shrink fitting does not "choke" a gun barrel.....

[3n00n]

I've whupped on several Chiclone andon a couple of them, a brass hammer left 'hoof prints' behind. The only metal test equipment I currently have here isBrinell dimple, butthat won't begin to test atRc scale.

Have you tried any hardness tests on a cheapie?

[DanoInTx]

howie1a - 8/15/2008  9:37 AM

it's 177 cal I'm not sure of the barrel dia since I am out of state right now but it's is on my TF78 maybe that is a help howie about 1/2 to 5/8 inch dia howie  PS the surface area pressed is approx 1/2 inch

14.1 mm if I recall correctly.

[DanoInTx]

If you read Dr.Frankenguns post you'll realise that he made the muzzlebrake flush with the end of the barrel, then after it was shrunk on he turned it on the lathe till they matched....just squared it all up.  Those ARE rifleing marks because that IS the barrel.  He mentions in his post that it was such a clean fit that when he turned the barrel/brake combo post-shrink operation you could not see the seam.

So we have two actual hands on verified barrels that were choked by shrink fitting muzzle weights (happy I didnt use the no go terminology? ) and here bhawanna is still trying to tell us that is some kind of an internet hoax being put on by guys who just like to try stuff out to see if it actually works.

I think someone needs to leave the drawing board and get into the shop. Dont forget, acording to all known laws of aviation, bees should not be able to fly either...

[Bhawanna]

i NEVER said it was a hoax...i just wanted data....WHICH HAS NOT BEEN VERIFIED!...the only DATA collected was done by the "feel" of the pellet being pushed down the barrel with a rod....ain't that scientific?   when someone takes a calibrated bore-micrometer in a metrology setting  and does ACTUAL measurement testing on this then i might believe it.  meanwhile i'll stay on the "drawing board". ps....bees were designed and made by GOD, not engineers, machinist, tool makers, or airgun mechanics.

[Bhawanna]

if this is such a simple and easy way to choke a gun barrel and the technology has been around for years (earlier post from someone), why haven't any gun makers used it?  it seems to me that someone(weihbrauch, bsa, whiscombe, theoben, crosman, beeman, gamo,sig-sauer, browning, FN, winchester, springfield, remington, ithica, fox, beretta, colt, etc...)would have or would be using it or are they not as smart as forum mechanics?......just curious?.....isn't that an interesting thought?.....maybe a "patent" should be put on it before one of the gun makers reads this forum and starts using it.......fuel for thought.

Have fun arguing with yourself. You've proven that you can not see beyond your own thoughts to see someone elses actions.

This is how things change. Someone says it cant be done, lots of people jump on and agree until someone says "why" and gives it a shot.

Have fun debunking things that have already been proven oh disbeliever of the blatently obvious.

[Machinist]

Gentlemen:

Would like to call attention to a missed detail. The Frankengun site clearly stated that both barrel and muzzle choke were machined to a #1 MT, which stands for Number One Morris Taper which would give the barrel a relatively thin wall around the bore. The reduced cross-section will satisfy Bhawama's argument and the only limit on compression is the tensile strength per unit of the shrinking band satisfying you other guy's arguments.

If I could own only 2 books they both would be bibles. The Holy and the equally useful Machinery's Handbook cause what the first may not answer the second will.

Machinery's Handbook is priced through Enco at about $65. All of the spec's. needed to satisfy the arguments of this thread are in this bible for the shop. I can not over emphasize the necessity of owning this book. When I studied engineering, this was the first book required but it is written so clearly and so concisely a 6th grader can understand it. It even contains several variations of both hot and cold blueing formulas. I wouldn't get out of bed without a copy of this book! After buying one you'll be saying "Amen brother".

Mike

[Machinist]

Bhawana:
The data and spec's. you are looking for are found Machinery's Handbook. The "other bible". Since you are a ME, I'd bet you have one, if it hasn't been stolen or lent and not returned.
Mike

[Machinist]

Machinery's Handbook also lists thermal expansion coefficients for most known metals and many other materials. BTW, I would not worry about a "hot" muzzle choker annealing a production airgun barrel.

All of the production airgun barrels I've played with are "dead soft" already and I've not found a heat treated tool steel production airgun barrel yet. Ever wonder why CDT is so emphatic in his warning not to use brass rods or jags in airgun barrels?

