Bore Lapping

[JonnyV]

Having read through past posts on bore lapping, I would like the opinions of guys on here who have actually done the process.

Did you use the Wheeler kit or something like it?

Did you load with BP or a light charge of pistol powder?

What barrel did you start off with and did the process improve accuracy or fouling control?


Thanks!!

[bobw]

Did you ask Kirk if he thinks his bores need to be lapped? Polish a bore the right way use paper patched bullets..Bobw

[JonnyV]

Wow that's very helpful, thanks Bob.

[mike herth]

I found it helpful, thanks Bob! But I have other issues.

[semtav]

Wow that's very helpful, thanks Bob.

Ha!!
I was going to say the same thing as Bob.

Last time I tried lapping, it was on my rebored 40-65 barrel. It was so rough it would lead up after a couple shell.
Tried shooting jacketed bullets and it would turn the bore solid copper colored.

Tried shooting the lapping compound system on cast bullets.

It was advertised as hand lapped when he rebored it.
Finally gave up and put it away.

Couple years later drug nit out and tried paper patch in it. Never looked back.


So......
. Bob's advice is really good advice.

[JonnyV]

Bob has a bit of caustic wit about him and he knows I shoot greasers. He did take several minutes out of his practice at the Q this year admonishing me on all the reasons I needed to switch over to the diapers.

I got the idea of bore lapping in my head going back and re-reading a lot of old posts on this forum. Apparently there are reasons to do it, and some barrels may benefit more than others (even paper patch barrels). Generally, I like to collect as much information as I can and then decide if I should do it or not. Lots of times I'm asking questions for this reason. No offense to Bob...

[DaveC]

I do fire- (pressure-)lapping now and again.

Have never done it on a barrel that shoots fine already, with the idea that it will be “even better” afterwards. (I grew up reading the story about the fisherman, the magic fish, and the greedy wife.) But on a chamber that has a rough leade, a revolver that might have pinch points, or a rifle with the usual scuzzy (but still shootable) barrel frequently found on gun-show souvenirs (my .45-70 flatside Highwall, for instance), here’s my procedure.

Develop some kind of optimum plinking load, based on the grouping at 50 yards. If 4” is the best it does, make up 20 of the loads for starters.

Cast up from range scrap, or anything else cheap or free, some Ideal 457191 300-gr bullets. You need neither length, weight or perfect castings. Get two strips of mild steel and some Clover 320 grit valve-grinding compound. Put a blob of this compound on one of the plates and spread it around with a popsicle stick. Put the bullets on the strip, and with the other strip, roll them back and forth to load the grooves with the abrasive, and press it into the lands. Renew and spread the abrasive as it gets used up. I make up 50 of these bullets, and with tweezers put them into a foam plastic holder for .45 Auto ammunition, found in the trash barrels at rifle ranges.

To the range, I take the rifle, a cleaning rod, brush, jag, lots of patches, rags, scissors, tweezers, a piece of 3/8” dowel, a re/decapper, primers, a powder measure set to throw ~10gr of Unique (or something similar that will get the bullet out the barrel at low velocity), some targets, the block of bullets, and one .45-70 case; ideally one I’ve tossed because of mouth cracks or something minor like that. And of course, the bench rest, scope and all the other stuff you’d take shooting. Set up like you’re going to test some loads.

Prime the shell, drop in the charge, put an abrasive-loaded bullet in the chamber as deep as possible with the tweezers, and press it into the leade with the dowel. Follow it with the charged case, aim and fire at a target. Remove the case, wipe it, and the breech, with a rag, reprime the case, load and fire four more times.

Clean the bore with a patch soaked in solvent, then brush the bore vigorously, and clean again with patches and solvent. Then fire five more lapping rounds as described, and clean and brush again, as described. The worst spots in the barrel will build up lead, which will protect those spots from being polished by the abrasive. Get it all out. As you keep shooting, the amount of lead you see on the patches will (hopefully) diminish.

Keep track of your “groups” on the target. They may tell you something. But after some number of lapping rounds, I clean bore, chamber, breech and everywhere I can reach with patches, solvent, tweezers and rags, and shoot a group with the “optimized” load. Then I go back to the fire-lap loads, five at a time, and clean.

