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Double Rifles, Single Shots & Combinations >> Building Double Rifles & Gunsmithing

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szihn
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donor shotguns?
      #325383 - 04/03/19 03:04 AM

OK, here is a post for sake of gathering information

The question is:
For donor shotguns, which ones are the "most preferred" for a small frame gun like a 303, 9.3X74R and 405 Winchesters) and for a heavier frame for 450s 470s and 500s?

What do you guys prefer for making a double from a shotgun?

Edited by szihn (04/03/19 03:05 AM)


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Daryl_S
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Re: donor shotguns? [Re: szihn]
      #325386 - 04/03/19 05:33 AM

The ctgs noted, especially the small bores, are 46,000 (.405Win) to 53,000psi (.303) rounds. Even the 9.3x74 is a 49,000PSI round. The NE rounds run 41,000 to about 44,000psi. Maybe the question should be, are these suitable for putting on a shotgun action?

Are shotgun actions that were designed for 12,000psi rounds suitable for these pressures?

I know it's been done, but should it?

--------------------
Daryl


"a rifle without hammers, is like a Spaniel without ears" Edward VII


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Hunter4752001
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Re: donor shotguns? [Re: Daryl_S]
      #325393 - 04/03/19 08:53 AM

In assessing the actions, PSI is only part of the equation. The rearwards thrust applied to the locking mechanism is a function of the pressure times the internal area of the case head. This implies that a narrow cartridge can be handled by a relatively weak action whereas a wide bodied case needs a much stronger action. Area varies with the square of the radius. This implies if the new cartridge is half the width then then the pressure can be four times the original and still have the same thrust.

A practical example is the Baikal SxS which is available in 30.06 and 45/70. Baikal recommends keeping the 45/70 to sub 28,000 psi loads. However I've heard people claim that because the action can take 30.06 pressure levels, then they can load there 45/70 all the way up. Not so! If you do the maths, 28,000 psi times the internal area of the 45/70 case head produces a thrust equivalent to that of a standard 30.06 cartridge.

(Isn't life a bitch. All you want to do is muck around with guns, ammo and steel and some p*#@k tells you to do the maths!)


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szihn
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Re: donor shotguns? [Re: Hunter4752001]
      #325402 - 04/03/19 04:10 PM

You are 100% correct in your comments Hunter. Thrust over area is not the same as pressure.

I know of several doubles that were made on the old Browning BSS shotguns and they have been fine. From what I gather, the steel in those guns was VERY strong. There is nothing at all remarkable about the design at all. Just good strong steel. The actions were made in japan.

Double guns in the USA have fallen out of favor with manufacturers and I know of none that are still made in the USA. So I thought I'd ask what others were using these days and see what reports might be found among the readership. I believer the Ruger Gold Label was the last one made in the USA by a major arms company. Ruger often is known for making very strong guns, but I have not heard of anyone making rifles on a Gold Label yet.

Comments?


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NitroXAdministrator
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Re: donor shotguns? [Re: szihn]
      #325408 - 04/03/19 07:43 PM

Alan Moon, 4seventy I believe is his alias, has one or two double rifles built on shotgun actions. I believe one is a Ruger under and over. Perhaps see if he can chime in, if he is around.

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NitroXAdministrator
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Re: donor shotguns? [Re: Hunter4752001]
      #325409 - 04/03/19 07:45 PM

Quote:

In assessing the actions, PSI is only part of the equation. The rearwards thrust applied to the locking mechanism is a function of the pressure times the internal area of the case head. This implies that a narrow cartridge can be handled by a relatively weak action whereas a wide bodied case needs a much stronger action. Area varies with the square of the radius. This implies if the new cartridge is half the width then then the pressure can be four times the original and still have the same thrust.

A practical example is the Baikal SxS which is available in 30.06 and 45/70. Baikal recommends keeping the 45/70 to sub 28,000 psi loads. However I've heard people claim that because the action can take 30.06 pressure levels, then they can load there 45/70 all the way up. Not so! If you do the maths, 28,000 psi times the internal area of the 45/70 case head produces a thrust equivalent to that of a standard 30.06 cartridge.

(Isn't life a bitch. All you want to do is muck around with guns, ammo and steel and some p*#@k tells you to do the maths!)




What an excellent and informative answer.

And yes every now and again, someone acquires a .45/70 el cheapo rifle and immediately thinks it can be rechambered to a .450 NE.

--------------------
John aka NitroX

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Ripp
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Re: donor shotguns? [Re: szihn]
      #325411 - 05/03/19 02:14 AM

Quote:

You are 100% correct in your comments Hunter. Thrust over area is not the same as pressure.

I know of several doubles that were made on the old Browning BSS shotguns and they have been fine. From what I gather, the steel in those guns was VERY strong. There is nothing at all remarkable about the design at all. Just good strong steel. The actions were made in japan.

