Lead Lapping

[bigcountry]

Has anyone lead lapped a marlin barrel? How much did it open up the barrel lands and grooves? Did it help?

[stubshaft]

I've lapped all six of my Marlin barrels both in Ballard and microgroove. They opened up .0015" on average. More importantly I have found they usually have a slight constriction by the barrel band that was removed.

[bigcountry]

So I have done old rifles. But this is a newer rifle. Kinda scary pouring molten lead down to make the slug. What grit progression did you use? I notice at the throat its very rough. and would like to smooth that out a bit.

[Norske]

I haven't had the courage to try this, but a well-known cast bullet gun writer suggested using lead fishing egg shaped sinkers for slugging a bore. They are pure lead so are soft enough to get into the bore, and he claimed they weren't difficult to push through. However, Murphy likes to haunt me, so I haven't tried it. I think the trick is to match the bore/sinker diameter closely.

[john.k]

If not familiar with the pitfalls ,the muzzle can be bellmouthed ,ruining accuracy......Its also possible to get a jam with a too tight lap and grit ,and have a considerable obstruction.......What surprised is that marlins "Deep grooved Ballard rifling" is actually only .0025" deep.....seems the "deepgroove " is no such thing ,and simply the old microgroove with half the number of grooves.

[stubshaft]

I've been lapping barrels for years and use an article from Guns &Ammo which was printed in the mid to late 60's as the basis of my lapping. I use a patch jag which has been wrapped with cotton twine on the end to seal the bore. I oil the bore and stand it vertically and place the jag into the bore about 1" - 1 1/2" deep. I heat the barrel slightly and pour pure lead into the bore to make the lap. Two things become readily apparent and they are that the lead will NEVER adhere to the oiled bore and that the pure lead lap cannot be too tight. The only way the lap would be "too tight" is if the bore are was ALREADY OVERSIZE, and even then being pure lead it can still be pushed through the bore. I also put a formed cartridge case in the chamber which has had a flat based bullet reversed and crimped only slightly protruding from the case neck. This is to insure that I can take full strokes with the lap and not have it fall out in the chamber.

I generally start with 400 grit compound (I have an old NECO lapping kit) and withdraw the lap slightly after every 4 passes to recharge the lap. I will also take a mill file and use the corner to score the lap allowing it to hold more of the compound. With the coarser compounds you will wear out laps very quickly and have to repour/remake them as needed.

I usually go to 800 grit and then switch to Flitz to polish the barrel.

[bigcountry]

If not familiar with the pitfalls ,the muzzle can be bellmouthed ,ruining accuracy......Its also possible to get a jam with a too tight lap and grit ,and have a considerable obstruction.......What surprised is that marlins "Deep grooved Ballard rifling" is actually only .0025" deep.....seems the "deepgroove " is no such thing ,and simply the old microgroove with half the number of grooves.

Yes, very shallow.

[bigcountry]

I've been lapping barrels for years and use an article from Guns &Ammo which was printed in the mid to late 60's as the basis of my lapping. I use a patch jag which has been wrapped with cotton twine on the end to seal the bore. I oil the bore and stand it vertically and place the jag into the bore about 1" - 1 1/2" deep. I heat the barrel slightly and pour pure lead into the bore to make the lap. Two things become readily apparent and they are that the lead will NEVER adhere to the oiled bore and that the pure lead lap cannot be too tight. The only way the lap would be "too tight" is if the bore are was ALREADY OVERSIZE, and even then being pure lead it can still be pushed through the bore. I also put a formed cartridge case in the chamber which has had a flat based bullet reversed and crimped only slightly protruding from the case neck. This is to insure that I can take full strokes with the lap and not have it fall out in the chamber.

I generally start with 400 grit compound (I have an old NECO lapping kit) and withdraw the lap slightly after every 4 passes to recharge the lap. I will also take a mill file and use the corner to score the lap allowing it to hold more of the compound. With the coarser compounds you will wear out laps very quickly and have to repour/remake them as needed.

I usually go to 800 grit and then switch to Flitz to polish the barrel.

How much did lands and grooves grow on barrels like marlins?

[OverMax]

Had me confused for a moment. Not in anyway critiquing just clarifying a bit for my own benefit. Is Lead lapping one in the same technique called> Slugging the Barrel? If so, the only barrel I've slugged is a Win 94 32 special just prior to paper patching its NOE cast. Didn't pour lead. As told here. Used a cat fish sinker. Worked good.

[rockrat]

Lead lapping is NOT the same as slugging a barrel.

[c0wb0y84]

I’ve put some lapping compound on slugs and pushed them through as if I were slugging a barrel. It didn’t do as much as I had hoped but it did improve the barrel.

[stubshaft]

How much did lands and grooves grow on barrels like marlins?

It depends on what you are trying to accomplish and the barrel you are working on. I've removed slight constrictions with an increase of only .001". The trick is to go SLOW and not be too aggressive.

[bigcountry]

It depends on what you are trying to accomplish and the barrel you are working on. I've removed slight constrictions with an increase of only .001". The trick is to go SLOW and not be too aggressive.

I got a new 1895 and the bore thru a scope is rough as a cob. When I first started shooting cast thru it, I thought it was leading, but it was actually rough. So main reason is to make it easier to clean.