[Greenhorn Dave]

Advice please:

A few years ago I bought some Beartooth supplies and overdid it and firelapped a stainless 44 SBH too far (more than 100 rounds). The problem was my failure to carefully inspect the barrel periodically during the process. After that, it sure cleaned up easy and it shot pretty good groups (about 2" @ 25 yd), but the beginning lands were significantly ground down about 5/8 inch into the barrel. The lands looked like tapered ramps, gently rising and widening from the end of the forcing cone, and each land was worn different than the others.

I have finally had a new barrel installed, mostly because I wanted a longer barrel, and want to try firelapping again, but not overdo it.
Bill McConnell’s “Firelapping in 36 Rounds” published at this website is my guideline this time, but I have a question. In Bill’s article he states that lapping bullets larger than the cylinder throats waste a lot of the grinding on the throats before they get to the constriction just past the forcing cone. Does it make sense to swage the lapping bullets to slightly smaller than the throats before firing them into the constriction?

I slugged the barrel at the forcing cone and the muzzle. At both ends the diameter of the grooves is .430, but there is a constriction just in front of the forcing cone that I can feel when pushing the slug down from the muzzle – right where the barrel is screwed into the frame. I don’t know exactly what that measures, but it is less than .430
The 6 cylinder throats have all been honed to .4315. What if the lapping bullets were swaged to .431 before adding compound and firing?

I will again be using Beartooth’s lapping compound.
Thanks.
Dave

 

[Bill M]

Hi Dave,

No problem with the Super Blackhawk. No bullet swaging necessary. Ruger makes it cylinder throats big enough on the SBH that you should not have a problem lapping the barrel. The cylinder throats are still considerably larger than the bore so there will be a lot of cutting power when the lapping bullets get into the barrel. Don't be surprised if when you're done the cylinder throats and a couple ten thousanths of an inch larger though.

Remember to wire brush the bore every six rounds just after giving it a good squirt of Break Free or equiv. It is neither necessary or desireable to clean the bore between sets. Only wire brush and Break Free. If it seems like all you're doing is making one big mess, you're doing great. After 36 rounds, then clean everything up well and access.

Enjoy

 

[Greenhorn Dave]

Hi Bill -
Thanks for the good and reassuring info.
I am not sure, but with my previous experience the lapping bullets may have had extra cutting power because I put plenty of pressure on the rolling plates and rolled each bullet in the compound for maybe a full minute each. They were really gritty even after being wiped dry.
A little more throat wear is OK with me, and of course each throat gets only 1/6th of the action that the barrel gets.
Thank you.
Dave

 

[Bill M]

Good deal Dave. Be sure and let us know how it turns out.

 

[Greenhorn Dave]

Bill -
Well, I finally got a Round Tuit -- tho' it IS less than a year since I wrote about firelapping my new barrel.
Today I Firelapped 24 rounds and still had a very noticeable constriction just in front of the forcing cone. Since the barrel was threaded in farther by a gunsmith to tighten the cylinder-barrel gap, that probably put more than an average amount of constriction on the barrel. Just a guess.
Then I got to thinking about your recommendation to wire brush and lube every 6 shots. The first shot afterwards has smoke, the second has just a little smoke and that seems to eliminate the Breakfree. So, I increased the frequency to wire brushing and leaving the barrel wet after every 2 shots. I'd just roll out the cylinder, do the job, roll the same 6 back in and index it for the next 2 shots and so on. That seemed to be reducing the constriction faster.
Now I have shot 42 lapped bullets through it and the target group is reduced by more than half. Very good for me - less than 1.5x1.5 inch with my overgrip hand resting on a sandbag at 25 yards with a favorite load. Before, I was happy with 3x3.
When I shove a sizing bullet down the barrel (see the P.S. below), there is still a little bit of constriction at the forcing cone. If it was your gun, would you run a few more lapping bullets through or leave it alone?
P.S. - I am using the front end of cutoff hardcast Beartooth Bullets instead of sinkers to test for constriction. I hacksawed a few .432 265 WFN at the crimp groove and they tap down real nice with a plastic head hammer. I was very careful to saw them off square with the crimp groove with a fine tooth hacksaw blade, so I keep that flat surface square with the muzzle face as I gently tap the bullet into the muzzle. I reuse them for more than one pass by carefully inserting them onto the muzzle lands (after cutting off the flashing around the base after the first pass) and they pass through a lubed barrel with great sensitivity. They seem to snap back a little since they are hard, but that is OK, and I can definitely feel the constriction at the forcing cone end of the barrel. The cutoff 265s (could be any 44 cal BTB LFN or WFN I suppose) are easier to lineup and start with less striking force than lead sinkers were for me.
After starting with the plastic face hammer, I move them partway down the barrel with a short piece of 3/8 wood dowel, then switch to a about a 10 inch long 3/8 aluminum rod around which I wrapped some masking tape in a few places to make the rod fit pretty snug in the bore and keep the aluminum away from the barrel lands. Also I filed down the edges of the aluminum rod ends to be sure I wouldn't nick the barrel muzzle if I was careless. Also, I learned to put a wad of t-shirt material in the cylinder gap to catch the sizing bullet and to make sure to keep the rod from smacking the firing pin hole.

 

[Bill M]

Hey Dave,

Sounds like you have everything under control. As you have explained your understanding of the wire brushing and the generous application of the Breakfree and important parts of the firelapping process, I'd say you are a master of the process. There is no reason you can't run a few more lapping rounds down the bore to remove what' left of the restriction. Personally though I tend to measure success by accuracy. If you have a long range tack driver with a bore that tends to stay clean with good bullets then you are near perfection. My humble suggestion would be to get out and shoot the gun for a while and then decide if you feel it needs more lapping. Either way you are the winner. Good job.

Bill

 

[Greenhorn Dave]

Good idea. I'll just shoot the thing and postpone any additional lapping.
Thanks for all your good advice.
Dave