finishing a crown

coyote

coyote

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There seems to be more than one way to skin a cat, I'm curious as to what steps you use to finish a crown.
I've always done lathe cut through the headstock .
PTG Manson JGS and others also offer tooling to do it without a lathe. How about lapping , chamfering .

It would be interesting to hear about what you think is the best way.
 
I machine in the lathe and finish using a piloted 60 degree chamfer reamer. The reamer leaves a smoother finish than the machining and it shoots well right away as compared to a machined edge that may require a few rounds to 'wear' the edge off.

The smoother finish with the reamer was verified by a US Benchrest Shooter who had access to an electron microscope. I sent him a sample crown to compare to all the machined crowns he was inspecting.

I have found no difference in accuracy with either method but the crown isn't as easily damaged when finished with the 60 degree chamfer and it is so quick to do. Seconds...

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I've used in the past a mouse ball and a brass lap. The mouse ball worked pretty good, but it's damned hard to find them now. That's why I went to brass laps. Bought a Manson kit from Bighorn Sales and use that now. Much better and way quicker.
 
I use either Manson or ptg form tools for crowns. I've got them in quite a few different styles and they work well and are fast. I've also done the 60 degree chamfer that gun tech was talking about, but I only have it in the #3 size. Just 2 more tools I need t buy in this never ending story they call amateur Gunsmithing.
 
The brass screw and lapping compound is often recomended. And if the end of the muzzle is accurately square it'll work. But far too many folks seem to feel that they can hack the end off with a saw, file the end by eye then use the brass screw to get match grade results. The screw lapping trick will only work as well as the squareness of the end prep. If the end is off then so will the lapping.

I'd suggest that lapped or counter sunk will always work best if it's done on a lathe prepared end with great care taken to ensure that the last few inches of the bore is running true.
 
Brownells must have been monitoring the site . . .

h ttp://www.brownells.com/GunTech/Tech-Tip-Crowning-And-Chamfering-A-Muzzle/detail.htm?lid=16946&cm_mmc=Email-_-Spop-Email-_-lm_12050596-_-
 
Melin makes a decent double ended countersink 60°(and other angles, I get them from kbc). I have a few for my regular work so I use that to break the rifling edge and maybe go another .01" while its in the lathe, quick and easy. I see no need for a pilot since its already all dialed it, hand work would be a bit different.
 
The pilot is there for a bore which isn't 100% concentric.

Unless you are dialing in your barrel on the bore itself, which would be quite a trick on a .22 or .223, you may need the pilot to make sure the reamer does an even job. It will still be out a tiny bit, if the pilot can turn, but it will be out a lot less than if you dial in the barrel on the outside, then use a countersink and hope for the best.

Most good rifle barrels are extremely concentric. If you're working on a less good barrel though, which is usually what people ask you to re-crown, you may want a piloted reamer to get the best possible results.

I still cut crowns at 11 degrees, from the inside out, as I was taught. The piloted reamer is awfully appealing.
 
coyote said:
There seems to be more than one way to skin a cat, I'm curious as to what steps you use to finish a crown.
I've always done lathe cut through the headstock .
PTG Manson JGS and others also offer tooling to do it without a lathe. How about lapping , chamfering .

It would be interesting to hear about what you think is the best way.
Click to expand...

Depends if the barrel will go in the lathe. If it will it gets cut that way, if not il use the brownells crowning tool, taking careful cuts so it doesnt chatter.
 
To dial in the bore of a rifle barrel, I use plug gauges - precision ground cylinders that slide into the bore. Have a selection for the calibers I do most. Got them from meyergage.com.
 
Barrels are turned between centers but bores are seldom straight, so if one shortens a barrel by 2 inches or more you often find concentricity is off, sometime just a little, sometimes a lot... that's where a precision bore gauge makes it easy to dial the bore in.

The tolerances these gauges are made to is amazing.
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I have seen factory barrels that had a muzzle face that was not perpendicular to the bore..... as well as slightly eccentric
 
AP said:
I have seen factory barrels that had a muzzle face that was not perpendicular to the bore..... as well as slightly eccentric
Click to expand...

That's where finishing the crown with the piloted tool really shines... it makes the 'exit' square to the bore with no lathe set up... in seconds...
 
Thank you guys for all the great replies, like I said in my opening post I have always done them in the lathe through the headstock which involves setup time.
The piloted reamers seem to be the cat's meow with no setup required, a friend of mine has received his piloted center reamers from Dave Manson and is also pleased with them .
He also tells me the crowns cut with them are every bit as accurate as what was previously done in the lathe.
I will be ordering piloted reamers they will be nice for recrowns and chamfering lathe cut crowns..
 
You know I very seldom have different to say than Guntech, so I often don't say too much! I once used am 11 degree piloted reamer which cut pretty good. It was ordered to cut 223 and up and one day I tried to cut a 223 crown. Turned out it would not cut a 223 and as soon as it touched the crown it rolled over enough steel so that I couldn't get the pilot back out. I cut the barrel off and undid the screw and extricated the reamer and part. I was told to send it back and he would fix it. I sent it back for a full refund. Now I just use do them with a cutter in the lathe and use a JGS 60 degree reamer to just trim. Works great. The bad reamer was from PTG.
 
Ian,

My first piloted chamfer reamer was custom made by Keith Francis (JGS), one reamer with an assortment of pilots to fit it back in 1970 ... a few years ago I bought a used set of 3 reamers (JGS) that accept the pilots from the chambering reamers. (3 different hole sizes)

Hard to beat JGS or Manson.
 
Ian Robertson said:
You know I very seldom have different to say than Guntech, so I often don't say too much! I once used am 11 degree piloted reamer which cut pretty good. It was ordered to cut 223 and up and one day I tried to cut a 223 crown. Turned out it would not cut a 223 and as soon as it touched the crown it rolled over enough steel so that I couldn't get the pilot back out. I cut the barrel off and undid the screw and extricated the reamer and part. I was told to send it back and he would fix it. I sent it back for a full refund. Now I just use do them with a cutter in the lathe and use a JGS 60 degree reamer to just trim. Works great. The bad reamer was from PTG.
Click to expand...

Same here. I crown as does Dennis because it works.

Ian, it's weird, more sad really, that your experiences regularly mirror mine. I think my bad 60` cutter is still here, not worth sending back. The grinding wheel used at PT&G had too large a diameter to get in close enough to cut a small diameter bore.
 
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