Can a Model 24 Winchester 12 guage be converted to a double rifle with barrel inserts and withstand the pressures of the .470 Nitro? If so, how long will it possibly stay on the face with standard loads? The shotgun in question is in very good shape and tight on the face.Overall condition of the gun is excellent. If not recommended for the .470 Nitro pressures, just how much pressure can it reasonably/safely withstand, i.e. recommeded calibers for a double? Or....make any caliber I want out of it, just double or triple my life insurance. I know of two problems that have to be worked out with this; one being the extractors liked to climb over the rims since they were rounded and I can't remember the other. One of the smiths said he liked to keep the barrel length to 20 inches and I wanted 22 or 24 inch. Twenty seemed just a tad short?? What say? Thanks, Mike

this might help
https://forums.accuratereloading.com/eve/forums?a=tpc&s=518103&f=9411043&m=853104161

do you have a copy of ellis' book on building them?

part of the issue with american guns is the lack of proof housing... one has no CLUE as to what pressure, as a MINIMUM and that bolt thrust the gun has been built to.

In fact, *I* would be looking at english, spainish, french, german, or belgan (sp) doubles, with dual underlugs, and some form of third member. The third member is for axial/twist, not to keep the action latched DOWN. this would be a waterfowling piece, under NO circumstance would it be a upland game (too light) and I would be comparing the hell out of the proof marks, (more later)

most american shotguns have the following short comings from the building a double rifle aspect.
1: no third member
2: single lugged
3: double lugged but SCREWED on
4: flimsy connections (fox mod 31... 1/2 moon... see it once and you'll know)
5: unknown (till sammi) pressure proofing.

if you don't have a FIRM grasp of bolt thrust, I will suggest get ellis' book asap.

as for barrel length... the gunny may have an OPINION, but, at the end of the project, YOU have bill... 20" would be cute... and would cost you 50-70 fps... which means you would have to load with MORE pressure to get the published vel. of a 470... MORE pressure on a shotgun, to put a fine point on it. DUMB idea overall, on the gunny' pov, as one will try to load to classic vel... that's why you would build one

jeffe

Thanks all for the feedback. After taking a second look at the project at hand and regaining my sanity I've discarded it. I do need to obtain a copy of Ellis Brown's book on the conversion though as someday I would like to pursue this. However, in the meantime I'm looking seriously at Butch Searcy's new model that is going to sell for around 8K. If I understood him correctly when I talked to him last week his double parts are being machined here in the US and shipped to Africa for assembly in order to trim labor cost and offer it at a more desireable price. Thanks again for the advice which I always give serious thought, Mike

In regard to pressure you can calculate the pressure against the surface area of the shotgun shell case head and the pressure against the case head of the proposed rifle cartridge to get a comparison of the two rounds.

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Originally posted by ireload2:
In regard to pressure you can calculate the pressure against the surface area of the shotgun shell case head and the pressure against the case head of the proposed rifle cartridge to get a comparison of the two rounds.

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ireload...
yep.. ellis has the math in his books, and I don't have it in front of me to tell you.. a gunsmithin buddy has it...

there is a MAJOR fault, IMHO, on his math...

he uses PROOF loads of the shotshells against SAAMI standard loads of rifles...

in order words, if it was EXACTLY the same, every round fired in the rifle would be AT LEAST the proof load for that action...

what does that mean?

proof loads are 30 to 50% higher pressure than operating loads... and, frankly, even name guns have failed sustained firing of proof loads.


Just wanted to inject a little sanity into this one...

so, I am going to be building a 45/70 on a 12ga... and keeping the pressures low, to keep the thrust down...

it aint an african load.... it's a texas piggun load.. but I'll have that double...

then, and only after a good bit of time with it, will i be looking at doing it in 470

jeffe

Jeffesso, Thanks again for the concern and the much needed advice. If you would post the progress here on AR on the 45/70 I'm sure it would make for very interesting reading and viewing if you'd take pics also. Good shooting! Mike