12ga chamber adapter in 243win

[finstr]

I have a fairly new chrome moly 243 win barrel that came off of a Weatherby Vanguard. I'd like to spin it up on the lathe and make a chamber adapter out of it to fit a single shot 12ga.
I plan on cutting the rifle barrel down to approx 14" and recrowning it.
Then profile the OD to fit the 2-3/4" shotgun chamber.
I'm sure this is doable but is it dangerous? Too much chamber pressure? How about rearward thrust?
I have seen chamber adapters from other companies but seldom in rifle calibers.

[M-Tecs]

Bolt thrust and firing pin size would be my areas of concern.

It would be safe on a TC Encore but for others it becomes much more questionable.

The sub gauge adapters work very well. The cartridge adapters not so much.

http://www.thefirearmblog.com/blog/2014/05/22/utility-12-gauge-caliber-adapters-good-bad-ugly/

[BeeMan]

Bolt thrust and firing pin size would be my areas of concern.

It would work on a TC Encore but for others it becomes much more questionable.

Same concerns here, plus material and strength of the particular single shotgun frame.

[Texas by God]

Don't do it. No break open shotgun made will stand that pressure for long. I know about NEF Rossi etc. But they use special steel frames with small firing pins.
Sell that barrel and get a break open .243-CDNN has Baikal .243s for $189 today.
Best, Thomas.

[finstr]

Thanks for the input fellas. Just wondered if it's doable.
I'd like to have a test lab where I can do this type of stuff and safely blast away just to see if the gun will fail. If it is a colossal failure it would be neat to look at the carnage without shedding blood! Lol Kind of a Mythbusters type of thing.

[Texas by God]

Truck tire & trigger string and a Big tree to hide behind....been there done that.

[finstr]

Truck tire & trigger string and a Big tree to hide behind....been there done that.

Funny, that's exactly what i was thinking!

[Texas by God]

Baling twine to tie the gun to the tire. I've tested suspect guns this way as well as my first rebarrel jobs. Stay behind the tree. You can look After the shot to assess results. I wouldn't try blow-up tests; that's stupid.
Best, Thomas.

[nekshot]

I understand the wondering mind and what if theory but this type of stuff can make us look like we need federal help to keep from hurting ourselves or others and I hate their intervention! Read up on ackley blowing up guns and you will be satisfied. Remember, if the gun did not come apart after a torture test that is not necessarily the end of the story. It could let go later on with a normal load and of course the blame will be on the manufacturing party rather than the idiot who over did it.

[Ballistics in Scotland]

I understand the wondering mind and what if theory but this type of stuff can make us look like we need federal help to keep from hurting ourselves or others and I hate their intervention! Read up on ackley blowing up guns and you will be satisfied. Remember, if the gun did not come apart after a torture test that is not necessarily the end of the story. It could let go later on with a normal load and of course the blame will be on the manufacturing party rather than the idiot who over did it.

You wouldn't mind it as much as an ambulance crew's intervention. There are plenty of shotguns with modern alloy steel receivers which can make a good .45-70 or 11.15mm Mauser, including with smokeless loads which somewhat exceed black powder. The same might apply to some, not all, older ones, well made and with top extension and crossbolt. But .243 is a very unrelaxing proposition.

I also agree about amateur proof testing. It can indeed create damage which will only show up later, and rifles fail in different ways. I never yet heard of anyone trying it with an artificially induced head separation, for example.

[finstr]

I started doing some quick research on rearward bolt thrust. Looks like the .243 has aprox 8500-10,000 pounds. The 12 gauge is a mere 6500 at best.

[pietro]

.

What could possibly go wrong ? ? ? ? [smilie=b:


.

[footpetaljones]

My math puts the bolt thrust at 10500 lbs and the hoop stresses at 140 kpsi. Way past "bad idea" territory and into "I already called an ambulance" territory.

[DLCTEX]

I used the tire and string method to test an old Damascus barreled shotgun when a teen ager. The first pull didn't fire, but unknown to me ( I was in a hole with my head down) it turned the tire., the second pull blew a hole in the grain tank of grandpa's combine. The gun held.

[Texas by God]

Granpa warm your britches up?

[EDG]

Most old break open shotguns have cast iron frames with huge firing pins. Those firing pins are aimed right at your face with a hammer gun and a high pressure rifle round can blow them back at you.

