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Thread: Abrasives & PP Lapping

  1. #1
    Boolit Master Good Cheer's Avatar
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    Abrasives & PP Lapping

    Well, it's time to go back to resurrecting an abused rifle.

    What abrasives have you tried for fire lapping with paper patches?

    Grinding compounds smeared on the patches before firing?
    Dry powders rubbed on the patch?
    Dry powders sprinkled on a fixative coating?
    What kind of results have you achieved?
    How much larger was the bore next to the chamber versus at the muzzle?

    Can you determine how much metal removal was achieved for how many shots fired?

  2. #2
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    ShooterAZ's Avatar
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    I used a dab of JB Bore on 20 or so paper patches used in a crusty Mosin Nagant. I don't believe the amount of metal removed would be measurable. It was more of a bore polishing, and it worked quite well in that respect. Barrel got very hot! Regular patches with no lube will achieve the same results, although it will take quite a few more rounds down the barrel.

  3. #3
    Boolit Master

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    It could be done with the purchase of a fire lapping kit and substitute the PP for the jacketed. Most of the time the dry lapping compounds come in a way bigger quantity than is needed for this job. The ideal way is to patch the bullet and let dry if wet patched. Then spread a light layer of compound on a piece of flat gage stock. (you can distribute it evenly with a soft brush.) lay a bullet on it and roll between a second piece of gage stock with light pressure to impregnate the patch with the lapping compound. Depending on what you are trying to do 240-280 to start working up to 400-600 should do the job. Cutting will be more aggressive and faster at the chamber end due to the abrasives being sharper and more of it. You will work a slight taper into the bore which isn't a bad thing in reality. Steel hardness, paper used, abrasives used, velocity. and number of rounds fired with each grit will all affect size increase.
    What are you trying to do here, remove tool marks, smooth pitting, smooth cleaning rod damage, or sharpen rifling. A paper patch may cause corners to radoius a little

  4. #4
    Boolit Master
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    What caliber and delivery system are you planning?

  5. #5
    Boolit Master
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    The paper alone will shine the barrel, unless it is a sewer pipe.

  6. #6
    Boolit Master Good Cheer's Avatar
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    Click image for larger version. 

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    It's a 6.5 Dutch carbine dated 1915. Long story. The seller wasn't truthful. The bore was coated with the soft nickel jacket material from corrosive surplus ammo. When cleaned with bore solvent the rotted iron started falling out. The carbine was purchased for a plinker and a small game cast gun, so after a cross country relocation and before doing something entirely different, the project is being resumed to try to polish it out to a usable condition.


    The worse of it is at the muzzle. The rest of the bore is now cleaned up pretty good. The area directly in front of the chamber is of course on the large side due to the the use of corrosive ammo and the polishing to smooth it up.
    Click image for larger version. 

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  7. #7
    Boolit Master Good Cheer's Avatar
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    Where the bore and groove diameters might end up really doesn't matter so long as a boolit can be patched up.

    Having it rebored to .30 or .32 bore and new reloading dies made is a possibility.
    I'd certainly rather have 6.5 but that would be a rebarrel, replace the sights and reblue as well as new dies.
    In the past the fire lapping was done with very aggressive cutting valve grinding compound and also with silica sand.
    If fire lapping gets it to plinking condition then great. If not then oh well, nothing lost and knowledge gained.

  8. #8
    Boolit Master
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    I have used variations of my old Schutzen loads of 12-14 of 4227 (32-40 case) with 1-25 lead. Abrasive mixed with lube and heated boolits and then pan lubed, breech seated fat boolit and popped. My thoughts were the breech seating may not be as aggressive on and save the throat a little. Are you going to do a little something with that muzzle? Good luck with your patient doctor, several of these cases live here and I understand the feeling/pain.

  9. #9
    Boolit Master Lead pot's Avatar
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    The problem with fire lapping is the throat getting eroded to much. Take your time and cast some bore slugs. Index them so you use the same groove the slug was cast in. put a mark with a felt sharpie on the muzzle and core when you push it out. Pouring a slug around a 17 or .22 caliber bore brush makes a good adapter for the cleaning rod. Start with 200 grid Clover compound and end polishing with 600 grid.
    You will never get out all the pits if the bore is rough but the pits will get smooth enough that the rifle will still shoot. Fire lapping is the last thing I will use.
    If you must fire lap I would breach seat the bullet just ahead of the throat with a groove diameter slug and finish the throat by hand.
    Kurt

  10. #10
    Boolit Master 303Guy's Avatar
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    Be careful with rolling compound into the patch. I did that once and the patch would not let the neck go. I ended up with a brass jacketed boolit and a neck-less case!

