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copper fouling

23 Dec 2011
@ 04:52 pm (GMT)

tim charteris

hi there

ive been trying to get my browning x bolt to shoot
but have found that im not getting any fouling after 40 rounds since the last clean i would have put maybe 100 -150 rounds through the rifle and im getting groups any were from .5 up to 3 inches but it seems to throw a flyer to the right some times making sub moa groups into 3 inch groups
my load is laupa brass with fed primers and 44.5 grains of ar2206h and 168 gr a max and not getting to much pressure the rifle has factory bedded wooden stock and a free floated barrel
could the lack of fouling and the ramdom groups be caused by an over sized bore

cheers tim


23 Dec 2011
@ 05:52 pm (GMT)

tim charteris

Re: copper fouling
hi there again
so i was puttin the gun away but decided to check the bedding and after playing around found that the front action screw when done up tight gose through the action and hits the threaded part of th barrel is this normal cause it dosent seem right the stock seems tight but would i be best to take the screw down a bit buy grinding some of the end

cheers tim
26 Dec 2011
@ 07:53 am (GMT)

Nathan Foster

Re: copper fouling
Hi Tim, the front king screw should definitely not be bottoming out. This may well be the cause of your wide fliers.

You have two choices, either grind 40 thou / 1mm of the king screw and re-chamfer it, or if you want to re-bed the rifle, you can use the fresh bedding to lift the action up a tad and create the clearance needed. To determine whether this may be beneficial, check the current bedding to see how well it is adhering to the stock. Typically, the Browning and Winchester bolt action rifles have been given a squirt/blob from a hot glue gun in the area of the recoil lug. The stock is not keyed into or prepared in any way. Over time, cleaning solvents and oils attack this weak layer and accuracy is lost, usually at the most inconvenient of times. So check the bedding carefully with each dis-assembly / reassembly.

The bore may well be slightly oversize or, a more common occurrence of late is button chatter marks within the bore, resembling what looks like the threads of a bolt. This is caused by vibrations during the buttoning process and can be as a result of the use of inferior lubricants along with a host of possibles. The peaks of the chatter marks will be within tolerence, the troughs being over size. The projectile then rides on the peaks, obtaining very good accuracy without fouling while pressures remain very low. However; after a period of time and wear, as the peaks of the chatter marks are worn down, groups open right up. This is very common on Savage rifles and is, as of 2011, something I am seeing within Japanese bores.

On the other hand, the over all tolerneces may well be loose, it is hard for me to determine without having the rifle here.

The 44.5gr charge is usually fine in U.S made .308 rifles but not so for the Brownings as these are usually machined to tighter specs, the sweet spot being around 43 grains for 2670-2700fps (22" barrel). So there is definitely an element of lower than normal pressures there somewhere.

For now, I think we need a step by step plan of attack. What I would like you to do, is grind the king screw back a touch, just enough to relieve it. Try it at the range and see how it goes. The rifle may well settle right down. Better to do it this way than to go through the hassle of a proper bedding job, then find the bore has a problem.

When cleaning the rifle, I want you to listen for a whistling sound when using either a ram rod or pull though. If you hear this sound (also sounds like running your fingers across a pitched tent), the bore has chatter marks and the bullet will indeed be riding on peaks.

Merry Christmas, Nathan.

23 Apr 2012
@ 11:30 pm (GMT)

Cade Sutton

Re: copper fouling
Interesting - my Browning .223 tube doesnt seem to be producing copper fouling at these early stages - about 120 rounds through in total and no sign of blue goo after using Sweets...... Scary


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