Crown Touch-up

[quickdtoo]

A simple way of checking the crown of a rifle is to clean the crown then shoot a few rounds, then look at the crown, you'll see a starburst shaped splash of fouling surrounding the bore, it should be even and concentric to the bore, a poor crown can result in an uneven pattern such as in the left pic below, the other pic is after touching the crown up with a ball bearing and 220gr, then 440gr lapping compound.

Tim

   

[knight0334]

Definitely a good tip.  That should be added to the FAQ's. 

[quickdtoo]

It is, that's why I posted it, I thought it was already in there, I've posted about it before a time or two, but I never did get it in there, so I had to create a new thread.

Tiim

[OR-E-Gun Bill]

Couple questions Tim.

Any particular size ball bearing best for different bores?

Are you attaching the ball to a rod or dowel to aid in slowly turning the ball on the crown?

Thanks,

Bill

[quickdtoo]

Depends on the type of crown on the muzzle, a recessed target crown will be harder to use a large ball bearing that's easy to handle, but I've also used a small carriage bolt to do the work on my 17hmr Sportster which the previous owner couldn't get better than 3" 100yd groups with, that's why he sold it to me cheap! It can be chucked in a drill to expedite the process, there's another link in the FAQs under Accurizing that covers actually reshaping the muzzle. I've thought of epoxying an appropriate sized ball bearing to a short piece of aluminum cleaning rod to be used as a handle or even chucked in a drill for speedier use as with the carriage bolt.

Tim

http://www272.pair.com/stevewag/muzzle/mz.html

[Nightstalker6117]

Quick ...  I am so glad you posted this. I have an HMR that I don't think is as accurate as it should be and I have always questioned the crown. To me it seems as if I have a burr or two. So do you thing it will center up just fine even with the burrs or should I lightly grind those down first. Also do you just roll the ball bearings back and forth by hand with the lapping compound on or what is your technique. Thanks for the info.

[McLernon]

You can check for burrs with a 'Q-Tip'. If the fiber is pulled off by contact with the muzzle crown you have a tiny burr. Then recrowning per Tim's method should be done.

Mc

[just bill]

You can check for burrs with a 'Q-Tip'. If the fiber is pulled off by contact with the muzzle crown you have a tiny burr. Then recrowning per Tim's method should be done.

Mc

 ..............Nice "tip"............

[quickdtoo]

To me it seems as if I have a burr or two. So do you thing it will center up just fine even with the burrs or should I lightly grind those down first. Also do you just roll the ball bearings back and forth by hand with the lapping compound on or what is your technique. Thanks for the info.

I'd rotate it back an forth to keep it centered, if you try to roll it, it might climb off center slightly and make the crown uneven.

Tim

[just bill]

Can some explain or show the same but with using the round head brass stove bolt method?

I use to have a link saved,  I had found but deleted it apparently

[quickdtoo]

You mean this one in the link I posted earlier that's in the FAQs?

[OR-E-Gun Bill]

There is a mention of using a brass round-head screw in the recrowning process in this Midway article on shortening a rifle barrel.

http://www.gunsandhunting.com/Midway_sept.html

Bill

[Hammerspur]

I have two laps, a 45 degree brass Brownell's #080-624-045 and an aluminum one I made for large bore work (.58 cal):



I like the brass carriage bolt lick... filing that one!

[351 power]

i dressed a muzzle crown with a sharp drill bit turned by hand. then polished it with with a marble wrapped in sand paper. those pics of powder residue were the same for me, before and after