I had a Holland QD brake installed on my Savage 10FP .308 about 300-400 rounds ago. The gunsmith was Mark Pharr. We both looked at the crown before he installed it and agreed it was sharp. It was shooting some tight groups at the beginning. I noticed lately I hadn't be able to pull off those half inch 5 shot groups, so I figured it needed a cleaning. I was looking at the muzzle today and noticed that the bottom half of the crown is not sharp anymore but the top half is. The directions for installing the brake state that the muzzle should be flush with the first port. The Savage barrel has a recessed crown that sits back about a 1/16" and I should note that for whatever reason the muzzle sits back about a 1/16" from the first port. I cleaned with a Dewey bore guide, Tipton carbon fiber rod, brass jag, and Butch's. I have cleaned 3 to 4 times in 475 rounds. Could the brake have caused the crown to lose its sharpness on the bottom, or did I do it somehow by cleaning it? I will try to get pictures tonight if possible. Any opinions would be greatly appreciated.
Gunsmithing Can a muzzle brake cause crown erosion?
- Thread starter One_Man
- Start date
Re: Can a muzzle brake cause crown erosion?
Chances are it's the cleaning but...
Most of the high heat and pressure is occurs at the breach end, if it were going to erode the crown it would do it evenly. I doubt very much that your brake is causing your crown to erode.
If your crown is not cut square to the bore then the crown could wear unevenly and the brake could accelerate this.
If the threaded portion of the barrel is even with the front brake port that is all you need to worry about. You don't really want any threads showing on the brake. The reason is if the barrel is pushed further back and the brake is showing threads this can cause turbulence with the escaping gas that could screw with your accuracy and diminish the brakes effectiveness.
Chances are it's the cleaning but...
Most of the high heat and pressure is occurs at the breach end, if it were going to erode the crown it would do it evenly. I doubt very much that your brake is causing your crown to erode.
If your crown is not cut square to the bore then the crown could wear unevenly and the brake could accelerate this.
If the threaded portion of the barrel is even with the front brake port that is all you need to worry about. You don't really want any threads showing on the brake. The reason is if the barrel is pushed further back and the brake is showing threads this can cause turbulence with the escaping gas that could screw with your accuracy and diminish the brakes effectiveness.
Re: Can a muzzle brake cause crown erosion?
Parkincense,
Funny you bring this up, we had a very similar situation with one of our client's weapons. Custom 308 with muzzle brake all of a sudden wouldn't hold sub 1/2 moa groups. For several weeks, he tried everything he could think of but nothing seemed to help. Finally he gave the weapon to use to check out.
We verified his problem at the range with him and and then had our shooter try his weapon. Same problem, nothing smaller than 3/4 moa and lots of 3-2 and 4-1 groups but nothing was consistently the same.
We took the weapon to the shop and bore scoped it. We noticed quite a bit of copper fouling but not enough to cause his problem. Then we noticed tiny black specks of something stuck to the bore. When we pulled the muzzle brake, we observed what looked like erosion on the crown but not even, sporadic in depth, and angular location.
Here is what we determined. While using the carbon fiber cleaning rod, at some point in his cleaning process the carbon fiber was rubbing on a sharp edge (either end of freebore or acutally on muzzle). Anyway, small (very small) pieces of carbon fiber shavings found their way into the bore and upon firing bonded to the barrel. The pieces that didn't bond inside the bore made it to the muzzle where the heat and pressure bonded the particles to the crown.
We scrubbed out the bore until all the particles were removed then using an exacto knife very carefully removed the carbon fiber from the crown and then re-polished the crown.
Took it back to the range the next weekend and fired 10 rounds to settle everything back in and foul the barrel a little. Next two groups of 5 rounds each were both sub 1/2 moa again with (factory match ammo).
Since your crown is recessed I was just wondering it the same thing was happening and the build up is taking place at the recessed step.
This was a very rare problem and may not be the cause of your loss in accuracy but it's worth looking at.
Parkincense,
Funny you bring this up, we had a very similar situation with one of our client's weapons. Custom 308 with muzzle brake all of a sudden wouldn't hold sub 1/2 moa groups. For several weeks, he tried everything he could think of but nothing seemed to help. Finally he gave the weapon to use to check out.
We verified his problem at the range with him and and then had our shooter try his weapon. Same problem, nothing smaller than 3/4 moa and lots of 3-2 and 4-1 groups but nothing was consistently the same.
We took the weapon to the shop and bore scoped it. We noticed quite a bit of copper fouling but not enough to cause his problem. Then we noticed tiny black specks of something stuck to the bore. When we pulled the muzzle brake, we observed what looked like erosion on the crown but not even, sporadic in depth, and angular location.
Here is what we determined. While using the carbon fiber cleaning rod, at some point in his cleaning process the carbon fiber was rubbing on a sharp edge (either end of freebore or acutally on muzzle). Anyway, small (very small) pieces of carbon fiber shavings found their way into the bore and upon firing bonded to the barrel. The pieces that didn't bond inside the bore made it to the muzzle where the heat and pressure bonded the particles to the crown.
We scrubbed out the bore until all the particles were removed then using an exacto knife very carefully removed the carbon fiber from the crown and then re-polished the crown.
Took it back to the range the next weekend and fired 10 rounds to settle everything back in and foul the barrel a little. Next two groups of 5 rounds each were both sub 1/2 moa again with (factory match ammo).
Since your crown is recessed I was just wondering it the same thing was happening and the build up is taking place at the recessed step.
This was a very rare problem and may not be the cause of your loss in accuracy but it's worth looking at.
Re: Can a muzzle brake cause crown erosion?
Wouldn't know. Would only say all my rods and implements are made of stainless steel or coated steel. No false copper indications, and with a good rod guide and sensible cleaning techniques, very benign to the bore. Carbon fiber is a great synthetic structural material for stocks and such, but I keep such substances away from my bores. Just a feeling, but I pay atention to such.
Greg
Wouldn't know. Would only say all my rods and implements are made of stainless steel or coated steel. No false copper indications, and with a good rod guide and sensible cleaning techniques, very benign to the bore. Carbon fiber is a great synthetic structural material for stocks and such, but I keep such substances away from my bores. Just a feeling, but I pay atention to such.
Greg
Re: Can a muzzle brake cause crown erosion?
Buzzsaw,
The Tipton carbon fiber rods are just fine, we use them all the time in our shop.
The problem was the application / technique. The client has a B&C fully adjustable tactical stock. The butt plate was set high enough to cause a slight bow in the cleaning rod during the cleaning process. This is what caused the rubbing and eventually the shaving of the rod.
Buzzsaw,
The Tipton carbon fiber rods are just fine, we use them all the time in our shop.
The problem was the application / technique. The client has a B&C fully adjustable tactical stock. The butt plate was set high enough to cause a slight bow in the cleaning rod during the cleaning process. This is what caused the rubbing and eventually the shaving of the rod.
Re: Can a muzzle brake cause crown erosion?
Which probably would have been prevented with a proper bore guide.
To the OP, I doubt it's the brake causing uneven erosion. If that were the case then my suppressor would be destroying the crown on my HBAR. I pulled the QD mount off yesterday and just had a bunch of nasty carbon over a crisp crown.
Which probably would have been prevented with a proper bore guide.
To the OP, I doubt it's the brake causing uneven erosion. If that were the case then my suppressor would be destroying the crown on my HBAR. I pulled the QD mount off yesterday and just had a bunch of nasty carbon over a crisp crown.
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