[izzyjoe]

Well, that sounds like fun!

[Wagnerwerks]

I have a set of Chiappa adapters. I blew the firing pin out of my old beater shotgun with a little hotter than it should have been 357 load when the fat firing pin blew out the primer. Yeah. Good times.

[Survival Bill]

it would make a great youtube video!

[Drm50]

Besides cast frames on old guns and the pot metal frames on newer ones in addition to large
Firing Pin, nobody has mentioned head space.

[kywoodwrkr]

Besides cast frames on old guns and the pot metal frames on newer ones in addition to large
Firing Pin, nobody has mentioned head space.

Nor frame in question???

[Mauser 98K]

the shotgun is not a high pressure cartridge and centerfire is (12 gauge 3 1/2 in. 14,000 max psi Vs 60,000 max psi for most high velocity cartridges). there was a company a few years back who made pump action 30-06 on a shotgun action, the Remington model 760 Gamemaster was one, the results were not good. the frames would stretch over time and some would actually crack.

[Soundguy]

Winchester 101 shotgun frames were used to make grand European double rifles I believe.

[M-Tecs]

there was a company a few years back who made pump action 30-06 on a shotgun action, the Remington model 760 Gamemaster was one, the results were not good. the frames would stretch over time and some would actually crack.

Interesting since the 7600 that replace the 760 is still currently in production. The 760 Gamemaster was in production from 1952 till 1980 with a total production of 971,712 rifles and 67,726 carbines. Before the 760 it was the 141 and before that Remington's pump rifle was the 14 introduced in 1912. Remington has 106 years of producing a pump action rifle with millions sold. Someone must have not told them the results were not good.

A brief history here: http://www.shootingtimes.com/long-guns/longgun_reviews_ga_remmodel760_200903/

I really like my 760.

[reivertom]

Why risk it when there are already single barrel break action rifles on the market?

[Ballistics in Scotland]

Why risk it when there are already single barrel break action rifles on the market?

Personal achievement? Cheapness? I can think of snags that far outweigh those.

Besides the diameter and shape of the firing-pin, it is a very light one, often backed up by a rebounding hammer. I think that makes a blown primer rather more likely than it is with a purpose-made rifle action. Whatever hold the firing-pin in place is also a consideration. A screwed-in thimble is best, but a cross-pin, very likely in soft steel, may be strong enough for even the sort of gas that escapes from a ruptured shotgun primer, and yet let the thing be spat out violently if a .243 rifle primer goes.

Then there are the legal considerations, and those are big considerations, on which you need good advice, source-quoting advice, from people who know more about it than I do. Is the adapter meant to be removable? Then it is a shotgun, and you would probably fall foul of the 18in. barrel requirement. The 16in. requirement for a short-barrelled rifle sounds like it only applies to one made from a longer rifle or from scratch, not from a shotgun. But that isn't the sort of thing I would like to count on.

Good rifles used to be made on actions very hard to distinguish from shotguns, and in the traditional case-hardened mild steel. But they weren't .243s, and apparently small changes in design put a lot more metal into the decisive spot, which is the action bar below the breech face. These could include a little more width or depth, sidelocks and especially back-action sidelocks instead of boxlocks, or the rotary grip operated by the trigger-guard turning around a vertical axis. This last wasn't stronger because it "screws" the barrel flats down tight against the action table, as many imagine. That doesn't matter very much. It was because they took a smaller and mostly round bite out of the metal which resists the true, mostly longitudinal force exerted on the barrels. I don't think a rear extension in double shotgun barrels, especially doll's-head but even with a Greener-style crossbolt, was that significant. It might limit damage after something goes badly wrong... or mightn't... but I don't think it much reduces the chances of its going wrong.

Good double rifles are made on actions in the stronger investment cast alloy steels, but I would prefer a lower-pressure cartridge for those, and you can do very good work with some of those. It is also easier to handle a rimmed one. If I wanted a single rifle, I have seen very good ones built on the Greener GP shotgun, which is just a Martini with a wider breechblock and barrel threads to accommodate the 12ga case. But I would permanently fit the barrel liner with Loctite or soft solder, and have it end at a shallow step, possibly concealed by a sling swivel band, and have only the rifle barrel, gracefully tapered, forward of that.

