Barrel lapping bullets

[Civil War Life]

I have a rifle with a bore that is dark but has strong rifling. I was thinking of lapping it. I found a product that sounds like it might do the job. It is called Tubb Final Finish Bore Lapping System. Here is a link to the product:
http://www.davidtubb.com/ff-kit-323-8mm-cal
Basically you use their bullets to lapp the bore. Don't want to ruin the gun, but I'm sure that a lapp would help smooth the bore. Has anyone tried this and how well does it work?
Thanks.

[edward5759]

David Tubb bullets have corrected several problems that I have had in the past. One with a $1,300 dollar custom barrel I had made for a 338.
I know several people who run several finish bullets through every rifle they build.

[James K]

A bore is dark because it is pitted so some metal is already gone. Lapping the bore may smooth it, but only by removing more metal. Further, lapping will remove metal from the lands as well as the grooves, so I am not sure just what the overall effect will be.

Lapping a new barrel is a bit different because it smooths out the machining burrs and tool marks, and really is a fast "break in".

Jim

[thedaddycat]

This must be the "fire lapping" method someone talked about on another post I read. I've seen some advertising where the makers of accurized rifles have also talked about "hand lapped barrels". Is there any advantage of one method over another? Someone said that repeated shooting of a single round and then cleaning for barrel break-in did about the same thing just much slower.

[Slamfire]

I assume you have a 8mm surplus rifle. I would not lapp or shoot any thing abrasive down the bore. You will just be removing material and making the bore larger.

I have one Russian capture 8mm, barrel is dark and I believe the rifling wears out as I shoot it. I have stopped shooting it, because it is pointless, and accuracy is poor, but it is better to shoot your rifling out then remove it with a cleaning rod.

[edward5759]

I look at it this way.
If you are going to trash a barrel because it's dark why not try the Tubbs final polish bullets through it.
the bullets use a non embedding compound and the amount of metal removed is less than 1:10 of a thousand.
In the past a governments used Anhydrous ammonia to clean the copper from the barrel. General Pershing had all his rifles cleaned this way. The Anhydrous ammonia will torn the barrel dark. So you never know until you shoot it. 8mm is amazing accurate.
For the small cost of the Tubbs bullets over a barrel you might be surprised. Tubbs hold more records in rifle shooting than anyone I know. he would not produce a product that is going to harm a used barrel.

[Ballenxj]

First, my apologies, I know this is an old thread, but I am really interested in knowing if anybody here has used the David Tubbs loaded bullets for barrel lapping? If so, any improvements on accuracy?
I'm looking to use this on a 308 to get it totally dialed in before hunting season.
Thanks in advance.

[Dufus]

I bought a Savage Axis a couple of years ago to serve as a retirement present, and it was on clearance at Academy.

I scoped the barrel after I shot 5 rounds thru it. The barrel was so bad that I contacted Savage. They replaced the original barrel with one that was worse than the original.

Taking matters in my own hands, I bought some 150 gr cast bullets to use.

The NECO kit is the best in my opinion and I have been using it for many years.

http://www.neconos.com/

For 308 Win., I load 5-7 grains of Red Dot under the 150 gr cast bullet and with the NECO lapping compounds, it works really well.

http://www.neconos.com/details2.htm

[Unclenick]

Zombie thread. It's not a rule buster to revive one, but often a lot of the original participants are no longer active and won't see replies and many are less inclined to chime in when a thread already has a number of posts to read through to get to the modern addition, so it is generally best to start a new thread on the topic.

That's the kit I use. My first Garand came from the now-defunct DCM. Its barrel copper-fouled so badly that I could watch the groups opening up starting at about round 40 of the 50 round National Match Course. The 20-round 600-yard slow fire would start with some 10's and by round 35 I had at least one 9 and at least two more in 35-40, and then in the last 10, there would be at least two 8's and a lot more 9's and maybe a couple of 10's. Then after the match, it would take three or four hours of constant work with Sweet's 7.62 before it finally stopped coming out blue.

When I firelapped it with the NECO kit (using pulled M2 Ball bullets, not cast lapping bullets; the barrel had a long constriction the length of the contour below the lower band seat that needed to be straightened), after the first five coarse rounds it took about 60 passes with Iosso Bore Cleaner (soft abrasive like JB Bore Compound) intermingled with two patches of Butch's Bore Shine to get it clean. At each stage, the number of passes required to get the patches to stop turning blue got fewer and fewer. After the last set of bullets with the 1200 grit final abrasive, it took just ten passes to have no trace. So cleaning got much, much easier and accumulation of copper also stopped. Accuracy was unaffected for the first few rounds and no longer fell apart at higher round counts. Some guns have their accuracy improved by this method, but that element is hit and miss. I know of no instance of it getting worse. The cleaning ease is always greatly improved.

The NECO kit is expensive as these things go, but the laboratory grade abrasive they use works twice as fast and leaves a more uniform surface than you get with technical grades.

Lapping cannot reduce rifling except at the throat, which fire-lapping moves forward a thousandth or two. Once the bullet or lap has rifling marks, it abrades lands and grooves equally thereafter, gradually increasing the gun's caliber, but not reducing the lands preferentially to the grooves and it is very gradual. On the Garand, despite it taking the kit's maximum of 20 rounds of the coarsest abrasive to clear the long contstriction, slugs from the breech end of the barrel were only about 0.0003" larger and still well within the tolerance for nominally .308" groove diameter barrels. The British match teams often used to shoot a lot of .309" groove barrels and claimed to prefer them, though I think they were greasing their bullets. The bottom line, though, is a .308 bullet can easily upset that much with normal firing pressure, so 0.3083" is not going to bother them.

The even application of pressure applies to bullets without abrasive as well. If you have a gun that appears to be shooting its rifling smooth, that almost always turns out to be carbon glaze building up in the grooves. Slip2000 Carbon Killer funneled into the plugged bore and allowed to sit 15 minutes, then allowed to run out into a jar (it's still good) and the bore then brushed will reveal the carbon on its bristles and allow you to work a lot of it out. Repeat until your borescope shows the barrel clean, and you will be amazed to discover the bore color has lightened as well to that of shiny steel and that the rifling has magically re-grown. Carbon Killer is sometimes referred to as rifling fertilizer for this reason.

A slow, but an easier way to do the same thing is to let some Gunzilla run down the barrel and plug it and let it sit for a month or two, then patch it out. The two times I've done this, all the carbon then came out with the first patch and there was no scrubbing left to do. So it's a good approach for seasonal guns that are in their off-season.