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Lapping A Barrel?

Thescrawler

Plastic
Joined
Oct 8, 2011
Location
oregon, usa
So i am basically new to the site. I have read alot of threads on here and recieved some great information from them. I am hoping ya'll can help me out here.

So i am sure you have all heard of the Rossi Trifecta.....

Well here i am holding a giant pile of donkey spunk :willy_nilly: , not a great big surprise. So I love the portability of this rifle but i do not love the performance. I bought it in a .22/20ga/.243. so the .22 is fairly accurate (not as nice as my 10/22 but for a portable plinker will do), the 20ga functions and despite the short barrel does not shoot high as i thought it might. It is the .243 that gives me fits. I went through the break in process on the barrel and despite my efforts with factory or handloads it shoots like crap.

I sent it back to the factory after 4 days and told them to fix it. It is considerably better but not remotely fixed. I got to looking down the bore and realized there are chatter marks running nearly the full length. I honestly dont know if lapping will take those down enough to make it a half decent shooter. I can only figure this has to be the issue. I am not looking to make it a tack driver but I have a hard time putting any confidence in anything that wont shoot at least 1.5 inches at 100 yards. OF course i demand better performance out of everything else i own and most shoot under an inch.

Any help I can get would be wonderful. And dont tell me to sell it because i am already on that ledge lol. Thanks for any help!
 
buy a fire lapping kit, they are cheap, and generally effective, although i cant say how well it would handle chatter marks, but it wont hurt much as long as you dont go crazy. (it does erode the throat, so it will reduce the barrel life by some amount)
 
I always hear wonderful stories about those break action rifles but any of my customers who have tried them never seem to get much better than two or three inch's at 100 yards with them. Most of those clowns can shoot too so I have no reason to doubt them. I think its a combination of poor triggers, lock time and the fact that the guns don't lock up as solid as a bolt action. Most all pumps, semies, leavers and a lot of single shots suffer from this. I don't know that lapping would do any more than decrease your barrel life.
 
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I will agree with speer. Never seen lapping do anything, but make a barrel easier to clean. Accept that your rifle might not shoot better and buy something else.
Butch
 
So i am basically new to the site. I have read alot of threads on here and recieved some great information from them. I am hoping ya'll can help me out here.

So i am sure you have all heard of the Rossi Trifecta.....

Well here i am holding a giant pile of donkey spunk :willy_nilly: , not a great big surprise. So I love the portability of this rifle but i do not love the performance. I bought it in a .22/20ga/.243. so the .22 is fairly accurate (not as nice as my 10/22 but for a portable plinker will do), the 20ga functions and despite the short barrel does not shoot high as i thought it might. It is the .243 that gives me fits. I went through the break in process on the barrel and despite my efforts with factory or handloads it shoots like crap.

I sent it back to the factory after 4 days and told them to fix it. It is considerably better but not remotely fixed. I got to looking down the bore and realized there are chatter marks running nearly the full length. I honestly dont know if lapping will take those down enough to make it a half decent shooter. I can only figure this has to be the issue. I am not looking to make it a tack driver but I have a hard time putting any confidence in anything that wont shoot at least 1.5 inches at 100 yards. OF course i demand better performance out of everything else i own and most shoot under an inch.

Any help I can get would be wonderful. And dont tell me to sell it because i am already on that ledge lol. Thanks for any help!

Hi,

I'm not sure if the gun you are describing is the same as the Rossi 'pomba' single shot break open rifles they are marketing down this end of the globe, but if by chance it is, then I wouldn't expect them to do much better than hit the side of a barn door at 20 feet!

As a full-time professional gunsmith I have worked on and inspected alot of them, and this is what i have found: apart from generally very poor quality steels and machining work, the stud for the forend to attach to is WELDED to the barrel. In 99.9% of occasions this causes the barrel to bow down to some degree as the weld cools. Also, the wall thickness of the barrel tube is often way out of concentric by anywhere from 0.010-0.040", and the bores are most always bowed likle a banana.

The crowns, as you woudl expect are often rough, and a mile off concentric.

Sorry to be blunt with you, but if they are the same gun as what we have down here, then if you think you are going to shoot sub 1" groups with them, well quite frankly you're dreaming. They are a cheap, nasty gun and i wouldn't have one personally if i was given one for free....

My 2c worth..

Cheers,

Dean.
 
Lapping

I sure won't speak to the accuracy issue, but I had a Ruger Blackhawk in .44 mag... it's bore was so rough that you couldn't fire 50 rounds of handloads through it without leaving 20 grains of lead in the bore.(that may be a slight exaggeration, but you could tap the muzzle on a piece of typing paper and collect lead flakes)

Took it back to the dealer and bitched and was told that Ruger said 'fire a few hundred rounds of jacketed ammo through it and it will be fine.'

While that may have been one solution, it wasn't mine.

I cast a lead lap in the barrel and proceeded to clean up the barrel. You could not only feel the tight spots, but you could feel the bore cleaning up. Stated with 600 grit and finished up with 1200. After the third lap I quit.