[rking22]

The Rem 760 is NOT a converted shotgun. The reciever is similar to the small 870 frames but the lockup is entirely different. The bolt lockup is really quite like the AR , and everybody knows it the most awesome thingever!
Oh, on topic, dont go there. Not only is the case head thrust much too high it is over a smaller surface area in the weakest part of the shotgun frame. Even if it survived a test firing it could/will fail over time due to fatigue of the metal as it flexes under repeated use, ie no warning just boom!

[Goatwhiskers]

A little OT, but all this talk of firing pins reminds me of quite a few moons ago when I knew a guy who made a replacement pin for an old single from a large nail filed to fit. Was a bit too long, punctured the primer, blew the pin out and "nailed" the old boy in the center of his forehead. Bubba strikes again! GW

[rking22]

I got the visual, Bubba the Unicorn :)

[Ballistics in Scotland]

A little OT, but all this talk of firing pins reminds me of quite a few moons ago when I knew a guy who made a replacement pin for an old single from a large nail filed to fit. Was a bit too long, punctured the primer, blew the pin out and "nailed" the old boy in the center of his forehead. Bubba strikes again! GW

He's lucky it didn't get him in a vital spot.

As to fatigue, mild steel doesn't fatigue much. What is possible, though, is seams on inclusions in a forging which will stay together under shotgun pressures, but give way with a rifle. That can still happen in time, if the receiver has been overstressed but held together with one higher pressure proof load.

Cast iron, however, even good malleable cast such as has been used to make inexpensive shotgun receivers, doesn't need to fatigue. It is a good material within its limits, which a sizeable centrefire rifle cartridge exceeds.

[Mauser 98K]

apparently folks didn't know any gunsmiths or gun dealers back when the pump 30-06 was popular. i have seen cracked and stretched receivers on these things from some higher pressure military ammo..

[Texas by God]

I think the OP took the advice and decided not to pursue danger. This thread can now die peacefully.
Thomas

[M-Tecs]

apparently folks didn't know any gunsmiths or gun dealers back when the pump 30-06 was popular. i have seen cracked and stretched receivers on these things from some higher pressure military ammo..

Interesting since the 760 was chambered in the 270 Win with a chamber pressure of SAAMI 65,000 PSI. The SAAMI for the 30/06 is 60,000 PSI. Military ammunition is not covered under SAMII specs, however, the specs for M2 AP is 54,000 PSI and M2 Ball is 50,000K. The M1 Ball, High Pressure Test, proof load was only 67,500 PSI.

http://inetres.com/gp/military/infantry/rifle/30_ammo.html

http://www.guns.com/2011/08/16/the-secret-to-a-long-life-a-garand-diet-or-what-to-feed-your-m1-garand-part-i/

More interesting is the bolt locks into a barrel extension like the AR 15. The receiver just holds the parts together. I am having a hard time understanding how a frame stretches or crack when all the bolt thrust goes into the barrel extension?

http://leeroysramblings.com/Gun%20Articles/remington_760_7600_pump_rifle.html

The bolt and the barrel extension can be seen at the 4 minute mark.


https://www.youtube.com/watch?v=5FF6bTcnIkU

[Texas by God]

The 760 was also chambered for the 6mm Rem/.244- another higher than 30-06 pressure round! So don't use any cartridges that were offered in the 760 to make a rifle out of a single shot shotgun......

Sent from my SAMSUNG-SM-G930A using Tapatalk

[M-Tecs]

The 760 was also chambered for the 6mm Rem/.244- another higher than 30-06 pressure round! So don't use any cartridges that were offered in the 760 to make a rifle out of a single shot shotgun......

Sent from my SAMSUNG-SM-G930A using Tapatalk

The first barrel I chambered for someone else was a 6mm Rem on a 760. It was a Hart or a Shilen in a heavier contour. It was modeled after the 6mm Rem 760's that the AMU used to win the running boar competition in Oslo, Norway in 1960. It shot very well with the factory barrel and outstanding with the new barrel. It was his primary prairie dog and coyote rifle. I have no idea how many rounds he put thru the factory barrel but the throat was gone for 3 or 4 inches.

I have also read about them being chambered in .222 for that type of competition.