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Double Rifles, Single Shots & Combinations >> Building Double Rifles & Gunsmithing
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tward1604
.275 member


Reged: 14/07/10
Posts: 51
Loc: texas
shotgun to rifles
      #168396 - 24/09/10 09:58 PM

what makes a double shotgun unable to handle the higher pressure of big bore rounds are they not made the same way as your rifle doubles. And what is the bennifits the the chopper lump barrel over the monoblock system

Thanks
~Semper Fidelis~

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Thank you
SGT
USMC

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Huvius
.416 member


Reged: 04/11/07
Posts: 3526
Loc: Colorado
Re: shotgun to rifles [Re: tward1604]
      #168409 - 25/09/10 01:54 AM

Generally, there is more "meat" in an action made specifically for use on a rifle.
Although an action from a rifle and a shotgun may be dimensionally similar on the outside, inside there usually is more metal left in the rifle action.
Not only does this make the action inherently stronger, it also keeps a little more weight in the gun which is nicer in a rifle and helps to balance the gun a bit more since the barrels are heavier than shotgun barrels.
There was a little article in one of the recent Double Gun Journals recently on just this subject.
As for the chopper lump question, C.L. barrels seem to be preferred on a vintage rifle although there have been plenty of vintage rifles - even big bore nitro rifles made on shoe lumps too.
Monoblocking is a more "modern" practice - I am not sure when that became more prevalent as used in production gunmaking, but it is the usual practice when building up a rifle on a shotgun since most of the fitting of the lumps and other bites is already done for you. Done properly, this is a very viable method of fitting the barrels. There are many excellent examples right here on NE!
I suppose the benefit of C.L. barrels is that there is one solder joint between the breech ends of the barrels with a lot of area for a very strong joint. Each barrel being one single solid piece of steel from one end to the other. And, since they are "sandwiched" together they are inherently stronger when the gun is closed and in being fired. I say stronger, but really any accepted method of fitting barrels is quite strong and this may be splitting hairs. Chopper lumps are quite expensive though too.

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He who lives in the past is doomed to enjoy it.

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doubleriflejack
.333 member


Reged: 11/11/07
Posts: 352
Loc: Oregon, U.S.A.
Re: shotgun to rifles [Re: tward1604]
      #168417 - 25/09/10 05:14 AM

You asked why double shotgun was unable to handle higher pressure of big bore rounds.

Actually, pressure has little or nothing to do with bore size at all. For example, the British big bore cartridges, such as .470,, .500, even .577 and .600 are not considered high pressure, due to their large case size, while the smaller cased .458 Winchester is of higher pressure, due to that smaller case size. On the other hand, the little .270 is considered an intense cartridge, a high pressure cartridge, comparatively speaking. So, one cannot assume that big bore rifles are of high pressure, while smaller bore rifles are not. Pressure has no direct correlation with recoil either---one can have heavy recoil, with lower pressure, and little recoil with high pressure.
Double barreled rifles of all kinds, due to their design and bolting systems, are not suited to high pressure cartridges of any kind, though modern alloy steels have helped this situation considerably. Double barreled shotgun conversions are also obviously not suitable to high pressure cartridge conversions too, are not as large physically--not as much metal left in areas where needed, so one must be more conservative and use good judgment when converting them to low or medium pressure cartridges only; certainly never to high pressure cartridges. Chopper lump barrels were developed way prior to monoblock development, as a best method of construction, with far less likelihood of failure, but it seems likely now, that monoblocking is just as sound as is chopper lump barrel construction, as proven by numerous rifles built using monoblock system. Today, it is much more difficult, and more expensive, to make chopper lump barrels, rather than monoblocking, thus monoblocking being popular with gunmakers. Monoblocking is used frequently today for both double shotgun and double rifle manufacturing.

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tward1604
.275 member


Reged: 14/07/10
Posts: 51
Loc: texas
Re: shotgun to rifles [Re: doubleriflejack]
      #168420 - 25/09/10 07:42 AM

well the answer for the mononblock question was more than helpfull i was just curious about it so i figured i'd ask why not learn when you can. I don't know why i didn't think about pressure correlation not being a reflection of cartrige size i spend probably more time than i should looking at ballistics. so if i wanted to build a big bore double say in .470 NE where would i get the dementions for a atcion that could handle it.

--------------------
Thank you
SGT
USMC

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Tallchief
.300 member


Reged: 11/12/09
Posts: 108
Loc: Colorado,USA
Re: shotgun to rifles [Re: tward1604]
      #168687 - 29/09/10 09:13 AM

Definately get Ellis Browns excellent book on such conversions as he explains just about everything one needs to know.
TC

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doubleriflejack
.333 member


Reged: 11/11/07
Posts: 352
Loc: Oregon, U.S.A.
Re: shotgun to rifles [Re: tward1604]
      #168890 - 03/10/10 06:03 AM

For your proposed .470, or for a .450 NE, (or better yet, a .450 #2 for better lower pressure) or a .500/.416 Rigby (for a lower pressure .416 Rigby bullet), and numerous other cartridges too (not .500NE or larger, as they are too light in weight), any Good condition, tight bolting German action OF 12 GAUGE, with Greener Crossbolt, especially one made from 1950-1990, should work just fine---they did for me! If you can find one, one with 3" shotgun chamber, that was intended as a heavy waterfowl gun, will usually give a bit more weight for better finished balance between barrels and action/stock. I took class from W. Ellis Brown at gunsmithing school, prior to his writing book on subject, now in 2nd edition, and I just follow his methods, with a few of my own modifications in building doubles. Get the book and read it. I know a guy who built a .470 too, on converted Ruger 12 ga. O/U successfully too, something I found interesting.

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GroovyMike
.300 member


Reged: 07/04/09
Posts: 229
Loc: NY
Re: shotgun to rifles [Re: doubleriflejack]
      #168982 - 05/10/10 03:14 AM

I have 45-70 inserts for my 12 gauge .........

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Delight yourself in the Lord and He will give you the desires of your heart. Psalm 37:4

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