become less. The only method I've found for cleaning it off relatively quickly is a wire wheel on a Dremel or bench grinder. I know that current conventional wisdom is that Pistol-length Gas Systems are more reliable for 300 Blackout but I'm starting to think that Carbine-length with the proper sized port may be the answer. The testing continues... |
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Your using the wrong solvents to clean and lube the gun.
Sweets copper solvent to clean the copper in the bore out (works fast without the need of a lot of scrubbing), then CLP to clean the rest of the gun, including the chamber with a chamber brush and CLP. To lube, lube the upper receiver bearing parts with CLP, including the B/C inside and out. CLP has a cleaning agent that works both during cleaning (let the CLP sit on the parts for a few mins and the fouling will wipe right off), and while you are shooting to gun to prevent fouling build up as well. If you need a source for CLP, then BreakfreeCLP in the large spray can. |
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Quoted:
Your using the wrong solvents to clean and lube the gun. Sweets copper solvent to clean the copper in the bore out (works fast without the need of a lot of scrubbing), then CLP to clean the rest of the gun, including the chamber with a chamber brush and CLP. To lube, lube the upper receiver bearing parts with CLP, including the B/C inside and out. CLP has a cleaning agent that works both during cleaning (let the CLP sit on the parts for a few mins and the fouling will wipe right off), and while you are shooting to gun to prevent fouling build up as well. If you need a source for CLP, then BreakfreeCLP in the large spray can. You can try all the cleaners and copper solvents you want. I've tried all of them. The copper coating on some of the Bolts I've tested (Nickel Boron included) is fused to the Bolt and is so thick that when you use a wire wheel to try to brush it off it initially looks like a copper nugget that was welded to the Bolt. |
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Soak the bolt parts in CLP to let the cleaning agent do it thing (read clean the barrel while the B/C parts are soaking), in about 4 mins, you can flick any copper or fouling solids off the tail of the bolt with your fingernail. I will certainly give that another try. Thank you. |
| from reading one shot one kill's post, it looks like the reason that copper is getting deposited on the bolt is because of the size of the gas port in the barrel for the gas system to work. the edge of the gas port is shaving the bullet and the hot gas is welding the copper to the bolt. thanks for the insight one kill. |
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