Another keeper Roller

[mdeland]

Some day I would like to plug gauge and bore scope some exclusively paper patched bores. My guess is you will find that paper has a bore leveling effect just as does a lap slug only on a far less aggressive level. I would think this a very positive benefit, if it proved to be true.

[mdeland]

Well I cleaned up after 1250 lap trips with 400 grit and checked the bore with a plug gauge. Still had a tight spot so cast another lap and went down to 220-300 grit and removed the tight spot. Got her pretty well level as a .435 plug will go all the way through and a .436 will go part way in the muzzle and up about 5 inches in the chamber and indicates a slight taper in the bore, which is good.
I did find one of the pits near the muzzle has intruded the muzzle crown inner lap line. I will pull the barrel and re-crown back about .125 and refinish it to clear out the pit.
This is a really neat learning exercise to get a better handle on how well a pitted bore with still strong lands and grooves can be made to shoot accurately or not.

[mdeland]

I was having trouble getting the camera to focus on the pit just below the upper point of the shadow line. The dark spot in the blurred picture is a pit right on the end of the land. I will pull the barrel and trim back .125 which will put the inner crown in a pit free circumferential zone of clear steel.

I think it will be ready to test by Monday or Tuesday AM.
It totaled roughly 2000 round trips with 220 ,400 and 600 grit lapping compound . I had to pour 7 lap slugs if I remember correctly.
The bore shines like a new penny but the pits can still be seen clearly.

[Aviator]

Would you be willing to say how you go about creating the lap?
I assume you pour it in place in the barrel, and somehow it ends up attached to a rod and charged with lapping compound?

[John Bly]

Speaking of rollers, I got a lone Star Roller in yesterday to work on and I see that it does not have any kind of firing pin retractor at all, not even a spring on the firing pin. I was surprised to say the least.

[beltfed]

John,
Remember that the roller breech blocks "come away from the ctg head as they are opened
therefore in effect withdrawing the firing pin. So, no FP spring, etc needed
beltfed/arnie

[cw50-70]

Just be sure that the pin hasn't jammed in the fire position before slamming the bolt shut;-)

[mdeland]

I use one piece rods with a bearing swaged on the handle side then turn a tapered, grooved point to cast the lap on the business end. I cut a string groove above the taper. A string is wound on the shaft at the groove made for it until a dam is made of tight slip fit in the bore. The string is secured with a dab of super glue.
An old shell casing in drilled out in the primer hole to make a centering guide for the chamber to keep the grit covered lap rod off your bore while lapping.
The bore is lightly oiled and the rod inserted from the breech and run up bore to roughly 3 inches from the muzzle and the lower side marked with a magic marker for and depth index. The rod is pushed above the muzzle just far enough to heat up the lap rod point before the pour so as to get a good cast to it so it will hold the lap firmly. When the lead is ready the point is heated and the rod with drawn into the bore to your previously marked spot on the lower rod. Now pour the cast a steady stream until just under filling to the muzzle. If you go over you will have to push the freshly poured lap and trim with a file.
Now pull back the lap down barrel and let the muzzle cool to the same temperature as the rest of the barrel. This is important as the heat will expand the bore and make a slight different diameter.
If the barrel is really rough then make the lap short or you will never get it to move. Use pure lead for the first casts as it will shrink up more than will lead with antimony in it.
Once the barrel is cooled evenly then push the lap out about a half inch. Lube with oil and pull back into the bore running the lap back and forth full length to evenly lube the entire interior. Now push the lap end out the muzzle about a half inch and with your fingers wipe on a small amount of lapping compound all the way around the lap.
Pull the lap into the bore and find the rough and or high spots. You want to give a little back and forth shoe shine motion to these spots as you go on past always trying to blend the entire interior to an even feel of tension on the lap.
I recharge every 50 round trips and cast a new lap every 250 round trips in the bore as the lap will wear.
If I have the barrel off the action which is the usual case, I like to form the lap slut in the chamber end using a paper funnel to cast the lap ahead of the chamber throat.This method requires a longer lap so as to maintain index with the bore. Every groove and land will be slightly different ,especially in single point cut barrels so index to the cast slug is important. It is less so in button, hammer forged or broached rlfling, but still important in my opinion.
The reason for casting the slug in the chamber end is so that the freshly charged slug, which cuts most aggressively at first ,starts in the throat and not the muzzle. This is very important if you have a sloppy muzzle diameter. It is also important if you want to lap in some choke into the muzzle.
When charging a lap only about a half inch of the protruding end needs to have lap compound wiped on it as it will evenly distribute itself over the entire lap the first couple of trips up bore.



Ready for the lap pour after heating up the lap rod point and withdrawing back into the bore. I like a lap about 2-3 inches long in the muzzle and a bit longer in the breech to maintain index with the throat.

Mark the lower rod with a magic marker for your depth indicator when it is withdrawn into the bore for the lap pour.

[mdeland]

Photo bucket likes to repeat itself and post pictures out of sequence with the captions, sorry!

[mdeland]

Another point, the books will tell you to only use pure lead as a lap but I like to use lead with some antimony once the lap begins to move freely in a bore. The reason is because it shrinks less when cooled then pure lead and I feel holds diameter better over the lap life.
I do not like to bump up a lap either once it loosen up, with the use of a nut and thread on the rod in either end, because the ends will both be larger than the middle. It is better to cast a new lap where the diameter will start level and wear level.

[Perentie]

Thanks Mike. Great info, I should do that to my carbine.
Casting from the breech end looks harder to keep the back of the rod central as I guess you cant have the shell case there for a guide.

[mdeland]

I just find a pistol case that will slip into the muzzle, drill out the primer hole for the rod diameter and you still have a perfect muzzle guard to keep the rod off the bore.
You do need to make a rod stop for the muzzle or breach so as not to push the lap out and loose index. I make mine out of angle iron, weld on an end stop and line with leather to keep it from scratching the barrel exterior.

[Perentie]

Of course.
Bit early for me in the morning.
I was thinking the rod was still sticking out the breech end

[mdeland]

Yeah John, lots of roller models early on did not have firing pin retractors. Truth is I doubt it ever much of a safety issue with a properly cleaned and oiled gun.

[mdeland]

Remember to make the first laps of pure lead, and keep them short , especially in a very rough bore or you will never be able to get it to move at all! Pounding on it will only up set it and make it worse if it won't budge at first. It will have to be melted out and you will have to start over.
Once it begins to move freely than you can go to a stronger lead alloy that shrinks less and holds it shape and diameter better.