[rangerruck]

I want to cut a barrel, on a long barrelled 17mach2. It is a stainless , heavy barrel. I am wanting to cut it, not only to make it shorter, but to improve it's accuracy. I understand you do this, by finding out it's tightest spot, somewhere down the barrel. How do you determine this, and is there a video out there somewhere, showing this? Thanks.

[highorder]

I have no experience, but I would think that slugging the bore would show you the tight spot, especially of you were using a force guage inline with the rod you push the slug with....

Tagged for an education.

[rcmodel]

I've never heard of it, or of any gunsmith doing it.

You determine where to cut a barrel blank based on how long you want it to be.

A good .17 barrel shouldn't have any "tight" spots anyway.

rc

[Jim Watson]

Centerfire benchrest shooters use barrels 20" long or so. The Texas Warehouse experiments reportedly settled on 21 3/4" as the best all around length. I don't know if that would apply to a .17 rimfire or not.


Edit to confirm for krs:

Secrets of the Texas Warehouse at:
http://www.angelfire.com/ma3/max357/houston.html
says 21 3/4"

[krs]

"The Texas Warehouse experiments reportedly settled on 21 3/4" as the best all around length"

Wasn't it 21 3/8" Jim?

Either way, I've not heard of anyone trying to find a tight spot mid bore in order to decide where to cut a barrel.

There are legal limits, and most any modern barrel would guage so uniformly over it's entire length that trying to do this would not bring any measurable advantage. The technology of barrel drilling, rifling, and measuring is advanced-barrels are very good.

[rcmodel]

Especially .17 barrels.

Ain't much room for any less with them.

rc

[moosehunt]

I second what RC said earlier. I have never heard of that either, but for fear of sounding dumb, I was hesitant to be the first to say so.

[rangerruck]

I have heard it done many times before; the thinking is this- no bbl is made perfect. Within the bore, the diameter can fluctuate a bit, of course. it is not much, but even say .01 of an inch in difference, if you can find this spot, to being a bit tighter, as opposed to looser, somewhere after 16 inches, and cut the bbl there, and of course put a very good crown on it, you should be able to get a more consistent, non gas favoring or escaping or leaning to one side, type of exit.

[barnetmill]

There used to be something called an air gauge that was used to measure barrel uniformity. I have no idea of where to get one or how to use it. Many barrels have a sweet spot and some people will continually cut a barrel until they get the group that they want. I do not think that it is worth the trouble. I would pick what is considered the optimal length for the barrel in question and have a gunsmith shorten it and properly crown it. I would have first properly check the rifle's bedding out. If after all of this, it will not shoot, I would get another barrel.

[moosehunt]

If you have a barrel with .01 variation, you have a BIG problem!

The sweet spot you refer to has to do with vibration harmonics and the cutting is simply adjusting to that, no a tight spot in a barrel. And of course, there are variations in the diameter of the barrel, it just depends on how precise one measures. If you could measure to .0000001, you would find huge variation. But at .001, if you find any variation, then you've got a barrel that only has value as a pry bar.

Anyone can buy an air gage. Affording one and learning to use one are another matter.

[rangerruck]

I used .01 as just a reference and ease of understanding.
What I am saying is not so much to do with uniformity, allthough that is prefered as well. I understand that Douglas barrels has a barrel that is
in a very high class that you can buy called ' air gauge rated' , it is a standard
of theirs which means, when they air gauge tested this particular barrel,
it never varied more than 1/10,000 of an inch anywhere in it's diameter.
I simply want to cut to it's crown, at it's tightest diameter, somewhere after 16 inches in length.

[rcmodel]

I simply do not think you can find a .17 cal barrel with a "tight spot".

Those tiny barrels are extremely critical on bore dimensions, and I don't think the factory's are producing any with "tight spots" in them.
I rather imagine they are air guaged at the factory, and any that don't pass are either scrapped, or made into .22 barrels.

rc

[JohnBT]

Bill Calfee has written a bunch in Precision Shooting over the years on slugging to find the tight spot in a .22 LR barrel and the benefits of letting the barrel tell you where to cut. At one time he was even listing a source of .22 rimfire slugs.

