I'm re-conditioning an old Winchester M67 .22 rifle. The bore is in excellent condition save the last 1 1/2 inches. There was an insect nest in the muzzle and it caused a deep corrosion ring just behind the crown. Range testing showed groups in the 6-8 in category at 25 yds. The owner just wants his grandad's rifle made to shoot again. I'm thinking a counterbore may restore reasonable accuracy. What do you guy's think based on experience and how should I do it?

I would think it would work just fine. Over the years, I've had a few milsurps with counterbores as deep as 2". They all shot very well. I've shot a few where the rifling at the muzzle was for all practical purposes non-existent, they did not shoot very well.

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Put the the barrel in a 4 jaw in the lathe and dial it in as close as possible to the inside of the bore. Then drive in a 15/64th chucking reamer to the depth you want. This will essentially cut the crown. Then drive in a 1/4 inch chucking reamer 1/32nd of an inch short of the crown you created to give ample clearance and go shoot some muskrats.

This has been done to death over the years

Thanks Rod! I'm late to the party and don't know all of the tricks, but appreciate the tips.

Got around to doing the counterbore yesterday. Result was amazing! It went from the 6-8 in range and high to dead on and 1 in groups with irons. What's more amazing or just lucky is that I did it with a handheld electric drill.

Your results show that all these "gunsmith" tricks and tools are pure bunk. Dial in in indeed! A rusty drill bit is one of my favorite tools. That and a belt sander.
Good work.

It works fine for remington too.

I've done the same, just used a chambering reamer with the correct bore size pilot to clean up and recess a crown in a centerfire rifle.

So now a thread on "things that worked but I am still not proud of them.."
I enjoy reading you pros insight but I confess to the hand drill counter bore as well. Old Mauser 95. Don't know how it shoots yet.

I bought a Remington 521T barrel on ebay, intending to use it with a 511 receiver. It turned out to have bad corrosion in the last six or so inches from the muzzle. I cut off most of the bad part and counterbored it with a 7/16" drill for another two inches. It seems to be all right; it isn't like a 513T but it's better than the 511 barrel was. I did use a South Bend 10L and a four-jaw chuck, not that it would make a huge difference with a jobbers drill.

quote:

Originally posted by dpcd:
Your results show that all these "gunsmith" tricks and tools are pure bunk. Dial in in indeed! A rusty drill bit is one of my favorite tools. That and a belt sander.
Good work.

LOL

Reminds me of that: "Custom chambering with case hardened corn cobs while you wait!" joke that they had in one of the gunsmiths kinks books years back.

Ive never seen any pluses to a counterbore, a factory crown has worked for years unless one intends to use his barrel for a tent stake.

Agreed. But when you have a $30 .22 rifle it isn't cost effective to cut off the barrel, re-crown and re-cut the front sight dovetail. A simple counterbore proved to restore hunting accuracy in about 2 minutes.

quote:

Originally posted by Atkinson:
Ive never seen any pluses to a counterbore, a factory crown has worked for years unless one intends to use his barrel for a tent stake.

quote:

Originally posted by Atkinson:
Ive never seen any pluses to a counterbore, a factory crown has worked for years unless one intends to use his barrel for a tent stake.

If the cut/crown leaves the barrel less than 16 inches, the counterbore might save an otherwise unusable barrel.

How deep can you go? I have a Mosin Nagant that came with a 1 3/4" deep counterbore, but it shoots 8" groups. And a .301 plug gauge drops all the way through the bore. .302 drops to 4 3/8". A .303 to 2 1/4". Can I extend counterbore to 4 7/16" deep?

Also, if I don't have a counterbore, drill and ream okay?

I used to collect military Mausers and Springfields. The counterbore will salvadge an otherwise junk gun.

A Mosin Nagant that is shooting 8 inch groups will most likely cut those groups in at least half with a careful counterbore using a drill bit. I have seen lots of 5 and 6 inch counterbores done with drill bits. Make sure it is both large enough in diameter to do the job and sharp, hopefully a brand new drill bit

Thanks, airgun!