Lapping a pitted bore

[heelerau]

Gentlemen, I have a mates original Baker style sporting rifle, the bore has a little bit of pitting down near the breech. I am thinking of removing the breech plug and casting a lead lap to improve it. Now I did at the age of 15 lap the bore of an original Pat 53, I used valve grind paste, it did work ver well and the rifle shoots a treat ever since. Now I did that largely in ignorance, what do some of you chaps use for lapping? I realise that for fine machining marks you might only use a ver fine grit.
    I have also thought to try a greased hard felt wad over powder  instead. I will try that this next trip to the range on Thursday and see how it goes. It has worked well in my .72 bore rifle for multiple shots and ease of loading.  I have shot the rifle before and it does group just fouls pretty quick.

Kind regards

Gordon

[Scota4570]

I use cast lead laps and valve grinding compound.  I start at #100, then #220, then #320.  I make a breech plug blank with a hole to act as a bore guide.  I use a stout steel rod and don't not screw the lap in tight so it can swivel.  My problem is not removing material too fast, but too slowly. I usually raise a blister on my hand, it a a lot of work.  Even #100 silicone carbide grit takes a lonng time to remove much material. I use 10-32 all thread, nuts and leather washers to make my bore cast.  I polish the bore with rubbing compound and steel wool after. 

Others will have different ideas.  The above has been very successful for me. 

[smylee grouch]

Hi Gordon: I have used the valve grinding compound too and followed up with 400,600, and 800 lapping compound that i got from Brownells. Lots of work but it does work quite well.

[heelerau]

Thanks for that you blokes.  I will go and dig up some valve grind paste, then go to the finer Brownels' compounds. I have a Parker Hale two bander that might benefit from a good lapping too.

Cheers

Gordon

[rich pierce]

I have not found lapping to easily get rid of pits.  They are often deeper than expected.  Worth a try and it may work.  But once you’ve got a lead lap cast, you’re set up for freshing the rifling with cutters.  Making and inletting the cutters into the lap is the part that takes some fiddling.  The rest is easy but time consuming.