Fire lapping techniques

[longoval]

2 Dogs taught me how to fire lap. I have a 44 special New Model Flattop that we found had a slight constriction in the barrel where it threads into the frame. He walked me through a process and it took less than 18 rounds (I think closer to 12) to get it straightened out. That was awhile ago.

We followed a pretty typical process that involves using fired, unsized brass with a load of Trailboss. An oversized bullet was impregnated with 320 grit valve lapping compound by rolling it between two flat pieces of steel coated in lapping compound. The messy bullet was seated in a press and on to the next.

Fermin texted me a week or so ago about a new, improved process he was working on. His household seems to have some kind of ancient curse upon it because he has more guns that need fire lapping than you could imagine. His work is never done. He reminds me of that old red and white herferd bull in the Robert Earl Keen song, ”This Old Porch”. Nevermind.

Anyhow, I'll get some pictures up. He sent me these and he has confirmed that the process works as intended though thorough testing. From my perspective, the biggest advantage is less mess -- especially not getting the seating die packed full of lapping compound. But hopefully Fermin will chime in to provide details.

[longoval]

The pictures tell the story. Fired, unsized brass is still used-- it must be a slip fit for the cylinder being used. After charging the cases with an appropriate amount of Trailboss, a bullet is partially seated. Fermin used a vice rather than a press for this step. Then a good amount of lapping compound is applied liberally with a flathead screwdriver to the exposed part of the bullet. It is then fully seated, again with the vice.

[bigbore5]

It does seem simpler, if I could find some Trailboss. Stuff's gotten pretty rare nowadays. A mouse fart load of Red Dot will have to do it for now.

[bigbore5]

Btw, do you have to powder coat the bullets first? I usually lube all mine now.

[bula]

I'm thinking the bullets, that method to be on the soft side, and not PC'd. Correct me if wrong. 

[2 Dogs]

I was having trouble making firelapping ammunition for the 45 Auto Rim. The case wall thickness plus the diameter of the bullet was too big for the chamber. I ended up sizing the bullet down so I could get the ammunition to chamber. Using the Ram on my RCBS press I discovered I was having difficulty keeping everything straight and when the case mouth got to the grease groove on the bullet the Ram made it difficult to keep consistent pressure so I could seat the bullet exactly like I wanted. More, the case mouth itself was scraping the sides of the grit impregnated bullet. I tried the vise and had much better results.

I use a half case of Trail Boss in an unsized slip fit case. Keep in mind if you’re going to fire lap a longer barrel you need enough powder to exit your barrel. I used PC bullets here because they were what I had on hand and they are also pretty soft. I start the bullet in the case by hand as straight as possible. Then I use the vise to press the bullet into the case just short of the crimp and grease groove. I use a screwdriver to load lapping grit into the grease groove and crimp groove. I scrape off the excess and use the vise to seat the bullet so all the lapping compound covered. This is also keeping the lapping compound out of the powder. Chamber check for fit. If one gets hard to chamber I touch it with my crimp die until it will. Recovered slugs show plenty of grit impregnating the bullet. I get a good amount of compound on the muzzle. This works. It’s cleaner and more consistent. I can prepare ammunition and let it sit without worrying that the compound will foul my powder.

[gcf]

So if I'm understanding correctly, using the new & improved method, the lapping bullets are NOT embedded first. Is that correct?

I will say that the steel embedding plates process, has always struck me, as a royal PITA. Cramped fingers, compound everywhere, & as mentioned, the bullet OD increases to the point that chambering gets snug. Haven't had to size bullets down yet, but I could see it being needed.

Great idea seating with a vice - as opposed to the big bolt (or seating die) BTW.

[2 Dogs]

May 9, 2023 14:58:00 GMT -5 gcf said:

So if I'm understanding correctly, using the new & improved method, the lapping bullets are NOT embedded first. Is that correct?

I will say that the steel embedding plates process, has always struck me, as a royal PITA. Cramped fingers, compound everywhere, & as mentioned, the bullet OD increases to the point that chambering gets snug. Haven't had to size bullets down yet, but I could see it being needed.

Great idea seating with a vice - as opposed to the big bolt (or seating die) BTW.

With this process there is no need to roll the bullets before loading. Recovered bullets plainly show that they are well impregnated as the compound is squeezed out of the grease grooves. More, the muzzle clearly shows a ring of compound which tells me that the compound is making it out of the barrel. This is a much cleaner process.

[Odin]

May 9, 2023 17:52:00 GMT -5 2 Dogs said:

May 9, 2023 14:58:00 GMT -5 gcf said:

So if I'm understanding correctly, using the new & improved method, the lapping bullets are NOT embedded first. Is that correct?

I will say that the steel embedding plates process, has always struck me, as a royal PITA. Cramped fingers, compound everywhere, & as mentioned, the bullet OD increases to the point that chambering gets snug. Haven't had to size bullets down yet, but I could see it being needed.

Great idea seating with a vice - as opposed to the big bolt (or seating die) BTW.

With this process there is no need to roll the bullets before loading. Recovered bullets plainly show that they are well impregnated as the compound is squeezed out of the grease grooves. More, the muzzle clearly shows a ring of compound which tells me that the compound is making it out of the barrel. This is a much cleaner process.

Fermin, I know powder coated slugs were used in this example because they were on hand, but what about traditional lube? Any need to lube at all?

[2 Dogs]

May 9, 2023 20:41:36 GMT -5 Odin said:

May 9, 2023 17:52:00 GMT -5 2 Dogs said:

With this process there is no need to roll the bullets before loading. Recovered bullets plainly show that they are well impregnated as the compound is squeezed out of the grease grooves. More, the muzzle clearly shows a ring of compound which tells me that the compound is making it out of the barrel. This is a much cleaner process.

Fermin, I know powder coated slugs were used in this example because they were on hand, but what about traditional lube? Any need to lube at all?

Nope. The lapping compound becomes the lube. It forms a “grease laden abrasive” between the bullet lead and the barrel steel and quite simply does its work.

[stubshaft]

I've used both methods to firelap barrels. The key element is to use mousefart loads that will absolutly not lead the barrel. I used a 4 compound kit from NECO to do my revolvers and poured laps for some of my rifle barrels.

[Markbo]

I need to try this. 2dogs, which grits do you recommend?

[longoval]

I am guessing the Beartooth compound may be relabeled 320 grit Clover compound.

[2 Dogs]

May 15, 2023 11:41:10 GMT -5 Markbo said:

I need to try this. 2dogs, which grits do you recommend?

Pic sent via text.

[Gunny268]

2dogs, I've got a bunch of Veral's fire-lapping compound left. Would that also work for this "new" method? Or, should I try a finer grit compound.