Fire Lapping

[Calamity Jake]

I need to fire lap a 91/30 Mosine, I'm using 314299 at .315Ø impregnated with 180 grit clover compound then with 400 grit clover. There's a rough place in the bore that leads enough after 10-12 rounds to affect accuracy.
Being winter in Okie land I will do this in my garage with a piece of tree trunk for a boolit trap.

What is the best load to use for enough volicity to just exit the muzzle I have bullseye, red dot, green dot, clays, SR4759, SR4756 unique, 2400, 4227 and maybe a couple more.

[TCLouis]

I use very low powered loads with Bullseye or Red Dot for fire lapping and with them I would watch carefully for bounce back at the shooter using a tree stump to catch boolits. Make sure they leave the barrel also.

I like to firelap with boolits that barely make it out of the barrel, probably 400-7-800 fps.

[303Guy]

Right, so you want to keep noise down to a minimum. Bullseye would obturate the boolit in the case mouth which is what you want and also produce the lowest muzzle blast. A harder alloy would likely be best to minimise boolit diameter loss as it progresses down the bore. It's bulker which makes it easier to meter. Any subsonic load for that powder should be equally quiet so perhaps you could try a published starting load.

[flounderman]

If it doesn't get the bullet out of the barrel, be careful opening the bolt. pressure could still be in the barrel. I wouldn't use coarse valve grinding compound. I made a bad barrel a lot worse using coarse. all I had and I didn't think anything to loose. go lightly and slowly.

[I'll Make Mine]

Seriously -- no one else thinks it's a bad idea to shoot a rifle in a garage with log as a bullet trap? Not only is it likely to be against the law (if you live in virtually any incorporated town or city, or some counties), a surplus round for that rifle will penetrate well over a foot diameter log (it'll punch half inch steel plate, for heaven's sake!). If something gets crossed up you could create an extremely unsafe situation with this scheme; in my opinion even shooting a very light load under a heavy boolit in that kind of setup is asking for trouble even if the police don't show up.

[rststeve]

I fire Lapp in my garage all the time. No problem red dot is your powder about 2 grains will do you. Just tip muzzle up to shake powder back to primer. Then leter down slow and touch her off.

(North Carolina). you can't do this kind of stuff in an apartment building.

[kweidner]

I don't think I'd start with 180 either. 300 maybe. I have taken slight pitting out of a bore with 400. I use trailboss. Be careful as 180 will take metal super fast. Remember that it's under pressure so not the same results as you sanding with 180. Also unless your superman 400 to 500 fps is impossible. This works so much different than conventional sanding. I would recommend a finer compound. Check out the wheeler engineering kit.

[303Guy]

Yeah well, I do it firing into a steel tube straight down with boolit trap material in it. Full power loads are inaudible outside the shed. Great care has to be taken since for a moment or two the gun is loaded and primed and it really is a dangerous instrument. And a stuck in bore boolit really can trap the chamber pressure - for two days! Try opening that bolt. However, once the boolit starts down the bore it doesn't take that much to keep it going. Getting stuck in the throat is dangerous. If all you get is a 'click' with no hissing then quietly put the gun down with the muzzle in a safe direction, lock the bolt with the safety if possible and bury it in concrete! Or give it to someone you don't like to open. I opened mine after several days and all the pressure was still there! I was holding onto the bolt handle firmly and was able to stop it from flying back too vigorously. Even though I was expecting it it still took me by surprise! So do be careful.

But we are talking cast boolits which are not so prone to getting stuck. I did say to use published starting loads - that's because such loads have been tested.

[Nobade]

If at all possible, get your hands on a bore scope to use when fire lapping. I used to do it without one and always went too far. Now that I have one I can see exactly what is happening, and believe me each shot makes a very noticeable change. Also clean the bore well between shots and it takes less powder to get the bullet out the end of the barrel. The only time I ever stuck one was when I got lazy and fired two shots - you guessed it, second one stuck tight.

[Calamity Jake]

OK guys thanks for all the advice/help. I will leave out the 180 grit and just the 400 with 2-3gr red dot.

[curator]

I have done this numerous times using Clover #320 grit. I also advise against using a tree-stump backstop and low velocity lead bullets. These things can and do bounce back at you. Don't ask how I know, just trust me on this. I use a large wooden box filled with sand. Make sure your lap-bullets are BHN 10-12, not harder or softer and at least .001 over groove diameter, for best results. Roll your lapping bullets between two steel plates to embed the grit into their bearing surfaces. Load these in fired cases that have not been sized. 3 to 5 grains of Bullseye and tip the gun up to settle powder to the rear of the case and lower slowly to fire. Check to be sure the slug has exited the barrel EACH TIME or you will ruin your barrel with a bulge. (again, don't ask!) Scrub the bore after each 10 shots with a nylon/plastic bore brush wound with bronze wool or copper chore-boy filaments to take out any possible leading before firing the next batch of ten. You will notice the report and "thump" of the bullet will increase as the lap-bullets do their work. Usually 25-30 lapping shots is all that is required but tight spots, and reverse taper bores may need more than 50.

[felix]

Shooting in basement is fine. Put a soft wad of toilet paper over powder. Shoot lengthwise into a 2 foot hickory or oak log. ... felix

[303Guy]

You will notice the report and "thump" of the bullet will increase as the lap-bullets do their work. Usually 25-30 lapping shots is all that is required but tight spots, and reverse taper bores may need more than 50.

I have a reverse taper bore rifle. I wanted it as a long barrelled light weight paper patch rifle then though I would cut the barrel in half and make it into a pig carbine. I have another one for the long barrelled gun - cost me NZ$200! That one has a very good bore but not as large as the reverse taper one. That one measures .310 at the muzzle! The bore, that is.

Might I ask why the specific BHN of 10 ~ 12?