    Last edited by 303Guy; 08-27-2017 at 04:16 AM.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  11. #11
    Boolit Master 303Guy's Avatar
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    Good Cheer, I have a very accurate rifle with a bore like that. But mine has that bore condition throughout. I shoot jacketed's in it with a hard waxy lube melted onto the slight boat tail. This keeps the bore lubed. I get zero copper fouling in it. It seems the 'rust texturing' holds lube. It's a two-groove and has not proved successful with cast. The rough driving faces cut into the alloy and almost strip through.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  12. #12
    Boolit Master
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    Proper fire lapping kits are available from Brownell's. Why experiment and risk wrecking your bore ?

  13. #13
    Boolit Master
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    I think it is already wrecked by looking at picture, it is quality of life at this point. I have also read a few stories about individuals "wrecking" bores/throats with the kits. I wonder how it would act if you just smoothed it with a couple and tried PC as an experiment, pick up a thou or two with coating for loose pipe.

  14. #14
    Boolit Master
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    I would just use the paper patch, no abrasives. I totally ruined a 25-06 barrel that I fired corrosive primers in and had not cleaned. Who knew Winchester primers could be corrosive? I used 25-20 lead bullets, and valve grinding compound, and totaled it.

  15. #15
    Boolit Master 303Guy's Avatar
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    The idea of fire-lapping is to remove the sharp edges on the pits and that's about all. Just so the pits don't scrape bullit/boolit material off. I rescued a 22 barrel using kitchen abrasive once. My Dad's Orberndorf Mauser.

    I 'restored' a bore that literally had a layer of scale throughout the bore. It's now more like an 8mm and only shoots paper patch boolits. Mind you, I do have a fat cast boolit that I used as a polishing boolit by smearing Auto-Sol on the long nose. The Auto-Sol had to be freshly applied and pretty thick too as that was the 'lube'. The fired cases came out polished! No accuracy with them though.
    Rest In Peace My Son (01/06/1986 - 14/01/2014)

    ''Assume everything that moves is a human before identifying as otherwise''

  16. #16
    Boolit Master Good Cheer's Avatar
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    Decided to see how the cleaned was going.
    Shooting Lyman #266469 with a double wrap of 25% rag and 7 grains of Unique.
    Fired five off the front porch. The fouling shot was a flyer. The next two touched. Started getting excited...
    The last two hit the paper at 90 degrees.

  17. #17
    Boolit Master
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    The fire lapping kits tell you that if you lap with lead boolits the throat will move forward. With jackets not so.

    For cast, a bit longer throat is no issue. Not really even a big deal for jacketed as 1000s of Weatherby have long throats and still kill game with no issues.

    Again, a simple case of RTFI. Instructions DON"T come with the stuff you buy at NAPA or conjure up yourself.

    Save 25 bucks, ruin a barrel ...... makes perfect sense !

  18. #18
    Boolit Master
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    Quote Originally Posted by Eldon View Post
    Save 25 bucks, ruin a barrel ...... makes perfect sense !
    I'm pretty sure that the barrel in question would either be discarded or a candidate for a rebore so no real risk of ruining it. Is there such a thing as ruining it more?

    Ross Seyfried wrote an article about fire lapping a barrel that had a tight spot in the middle. It worked well using a cast boolit and IIRC valve grinding compound. He rolled the boolit on a pane of glass to impregnate the surface with the compound.
    Loaded them just hot enough to spit out the end of the barrel and I think it didn't take too many rounds to do the job.
    I have no idea how a barrel can be made tight in the middle though...

  19. #19
    Boolit Master
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    A couple of Marlins that have, come to live at this house were tight under the rear sight dovetail cut and one under front. I have not had a pin gauge fib to me yet. JM's they are, in letters and numbers and I think we all understand a late day and Friday afternoons don't we?
    Last edited by Gtek; 09-05-2017 at 10:03 PM.

  20. #20
    Boolit Master
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    I use Flitz.
    Available at almost any hardware store. I take two flat pieces of metal (?maybe 1 inch x 4 inches?), put a little Flitz on one plate and roll the bullet while pressuring the two plates together. Small amount of Flitz goes a long way. Roll up 4 or 5 and shoot away. Clean the barrel & inspect. Repeat as necessary. I only do the jacketed bullet and stay away from the brass neck. When chambered, the Flitz is way away from the throat. Cleaned up a bunch of rough and substandard barrels this way. It's never going to be a shinny new barrel, and future use will require more stringent cleaning & preserving. Once the pits are there, they are there. That metal is gone. Fire lapping will sure help out. Good luck.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check