JB Bore Paste to Lap a Crown?

[cznut]

Could JB Bore Paste be used to lap a muzzle crown using a brass lap?I just re-cut a slightly damaged crown on a rifle with a Brownells chamfering tool and a brass pilot I went easy as I could but still ended up with some fine chatter marks,crown looks great though under 10x magnification but you can see the chatter just a little bit...you input or advise appreciated

 

[JerrySharrett]

Could JB Bore Paste be used to lap a muzzle crown using a brass lap?I just re-cut a slightly damaged crown on a rifle with a Brownells chamfering tool and a brass pilot I went easy as I could but still ended up with some fine chatter marks,crown looks great though under 10x magnification but you can see the chatter just a little bit...you input or advise appreciated

First, if the chatter marks are completely symmetric they will not hurt accuracy at least the accuracy of the average production made gun.

Using something like JB or Iosso, you will not live long enough to get tool marks out lapping with them. They are made of abrasives that are much softer than steel. If you can find some AlO (Aluminum oxide you can get there eventually. AlO is still softer than barrel steel but it will cut some without embedding. You could use valve lapping compound (example, Clover Brand, most auto parts stores have it) but it is Silicon Carbide and will embed. Use care to not get it in the bore or if so wipe it out from the bore very carefully..

 

[TAJ45]

Not sure that I have any answers of any stripe but will mention what was recommended to me, what I did, results and let the comments ensue.

I had a CZ in the 17HMR some years back. Would really shoot well for several rounds then toss a couple. No sequence pattern. Finally, with a loupe found some minute nicks at the muzzle. Looked for lapping compound at parts stores etc but felt they were way too aggressive. I ended up with some buffing compound, used a slotted, round head brass screw and brought the 5 groups to being round and .75 at a hundred with no fliers. Maybe I should have stayed with it longer?