Coning and Lapping

[rancher]

What do coning and lapping a barrel involve (tools, time, money, etc.) and how much more accuracy do they give you? Thanks

 

[shortstring]

Coning the muzzle can be done with a tapered brass tool that someone makes. I don't know who offhand. But as I recall it uses emery paper to do the cutting. It can also be done by indicating the barrel in a lathe & cutting the taper with either cutter or tool post grinder. As to its effect on accuracy keep in mind that the most accurate round ball guns have no crown when shot as they load thru a false muzzle. All the crown does is allow you to load the gun .

Lapping is done by casting a lead slug in the barrel on the end of a rod & polishing the surface of the bore with grinding coumpound. As far as accuracy this can have a significant effect. If and this is a big if. If there was something wrong to begin with. You can't fix something that ain't broke. So if you are loading proper ball size with a tight patch & you're not chewing up patches. Or if you can't feel any loose/tight spots in the barrel then you might gain more as far as accuracy goes by working on load first.

 

Coning: I suggest you contact Joe Lane Wood (806) 352-3032 [email protected]. The tools Joe makes are made from bronze and when you buy one from him they come with a complete list of very accurate and detailed instructions. I have used one on my GPR and loading is now extremely easy (no short starter required) and accuracy was not impacted.

 

[J.D.]

What do coning and lapping a barrel involve (tools, time, money, etc.) and how much more accuracy do they give you? Thanks

Lapping can be done relatively inexpensively, depending on how involved you want to get.

Lapping can improve accuracy, but IMHO, it depends on what level of accuracy you strive for.

If you intend to shoot serious competition, then you probalby should lap the bore.

Most precicion shooters seem to prefer to NOT have coned muzzles. I don't know if part of this is tradition, or they consider coning unproven to improve or to retain accuracy.

The NMLRA sells a book containing detailed information on lapping. I think the title is "Shooting and Winning with the Champions".

I'm sure that you can find detailed informatrion on the net by running a search on barrel lapping, bore lapping, or some such.

DO NOT use valve grinding compound as a lapping compound, as some suggest. It might work, but since the grit is not uniform, and can cause more problems than it will solve.

J.D.

 

[Goldhunter]

+1 on Joe's coning tools!

 

[MSW]

I've coned the rifles i've built, but they're for my own use. if you're building for someone else, check first as people run hot and cold on this issue. Joe Wood's tool is great- easy to use and very accurate. conings detractors claim it hurts accuracy, but i haven't seen any effect in accuracy after coning a barrel with his tool (except that they're more fun to shoot, so you practice more, so you're a better shot, which wil go further than any gadget or thingamabob towards tightening shot groups).

good luck with your project!

msw

 

I've coned most of my rifles with Joe's tools, and I haven't seen any difference in accuracy. But then I shoot minute of barn (the broad side) :rotf:. Generally my groups are about 2-3" at fifty yards offhand, when the Gods smile upon me, and my caffene level is not so high.

Bill

I started with nothing and still have most of it left!

 

[longcruise]

I've firelapped about eight ml barrels so far and they have all benefited in terms of easier loading, easier cleaning and better accuracy.

The better accuracy I believe is due to the barrel doing less damage to the patch when shot. Some barrels are very rough and need lapping and others are just better quality.

TC barrels are button rifled and don't tend to have the sharp cutting edges of the cut rifled spanish made barrels but they also seem to have a tendency to have variations in the bore diameter that firelapping removes. If you have a TC barrel and can't feel any change in resistance as you seat a ball in a clean barrel, then leave it along.

If you have a GPR or one of the other spanish made barrels such as traditions or cva, the lapping will save you about 300 break-in rounds an a whole lotta frustration! :grin:

Green mountain barrels are pretty straight and smooth but still benefit from a bit of lapping either by hand or firelapping.