Generic barrel question .

[RBHarter]

How deep is too deep for grooves ?

I have a project in mind that might be just dumber than a bucket of rocks .
At one extreme we have micro groove with very shallow grooves , something like .005 . At the other end Ballard or like an SKS I had that was .316×.305 , so .011 . If we move up to the big guns or scale Micro groove up to 16" you can lay a tape measure on them .

I guess the question is , is there some ratio that gives a window or is it some ancient thumb rule like bore plus .007 or 1% ?

For my intention I would just lap an oversized groove up to the next cal . The barrel in question is a loss already so if it's ruined it's not a big deal . There's plenty for a rebore to something more useful but not to get to what I want . If I can keep most of the lands and add say .010 to the groove it seems like it should work . .248-.251/6/7 ........looks better as a pistol groove 25 cal from .243 than a rifle groove and that might serve me better anyway .
Time vs money ........

 

[KeithB]

I'd like to know how you are going to lap the grooves larger without lapping the lands also. I suppose it's possible but I really don't know how it could be done. Maybe I misunderstand what you're trying to do, I'm pretty tired right now.

 

[RBHarter]

It's a thing that's been rattling around for a long time .
I envision a poured lap and relieving the land lines before I do the lapping ...... Of course I visualized how to build a swaged brass follower to make a broach work too and in the end the tool integrity , pull angles , and about 14 other tooling limitations leave me with broken parts stuck , lodged cutters , etc . That's just with mental run throughs ........

Like I said if it doesn't work there's no loss . It doesn't matter if it takes 500 passes . Getting a 25 cal barrel is either as much as a new rifle or all but can't be had . There aren't any take off bull barrels to be had in 25 cal either . I was given a 243 push feed M70 barrel the gentleman said never shot well that has enough shank to cut and thread for a Savage . If it laps I'm in it about $150 if it doesn't it's only time .

All I want is a rimless 256 WM or a 25 ACP even if it's a stubbed 20 ga NEF .

 

[Ian]

Green mountain has a 25"x1.060" unturned blank for $108.

 

[RBHarter]

Need to have the 1.110 for the Savage , .005 ain't much meat to thread on a raw blank . Unfortunately I have to send that machine work out also . A Savage prefit is $400 . I suppose I could sell the 45 blanks .

 

[Bret4207]

It sounds like what you want to do is what was called "freshing" the barrel back in muzzle loader days. They didn't lap, they made a rod that ran on the lands and a cutter that did one groove at a time. The cutter was shimmed with very thin paper for successive cuts. This sounds exponentially more accurate to me than trying to keep lapping compound only in the groove. You can get shim stock these days in fractions of a thousandth.

As far as groove depth, I dunno. .010 isn't really extreme.

 

[JustJim]

I've freshed ML barrels, never a cartridge gun. I think Pope's 33-47 was a new bore and rifling (often on a used barrel: the thought being the shooting w/original bore somehow stabilized the barrel). 33cal was the smallest he could bore a 32-40 barrel.

I have sleeved (ok, "paid someone competent to sleeve") a barrel that was too small so it could be used in an action that had threads larger than the barrel OD. That Green Mountain barrel could be made to work in your Savage, or sleeved into a shotgun action.

Did we have a discussion about a 25 acp rifle on another forum?

 

[RBHarter]

The 25 ACP rifle has been kicked around by me several times as a direct CF replacement for 22 LR in a 22 mag action ......the barrel continues to stimey efforts .

This freshening thing sounds like what I need/want to do . I read a Pope article several years ago but didn't recall the details of technique .

Any suggestions for reading mat'l ? I've struggled with the "it can't really be that easy" lately .

 

[popper]

they made a rod that ran on the lands and a cutter that did one groove at a time - saw a video of a guy doing that, interesting.

 

[Bret4207]

I read about it in a Gun Digest to start with IIRC. One of the old ones edited by John Amber, probably from the 70's. I also saw mention of it in some gunsmithing books, but I don't know which one, I've got dozens. It's just a single point cutter following the groove that already there.

