Need help on how to do a deeply counterbored crown on a rimfire sporter

B

Boyd Allen

Active member
I put up a thread about this on the rimfire board, but I didn't think that anyone would mind if I brought it up here as well.

A friend, who does his own barreling, is putting a new barrel on his bench .22 rimfire. Because the local group that he competes with does not allow tuners, I have suggested the popular sporter contour that has an enlarged muzzle, and deeply recessed (a couple of inches) crown. Having never done this before, he is unsure about how to approach the problem, and since he does not use computers, I am doing some research on his behalf. What tool(s) do you use, and how do you go about it. The more detail the better. I will pass all of this along to him.

Thanks,

Boyd
 
OK, I'm shooting off the cuff here.... but I BELIEVE in a perfect crown.

I'd fit a prophylactic, a "muzzle brake w/no holes."
 
Thanks Al, but the rules that this fellow shoots under do not allow for muzzle attachments, so he will have to so he will have to back bore the muzzle, and crown at the bottom of the hole.
 
I would drill into the muzzle end with a .375"-.400" diameter drill bit to about .020" short of where he wanted the crown then using a small micro-boring bar open it up to whatever diameter he wants and finish crowning it with small cuts from the bore out to the major diameter of the counterbore...just time consuming...no big deal...but it may not give him the same results as a tuner...if he wants a certain amount of weight ahead of the crown he will have to do the math to estimate the weight of material left after counterboring...


Eddie in Texas..
 
A common solution, and I have used it, is to use a piloted throating reamer. For example, I use a 0.244 throater for a 22 cal barrel. I use a 25 cal (0.2575) throater for a 6mm barrel. This is where I want a rebated muzzle.

I have these throaters on hand where I want a chamber for a longer bullet than the reamer is ground for.
 
Ok, I'm a total noob, but I thought the purpose of a tuner was to adjust the vibration of the barrel; if tuners are not permitted, then what is the purpose of the deep counterbore? Are you going to shave off the muzzle as you go to tune the barrel after settling on a particular load? (Very interested in how this can be done re M882 9x19mm out of a 4.9" Beretta 92 bbl is supersonic - would like it subsonic...)
 
You must log in or register to reply here.
Back
Top