View Full Version : Reversed conr breech.

01-11-2008, 03:58 PM
I recall seeing it somewhere (on a rimfire action). Could anyone direct me to a photo?
Thanks in advance.

Sorry, I meant reversed CONE

01-11-2008, 04:28 PM

Bill Myers gave me a good pointer once on doing cone breeches. Take a 1/2" two flute ball end mill and use one flute like a form tool to make the radi. Works like a charm.



01-11-2008, 04:49 PM
Yes Ive heard that. But I dont understand in what way it is better than a straight cone?
And how thick should the edge be so as not to deform from the firing pin and for the extrctor to catch the rim?

01-11-2008, 06:51 PM
OSSI, it isn't better, it's easier, you don't need to set up to cut extractors. Some folks do it to try to be able to rotate a barrel to index it.

01-12-2008, 12:22 PM
The lip left can't be much more than .008/.010 and still have any extractor engagement. This couldn't possibly prevent damage should a firing pin hit it. The answer to preventing pin damage is that you simply can't let the pin hit the end of the barrel.

Also how can milling with a ball mill be easier than simply turning a cone shape on the barrel? I understand "easier than cutting for extractors" but I don't think it would be easier than the cone. I think we are missing something here that the guy that ball mills the barrels isn't telling us. Maybe he doesn't mill all around the barrel, maybe he just cuts the extractor groove on each side with a ball mill instead of a straight milling saw cutter.

01-12-2008, 01:21 PM
Yes pacecil thatīs true, .010 isnīt much. Probably not worth turning a cone vs making a slot for the extractor.
What I had in mind with the cone thing was that if you have the cone you could make the bolt in one piece instead of those two piece bolts common on rimfires. I have somewhere a pic of a rifle from one of the custom shops that used this reversed cone, just cant remember who it was.
Oh well..............,,,, its Heineken time soon here in Iceland. Maybe that will fix my memory.

01-12-2008, 06:02 PM
No, it's just to avoid that thin .010 rim that you DO cut extractor grooves. The thin rim is weak and won't properly support the case near the rim. It's a bad way to make a barrel in that location.
I don't know what you mean by "two piece". All rimfire bolts are ONE piece right back to the locking lug. If you could join the lug area to the bolt what effect do you think this would have? There would be no difference in alignment or rigidity so how do you think it would affect accuracy?

Kent Owens
01-12-2008, 06:19 PM
The bolt in my BR sporter is one piece, front to back, lugs and all. The front end rotates when you lift the bolt handle. All of them are not two piece.

01-12-2008, 07:14 PM
That's interesting, I guess I haven't seen all guns. What make is it?

Kent Owens
01-12-2008, 07:21 PM
It's a Kimber of NY action. A modified Mauser type design with claw extractor, better trigger. The firing pin goes down the center of the bolt like a centerfire and the barrel is offset toward the top of the receiver to allow the pin to hit the top of the rimfire rim. All the Kimber of NY rimfire actions are designed this way. Mine has a Benchmark barrel and is set into a custom stock. It's shoots pretty good.

01-12-2008, 08:06 PM
I've used both methods cut extractor groves and the coned. And I really can't see a difference in how they operate once they set up properly. Leave to large an edge on the cone and the rifle will have a tuff time extracting. Same holds true on the cut groves. So that part is a wash. Cones should never be used on a action that will allow the firing pin to contact the barrel. If dry fired that would cut a slot right down the cone until you either ran out of firing pin or moved enough metal to stop the pin forward movement by peening the metal out of the way.

To cut the cone with an end mill you place the end mill in a lathe holder and cut the cone on the lathe while the barrel is still in there and indicated in. You could conceivably cut it on a Bridgeport with a rotary table but if you going to do that you might as well just cut the extractor slots and be done with it.

Cones make indexing barrels very easy and you can still use the extractors on the bolt. And you can turn the barrel and re-index the action to 90 deg very easily. Providing your using a clamp action. With a threaded action there is no easy way to do it.



Mike Swartz
01-12-2008, 08:37 PM
Take a look at the Time Precision rifles. They are coned as well. Using a ball endmill is a no-brainer. Just clamp it in an Aloris tool holder and turn away. You don't do the cone in a mill(??). The only reason I can see to use a coned barrel is if the bolt is one piece and the extractors have to turn, ala the Time Precision. Once you buy the tools to do extractor grooves that's no problem either. It's a lot easier if you have a dividing head.

Mike Swartz