After that it ate my cast lead ammo with a minimum of leading... MUCH improved and worth the effort,

paul
 
It may surprise you to know the custom barrel makers lap with no finer grit than 320. Call and verify that if you don't believe me. If you really polish your bore you will have copper fouling problems. I do not shoot lead bullets, so I cannot say about them
Butch
 
I've noticed the same trend Butch and some of the guys are only lapping after final reaming and then running their buttons through. One guy I know does no lapping whatsoever. Going on the theory that he is only wearing out the barrel by doing it. His barrels always seem to shoot well so who am I to argue. I think they are more concerned with bore dimensions than the actual finish. Properly drawn buttons tend to leave a pretty nice finish as it is. I have noticed that a lot of cut rifled barrels show reamer marks on the crests of the lands and probably could be improved at least cosmetically by lapping before or after rifling. But I don't do anything about it. If the owner wanted Joe Blows barrel he wants Joe Blows theory's and practices and short my work to install it, that's what he gets. I don't make em, I just screw em on. The way I see it if there WAS, a right way, everyone would be doing it and they aren't.
 
As far as fire lapping, that would be a drastic plan unless i were to rechamber to a 6mm with a longer case, I.E. the throat erosion would not be an issue. I wonder if i could find someone to build me a new barrel to fit. Course if that was not an economical solution to the issue then maybe just building a pretty little falling block single shot about the same length would be a good idea :D. I was never expecting it to shoot sub MOA groups just hoping to hit that perverbial barn door within the kill zone of a coyote or preferably a bit smaller at 100. Thanks for your insite. As always you guys are a wealth of information.
 
I have used David Tubb's Final Finish with decent results on several occasions. A couple of times to revive match barrels that were going downhill. Even a Mini-14 shot better after I tried it.

If you don't reload this may not be an option. The kit comes with 50 bullets and they are meant to be loaded with a starting load (lightest load listed in the manual) of the fastest burning powder available fot that particular bullet weight/caliber. You shoot the ten coursest bullets first then clean the bore. With each succesive group of ten the abrasive plating on the bullets gets finer. The end result is a bright smooth bore.

There is a down side. The process increases the jump to the rifling. For a hunting rifle this probably won't matter.
 
Lapping probably wont do much in the way of improvement.

You can't make vanilla ice cream out of a turd.


You wouldn’t think so but...

My Ruger Super Blackhawk must have been made on the same day as Paul’s, an absolute POS that wouldn’t hold 6 inches at 50 feet. 38 rounds of MILDLY loaded JHP ammo dipped into a slurry of rottenstone and cutting oil performed the true miracle of turning a POS into tack driving ice cream. Truly an incredible improvement.

Do not attempt this procedure with factory or normal pressure ammo, as this procedure increases pressure and will likely damage-blow up you and your rifle!

Good Luck, Mike
 
oh come now.... a little shrapnel never killed anyone.... its kinda like broccolli, it just maimes....

Anyway yes i load all my own ammunition, if for no other reason than i can and have been doing so since i was about 10yo. At the time it was cheaper and i shot ALOT....

I am not sure i would want to fire 50 rounds of lapping compound through any barrel... that sounds pretty harsh.
 
For those that haven’t used Rottenstone, it’s a rubbing compound for fine finishing. It’s a fine powder, non-embedding, and it breaks down very quickly. Nothing gives a more slick, silky smooth action than lapping in a bolt with rottenstone and ATF. It’s also a good additive for the first step in tumbling heavily tarnished brass.
Have a good one, Mike
 
All revolvers have a choke in the barrel where it screws into the frame. How big this choke is is mostly determined by how new and sharp the dies were when the threads were cut on the barrel. Your lapping effort most likely removed or greatly reduced this choke resulting in the greatly improved accuracy rather than the smoothness of the bore. Taylor free bores are sometimes cut int revolver barrels to improve accuracy
 
Choke?

I believe that the only 'choked' area of a revolver could be the cylinder, not the barrel.
See: Brownells* Cylinder Throat Reamer for .45 Revolvers
The cylinder end of a revolver barrel has a forcing cone, which is larger near the cylinder, that gradually guides the bullet into the constant diameter rifled area of the barrel.
This slight conical area will accommodate a slight misalignment of the cylinder relative to the barrel.

Lapping will, of course, increase the diameter of a rifled bore. The lapping that I did on the Ruger SB was only enough to remove the crappy finish left by the factory. The purpose of the lapping is to establish a constant diameter and smooth finish.

One of the .22LR barrel gurus had 'slugged a barrel in order to trouble shoot a problem that he had, and observed that once a lead bullet is deformed, it does not 'spring' back to it's previous shape or diameter. When lapping a barrel you can feel the tight spots. Since the lap will not spring back once compressed to a smaller diameter, it will not remove metal from the loose spots very much if at all. Repeated casting and lapping will result in a bore of a very constant diameter.

Will this help accuracy? I don't know, but I suspect that it could not hurt.
If nothing else it appeals to my anal side.

paul
 
There are pros here.

Choke might not be the correct word, but tightening a thin threaded barrel, into a revolver frame.... can constrict/distort bore slightly at threaded area. Since this is the beginning of bore, bullet will be slightly undersize for travel through remainder of bore...

A forcing cone is part of the cylinder end of the barrel to help guide the bullet from cylinder into bore. It is also a kind of choke.. Proper forcing cone angles and size will improve accuracy, if original was poorly done..
 








 
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