 

[Ian]

I'm imagining taking the stem of a broken brass .30-caliber jag and turning it to just fit the bore, cross-drilling it for a tiny HSS cutter, drilling and tapping the end 6-40 or so, and locking the cutter in place with a scope base screw. Make one pull pass with a cleaning rod to follow each groove, advance the cutter a couple thousandths and retighten, repeat. The only issue is trying to take a .236/.243 up to a .250/.257 dimension. If you drill it out from both ends with an aircraft drill first it will be larger than .250 and you lose the grooves completely. Then there's the option of making a .243 Automatic by necking down the case a la .357 Sig....I mean how silly do we want to get? I'm on board!

The obvious solution is pick up a .223 Handi rifle for a couple hundred and a six-banger Lee .22 mould and powder coat a 3# coffee can full of bullets sans gas checks and launch them out of mixed garbage 5.56 brass with a pistol primer and 2.7 grains of Titegroup.

 

[JustJim]

Unless I had Keebler's elves doing my 25 acp handloading, I'd never get near such a project again. Those little cases are a nightmare to handle, and the charges and bullet weights so light that minor variations can have a major impact on POI.

A 32 acp rifle might be worth messing with. Someday I want a dedicated 38 wadcutter rifle. But never another anything in 25 acp. YMMV, of course.

 

[JustJim]

Forgot. I figured how to freshen a bore based on some letters from Bill Large, a couple articles in old Gun Digests, and a Pope catalog one of the guys had. I practiced on shot-out or rusted-out 1911 barrels (that was a mistake--short barrels are a pain to work with).

 

[Joshua]

I read one of those old articles on rifling cutting machines. Wooden frame and a hand cut wood main screw. The single groove cutter was advanced a thousandth at a time, the contraption used two slim wedges and a small locking screw to increase the cutter height.

 

[Bret4207]

I'm imagining taking the stem of a broken brass .30-caliber jag and turning it to just fit the bore, cross-drilling it for a tiny HSS cutter, drilling and tapping the end 6-40 or so, and locking the cutter in place with a scope base screw. Make one pull pass with a cleaning rod to follow each groove, advance the cutter a couple thousandths and retighten, repeat. The only issue is trying to take a .236/.243 up to a .250/.257 dimension. If you drill it out from both ends with an aircraft drill first it will be larger than .250 and you lose the grooves completely. Then there's the option of making a .243 Automatic by necking down the case a la .357 Sig....I mean how silly do we want to get? I'm on board!

The obvious solution is pick up a .223 Handi rifle for a couple hundred and a six-banger Lee .22 mould and powder coat a 3# coffee can full of bullets sans gas checks and launch them out of mixed garbage 5.56 brass with a pistol primer and 2.7 grains of Titegroup.

I haven't seen a Handi for sale in years, much less a cheap one in 223!

 

[Bret4207]

Unless I had Keebler's elves doing my 25 acp handloading, I'd never get near such a project again. Those little cases are a nightmare to handle, and the charges and bullet weights so light that minor variations can have a major impact on POI.

A 32 acp rifle might be worth messing with. Someday I want a dedicated 38 wadcutter rifle. But never another anything in 25 acp. YMMV, of course.

A 32ACP autoloader? That would be fun. If you mean a single shot, the 32 S+W/Long/H+R/Mag/327 works real nice in a rifle!

 

[RBHarter]

Bret , Dad left a NEF or H&R 30-30 with a 20ga barrel . The shotgun barrel is in pretty rough shape .

I think I'm getting a better idea of what I need to have . I have a piece of 1/4 brass rod that's a tiny cutter ...... More thoughts to think .

 

[fiver]

i'd forget lapping.
you'll end up working yourself to death for 20 minutes and gettin about .001.
broach cutting one groove at a time and rotating to each groove then opening the cutter would be he best bet.
airc that's how pope cut his barrels.

 

[Missionary]

There are many well done articles about "freshening " the grooves in Muzzle loaders. Was a very common practice used for couple hundred years during the so called "Golden Years" and into the 1950's.
We had a 200+ year old caliber .40 freshened about 10 years back.

 

[Snakeoil]

Shuttleworth made a .25-20 SS for a friend. He might have a barrel for you.