Barrel lapping for "Bubbas"

26 April 2003, 11:19

wildcat junkie

I have a basic understanding of how to lap a barrel using a lead slug poured into a bronze brush that is recessed in the bore.

Is this a good method?

If so, should I use dead soft lead, or something along the line of wheel weights?

What grit compound/coumpounds should be used?

I assume I should start with coarse compound and go progressively finer.

I want to smooth up a barrel on an Obendorf M98K that has smoe slight rust in the bore.

Would it be better to do this before or after rechambering and crowning?

26 April 2003, 11:43

<JBelk>

WJ--

For rust removal I'd use 0000 steel wool wrapped around an old bore brush. Pour boiling water down the bore until the barrel is too hot to hold first.......then scrub about twenty strokes with the steel wool. Repeat two more times.

That's as clean as it's likely to get and stay the same size.

If you MUST lap (I did several that didn't need it, too.) Use nothing but pure, soft lead and start with 320 grit.

Do all lapping before other work. There will be a rough and slightly oversize area at both ends where the load is reversed on the lap.

26 April 2003, 12:04

Atkinson

Lapping bores is something gunnuts do when they get bored or lay off their job, and have nothing constructive do with their time...barrel wear is barrel regardless of how you do it, shooting or lapping. [Wink]

26 April 2003, 12:09

wildcat junkie

quote:
Originally posted by JBelk:
WJ--

For rust removal I'd use 0000 steel wool wrapped around an old bore brush. Pour boiling water down the bore until the barrel is too hot to hold first.......then scrub about twenty strokes with the steel wool. Repeat two more times.

That's as clean as it's likely to get and stay the same size.

If you MUST lap (I did several that didn't need it, too.) Use nothing but pure, soft lead and start with 320 grit.

Do all lapping before other work. There will be a rough and slightly oversize area at both ends where the load is reversed on the lap.

Thanks Jack: I have been told that the lap must never completely leave the bore during the process. (for indexing purposes I believe)

How critical is this?

Should I make a new lap for each progressively finer grit, or should I leave the lap partialy in the bore and apply progressively fine grit?

What grit would you finish with?

26 April 2003, 12:41

Hot Core

Hey wildcat junkie, The "only" non-embedding abrasive I'm aware of is Garnet. I did some research on this 2 years ago and was a bit surprised to find that out.

Brownell's carries it in 600 and 800 mesh(proper term for Garnet). Don't have my notes near me, or I could tell you where to get it directly.

Interesting that no one mentioned that to you.

26 April 2003, 13:25

<JBelk>

WJ--

The lap should not leave the bore. It's too easy to mis the index trying to get it back in and lap a rifling corner round......if the lap never leaves it can't screw up.

A lapping cradle makes the job easy and virtually eliminates the barrel destroying rubbing of the rod in the bore instead of *just* the lap.

The barrell AND rod should be completly cleaned between grits.....REALLY cleaned of any grit. NOTHING beats a Bore Snake for that purpose. Use it *after* slurpy ATF and nylon brush douches dried by a dozen patches as first steps.

Look real close after 600 grit.........I'll usually skip to 3 micron from 600.

The tendancy is to quit too early on the rough (280&320) steps and over-lap the finest grades trying to correct mistakes made at the beginning.

email me an address and I'll send you some practice barrels.