Muzzle/Crown lapping? Restore a good shooter?

[Jeff Porter]

I have a rimfire barrel that has been very accurate with a wide variety of ammo. It has suddenly stopped being a tack driver and is now just a good barrel. ( not great).

I have run through a list of other things like firing pins and firing pin springs thinking it may be ignition but still not where it was.

I do not see any bumps or burrs on the crown but was wondering if touching it up with a brass lapping tool and some abrasive might help. What is your experince with lapping at the muzzle?

 

[DShortt]

Unless something has damaged the crown then that likely won't be helpful. Did accuracy degrade gradually or did it happen suddenly? Have you changed anything from what has been your usual routine?

 

[Bob3700]

I have a rimfire barrel that has been very accurate with a wide variety of ammo. It has suddenly stopped being a tack driver and is now just a good barrel. ( not great).

I have run through a list of other things like firing pins and firing pin springs thinking it may be ignition but still not where it was.

I do not see any bumps or burrs on the crown but was wondering if touching it up with a brass lapping tool and some abrasive might help. What is your experince with lapping at the muzzle?

Get a borescope and take a good look at the crown. U can usually see any damage or excessive wear if it exists.
I would also take a look just in front of the chamber to see if a lead ring exists. This can also cause a loss of accuracy.
A gunsmith can certainly touch up the crown without removing the barrel if that is what is needed.

 

[1813benny]

If there is no visible change at the muzzle, I would do a deep clean with a bronze-phosphorus brush, patches and a good solvent. I would place additional focus on the chamber area.

 

[1911nut]

What Benny said. And Try a Q-tip around the crown, if there’s burrs or scratches they’ll pick up the fibers.

 

[68Hoyt]

What rifle /barrel ?
It was shooting fine and suddenly degraded , what changed did anything change ? Did you clean it ?
Change ammo lots ?
Remove action from stock ?
Mess with scope ?
One day or several days it shot less accurate ?
Did you change or do anything different or did it in fact just all of a sudden shoot less accurate ?
Just trying to assist