Lapping compound?????

yooperchuck · Posted: Thu May 04, 2006 8:41 pm Post subject: Lapping compound?????

Thank you all who responded to my question regarding David Tubbs and his lapping rounds he sells. I think after reading all the fine advice I would like to do the lapping on my own. Can someone help me choose what I will need to purchase in order to lap my .308? I will be purchasing a new savage 7mm mag in two weeks and intend to lap the barrel before I ever shoot it. Would I use the same procedure for the savage 7mm as I would use for the .308 remmy?

popgun · Posted: Thu May 04, 2006 8:58 pm Post subject: Re: Lapping compound?????

Why don't you shoot it first and see if improvement is needed. Personally I would simply use a break in procedure that has been posted here recently. For a factory barrel a shooting break in procedure is usually going to give you the best accuracy possible. You will not get custom barrel accuracy by lapping any factory barrel.
If you are set on lapping everything you need to buy is at Brownell's.

DallanC · Site Admin Joined: Jan 18, 2005 Posts: 3571 Location: Utah

I have successfully used "lapping compound" to revive an otherwise poor shooting rifle... however I do it manually. The thought of "firelapping" makes my sphincter spasm LOL!

You can buy lapping compound at your local auto parts store. It usually comes in 3 or so grits, use the finest for your barrel work. If you chose to do it by hand be careful to run the rod all the way in then back out, full strokes not partial ones is the key. You are basically just trying to polish the inside of the barrel, not sand it down Wink

-DallanC

guncollector · Posted: Fri May 05, 2006 10:34 am Post subject: Re: Lapping compound?????

I wouldn't do this on a new barrel or one that was shooting well already but I have had great luck cleaning / polishing the bore of older rifles with a piece of nylon scouring pad - the kind you might use to clean rust off the surface of metal or to clean whatever. You cut a piece the size of a cleaning patch, put it on the end of an undersized bore brush, and back and forth a hundred or so times. Stay away from the muzzle and throat, i.e. reverse directions just before either the muzzle or the throat.

I have really improved accuracy and reduced fouling in military barrels with this technique.

Blaine · Member Joined: Feb 24, 2005 Posts: 260 Location: Maine

I get my lapping compound from Brownell's.....stock# 083-041-800. That is the 800 grit compound.

Blaine

DallanC · Site Admin Joined: Jan 18, 2005 Posts: 3571 Location: Utah

guncollector wrote:

Stay away from the muzzle and throat, i.e. reverse directions just before either the muzzle or the throat.

Be careful where you start stop... if you are going to do it before the crown or throat try to reverse direction in different places. This is because where you do stop / reverse the direction of the rod will have more friction and will wear that spot of the barrel fractionally more than the other places. This is why I like a steady "all the way through" for a direction motion.

-DallanC

yooperchuck · Posted: Fri May 05, 2006 7:24 pm Post subject: Re: Lapping compound?????

Thanks guys....you are all making me smarter every day........

mc223 · Posted: Fri May 05, 2006 10:18 pm Post subject: Re: Lapping compound?????

One thing I have learned over the years about barrel lapping is a little goes a long ways. If you use a very fine lapping compound you are less likely to over lap at the ends of the stroke. It is very time consuming to properly lap a finished barrel which means starting at the breech and making full passes through the barrel in one direction only.
Wheeler engineering makes a kit to impregnate your bullets to fire , hence lapping the barrel. Midway sells the stuff for about $16. I used the Wheeler lapping kit on an old and very corroded barrel in 7 Mauser. I started with poor accuracy. About 10 inches at 100 yds. After I had fired about 50 grit impregnated bullets and had cleaned the barrel the accuracy did improve to about 4 inch at 100 yds.

PaulS · Posted: Sat May 06, 2006 10:10 am Post subject: Re: Lapping compound?????

Lapping (tool surfaces) is done to remove the high spots so that the surface is smooth and planer (level). I thought that barrel lapping was for new barrels. Isn't it meant to remove the high spots that are left from the rifling process?I would expect a worn barrel to get worse with lapping instead of better. Corrosion causes pits, not high spots like machining does. That being the case, lapping an old barrel would make it sloppy, or sloppier rather than better. I guess if it works you just accept it.

Deleted_User_2665 · Super Member Joined: May 06, 2006 Posts: 380

I draw a line on what barrels need lapping/fire lapping.......

New quality centerfire barrels suffer the best improvement via a good and smart break in proceedure.....

Rimfire barrels and black powder barrels improve ten fold by firelapping via 20 or less shots using a slooooow slug and Mother's Mag Wheel Polish....

I have groups that have labled me a liar due to how well that system works........<grin>

mc223 · Posted: Sun May 07, 2006 9:37 pm Post subject: Re: Lapping compound?????

Lapping (tool surfaces) is done to remove the high spots so that the surface is smooth and planer (level). I thought that barrel lapping was for new barrels. Isn't it meant to remove the high spots that are left from the rifling process?I would expect a worn barrel to get worse with lapping instead of better. Corrosion causes pits, not high spots like machining does. That being the case, lapping an old barrel would make it sloppy, or sloppier rather than better. I guess if it works you just accept it.

I never said the barrel was corroded or pitted. It was in very good condition. It just was not as accurate as it could be as shown after fire lapping. The fire lapping process removes very little material. Usually less than .0003 but does tend to signifacantly smooth the barrel. this smoothing especially at the exit of the muzzle will help with accuracy. Maybe I could have just had the barrel recrowned.

PaulS · Posted: Mon May 08, 2006 7:50 pm Post subject: Re: Lapping compound?????

Mc223said

Quote::

I used the Wheeler lapping kit on an old and very corroded barrel in 7 Mauser. I started with poor accuracy. About 10 inches at 100 yds. After I had fired about 50 grit impregnated bullets and had cleaned the barrel the accuracy did improve to about 4 inch at 100 yds.

I am sorry - I misunderstood - I assumed that when you said the barrel was "old and very corroded" that it was pitted and in bad shape. I do a bit of lapping for pump parts that I build and .0003" is about right for lapping a well machined part. I ususlly use a sheet of crocus cloth on a machine block to do my lapping. I don't know what grit you would call it but I do know it is finer than 1200 grit.