Barrel Lapping

Discussion in 'Technical Questions & Information' started by CountryGunsmith, Feb 24, 2003.

  1. CountryGunsmith

    CountryGunsmith New Member

    Joined:
    Jan 29, 2003
    Messages:
    5,115
    Location:
    Deep Piney Woods of East Texas
    Mauser45
    Member
    Posts: 18
    (1/5/03 10:57:15 am)
    Reply | Edit | Del All
    ezSupporter
    Barrel Lapping
    --------------------------------------------------------------------------------
    Any one out there have any experience with lapping barrels or know of a good site that has detailed instructions? I've been searching and all I have found are general descriptions. I am very familiar with lapping in general but there are a few points that I don't know, such as;
    1.-What grit sizes are recommended
    2.- How much smaller than the groove diameter will the lap normally be after it cools and shrinks.
    3.- Is there a recommended lead/tin mixture
    I have been experimenting the last couple days using melted down fishing sinkers which I think are nearly pure lead and the laps come out about .002" under the groove diameter of the barrel after cooling. This seems to me to be OK, since the lapping compound grit will embed itself into the lead and size itself to the groove diameter as it is initially driven into the barrel. I found that I have to gently hammer the lapping rod down through the barrel a couple of times to get the lap loose enough to pull back and forth. ( it's still hard!). I use cerrosafe to measure the barrel at the muzzle and ahead of the chamber throat. then I drive a lead slug down through the barrel to find any tight spots. By measuring the lead slug and comparing it to the cerrosafe castings I can get a pretty good idea of the barrel dimensions. Currently I am using Clover 500 grit lapping compound (carbide). I would appreciate any help that you folks can give me. I'm gonna lap everything in sight before I'm done!

    kdub01
    *TFF Senior Staff*
    Posts: 1697
    (1/5/03 12:39:13 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Haven't hand lapped any barrels, although I have firelapped several using the kits supplied by NECO. They supply grits in 4 grades; 220 (coarse), 400 (medium), 800 (fine), and 1200 (polish).

    The barrels I've firelapped seem to group better and clean much easier. One thing to remember, tho - all these lapping processes are removing metal, just the same as so many bullets fired down the bore. All you're doing is accelerating the process of bore wear with the lapping to derive a worn barrel. Figured I lost probably 200 rounds of barrel wear with the lapping, but in the scheme of things this didn't bother me as I've only shot out one barrel in my life - a 25-06 Ruger #1 that saw some really hot loads.
    "Keep Off The Ridgeline"


    Mauser45
    Member
    Posts: 21
    (1/5/03 6:37:34 pm)
    Reply | Edit | Del
    ezSupporter
    Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Kdub01,
    Thanks for your reply. Knowing the different grit sizes will help. 220 grit seems awfully coarse to use on a decent barrel but I have to believe that they have tested their abrasive bullets thoroughly. I haven't tried the fire lapping method yet but it makes good sense. I have been checking in to it on the web and most people seem to agree that it does improve their accuracy. Sure sounds a lot easier than hand lapping! My main goal with hand lapping is to get my barrels as perfect as I can. No taper or tight spots. Match barrels are supposedly uniform within about .0002 and I would like to get my barrels this good, if I can do it without having to go oversize on the barrel dimensions. I ran across some info from Lilja Barrels that said that you can get a barrel too smooth if you use too fine a grit. This causes too much of an increase in bore friction and causes excessive bullet jacket fouling. Must be the opposite of having a rough bore. They didn't state what grit size they consider to be too fine.

    Zigzag2
    *TFF Senior Staff*
    Posts: 5109
    (1/5/03 7:32:10 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Howdy Mauser45, I only know of Warpig lapping the barrel of his shotgun, he had blisters on his lips before he got done.

    Welcome Aboard!



    Quote:
    --------------------------------------------------------------------------------
    "Tell the gossipers and liars I will see them in the fire" - Johnny Cash, Let the train whistle blow
    --------------------------------------------------------------------------------


    ZiggedandZagged@aol.com



    Mauser45
    Member
    Posts: 24
    (1/6/03 3:16:09 pm)
    Reply | Edit | Del
    ezSupporter
    Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Ha!! Good one Jigjag2! I'd recommend using a lot of oil if Yer gonna start lappin' the outside of a hot barrel. You want yer tongue to come out a nice golden brown. If you blister your lips like an over cooked hotdog, you aint doin' it right

    kdub01
    *TFF Senior Staff*
    Posts: 1719
    (1/6/03 6:32:10 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    piggie's gonna resemble that remark!!!!
    "Keep Off The Ridgeline"


    308bolt
    Member
    Posts: 44
    (1/6/03 8:15:07 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Don't lap barrels outside in the winter.
    You'll get your tongue stck.

    Zigzag2
    *TFF Senior Staff*
    Posts: 5130
    (1/6/03 9:07:30 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------


    Celt
    Member
    Posts: 12
    (1/7/03 1:34:02 am)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Actual hand lapping a barrel is NOT something to be done at home. Real hand lapping is a long learned skill at can easily ruin a good barrel if done wrong. It is also used to make the bore even and get rid of tight spots wich destroy accuracy.

    For at home "lapping" to smooth the bore to reduce fouling, the best methode I have seen is the Tubbs final finish kit.
    I would still just use the higher grit bullets to smooth it out, and start with 1/2 the number reccomended. There is no need to use all the bullets if a few will do the trick. Using more will only erode the throat faster causing a shorter barrel life.