Double guns in the USA have fallen out of favor with manufacturers and I know of none that are still made in the USA. So I thought I'd ask what others were using these days and see what reports might be found among the readership. I believer the Ruger Gold Label was the last one made in the USA by a major arms company. Ruger often is known for making very strong guns, but I have not heard of anyone making rifles on a Gold Label yet.

Comments?




I have a local friend here in my area who is a very good gunsmith..he too has built several double rifles using the Browning BSS shotguns... all seem to work just fine..last one was a .500 Nitro..

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Jim_C
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Re: donor shotguns? [Re: szihn]
      #325447 - 05/03/19 05:39 PM

There's a Ruger O/U in 30/40 Krag somewhere local--I knew the original owner. Hell-for-stout, but it has all the balance and grace of a Mauser T-Gewehr. I'm not sure anyone ever hunted with it, but I know it stood up to several hundred full-power loads without problems.

I just can't see putting the work into building a double-rifle that is THAT ugly.


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GGB
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Re: donor shotguns? [Re: Jim_C]
      #338656 - 04/03/20 01:53 PM

I also want to convert a shotgun into a double rifle. I have a Colt 1878 that was made in 1882. It's a 10 gauge. Who does such conversions?

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crshelton
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Re: donor shotguns? [Re: GGB]
      #338692 - 05/03/20 09:56 AM

GGB,
This a a really good book on the subject by a man that has built many DR from shotguns. He is also conservative when selecting the caliber so as to avoid selecting the wrong donor gun. I have hunted with him when he was using a rifle he made and can say that he is a good shot with shotgun and DR.

http://www.ellisbrowncustomshop.com/gunsmithing/

http://bundukipublishing.com/doublerifle.htm buy the book from this source and get an autographed copy.

Good luck and enjoy the book.

--------------------
CRS,NRA Benefactor Member, TSRA, DRSS, DWWC, Whittington Center
Android Ballistics App at http://www.xplat.net/


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Daryl_S
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Re: donor shotguns? [Re: crshelton]
      #338693 - 05/03/20 10:09 AM

This, is a nice rifle by Ellis Brown, but then, I am swayed by prejudice.


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crshelton
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Re: donor shotguns? [Re: crshelton]
      #338694 - 05/03/20 10:23 AM

GCB et al,
I have two such rifles made by a former member of this forum, birdhunter50. both are made on 12 ga actions and handle well -- as good as my 12 ga Parker shotguns!(which is saying something!)

Beretta GR-2 action proofed at 17,000 psi was the donor for my .45-70 DR which has never been stressed shooting 300 grain bullets at 1600 fps and 13,900 psi. When you read the book by Ellis, you will see how these pressures correlate. The maker hunted deer with this rifle for 10 years before passing. His widow then sold it to me.

Simson and Co Suhl action was the donor for my .405 WCF DR in which I shoot Hornady 300 grain ammo and my 300 and 400 grain hand loads. For those worried about pressure - don't; I use VV N133 and never approach the factory stated pressures for this cartridge. I have taken a lot of game from hogs to Nilgai and red deer with it; the .405 is a potent killer of large game and with my Winchester 1895 .405 I have taken bison, cape buffalo, water buffalo and many smaller critters.

For more details and pictures, please search this forum for posts by birdhunter50.
Here is the link to the .405 double report:
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=265159&page=0&fpart=1&vc=1

--------------------
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Wayne59
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Re: donor shotguns? [Re: crshelton]
      #338699 - 05/03/20 01:56 PM

Daryl that gun looks like it could stand a little exercise. Send it to me for a year or so and I will take it for a walk every day (except rainy days of course).

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Daryl_S
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Re: donor shotguns? [Re: Wayne59]
      #338705 - 05/03/20 04:32 PM

Yeah - isn't that nice. It is on Ellis' web site.

--------------------
Daryl


"a rifle without hammers, is like a Spaniel without ears" Edward VII


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3DogMike
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Re: donor shotguns? [Re: GGB]
      #338728 - 06/03/20 11:01 AM

Quote:

I also want to convert a shotgun into a double rifle. I have a Colt 1878 that was made in 1882. It's a 10 gauge. Who does such conversions?



IMO not a good idea.....two thoughts:
1) If the gun is in nice shape then you are destroying a relatively rare collector specimen.
2) A Colt 1878 shotgun action it is not likely strong enough for anything save a smaller 1880-1890's era black powder rifle cartridge, if that. Doubt you could find a reputable gunsmith to even try the conversion.....

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Daryl_S
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Re: donor shotguns? [Re: 3DogMike]
      #338739 - 07/03/20 05:34 AM

Those were my thoughts, too, Mike.
Even a long .45 calibre, like a 2 7/8" or 3" case develops 30,000psi using black powder, according to AArms & that is a large rim dia.

--------------------
Daryl


"a rifle without hammers, is like a Spaniel without ears" Edward VII


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GGB
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Re: donor shotguns? [Re: Daryl_S]
      #338795 - 08/03/20 07:46 AM

Howdy. Thanks for the replies. I'm still not sure I will even attempt converting my Colt. I did read somewhere that Colt had used the 1878 shotgun to make up dome riflesin 50-110 but they were special orders and not a catalogeditem.

