Starting Load for fire lapping 45-70?

[358owner]

I have recently purchased the LBT fire lapping kit and intend to use it to smooth the bore of my Marlin Guide Gun. Unfortunately, I do not yet cast my own  and am having a problem finding suitable cast bullets(air cooled wheel weight 12bnl), and low vellocity reloading data. In your instructions you mentioned that fast burning pistol powders are ideal for low velocity lapping, but the lowest velocity I could find was a 552gr at 1000fps using 12gr Unique, and 552gr at 1100fps using 20gr of IMR 2400. These are stated as starting loads and the manual does not recomend going below them.  Is this too fast? And if so, can I safely reduce them further? Also, who can I buy suitable bullets from for this use? :?

[Mikey]

358Owner:  I've just finished lapping the bore of my 444.  I used soft bullets supplied for that purpose, but loaded them over only 4 grains of Unique to just get them out of the barrel.

For firelapping you want the velocity to be around airgun velocities and just enough to basically get the bullet out the barrel.  I think 1K'/sec would be way too fast for that purpose.

I originally started with 5 grains of Unique under a 240 gn cast bullet, but found that it penetrated 6 inches of pine, longitudinally, so I cut the charge back to 4 grains of powder and the penetration and velocities were less.  

If you have a soft bullet that you are going to imbed with lapping compound and intend to use a small charge of smokeless powder, use some of the polyester quilt bat filler to hold the charge in place in the case, and let that slow moving bullet do its job.  HTH.  Mikey.

[Veral]

Mickey gave exactly the advise I would have.  Must have read my instructions?

[Mikey]

Veral - as a matter of fact..................... Mikey.