PDA

View Full Version : 1911 slide lapping w/ J&B?


Casimer
March 26, 2010, 06:08 PM
I have an old Sistema that has a rough slide to frame fit. That is, the slide's travel feels rough and uneven. But the slide will almost fall by gravity.

I'd had a Bomar sight installed, and the gunsmith squeezed the slide a bit, so I'd had a local gunsmith re-fit it to the frame. He hadn't lapped the slide / frame.

What I'm wondering is if I could use J&B as a light lapping compound, and just work the slide manually on the frame to improve their fit.

If so, should I mix the J&B w/ oil?

SilentHitz
March 26, 2010, 07:01 PM
Never used J&B, so not sure how it would work. I use the lapping compound from Brownell's...works very good for me.

sophijo
March 26, 2010, 07:08 PM
...or you could just shoot it. Oil and residue will "lap" it to a natural sort of fitment........just like Les Baer. :)

Jim Watson
March 27, 2010, 07:42 AM
My gunsmith laps 1911 rails with JB.
Be careful, JB cuts a lot faster when trapped between two pieces of steel than it does when scouring out bore fouling on a patch. I know my guy had to re-tighten one when he made too many passes the first time with JB. Now he makes only a few strokes with a little JB and then cleans very thoroughly.

Unclenick
March 27, 2010, 05:52 PM
Not just JB, but any compound will have its own particle thickness jammed between the sliding surfaces which makes it feel tighter than it is with the abrasive washed out. So be prepared to stop and wipe it off whenever you think you detect the slide resisting movement a little less. Then feel it with just light oil. It is better to let the last little bit burnish in with oil than to cut it.

If the thing falls open and closed now, you might want to tighten it to a rubbing fit before lapping in order to get the best fit. Note that squeezing the slide reduces horizontal slop, but not vertical. If the barrel is fit up tightly you want to leave vertical alone or you'll have to refit the barrel. If there is vertical play in battery that you want to remove to help tighten the barrel fit or to precede having a custom barrel fit, you need to peen the frame rails down before lapping, too. That is best done with special tools that protect the magazine well.

There is a revolver smoothing trick you may want to try? Mix a slurry of the JB and some well-shaken Breakfree CLP and lap with that. This burnishes some Teflon into the metal as you lap which helps smooth it up.

riverwalker76
March 27, 2010, 10:09 PM
I've heard of guys using Brasso for just the problem you are talking about.

It doesn't cut as fast as JB in my opinion, and it's a lot more forgiving.

Casimer
March 27, 2010, 11:11 PM
Thanks guys. I mixed a little J&B w/ Break-Free, per UncleNick's suggestion - just enough to give the BF a green / brown hue. Then I worked the slide twice w/ a little pressure, then several times w/ just the weight of the slide.

It's a huge improvement, nice and smooth.

This pistol has seen a lot of use. I think that it was an arsenal piece. The surfaces looked rough to begin with.

FM12
March 30, 2010, 07:12 PM
I had thought about this myself, thanks for the post and replies!!