grappling_hook
WKR
Some very interesting information here, and I'm glad the thread moved so far from barrel break-in.
A bullet moving at 3500 fps with extraordinary heat and pressure behind it does no damage whatsoever to the crown, yet somehow a brush pulled back through causes damage? BSI haven't read the whole thread so apologies if it's been covered, but saw the barrel cleaning procedure from Bartlein on the first page. I recognize that they know more about barrels then I ever will, so there must be a reason. But can a nylon brush really damage the crown? It seems like you'd have to push/pull the brush through an incredible amount of times for it to have any effect?
From Bartlein:
"If you use a brush, we recommend one caliber smaller or an old worn out one. Roll a patch around the brush. Always push the brush, Breech to Muzzle. Remove the brush before pulling your rod back through! NEVER pull the brush back over the crown. More damage to a good barrel is done from cleaning than actual shooting. The first to suffer is the crown. The crown is the last thing the bullet touches when it leaves the gun. Any damage here affects accuracy no matter what."
I, think, and it makes sense, is that potentially carbon deposits can get in to the bristles and cause damage by pulling the brush back through the barrel. There are probably other factors but I can see that as being a concern.I haven't read the whole thread so apologies if it's been covered, but saw the barrel cleaning procedure from Bartlein on the first page. I recognize that they know more about barrels then I ever will, so there must be a reason. But can a nylon brush really damage the crown? It seems like you'd have to push/pull the brush through an incredible amount of times for it to have any effect?
From Bartlein:
"If you use a brush, we recommend one caliber smaller or an old worn out one. Roll a patch around the brush. Always push the brush, Breech to Muzzle. Remove the brush before pulling your rod back through! NEVER pull the brush back over the crown. More damage to a good barrel is done from cleaning than actual shooting. The first to suffer is the crown. The crown is the last thing the bullet touches when it leaves the gun. Any damage here affects accuracy no matter what."
I call BS back! The amount of damage we see and the one part of the barrel that takes the most abuse that we see is the muzzles crown. Not just pulling a brush back over the crown but when guys drag a steel rod over the crown as well.A bullet moving at 3500 fps with extraordinary heat and pressure behind it does no damage whatsoever to the crown, yet somehow a brush pulled back through causes damage? BS
I call BS back! The amount of damage we see and the one part of the barrel that takes the most abuse that we see is the muzzles crown. Not just pulling a brush back over the crown but when guys drag a steel rod over the crown as well.
Can't tell you the number of barrels over the years...that all I did for the customer was recrown it and the accuracy was fixed/came right back.
Yes it's been argued....the bronze brush is 80 on the BHN scale and the barrel is 280ish. So yes the steel is harder...but as the old saying goes...why can water erode rocks! The water is softer than the rock so how can it be? One is repetition. Also the hard carbon particles can get trapped in the bristles...the hard carbon particles will also scratch the bore as well. I see signs of it all the times. You will see faint/slow twist marks going over the tops of the lands. This is from the bristles of the brush and or rod drag or a combination of both.
Goes back to the picture I also posted of the damage to the bore done with an abrasive cleaner. The abrasive cleaner in conjunction with the brush will amplify what is going on.
Also goes back to what I say....if you have a system/procedure you use to clean the gun and your not wrecking anything...I've got nothing to say. Also it doesn't mean the guy next to you is doing it better.
Also heat and pressure....I've seen the wear to the crown just from the gases exiting the bore of the barrel. We call it....gas cutting. That's why any barrel we do finish work on...we machine a 60 degree chamfer on the bore edge. This helps with the gas cutting effect as well as damage from shooters pulling the brush back over the crown edge as well. This was proven years ago. Even before Obermeyers time. Ever wonder why this is spec'd out on all the gov't test barrel drawings? It's on every single one that I can think of seeing.
i dont pull it back through because I just pushed the crud out. I unscrew the brush once clear of the crown and pull the rod back through with nothing on it. I also use a chamber guide at the breech.A bullet moving at 3500 fps with extraordinary heat and pressure behind it does no damage whatsoever to the crown, yet somehow a brush pulled back through causes damage? BS
I still say the best way to crown a barrel is by doing it in the lathe. Either by single point cutting it or a piloted tool. The only thing you have to be careful about with a piloted tool is make sure you have the proper bushing size fitted. Plenty of cutting oil. The chamfer we cut on the crown's bore edge for a size comparison is about the land width of the rifling when you look into the bore. You don't need anymore than that. What you want is no burr left at the bore edge and the chamber to be even/concentric all the way around.Frank, what is your experience with the effectiveness of folks who use the at-home chamfering solution of putting a brass screw in an electric hand drill with valve grinding compound to touch up and lightly chamfer (not full recrown) the inside edge of the crown? Has it worked okay, damaged/worsened accuracy, or been a quick cure for accuracy issues that you've seen? I imagine someone like you would always use the best tool for the job-- and that many of the ones you've seen might be screw-ups that people bring to you to fix-- but wondering if you have experiences to share.
Thank you for your contributions, it's great to see you on this forum.
No I have no data that supports the nylon brush causing any issues per say in regards to the crown.Frank,
Regarding pulling the brush back into the bore from the crown, do you have any comparative data on damage to the crown using nylon bristle vs. bronze bristle brushes?
Thanks