Lapping A Barrel

[shortgrass]

Nitriding leaves a super hard, thin layer. I checked a couple on the Rockwell Tester and they checked 65-68c. That thin, hard layer can be cut with carbide. After you're through the nitrided layer, HS tooling can be used. So, if you have a carbide chambering reamer, no problem! But, as has been discussed to death, carbide tooling can create its own set of problems for those who can't deal with the accelerated speeds and feeds associated with carbide tooling. I have had zero problems with carbon. But, part of my cleaning routine involves the use of a carbon cleaner. I don't let carbon get a "foot hold' to begin with.

 

[L.Sherm]

I'm just the messenger from what I was told about his experience with nitride.
There was a company advertising him using there nitriding is the reason I talked to him about it. He told me 1 barrel it worked o.k the second one it ruined and never again and that's when he told me about his friends experience also.
What I can tell you for a fact is I have seen it change the bore dia. on barrels that were sent in that were measured with deltronic pins before and after the bore got bigger and this was on a big batch of barrels that were sent off and measured after they came back.
About 75% got bigger all SS ones the CM didnt change. Was it the process of the nitride by the company, probably but it's just one experience I've had just with this particular company.

 

[shortgrass]

Barrel mftrs have guys whose job it is to lap barrels all day. Yet they cut off or mark 3/4 inch at the muzzle to be taken off. Now how does anyone realistically think someone is going to home or gun shop hand lap a finished barrel and not damage the crown and last 3/4 inch? Does not pass the common sense test yet everyone thinks they can do it

The custom barrel makers a have a "lapping table" set up. A heavy , steel legged bench that's lagged to the floor, a station to melt the lead (with positive flow-thru ventilation), a station to poor the lap, and a station to hold the barrel securely during the lapping (like a quick release barrel vise). The 1"- 3/4" that needs cut-off is where the direction of the lap was reversed. There is certainly and "art" to successful lapping of a barrel. It is the last operation (besides inspection) in the barrel making process. Think, cost of steel, cost of cutting the steel to the desired length, deep hole drilling, reaming, some lap then, rifling, profiling. The costs accumulate. If the lapping is messed-up, all that can be done is to re-drill to a bigger "hole" and start again. The costs of the initial drilling, reamer, rifling are all 'out the window'. Not a good way to operate a profitable business. I see 'hands-on' instruction as the preferred method of 'learning how'. Any are free to experiment to their hearts' content.

 

[Mram10us]

Mram, Consider a Harrells tuner/brake on that finicky 7/08 AI....Get ready for the shock of a life time!

Can Black Nitride barrels be "set back" for a second/third chamber? Melonite barrels I read can not be set back, destroy's reamers...what I read.

With these high quality barrels, copper is not what I worry about as it easily comes out, the darn carbon is another can of worms.

Thanks KC. I kinda like my brakes to be honest. I have zero knowledge on nitride or melonite. Defer to shortgrass, Alex, Sherm, 25wsm ... etc.

 

[birdiemc]

I have had around 75 barrels Black Nitride treated, 6 of them for myself. In mine I have not had any problems with copper build up. I have not had any reports from customers about any fouling concerns. I think the only problem I heard of was when one had some trouble with load development,,,, and he was having trouble trying to find a load for a 130g bullet in a .300 UM case. And, he was kinda' unflexable when it came to what bullet he insisted upon using. Go figure! I have read reports of accuracy issues after nitride treating. I have not experienced any myself, but I'm not BR shooter,,,,, just an avid varmint hunter. As for surface finish, I am under the impression the custom barrel makers (Krieger, Hart, Batlein, Lilja, etc.) don't go beyond 320-400g when lapping.

I read a post in another forum recently where a guy said he had talked with 2 barrel makers and was discussing how they lapped them, dont recall which 2 for sure but think it was kreiger and bartlein, what this fellow was reporting was in line with what you said...no mirror finish, I thought he said 600grit but I dont remember for sure and can't find it again go figure.

 

[shortgrass]

I read a post in another forum recently where a guy said he had talked with 2 barrel makers and was discussing how they lapped them, dont recall which 2 for sure but think it was kreiger and bartlein, what this fellow was reporting was in line with what you said...no mirror finish, I thought he said 600grit but I dont remember for sure and can't find it again go figure.

The barrel makers can be quit protective of the actual process they use, and I can not blame them 1 bit! It has taken each of them serious $$$ to get to where they are at, plus the countless hours no doubt involved, too. I can be that way, myself. I have spent my life machining, mostly in job shops. I paid my own way through gunsmith school ( a full 2 yrs, yr 'round, audited 2 more semesters, have taken 3 more NRA Summer classes since). Gunsmith school requires supplying all of your own components. Actions, barrels, stock blanks, tools like files, screw drivers, hammers, punches & gouges & chisels just to name a few of the 'extra' expenses beyond tuition. Just "giving away' what has taken many $$$ and a life time of learning and experience often goes against my 'grain', so I understand where the barrel makers are coming from.

 

[birdiemc]

Just "giving away' what has taken many $$$ and a life time of learning and experience often goes against my 'grain', so I understand where the barrel makers are coming from.

I certainly don't fault you for that, but I do very much appreciate what you do give away around here. I have learned a great deal from those of you with lifetimes of experience. Like I mentioned in a different thread, I turned down a pin taking final .015 cut yesterday and nailed it, had it not been for advice I have read from folks like you I would still be trying to sneak up on it .001 at a time and end up blowing it like I used to.

 

[BountyHunter]

I'll throw her in the lathe and recrown Problem solved

Not really, talk to the mftrs, you need to take off about 3/4 inch. Recrowning will not fix it, but then the mftrs will love you; you get to order a new barrel.

 

[Mram10us]

Not really, talk to the mftrs, you need to take off about 3/4 inch. Recrowning will not fix it, but then the mftrs will love you; you get to order a new barrel.

So, if I lap this barrel, you are saying I need to remove the last 3/4" and recrown?

 

[L.Sherm]

It depends on how much you lap, you have to remember barrel manufacturers prelap to remove reamer marks left by the bore reamer after drilling that's were most of the lapping happens.

 

[Mram10us]

It depends on how much you lap, you have to remember barrel manufacturers prelap to remove reamer marks left by the bore reamer after drilling that's were most of the lapping happens.

Not much lapping here. Plus, it will be with a finer paste than most use for lapping at the factory. I planned on using jb bore paste for now and see the results

 

[shortgrass]

It depends on how much you lap, you have to remember barrel manufacturers prelap to remove reamer marks left by the bore reamer after drilling that's were most of the lapping happens.

Not all custom barrel makers lap after reaming the bore. Some only lap after rifling,, button rifled barrels in particular.

 

[L.Sherm]

I beg to differ on the button ones, if you pull a button through before all tooling Mark's are not out they just get ironed into the grooves and lands I've done it both ways.

 

[L.Sherm]

Here are some processes that pac-nor and Douglas do and a thread that Frank Green describes with Bartlein.