Thread: tidy up crown on .22lr

There have been numerous hints on a brass screw used to do this...does anyone care to give a more thorough/detailed account of how to do this please???
Ive got the wee powerdrill honing stones on hand too but something less drastic might just bring an old gal back to fine form again.
thanks in advance

A round-head screw of a diameter greater than the bore but smaller than the barrel itself, in a drill so the head is exposed. Use some valve grinding paste or cutting compound if you are a bit nervous, at moderate rpm, constantly changing the angle slightly will form a slight crown at the muzzle by grinding down any high spots and evening the surface. Stop and check and replenish the paste as needed. Some Blu tac inside the muzzle end of the barrel will prevent scratching the rifling as the grinding paste tends to travel a bit!

https://youtu.be/bkJby5YVXFU?si=SYo0Z0XvY8In5RpJ

I used a brass screw with a round slotted head from Mitre 10. I chose the size that was about twice as big as the bore. I think it could have been smaller. I checked the head of the screw for flaws such as burrs. All was well. I mounted the screw in my trusty Makita drill and selected the slow speed range. I pushed a bit of toilet paper into the muzzle to stop valve grinding paste getting inside the bore. I smeared some valve grinding paste onto the head of the screw and ran the head of the screw lightly on the bore of the muzzle of the rifle at a varying angle for a few seconds, lifted it and smeared the paste a bit and did this a few times until there was a bevel in the muzzle which went below the grooves of the rifling. It is essential to make sure that there is no bias of the screw/bore interface. So, shift the barrel to different positions to compensate for the probable bias in the way the electric drill is held to the muzzle. I checked for uneven result periodically with a bore scope. When the level was below the grooves of the rifling I changed to 600 grit diamond paste until the coarse scrapes of the valve grinding paste were gone and replaced by a smooth surface. It was an easy process. I didn't need the bore scope but I wanted to be sure that I was not creating a problem which was not visible to the naked eye. A magnifying loupe would have been quite enough to inspect the muzzle, and this is what I used for another couple of rifles. The valve grinding paste was not of good quality. It was imported from India and the only product in the auto shops. I don't recommend it (comes in a small tallish round tin). The grit size is not consistent. A coarser grade of diamond paste would have been ideal, before finishing with the 600 grit. The size of the screw head was a bit big and it took too long to create the bevel. A smaller head would have got there quicker. I bought a few different sizes and found that a small acorn-type brass nut on a screw worked better on other rifles. It all takes about half an hour, including clean up of the muzzle. I had a muzzle refaced at Gunworks later and they did a great job and it was not expensive. But I had to leave the rifle and then pick it up. Also, doing the job myself gave me some satisfaction. Don't use a stone of any kind. That would be brutal and may produce a muzzle/bore that is not symmetrical. Just gentle centering weight on the power drill/screw is all that is needed with regular refreshing of the grit. It is just like doing a valve grind but easier with the electric drill.

An old budhy method was to use a steel ball bearing a little smaller diameter than the muzzle and some fine valvd grinding paste. Thumb pressure on the b bearing while drying the socks by the fire and supping a lint mug of brew.

Just get a drill bit wider than the bore but less the muzzle, and simply cut your own recessed crown.

I just do it with a normal hand drill aiming it straight up and down by eye and despite what you might read it doesnt have to be exact (or I am pretty good at doing it perfect) and it doesnt even change the point of impact at all. Just aim it as straight as you can and drill it out a bit, eighth of inch down. Or counter bore it as far as you like to get into clean rifling...Put a couple of shots through to smooth any burrs.


I have done the method with round head screw with valve grinding paste several times and I have done the above as well and it works as well or better frankly.

Funnily enough I was picking up some supplies on Sunday to do this very thing, had a hand me down .22 semi with a bulge and a ring in the barrel. Hacksawed the barrel after work yesterday, filed flat, evened out with reducing grades of abrasive paper, rounded off the edges, then did the brass round head thing. Tested this evening and groups super tight at 25m, will check on the weekend at 100m. Could be tidied up a little bit, but as long as it groups well at a hundy will leave it at that and cold blue it

If doing the abrasive method, a 3m earplug inserted level with the muzzle works as a really easy plug. Doesn't get in the way, and keeps the abrasive paste where it should be. Push it out with a cleaning rod, and 99% of the abrasive compound goes with it...

A brass round headed screw of the right size will do this in only a few minutes, you don't need to do much to clean a crown up sufficiently. If there is damage, counterboring is probably quicker but I try to be minimum-invasive to start with and step up to the more bubbafied options as the first options don't work haha.

This thread reminded me of this article i read a while ago
https://rifleshooter.com/2018/03/do-...fect-accuracy/

Identify your target beyond all doubt because you never miss (right?) and I'll be missed.