Fire Lapped Swede

I was brought a 94 Swede cavalry carbine that had an extremely rough bore. It would shoot the Lee cruise missile unsized, but with poor accuracy. Jacketed .284" bullets would not stay on a target more than 15 yards away, and even there some of them keyholed. I bought a box of Hornady 160 grain .267" bullets for the Carcano, and tried them. I blew a couple of primers until I seated the bullets far enough off the rifling, and then it would keep them in four or five inches at 68 yards. I decided there was nothing to lose by fire lapping it.

In order to get the cruise missiles to chamber, I shortened the neck of my five lapping cases until the boolits would chamber seated backwards. I fired 15 with 240 grit, and ten each with 600 and 1000 grit, cleaning after every five rounds with several Kroil-soaked patches, brushing, more Kroil patches, and finishing with JB bore paste and Kroil patches. (Fortunately I bought a gallon of Kroil some time back.)

The bore now looks shiny, and I can seat the .267 bullets to a reasonable length. The bore slugs .267 at the muzzle, which is the tightest point. With the Carcano bullets about .120" off the rifling, I got about 1750 fps with 29 grains of H4831sc. Five-shot groups at 68 yards were 3" or a little better with the iron sights. I am going to try to work up to at least 2000 fps, as the owner of the rifle wants to use it as a deer rifle in the brush.

It occurs to me that it might also be possible to lap corroded .308 barrels out to accept .312 bullets as well. Chamber necks might have to be reamed to do that. With the drying up of 1903 Springfield barrels, that might resuscitate some rifles.

I’ve never noticed anything but improvements with fire lapping. Of course, it has to be done right, as you are doing, with cleaning and checking every few shots, and lead boolits, not jacketed.

IME, you could not lap that barrel out 4 thousandths in a lifetime.

On a smooth barrel, you might be right, but that 240 grit cuts pretty fast on a rough bore. I have a 1903A1 with a very rough bore that I think I will try it on. It has what appears to be a small particle of steel "ironed" into the bore a few inches back from the muzzle that might profit from it too.

Another thing about the way I did it, I used a bore riding boolit with the grit embedded in the unsized driving portion, and the nose inserted into the case. That makes the lapping portion considerably larger than the usual method.

I too have a 94 carbine with a rough bore. I gave up on cast in it, even after firelapping. Try a max charge with some 160 Hornady round nose. Mine still looks like a sewer pipe, but sticks right around an inch at 50 yards with the iron sights. I have always gotten very good accuracy from that particular bullet in the Swede.

Hi dubber, I tried the .264" Hornady 160 RN, and it went through the target sideways at 15 yards. I tried the .267" version for the Mannlicher-Carcano, and it works pretty well now that the bore is smooth and enlarged. I just have to be sure to give it about .120" run before it hits the rifling.

This carbine was one that came in before ATF changed minimum barrel length from 18" to 16", and the importer had welded on a short extension. In order to get a crown cutter down to the rifling, I cut this off flush with the nose cap, then recrowned. Still didn't help, so that was when I decided to try the .267" bullet. It seems to be the answer. I haven't tried cast since I lapped it. It may now be too big for the bore riding part of the cruise missile.

Much simpler to buy a 35 Rem bbl from Brownells and have a better "deer in the woods rifle". OR send it to JES and have it rebored to sumthin'.

I chronographed nine rounds of the same load and discovered that the first two rounds were much faster than the succeeding rounds. After several rounds, the velocity stabilized at about 150 fps less than the first two. Also, the barrel was very hot. I theorized that the pressure was high on the first rounds, then dropped as the barrel heated and expanded. The bore slugged .267" when cold, and that was the diameter of the Hornady #2645 bullet I was using. I did another round of fire lapping using the 240 grit compound, and it now slugs .271" at the breech and .269" at the muzzle. The high pressure/velocity on the first rounds problem went away, and accuracy is still excellent. Pressure still seems to be higher than one would expect at the velocities I am getting, so I suspect I may need to turn case necks a little to accommodate the .267 bullets. At any rate, an unusable rifle is now back in service. It has taken a lot of man-hours, but what's time to a hog, as the old joke goes.

I tried the same thing with my late model nickel steel 1903A1, and have not had much luck. I suspect the steel in it is much harder than that in the Swedish Mauser. Also, the boolit I am using for lapping -- 314299 -- does not have nearly as much bearing surface as the Lee cruise missile that I used on the swede. Twenty lapping rounds with 240 grit MAYBE gained half a thou on the bore, and smoothed out the embedded piece of steel enough to notice if you use your imagination. The embedded piece is about 3" back from the muzzle. Has anybody had any luck counterboring a barrel that much?