I think Machinery's Handbook explains that also but don't hold me to it.
 

Mike

[melloroadman]

Roger to answer your questions. It is not a easy process if you will see what Fix had to do to get the job done. It is time consuming , and a fix for the after the fact case. It is cheaper and faster for the manufactor not to choke or to swelt some thing on the end of the barrel to reduce the size. Also it is easier for custom barrel makers to buy or custom make tapered reamers to take care or the choking. Also some finely made barrels are not choked at all but the cost of the barrel is more than what most air shooters will pay . Marvin

[3n00n]

The science of metallurgy is complicatedenough to require fields of study in hardening, temper, composition, pressure or forge treatment, as well as precipitationstructure conditioning.

`

When heat, stress, or certainchemicals are introduced to the ferrous crystalmatrix, results are predictable to a certain degree. Some problems would bebrittle martensite, which is why tempering processes are used.

Austenizingsteel followed by quenchingafterward, the ductileor brittle propertiesare then adjusted through tempering processatspecifictemperatures for a settimewhile forge pressure and introduction ofchemicals that increase carbon for additional tensile strength in some cases is how simple 10 series steel is fabricated.

`

Once annealed, the work hardeningcreated byreaming and pulling a button isn't likely to reach very deep into crystal structure. Makes me wonder what temperature and pressure on the OD is actuallydoing to theworked surface?

`

The conjecture does lead to some conclusions that seem inconsistant with with the application of the 'fix' process, although without actual tests, the rubberband material in question may be 'conforming' to the bronze sleevebut also possible is crystal 'restructuring' of the worked surface.

Either would increase 'felt resistance' although without air gaging and actuallylooking witha quality magnifyingborescope,it is doubtful thatthe exact answer could be known.

`

Anyone herehaveairgage equipment and a quality magnifying borescope?

[Jaymo]

I bet I could choke a brass Benji barrel with a shrink fit choker. Anyway, My Baikal barrel is .510 OD at it's thickest. It has a groove diameter of .217. The muzzle is threaded for the front sight retainer nut. The threaded area has a minor diameter of .445 and a major diameter of .465. Bear in mind that I measured all of this with my digital calipers. The groove diameter is probably off just a hair. But the ODs should be right on.  I guess it's supposed to be 12 mm x 1.25mm.  In order to shrink fit a choker, I'd probably turn the threaded portion down to the minor diameter or less.
My question is could I choke this bore with a shrink fit muzzle weight? I was going to use steel from a golf cart axle, or a pallet jack load wheel axle, or mild steel shaft, or a section of an 8mm Mauser barrel, turned and bored to size.  Or am I just going to be making a really nice muzzle weight that doesn't need pins or set screws to retain it?

[Jaymo]

I'd bet a Crosman 2100 Classic or .2200 Magnum barrel or a Daisy 22SG barrel(if you can purchase one) could be choked in this manner due to the OD being so small, like a rimfire barrel liner.
Though I think the Crosman 2100 barrel is already choked. Otherwise I can't see a reason for the groove around the muzzle end of the barrel. Looks like it was choked with a dull tubing cutter. Something I was thinking of doing, myself. I bet I could choke a barrel with my hydraulic collet press/hydraulic hose crimper with a number 3 or 4 collet. That, of course is a proven machanical way of doing it. Hey, there's an idea. I can shrink fit a muzzle weight onto the barrel, and then squeeze it with my hose crimper. If you rotate it about 5 degrees after the first crimp and crimp it again, it will eliminate the lines left by the collet. Then I can chuck it in the lathe and dust a few tenths off it, and polish and blue it.
Thanks everyone for the ideas. Regardless of whether or not I can shrink choke it, I know I can shrink fit the choker onto the barrel to eliminate the need for screws/pins, and then press choke it.
Heck, why didn't I think of it before.

[RCnMo]

Wow! What an interesting post. From what I gather with all this information, If I truly wanted to choke one of my barrels, I would center the BORE, not the barrel in a lathe and turn the last inch or so down to a thin wall. Then slip a heated undersized choker over the thin protrusion and let it cool. I have fixed an axle on an old pickup this way and once that ring cooled, it stayed. I may try this on a cheap rifle in the future.