Lapping a barrel

[machinegun]

Planning on lapping a rifle barrel in the hopes of increasing accuracy. Have been told that bon-ami may do as good a job as JB compound. Anyone have any experience with this?

[felix]

Yes, depends on the barrel material for how fast it works. Calcium carbonate is quite soft compared to silicon dioxide. ... felix

[yondering]

Are you "lapping" or "polishing" the bore? There's a difference. JB compound will polish nicely, but it's not going to remove barrel constrictions, which is generally the purpose of lapping.

[truckjohn]

Yeah,

I wouldn't fool with Bon Ami..... Very very very very soft.
It is advertised to "Not Scratch your pots"..... which are mostly soft stainless.

We need something that will actually abrade away the steel.... like real Lapping compound.

Personally, I would leave the true Hand "Lead Lapping" operation to an experienced smith.... unless you can afford to ruin a couple barrels for the sake of learning. If so, buy a couple "Clearance" type used barrels, and lap away..... I put a nice "Fishbowl" in the middle of an old Marlin barrel this way.

On the other hand... I have performed Fire Lapping on a couple of guns now -- and it worked extremely well.

My own experience with fire lapping is.....
1. Only do the fewest rounds possible to remove the restriction/clean up rough spots.
2. Clean clean clean after with Soap and Water.
3. Clean more with soap and water.
4. Keep cleaning with soap and water.
5. Shoot about 30 rounds standard ammo, clean per regular schedule.
6. Clean clean clean clean.
7. Work up new reloads to compensate for lower velocities.

Thanks

John

[machinegun]

A good friend (high master rifle shooter) described lapping as others have described polishing in this thread. The barrel has no restrictions, I simply want better groups. My best groups with cast boolits (after a thorough cleaning) has been about 1.5" at 100 yds.
I want better.

[felix]

Get a BR gun to start with, and learn to read conditions. Then you'd have groups hovering around 1/2 inch at a hunnert using cast boolits. ... felix

[machinegun]

I already have rifles that shoot sub MOA. Now I am working with this one and would like for it to at least shoot MOA.

[wiljen]

800-1600 grit clover compound jumps to mind.

[yondering]

Other than 1.5 MOA, what other "symptoms" does your rifle have? Excessive fouling? Rough/pitted barrel? Or just doesn't shoot as well as you'd like?

If accuracy is your only reason to polish the barrel, you should probably be looking into other things on the gun first. Proper action bedding, load details, boolits, lube, powder, etc are all things I would get squared away before lapping. Rifle barrels I have polished, that did not have barrel constrictions, showed little to no improvement in accuracy. They did shoot much cleaner afterwards, but maybe that's not what you're after.

Don't lap or polish your barrel just to do it, without being aware of what results you will get. You may trash a perfectly good barrel.

[Bass Ackward]

Planning on lapping a rifle barrel in the hopes of increasing accuracy. Have been told that bon-ami may do as good a job as JB compound. Anyone have any experience with this?



If you have nothing wrong dimensionally, chances are lapping will be disappointing. Especially the way you are wanting to do it.

Since you have many accurate rifles but little in the way of success that satisfies you, I will say you have a problem of bullet fit. 99% of the time proper bullet fit and design will produce better results. My advice to you is to slug first. Slug your throat and your bore. This will give you a better idea of how to fit a bullet to do well and how you have to size it.

Once you get bullet fit correct, cast will shoot as well as jacketed. Almost anything works well. Once you are satisfied, I recommend the Tubb's system for minor work.

[machinegun]

After several dozen patches (only a few out the bore) using JB compound and the traditional cleaning, I was able to get a three shot group down to .392" using 42 gr of reloder 15 pushing that 280 gr cast boolit.
The more powder I used above 42 gr the larger my group got. But still, my worst groups now are as good as my best groups two weeks ago.

[Bass Ackward]

After several dozen patches (only a few out the bore) using JB compound and the traditional cleaning, I was able to get a three shot group down to .392" using 42 gr of reloder 15 pushing that 280 gr cast boolit.
The more powder I used above 42 gr the larger my group got. But still, my worst groups now are as good as my best groups two weeks ago.


Congratulations. After spending the time, you have reaped the rewards.

Gotta love that RL15.