Here's one mention, an excerpt, from the process of "BARREL EVALUATION"

"After about fifteen minutes and what I counted to be twenty-five total passes through the barrel, Bill is satisfied where his cuts need to be for the chamber and the crown. He cuts the barrel at the crown and chamber marks with a hacksaw. My 28” barrel blank is quickly down to 23.5”. The process may be based in science but the evaluation is a practiced art. The attention to detail is impressive, and it will define the entire build. With the barrel evaluation complete, we move on to the initial machining."

http://benchrest.com/articles/articles/20/1/A-Rifles-Tale/A-Rifles-Tale.html

I don't know if anyone has tried a .17 yet. Can you feel a tight spot when pushing a patch?

John

P.S. - I see Tony Boyer had Mr. Chalfee build him a rimfire br rifle. Now he's going to win everything, cf and rf. :)

www.benchrest.com/forums/showthread.php?t=61457

[rangerruck]

I must say, whenever I clean the 17, the whole darn thing feels tight!!!! This kind of expertise, to slug a 17 barrel, would be way above my paygrade. Needs someone with years of experience, and a very delicate touch...

[Jim Watson]

slugging to find the tight spot

Well, not exactly. The linked article describes slugging to determine the location and degree of taper and choke intentionally lapped into a good quality barrel. Not like chopping off a mass produced barrel where the cutter or button slipped somehow.

[RyanM]

If the main concern is powder gas's effect on accuracy, your best bet is to leave the barrel alone. You're unlikely to be able to crown the barrel yourself as uniformly as the factory job, unless you've got a full gunsmithing shop.

What you could do is have the end of the barrel ported by a pro. All the powder gas blows out the ports, and the bullet keeps going through that last 1/4" of barrel just by momentum. No possibility of the muzzle blast screwing up accuracy at all.

[krs]

Tony Boyer wasn't buying that three year BS project - that guy planned to put a rifle into Tony's hands as an attempted advertizing ploy. Read through the thread you posted, JohnBT.

Bill Calfee and his "Magic Hands" technique of determining where best to chop off a tube. Uh - huh, what? :)


--------------------------------------------

Something about air guaging that I'd thought was more widespread knowledge than it would seem to be:
"What is "air-gauging"?
Air gauging is the method used to determine the fluctuations of land and groove heights in the interior of the barrel by using a constant flow of air through a probe. The gauge is adjusted to a given mean using a true, determined sizer head. The probe is then inserted into the barrel. The operator watches the fluctuations from the mean as the probe is moved through the bore. Our air gauges are accurate to 50 millionths of one inch."

that from the EX Shilen Barrels website FAQ's (Shilen sold out and his company is under new management)
----------------------------------------------


As far as I last knew Tony had retired from shooting and was spending his time on his ranch and periodically taking in students for one-on-one expensive shooting seminars in wind doping/BR shooting.

[JohnBT]

"Not like chopping off a mass produced barrel where the cutter or button slipped somehow."

The point being, that's what Mr. Calfee has written about in great detail in Precision Shooting. Among a bunch of other things, like all of the championships that have been won with his rifles. And he's humble about it. :)


"Read through the thread you posted, JohnBT."

Then you must have skipped post #5.

"Talked with Tony at the Shamrock about this project. The main holdup was getting everything together. The stock was finished and ready for bedding just before the shamrock this year and Tony didn't know if Bill was going to be interested in building it or not after all this time. Well, I guess we got our answer and apparently after Bill received all the parts....I would call it fast. Bill had nothing to do with the assembly of parts....just building it. Bill did of course give him guidance on what to buy. Hovis"


And Bill Calfee doesn't need the additional business or any advertising. John

[Jim K]

Taper and choke? Are we talking about a rifle barrel?

If so, please explain.