    The lead laps are an old fashion and non accurate way to hand lap, as you have proven by the shrinkage. lead also will not make the bore consistant in diameter. If the area of the bore that you make your slug in is smaller than another part of the bore, it will not work. That is the case 99% of the time.

    I lap bores in a much different way and use guages while doing so. These guages are in .00010 incremants.

    I will not go into how I do it because it is not for use at home and I dont want to share trade secrets

    FWIW,
    Celt
    H.D. Rifles

    warpig883
    *TFF Staff*
    Posts: 5783
    (1/7/03 3:29:11 am)
    Reply | Edit | Del
    ezSupporter
    Re: Barrel Lapping
    --------------------------------------------------------------------------------
    please send the lube to me, I got blisters trying to do this by hand.



























    ZZ you are a EVIL man
    Ignorance is a crime in 49 states. In the other one it is bliss. Edited by: warpig883 at: 1/7/03 12:24:39 pm


    Zigzag2
    *TFF Senior Staff*
    Posts: 5144
    (1/7/03 12:29:51 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    hey, don't you know you're supposed to switch hands?



    Mauser45
    Member
    Posts: 36
    (1/17/03 7:15:12 am)
    Reply | Edit | Del
    ezSupporter
    Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Celt, thanks for the input! I agree 100% that lapping is not a process to be used by just "anyone"! Unless a person has some experience at lapping they will do more damage than good! As a toolmaker I am experienced at flat and cylindrical lapping as well as precision measuring, so I regard myself as a "safe" person to experiment at barrel lapping . I am assuming that you are using Deltronic Pin Guages to measure the bore diameter? Sounds like a really good idea since you can slide them down the barrel and increase the size until they stop in the barrel. This would show any tight spots and you could measure how far down the barrel the tight spot is.
    I have several "scrap" barrels to play with. There are a LOT of problems with this proceedure. The slugs wear down after on ly a few strokes so you have to frequently cast a new slug to try to maintain a tight fit. Lotsa luck!! By the time you have managed to get the slug down the barrel a couple of times or enough to be able to "free it up" so that you can pull it back and forth, the slug is already loose in the barrel! If you can pull and push the slug down the barrel it has to be smaller than any tight spot in the barrel ( or it would stick at that point). At this point, I am assuming that the custom barrel makers lap their barrels just to make them smooth, to cut down on bore fouling . My reason for lapping a barrel was to be able to get the dimentions in the barrel uniform from reciever to muzzle, however, this does not seem to be a very good way to do it.
    I haven't tried fire lapping yet but it sure seems to be the way to go! That bullet is a lot harder than a lead lap and when it slugs up to fill the grooves and screams down the barrel it surely ought to grind out any imperfections and undersize areas.


    kdub01
    *TFF Senior Staff*
    Posts: 1824
    (1/17/03 3:26:08 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Mauser -

    Suppose you could always "bump up" the lapping slugs when they get too loose - compressing in a vise or smacking them with a mallet.

    With the fire lapping, you have your choice of either using reduced load jacketed bullets or provided caliber specific lead bullets. I've used the provided lead bullets to slug the bore after fire lapping sessions to check for progress and have been able to determine tight spots if left after the fire lapping. The directions that are provided by NECO (haven't ever tried the other kits) are fairly detailed so that you can lap to the degree you desire. I've lapped a couple of 6.5 bores and still have lots of grit compounds left over for a bunch more. If wanting to lap other bores, all that is needed is the specific lead bullets to gauge progress.
    "Keep Off The Ridgeline"


    Celt
    Member
    Posts: 14
    (1/17/03 11:19:19 pm)
    Reply | Edit | Del Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Mauser,
    I know the woes of the lead lap. That is why I do not use it anymore.

    one has to be very carefull of sticking guages in the bore too. When the method i use was being developed, there was a couple barrels that got trashed because of a stuck guage.

    I cant really go into detail on how I do it because the guy who started developing it has asked me not to. Since he offers this as one of his services, I will not let the cat out of the bag. I personally do not offer that service because I am in the business of building rifles with great barrels that do not need it. If a barrel is bad enough to have to alter the dimensions inside, the cost I would have to charge for lapping would be over half that of a new barrel. Then, it is guaranteed to shoot.

    Fire lapping can be a great way to smooth the bore for fouling, but From what I have seen, it does little to relieve tight spots.

    about .0004 is all you can safely alter a bore, but usually it is enough.

    If a barrel is loose at the muzzle the best bet is to cut a couple inches off and recrown.

    FWIW
    Celt
    H.D. Rifles

    Edited by: Celt at: 1/17/03 11:22:23 pm

    Mauser45
    Member
    Posts: 39
    (1/19/03 7:27:00 pm)
    Reply | Edit | Del
    ezSupporter
    Re: Barrel Lapping
    --------------------------------------------------------------------------------
    Thank you everyone for all of the replies on the subject of lapping. The information that you people have provided will no doubt save me a lot of hours of experimenting. Lapping is something that I always wanted to try and I finally got around to it. I am disappointed, because I had thought that it was "The Method" that you used to make perfect barrels or to make them more accurate. Having to use lead seems to be the weak point in this method, it just doesn't maintain its size long enough to accomplish much.
Similar Threads
Forum Title Date
Technical Questions & Information Crowning a barrel Monday at 10:10 AM
Technical Questions & Information Dan Wesson barrel removal? Nov 18, 2014
Technical Questions & Information Rifle scope height above barrel Nov 15, 2014
Technical Questions & Information What is the approx. cost of changing barrels and cal. Nov 5, 2014
Technical Questions & Information Does Linseed Oil form a polymer layer when baked on a barrel? Oct 28, 2014

Share This Page