Generally, what I see as the exercise progresses, is some shrinkage of both the lapping load groups and those of the optimized test load. The bore will get shinier as things progress, and I notice the barrel gets warm from the friction of the lapping loads and stays warm until the test loads sweep the embedded grit out of the barrel.

Where to stop? Kind of an operator judgement call. I’ve done as much a 100 or more lapping rounds before deciding this is as good as it gets. Using this process (developed by Merrill Martin in Precision Shooting back in the 80s), I’ve never made a barrel worse. In the case of the Winchester, groups that averaged 4” @100 before lapping got down to 2-1/2”, sometimes less.

Innovations on the process, like machine-gunning the lapping loads downrange, using abrasive-coated jacketed bullets, using full-velocity/intensity loads for lapping, I haven’t done. I do notice those that do are the ones that complain On Line that “I ruined my barrel by fire-lapping. It doesn’t work.” Draw your own conclusions; I’ve drawn mine.

Throw away your single reloaded lapping case. If it gets mixed back into your others, it will scratch dies and abrade everything else it touches. You can save it for further lapping, but it’s finished otherwise.

Not exactly a fun day at the range. But it is shooting, and you don’t have to set the barrel up with stops, cast laps on a rod, and do the physical work of hand lapping. And then haul everything to the range to see if you’ve improved things. And then go back to the shop for more. I have done this, but fire lapping is somewhat less physical effort, anyway.

[JonnyV]

Thanks Dave. I had read a description of fire lapping on the web somewhere a few years back but couldn't find it again. Your account fills in the gaps.

[kwilliams]

Jonny V never said he was lapping a Shiloh, although maybe he is. The LBT method is done by seating the grit slug as deep into the case as it will go, different than the breech seat method just described. The LBT method I have used and did make a improvement on the machine marks that caused leading. This barrel still had issues so I rebarreled the gun and this winter will use the long lead lap and will be able to achieve a bit of choke while at it.
kw

[bobw]

I still stand on what I said, take it anyway you want. Run a 1000 rds of ppb thru a barrel and it shines like the sun in a mirror. Not part of a ppb'ers routine to have to pound a cleaning rod thru his barrel to remove lead. That is part of the greaser shooter realm. You want answers but don't like what is freely and generously given. Suit yourself. bobw

[JonnyV]

It’s not liking or disliking your answer Bob. It’s that I was looking to get info on bore lapping. There are 20 rifles in my safe. Everything from 22’s up to my 45-90. Only two rifles I own would be candidates for PP bullets (45-70 Shiloh and 45-90 CPA).

As far as my reasoning behind asking goes, I have four lever actions that I am looking to go all black powder with. You can’t be running bore wipers or blow tubing when you’re out levergun shooting. Dan T posted on here that lapping a barrel would help greatly with fouling control. I might try it first on a Chiappa 45-70 1886 I have, and if it works, move on to my 45-60 and 44 special leverguns. Might try it in my 30-30’s too. And yes, if it works out I would very likely do it with the Shiloh and the CPA as well. I want to learn the ins and outs before I just haul off and do something though.

[Kurt]

I have lapped barrels, mostly muzzle loaders but also BPCR barrels.
If your barrel was button rifled and not honed before the button was pulled through it will look like a wash board like the bore below that is new unfired. Those ripples are only microns deep, I doubt that you can even measure them.
I will go along with Bob about shooting PP bullets The second photo is the same bore with PP bullets shot through it. I never have finished lapping a bore that looked this smooth using fire lapping or hand Lapp with slugs made of lead or turned brass for tight spots

IMG_11802.jpg

bore 4 (2) 3.jpg

[bobw]

Thanks Kurt, now if you would be good enough to explain to Johnny v how to make his 45-2.4" cpa shoot using ppb's of course. As I recall that was the very gun you went straight with at the Mt 1000 on target 2 or was it #3?

[JonnyV]

I didn’t get any 8-straights. My partner Dave did on the 600. I screwed myself three times out of a pin. There’s always next year.

That CPA shoots really good.

[Kurt]

Bob,

It was the .44-2.6 at the Mt 1000 target #4 after changing the load because of only getting a 50% hit and the .45-2.4 on the big hill at the 1023 I went straight.
I cant tell anyone how to make their rifle shoot. Ladder loads and time behind the butt plate might do it.

Bob I retired the large capacity cases and gone with the little .38's. The .45-2.6 tore up both eyes at the Q last June and couldn't shoot it.