As for air gauge testing, it is the use of a precision plug that is forced through the barrel by air pressure, with a measurement of the amount of air that escapes past the plug. That allows the tester to determine the high and low spots in the barrel and their location. Most barrels today are made so well that such gauging is pointless, but some makers do it mainly to let the customer feel good.

Incidentally, a good air gauge reading does NOT mean the barrel will shoot. It simply eliminates one variable in the search for accuracy (and lets the customer feel good).

Jim

[krs]

Incidentally, a good air gauge reading does NOT mean the barrel will shoot. It simply eliminates one variable in the search for accuracy (and lets the customer feel good).

and that, "lets the customer feel good" is what all the verbage about "taper and choke" etc. would seem to be, with all due respect to the work of Mr. Harry Melville Pope.


JohnBT,
I'll submit that if you put any competent rifle into the hands of a championship shooter that rifle will shoot championship scores.

It's sometimes a surprise for some that the rifle won't shoot those championship scores by itself, no matter the persuasiveness of it's maker or the gullibility and the hopes of it's owner.

[JohnBT]

And if you put an exceptional rifle into the hands of a championship shooter?
For instance, Gary Mitchell's famous rimfire benchrest record-setting Suhl, Old Blue, was already a record-setting rifle when he bought it from K.C. Young. Mr. Young owns the local range where I do a lot of shooting. I guess I missed my chance. Oddly enough for a .22LR, it's a 1 in 19" twist.


"Taper and choke? Are we talking about a rifle barrel?"

Sure, owners of Anschutz barrels are frequently advised not to shorten them by cutting length from the muzzle end because it will remove the choke.
Many barrels are lapped to leave a tapered bore. I don't know if hammer forged barrels are tapered and I haven't researched it.

Here's a page from the well known Border Barrels site. Button rifled, 6 grooves, 1 in 16" twist and taper lapped. (note: their world famous barrels are all cut rifled.)

www.border-barrels.com/archer.htm

".22LR 6 16 Taper lapped toward muzzle"

[rcmodel]

All this about taper-choked, hand lapped, custom-built, one-of-a-kind match barrels is all well & good.

But it has nothing at all to do with the OP's question about cutting off his factory .17 barrel.

It has none of the above features.

rc

[JohnBT]

"All this about taper-choked, hand lapped, custom-built, one-of-a-kind match barrels is all well & good."

You think it's well and good now, but originally you'd never heard of it. And a lot of folks seem to think it's voodoo. The guy asks a reasonable question and we're discussing it.

The point being, the tight spots are found by feel and some smiths do cut at that point rather than at the old "Well do you want a 20", 22" or 24" barrel?"

John

[rcmodel]

but originally you'd never heard of it.
I assure you sir, that I had heard of it many years ago.
Bore taper that is.

I was air guaging barrels for 5th. Inf AMU in 1968.

Tapered or choke rifling has been in use by Anchulz, Walther, and others for a very long time.

Even Colt did it to some extent on Match revolvers at one time.

I had just not heard of anyone finding a "tight spot" in a .17 caliber barrel in order to cut it off there!

rc

[Jim K]

Yep, I had heard of choke rifling, just didn't know it was so common. I still have doubts that it really does anything except "make the customer feel good."

Oddly, the British once went the other way. From its adoption in 1902 to 1917, the SMLE had rifling grooves cut to be deeper at the muzzle (.0065") than at the breech (.005"). I am not sure what the idea was, but it went by the boards in the WWI emergency and was never revived.

And a fellow named Gerlich developed a tapered bore (both lands and grooves tapered from breech to muzzle) years ago that supposedly gave some tremendous velocities and was the talk of the gun world. The taper may have worked (at great trouble and expense) but he really got his super velocities the old-fashioned way - he used more powder. The German army used the idea in an anti-tank gun, but with indifferent results.

Jim

[krs]

JohnBT,

If the person you refer to as "The guy asks a reasonable question" is me I'm afraid that you've misinterpreted my interest here, and I guess you missed my reference to Harry Pope?

