Just got done using Marshalls kit to fire lap my 444 Marlin. Unbelievable difference in accuracy!!!!! I would wholheartedly recommend this kit to anyone looking to enhance the accuracy of any rifle or pistol. Now, if my Beartooth Bullets would just get here (I know, they are a bullet worth waiting for), I can really turn this rifle into a tack driver!!!!! My compliments to Beartooth on their Fire Lapping Kit...Great product!!!!
DOK; The bore looks like it has been chrome plated! Right off the bat I noticed that the velocity increase was there......my group printed about 1 1/2 to 2 inches lower than it did before...with the same load!
I've had excellent results with a number of revolvers, pistols and rifles via fire lapping. All except a .22 showed verifiable accuracy imporvement. Amazing how nice and shiny they get, isn't it? I just fire lapped (five grits with 10 shots each and then clean) the new 45-70. I use gas checked bullets but some leading still occurs, but a lot less with the fire lapping and easiliy removed with the Lewis Lead Remover.
DOK; The "load" I used to verify accuracy improvement, was just a load, and the bullets were not properly sized for the bore (.430 rather than .432 as they should be). It shot 3 to 3 1/2 inch groups out of my rifle (25 yards) before the fire lapping. To my way of thinking, if the fire lapping had any noticable effect the reduction in group size would be easily noticed. To my surprise, the groups after fire lapping where in the 1 to 1 1/4 inch range (25 yards)! That is a substantial increase in performance.......and no leading was observed! I can only imagine what a properly worked up load with correct sized bullets will do!!!
Jim; The original lead cut at the chamber throat from the factory rifling process is still quite sharp, and my test cartridge "indents" at the same spot on the bullet as it did before the fire lapping process was done. So, I guess my answer would be, very little, if at all.
I've firelapped a number of M1 Garand barrels when I was replacing them on club guns. It was necessary to clear out the constriction the asymmetric military barrel contour produces when the barrel blanks haven't been fully stress-relieved. I have one of those armorer's throat wear gages that goes from 0 to 10 thousandths (from "new" to "replace"), and a muzzle wear gage. Between those and slugging the barrels and mic'ing the slugs, I found the bore at the muzzles opened around one ten thousandth in diameter, the breech end of the bore opened about three ten thousandths (and the constriction was removed; another three ten thousandths in these barrels), and the throat wear registered just about an even one thousandth. This means that if the barrel had started out straight, it would be about a ten thousandth wider at the muzzle and gradually tapered up half a thousandth to the breech. Not a bad condition to have, especially for cast bullet shooting.
As an aside, the first Garand barrel I firelapped was on my own gun and was the military barrel that came with it. That barrel fouled very badly, but it shot well when it was clean. After bedding the gun, it would put 168 grain MatchKings over 46.4 grains of IMR4895 into 0.7 moa at 100 yards from the slinged-up prone position. But after about 40 rounds, the groups would fall apart and it would take hours of repeated application and soaking in Sweet's 7.62 to get it clean again. This was circa 1993, and the super-aggressive water-based copper solvents we have today had not been developed yet.
When I firelapped that gun, I monitored the cleaning. I was using bullets pulled from M2 ball over 8 grains of Unique for the lapping, but that worked because the crimp indentation on those bullets keep the bearing surface small enough to pressure-form completely to the bore. If you don't have jacketed bullets with that limited bearing surface, you will get more complete and even results from Marshall's lapping bullets. Regular jacketed bullets don't tend to fill the grooves completely. After the first five rounds it took two passes with Shooter's Choice, followed three sets of double patches wrapped around an undersized .270 bore brush and smeared with Iosso Bore Cleaner (equivalent to JB Bore compound) and run back and forth 20 times each, with additional patches of Shooter's Choice between 20 stroke sets to finally come clean. And that was just the copper accumulated in 5 low power lapping rounds. By the end of the process, two Shooter's Choice patches and one Iosso Bore Cleaner double patch run only ten times back and forth was all it took to clean. About 6 times less effort. The gun didn't shoot any more accurately in that instance (it was already up to the rest of the gun, not to mention the shooter) but it stopped losing accuracy in the middle of the slow fire phase of the 50 round National Match Course. That was all I needed. Cleaning after a match became much less work, obviously.
I did some fire lapping about 10 years ago and it did clean up the bore, but it extend the throat some. I would be interested in the 'kit' you refered to.
Jim - if you go to the home page, click on Ordering Info in the left hand column, then click Price Sheet at the bottom of that page, you'll pull up the BTB pricing sheet which lists the BTB lapping kit on the right side of that page.
Thanks I'll give it look see. I have several guns I would like to lap. Over the last few years I have hand lapped them with the same abbrasive I used for the fire lapping. It is much slower but it gets the job done and I have alot more control over it.
I really recommend Marshall's book, listed along with the firelapping supplies. He explains how to do it, how not to do it and why you do it his way, plus what to do when something go wrong.
Bye
Jack
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