To lap or not to lap is the question

[got_lead?]

Hello all

I just got around to working up some cast boolit loads for my 1894 marlin in 357. I'm working with 38 cases and 158 grain boolits. The rifle seems a bit finicky about finding the sweet spot. And I'm wondering if lapping the barrel might help the ricle to be a little more forgiving of loads

The barrel slugged at .3588, and the constriction at the chamber end was .3584.

Regardless of the popularity of fire lapping, I am a bit leery, and would prefer to lap the barrel in the conventional sense with a cast lead lap and al ox abraisive.

I might be game to fire lap with fine abraisive when I have the constriction removed.

Each method has its merits and caviats. Any suggestions would be helpful.

[outdoorfan]

If your constriction is towards the chamber end of the barrel, then firelapping with a soft boolit of maybe 8-10 bhn will work great at taking out that small constriction without messing anything up. Hand lapping works to an extent. You could start with that, and once you get most of the constriction out, switch to firelapping. The firelapping will keep your bore at more proper dimensions and keep things uniform, if you do it correctly.

I just lapped my rossi 92. I did a fair amount of handlapping to reduce the constriction near the chamber, then finished with firelapping. If you're careful, that can work well and reduce the amount of time you spend firelapping.


Edit: As to answer your first question, I believe that getting rid of that constriction in a controlled manner will give you more options, and the gun will shoot better for you.

[btroj]

My Marlin 1804c was very picky about loads and bullets. It didn't shoot anything well until I got a Mihec 359640 mould. That bullet shoots very well.

My rifle has a very abrupt throat with a steep angle which doesn't allow a SWC to center up very well. The 640 store bullets with a tapered ogive center up much better and accuracy is amazingly better with it in my rifle.

Never fire lapped mine. It didn't lead so I wasn't worried about that. The minor constriction you have isn't likely to be a big issue for accuracy.

You just need to find the right bullet and load. I will say one thing for mine, the faster I push a bullet the better it generally shoot.

[1bluehorse]

Handlapping if done incorrectly will damage the bore..leave that to a professional...fire lapping is quite easy, albeit a bit messy and a little time consuming..with a bore like you describe a dozen or so fire lapping rounds is probably all you'd need. Beartooth Boolits sells a kit with everything you need including a good little book. Read it..follow the instructions to the letter...you'll end up with a shiney, tapered bore that you'll have to work hard at to get it to lead...you'll likely not only pick up accuracy but a bit more velocity as well..

[truckjohn]

Do not hand lap a finished barrel with a lead lap.... You will bell the muzzle and leade/throat ends of the barrel where the lap changes directions....

I have personally found that fire lapping a barrel is extremely effective... I have done it on a couple barrels and the results are always good.

Thanks

[longbow]

Mine is an 1894 in .44 mag but I was getting leading and poor accuracy so had the same questions ~ fire lap/hand lap? I had decided that it I messed up the barrel then I would buy a new barrel with faster twist anyway.

So, after reading on the Marlinowner's forum about tight spots under dovetails and roll stamping I decided slugging the barrel carefully was the thing to do. Sure enough, 3 or 4 tight spots! Well, since mine is microgroove, there isn't a lot to lap out before one might have a smoothbore or at least messed up rifling.

I decided to hand lap and it worked well for me.

I used a lead lap with muzzle guide and started working the tight spots until the lap passed with little to no extra resistance, then started stroking from breech to muzzle with more strokes further down the barrel with the intent of producing a slight choke effect to the muzzle so little working of the lap at the muzzle except for a few full length strokes after working progressively from the breech.

Not sure if I produced a a tapered/choked bore to any effect but certainly did not bell the muzzle or do any damage.

In the end, the tight spots were gone, leading virtually stopped and accuracy is good now.

That is what worked for me anyway.

Longbow

[got_lead?]

I choose to hand lap. There were two places that I could feel constrictions. The throat and under the rear dovetail. The throat constriction was by far the worst.

I chose hand lapping because it would seem to maintain the lands and grooves better than fire lapping, which wears the lands more aggressively than the grooves at the throat. Ie, the smooth bore. Now there is only a minor constriction at the throat and the slug measures .3588 all the way through the barrel. Slugs push through much smoother now. I might get a chance to shoot it this weekend.

[plinky56]

Definitly fire lapping will be the best solution. Get on beartooth bullets site and read about the process and if you want to try it, i'll walk you thru it. You need to reload, have some cast lead bullets preferably softer but not set in stone, and 320 grit clover lapping compound. My blackhawks get tapered and remove .003 restrictions in about 20-30 rounds. Not hard to do at all, and i'll tell you of a method where you won't have to measure to get the restriction out.