Anyway, I would think of a person who claims to be able to determine accuracy in a barrel by an analysis of the effort it takes to push a patch through a bore, and does such studied "analysis" for the purpose of convincing poor innocents to give him their money to be a charlatan. That term chosen because I don't know of a more polite way to say it.

[rangerruck]

So then, Lets just say, that I am a pretty good shooter, decent technique, have a real feel for the weapon and what it can do. Have shot 1000's of rounds through it, etc.
And lets say, that for a 5 shot group, I can regularly ragged hole them at 50 yds, and at 100, sub .5's I can pull, when I am up to it. Do we have any consensus here then, that air gaugeing and recutting the bbl, On a 17 cal., would do me any good? Or maybe I should ask, without air gaugeing, would it even be possible to find it's tightest spot near the muzzle, just by slugging?

[moosehunt]

--No.

[rangerruck]

no , to which part; consensus, air gaugeing good or no good to do on a 17, or slugging no good?

[rcmodel]

It might help if we even had a clue what .17 your are talking about.

Is it a .17 Hummer RF?
A .17 Remington CF?
A .17 Wildcat with a $500 custom barrel?

Anyway, if you are getting sub 1/2 MOA already, I seriously doubt cutting the barrel off is going to improve it.

A tiny puff of wind can open up a .17 caliber group at 100 yards more then that.
The lower velocity you would get from a shortened barrel would make it worse.

rc

[rangerruck]

"I want to cut a barrel, on a long barrelled 17mach2." first sentence!
It shouldn't matter, it is still going to be very close, i think the diff in diameter
between the rimfire and the centerfire is .172, and .177, maybe even less.
I myself think that any little bit that helps, helps.
My round is still going 2000fps by the time it gets to 100yds, so wind deflection is not as bad as you think; not as bad as a 22 or 22mag anyway; about 1/2 or 1/3 that.
There is not enough of a diff in speed, between 16 and 22 inches, to worry about. from 16 inches to 22 inches, the speed is near or at the top of it's arc.

[JohnBT]

"I would think of a person who claims to be able to determine accuracy in a barrel by an analysis of the effort it takes to push a patch through a bore"

That's not what he claims slugging accomplishes. He simply says that he has seen the benefit of cutting at a tight point, not that he can tell how accurate a barrel is by pushing something through the bore.

You never know until you shoot them, but he has done that - shoot, cut, shoot, etc. People are still standing in line to buy his guns and then winning with a lot of them.

That reminds me of a stranger I spent some time with at the range one day a few years back and who had some very nice custom bench rest rifles and many detailed ideas about how to build more good high-dollar rifles. Now he's partnered up with Clay Spencer and will be taking over his business. There are just some people who are full of ideas and have the energy to try them out to see what works. Mr. Calfee and Mr. Spencer certainly fit the bill.

John

[moosehunt]

No to consensus that air gaging and recutting is going to benefit you. I think you're pissing in the wind. I realize that opinions are as common as butt holes, but you have mine! Good luck. Gunsmiths need to make a living too!

Spay & neuter your kids.

[Bart B.]

The vast majority of match winning and record setting barrels don't have a tapered bore. Extremely uniform bore and groove diameters are the norm. "Choke" bored barrels were first used over a hundred years ago but have never been proved the best way to go.

All Douglas barrels are air gaged. How else could they tell which ones have the most uniform groove diameters then sell them as "Premium" grade ones? Just because a Douglas barrel is a premium version, that doesn't mean it's a tack driver. Some of these barrels have groove diameters too big for good accuracy as well as non-uniform twists.

More often than not, the most common cause of poor accuracy from a barrel with perfect bore and groove diameters is the twist rate jumps around. This is most common in button rifled barrels as the twist is controlled by the homogenous properties of the steel; a soft spot lets the button turn less; a hard spot turns it more. Cut rifled barrels tend to have more uniform twists as the barrel is turned by the rifler's head and not the cutting tool peeling off metal. There are folks who will measure the twist uniformity in barrels.