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Barrel Recrown
dfletcher
Member Posts: 8,179 ✭✭✭
I have a 30 caliber barrel that needs a recrown and I'd like to do it myself. I'd like to do an 11 degree crown.
I'm capable with respect to hand tools and have looked at Brownells, Midway, etc. I see PTG offers cutters, what do I need to do the recrown work?
I'm capable with respect to hand tools and have looked at Brownells, Midway, etc. I see PTG offers cutters, what do I need to do the recrown work?
Comments
Best way is with a lathe and a single point tool. Just set the compound at 11 degrees, and feed with the compound. Trouble is holding the barrel without damaging the bluing (if it's blued?), or running the muzzle end in a steady rest. If you have centering "spiders" on the lathe headstock back end, or for the steady, it will not damage the bluing.
I have a hand operated piloted cutter that yields 45 degrees. All you have to do is cut past the rifling, roughly .004" or .005" on each side, to yield a crown that is accurate. The remainder of the crown width is cosmetic only.
Edit: That Manson video & tool look like they work good. I will still maintain that to touch up a crown you only need a tiny 45 degree chamfer. My .222 benchrest rifle has had the crown touched up this way, it shoots in the .2" consistently, sometimes in the .1". Guess this is the proof. Keep this in mind when deciding which method "works".
I should add, don't know if it makes a difference, but the barrel is threaded 5/8" X 24 for a brake. The amount of metal being removed is the difference between .308" and .625" - just over 3/10".
Doug,
I do believe, that the 11 degree cutter, should be reserved for cutting the forcing cones on revolver's. Or, that is mostly what they are used for. I would go with the 45 degree crown, and preferrably go with a lathe cut, if you can find a decent local machine shop, that should be no problem for them, and not cost much.
Best
The underside of the valve goes into the bore first, and valve grinding compound goes on the valve's flare where the stem meets the valve.
I rotate it with a hand drill for about an hour, or until I have passed the first set of grooves.
I have had excellent results, and the method is almost foolproof.
When the crown looks as good as you want, use the steel ball on the high spots to smooth the rest of the metal (the valve leaves a small ridge around the lip).
It just takes time and patience, but it works.
You could probably create whatever degree crown you want by removing metal from the valve "flare".
quote:Originally posted by dfletcher
I should add, don't know if it makes a difference, but the barrel is threaded 5/8" X 24 for a brake. The amount of metal being removed is the difference between .308" and .625" - just over 3/10".
Doug,
I do believe, that the 11 degree cutter, should be reserved for cutting the forcing cones on revolver's. Or, that is mostly what they are used for. I would go with the 45 degree crown, and preferrably go with a lathe cut, if you can find a decent local machine shop, that should be no problem for them, and not cost much.
Best
Checking some sites the 45 degree cutter looks most popular, I picked up a PTG made cutter, handle & pilot from Brownells for about $60.00. The task seems pretty straightforward. I've drilled & tapped before, built up 1911s and Smiths and have a pretty good idea of what I can and can't do correctly. This seems like pretty straightforward and slowly done hand work.
I wish we had a good gunsmith somewhere close to San Francisco. I'm willing to drive but hate like heck to mail stuff off. I often need minor work done, such as a bolt handle knob added or small part blued. But losing a bolt or some such part in the mailcauses all sorts of problems, I just don't want to take the chance something goes missing in the mail/UPS.
I've got one of these. It works great. Far better than other basement solutions. The link is on the 'show more'
I've got one of these. It works great. Far better than other basement solutions. The link is on the 'show more'
I've watched the video. According to the video their carbide cutter "will cut a chrome lined barrel" and that makes me consider that a plain old hardened steel cutter will not cut a chrome lined barrel - or at perhaps not cut it cleanly?
It's always fun to read the broad range of opinions regarding topics such as this. Usually it's a good indicator of which process or tool is making headway in the market.
While advertising writers and manufacturers want to make a particular tool or process seem like it is the solution to the amateur's dream of performing some technical task related to firearms simply, the reality is that every solution except for one or two is never perfect. There is always a compromise or several which cause the job to be less than it could be unless performed properly. This is the case with crowns.
Most factory firearms will perform to an average or slightly better level without much work. However, some small tuning tricks can improve accuracy or performance slightly. Unexplained degradation of of performance can sometimes be tracked to some inexplicable damage to the crown.
The interior edge of the crown is the very last point which touches the bullet and therefore has any influence on that bullet. In order for the crown to perform the best, it must be perpendicular to and concentric with the bore line. This is fact.
The shape of the crown beyond that interior edge has little if any great impact on the bullet. A case has been made for the 11-degree crown based on plasma physics and some extreme high speed photography. But flat crowns, radius crowns and crowns of other angles, all prove to be just as accurate as long as the rifle is accurate before the crown was made. This is what belies the statement above. The rifle has to be accurate before the crown is changed or fixed because the crown in and of itself will NOT make an average 1" rifle shoot in the .1's or even the .2's.
Here's what can happen with hand turned crowns:
And here is a properly executed crown finished with a 60-degree chamfer:
Anyway, choose what works for you and make sure that you are cutting perpendicular/concentric.
Best.