Lots of confusion about firelapping, I think.
The process will improve cleaning.
It often improves accuracy, but not always. On rare occasions it worsens accuracy. In a paper delivered to the National Defense Preparedness Association, NECO was able to show an average of 15% reduction in group size for 27 .22 rimfire rifles belonging to a college shooting team. That's a typical result for a commercial barrel with no overt defects, like constrictions.
Simply shooting regular ammo or hand loads will not do the same thing firelapping does. I had a good 1000 rounds through my first Garand's military barrel and despite two break-in series it still fouled so badly that it began losing accuracy between rounds 30 and 50 and would take all night to clean afterward with Sweets. After firelapping it never lost accuracy during a match due to fouling again, and cleaning became a breeze.
David Tubbs Final Finish system is not firelapping, it is fire polishing. The former will remove constrictions in the bore, the latter does some, but not efficiently. Tubb is interested in re-polishing shot-out throats and resurfacing bores. His method does that. But his loads use jacketed bullets that are too springy and fire at pressures that add to that springiness in keeping the bullets upset against the bore. This happens whether they are in a tight area or not, so they tend to act on the whole bore surface equally, wide spots included. Firelapping, done properly and at very low pressure will, like a lead lap, cut the constrictions but do a lot less to the wide spots after passing through a constriction which narrows the lapping bullet.
In general, firelapping is done with lead bullets at about BHN 10-12. That is not hard enough to be very springy, but not so soft the light lapping charges upset them or that they can't keep the gas sealed well enough to prevent excessive fouling. Wheel weight metal bullets with a couple of percent tin added will usually work, but you want a really light load of something that doesn't bump the base up. Trail Boss is great for this.
The reason for coarse abrasive in the graded firelapping kits is to speed cutting away of constrictions. You can use fine abrasives exclusively if you have the time to fire enough shots to to do the job. At least one custom rifle maker I read comments from long ago didn't want to see anything either finer or coarser than around 320-400 grit, claiming you need a certain amount of fouling pick up to get a barrel to settle. I'm not convinced of this, but I thought the opinion ought to be included in the discussion. It explains why single grade methods are still popular.
The abrasive loaded bullet encounters the same rough spots a plain bullet will by moving in the bore the same way a plain bullet does. While it is true there is no cross-cutting to remove the abrasive scratch marks, it is also true bullets only travel in the direction of the abrasive scratch marks and don't benefit particularly from a polished surface free of marks in either perpendicular direction. Nonetheless, in stepping through finer grades when firelapping my above-mentioned Garand, the number of patches needed to clean it after each five rounds steadily decreased, and the surface appearance became smoother, so the finer grades contributed a positive difference. I suspect they don't fill the valleys left by coarser abrasive grit quite as well as they attack the peaks. You could exaggerate that effect by using harder bullets, like the Tubbs bullets, for polishing after removing constrictions with the softer ones.
Firelapping does not wear a barrel out. It changes its geometry some, and you start the wear from there. Done properly, at low pressure it will move the throat forward a thousandth or so (that's what my Garand's throat wear gauge showed). My borescope shows it does take the circumferential reamer tool marks out of the throat by exchanging them for longitudinal smoother abrasive marks that don't tend to foul. Unlike a high pressure and temperature load, rapid erosion does not occur. The effect is much more controlled.
Should you firelap or hand lap? It depends on what you are going to shoot through your gun. For cast bullets, firelapping tapers the bore down slightly from breech to muzzle which is supposed to help them shoot. A third to a half thousandth taper is typical. Hand lapping straightens the bore. Frankly, I can't tell any consistent real difference between tapered-down and straight bores. Both seem to work. Tapering wider from breech to muzzle, though, is ruinous to lead bullet accuracy. If found in a factory gun, it must be corrected, same as a constriction, before lead bullets will shoot. Ether lapping method will correct a reverse taper.
Hand lapping probably removes the least total amount of metal since it lets you feel exactly when you are done. If you want the best of both worlds, do both. Hand lap the constrictions out, then shoot finer polishing rounds to clean tool marks out of the throat and smooth the bore surface. Using a bore scope helps see the effects and know when to stop.
How to tell if you need to do either? Slugging is your friend. Pure lead (cast bullet alloy is too elastic) slugs at each end of the bore and pushed right out to let you measure their diameters, and slugs pushed all the way through an oiled bore, one from each end, will tell you exactly where the problems are. It lets you pretty clearly feel any constrictions. NECO has you check firelapping progress with another pure lead slug every five lapping rounds. I found that effective.
The lever rifles have relatively thin barrel walls and dull dovetail cutters or cutters fed too fast tend to indent the bore under the cuts for sights or magazine tube hangers. These can be bad enough to interfere with jacketed bullet shooting and are commonly bad enough to mess with lead bullet shooting. They are the most likely you are to encounter for lapping.
If you don't find a constriction when slugging your 1895, be aware that a deflective or bent magazine tube can also open groups up by how it bears on the hanger. The stock fit can be an issue, especially the front. Have that checked by an accuracy smith if it's a problem, or send the rifle to Marlin factory service with an accuracy complaint. They are used to finding and dealing with this kind of problem. You might want to read M.L. McPherson's stuff on accurizing the Marlins. Some is in past issues of Precision Shooting and some is in his book, Accurizing The Factory Rifle.
I see reports from guys getting sub-moa from the Marlins on occasion, but I think under 2 moa is a reasonable expectation for a factory gun when you get the basic ducks in a row. There is no end of possible fiddling after that.
I wasn't expecting a tack driver, but at least for all the bullets to be inside the circles. The safest place with this gun is where I'm aiming right now!
