How many grains of trail boss to fire lap?

[ian45662]

I am going to fire lapp my 45/70 which has a 32" barrel. I was wondering how many grains of trail boss would be enough to just get the boolit out of the muzzle?

[firefly1957]

It would help if you said what bullet weight and material. Be careful about going with a to low of a load with grit on it you do not want to have to use a rod to push a stuck bullet out it will alter the fire lapping process. It would be best to Stick with a minimum load for consistent results.

Hodgden lists 8.0 grs of Trailboss for 699f/s with a 485 gr cast bullet. http://data.hodgdon.com/cartridge_load.asp (use 45-70 trapdoor data)

[ian45662]

Sorry I don't know why I didn't. It will be 500 grains with an alloy that will be about 30:1. The bore isn't bad but I keep getting leading. I have tried just about everything lubes alloys different boolits at different sizes so this was the last thing I was going to try. The gun was made by pedersoli so I'm a little surprised but oh well

[geargnasher]

You say the bore "isn't bad", what exactly do you think firelapping is going to do to fix it? I think you're getting the cart before the horse here and need to do some more work before you go to extremes with your rifle. Sometimes firelapping or hand lapping is called for, sometimes it isn't, and lapping a gun just because you're out of ideas on it's leading problem probably isn't going to help.

Also, I have the best results from an alloy that's about 12-13 bhn or so, and enough powder to just barely get the boolit out of the gun, which is tough to estimate sometimes. You can experiment by reducing the starting charge some and when you think you have it, switch to the laps.

If your rifle leads visibly, it's either because the boolit is losing its seal with the bore somewhere along the way and allowing gas cutting, or there are rough spots or copper fouling that are tearing lead from the boolit as it passes by. Troubleshoot the load with that in mind and see what you come up with.

Gear

[ian45662]

Well I have tried about everything. Different alloys sized from .460 down to .458. I have tried different lubes crimp and no crimp. Straight wheel weights and wheel weights cut with soft lead down to about 30:1. I have shot actual 20:1 with soft lead and tin. The barrel slugs at .458. I am going to run a soft lead bullet slow with fine grit 600 grit. My home is to smooth out the few rough spots I see and to give it just an ever so slight choke.

[geargnasher]

What powders and charge weights have you tried?

Gear

[ian45662]

I'm shooting black powder out of it. I have shot goex and swiss

[MT Gianni]

When you push a slug through it are there spots that reequire different levels of force? Is the front 4" measurably smaller than the muzzle?

[ian45662]

I just pushed it into the muzzle and back out.... I will try thAT when I get home though

[ian45662]

I pushed a slug in the breach area and it is about .0005 or .001 SMALLER than the slug at the muzzle

[MT Gianni]

It may well be a candidate for firelapping.

[303Guy]

I'm not sure that a 'barely enough to exit the muzzle' is indicated for fire-lapping. I suspect that a harder alloy and a quite a bit more 'oomph' is better but don't quote me. The boolit must not obturate under firing or it will cut into the larger sections of bore. In theory the grit wears down and cuts less and less but I prefer the idea of no bump up at all (that's the idea behind a load that only just gets the boolit out the bore). A hard boolit must be larger than groove to work properly I believe.

[ian45662]

So you think I should go just straight wheel weights? A load that will do more than push it out the muzzle but not so much that the bullet will bump? Should I size .458 or 460?

[runfiverun]

i'd call the maker..
firelapping a thou out of a bbl is about 1-2 kajillion shots

[ian45662]

Its closer to .0005 or less. Out of the dozen or so times I took the measurements I got .001 one time so I think it was a false reading. The muzzle end is just a little bigger than the back end for sure.

[zuke]

I've gone down as far as 2 grain's of Trailboss,and the sceond one got stuck at the muzzle!
Go with a minimum of 5 grain's and you'll be OK.

[runfiverun]

one of my shooting buddies just went through the muzzle bigger thing, he ended up having some of the bbl cut off and the sight dovetail recut.