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Daryl_S
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Re: donor shotguns? [Re: GGB]
      #338796 - 08/03/20 08:16 AM

I'm sorry - don't know anything about the Colt.

--------------------
Daryl


"a rifle without hammers, is like a Spaniel without ears" Edward VII


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4seventyModerator
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Re: donor shotguns? [Re: Jim_C]
      #338817 - 08/03/20 08:34 PM

Quote:

There's a Ruger O/U in 30/40 Krag somewhere local--I knew the original owner. Hell-for-stout, but it has all the balance and grace of a Mauser T-Gewehr. I'm not sure anyone ever hunted with it, but I know it stood up to several hundred full-power loads without problems.

I just can't see putting the work into building a double-rifle that is THAT ugly.




Yep, there has been a lot of fugly shotgun to double rifle conversions done on a variety of actions over the years, by people who don't understand what a double rifle is or should be.

Luckily here in Aus we have had a small number of gunsmiths/gun makers who did know how to do it right.

Guys like Ron Webb, Jack Millar and Alex Beer.

Alex Beer has built DR's with slender lines and correct balance completely from scratch, not shotgun conversions.

Ron Webb and Jack Millar have done DR conversions using the Ruger Red Label 20 gauge blued and/or stainless frame, which have been done right.
I've personally handled and shot 3 of Ron Webb's Red Label doubles and they are very well proportioned and balanced, and are very fast to get on target.
Of course these guns were built many years ago when there were very few DR's available on the market.
Things are very different these days in the DR world with bucket loads of double rifles available on both the used and new markets.

Things were very different back in the 80's and 90's when even projectiles, cartridge cases and reloading dies were not easily available for the big British cartridges.

Those who have come into the double rifle world in the last 15 years or so, don't realize how easy they have got it!


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4seventyModerator
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Re: donor shotguns? [Re: 4seventy]
      #338819 - 08/03/20 09:01 PM

For anyone contemplating converting a shotgun to a double rifle, the book mentioned above by Ellis Brown does indeed contain a lot of useful information, and is a very good place to start.

However now might be the right time to again mention that there are some errors concerning Breech Thrust calculations in the first edition of this book.

These errors are on page 19 of the first edition.
I don't know if these errors have been corrected or not in later editions.

The errors relate to calculations using Proof pressure, cartridge case dimensions, and chamber pressure, to obtain breech thrust figures.

The math is not done correctly, resulting in a GROSS over estimation of the breech thrust that a particular action supposedly endured and passed during proofing.

Breech thrust is a very important factor with DR's, and getting it wrong is a very bad idea.


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crshelton
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Re: donor shotguns? [Re: 4seventy]
      #338854 - 09/03/20 06:03 AM

4seventy,
So it was the arithmetic that was in error, but not the formulas ?

I have the second edition only.

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4seventyModerator
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Re: donor shotguns? [Re: crshelton]
      #338918 - 10/03/20 04:09 PM

Quote:

4seventy,
So it was the arithmetic that was in error, but not the formulas ?

I have the second edition only.




He was calculating breech thrust of the load used to proof the donor action, and the formula he had been using up to that point was correct, that being cartridge chamber pressure multiplied by the AREA of the cartridge case head.

He claimed that the donor 16 gauge SxS was made in East Germany after 1950, and that it was proved at 32,000+psi!!

32,000+psi is an extremely high proof pressure for the 16 gauge, which would have a cartridge service max pressure of no higher than 12,000 psi.
32000+psi would be the service max pressure of 12,000 psi x 270%!

On top of this came the error.

Instead of multiplying the 32,000 psi by the AREA of the case head, he multiplied it by the case head DIAMETER! (.810")
This gave a totally incorrect figure of 25920 pounds force against the breech!

To give you an idea of how high 25,920 pounds of breech thrust is, it's very close to the breech thrust of a 140% proof load for The 460 Weatherby Magnum!

If he'd correctly used the case head AREA (.515 sq inch) instead of the DIAMETER, the breech thrust figure would have been approx 16,480 pounds NOT 25,920!

But I'm still suspect of the claimed 32,000+psi proof load, and have to wonder if it is correct. Sounds way too high to me. If so, the true breech thrust figure would be considerably lower again.

The bottom line is that the errors that were made, suggested that the particular 16g donor action was much stronger than it really was.


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crshelton
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Re: donor shotguns? [Re: 4seventy]
      #338949 - 11/03/20 01:59 PM

4seventy,
Thank you. I have recalculated the pressure numbers for both my double rifles made on shotgun actions and all seems OK. For instance, the Beretta 12 gauge factory proof pressure was stated to have been 17,000 psi.

In a day or two, I will have time to revisit that section of the edition two and look for the error you mention. I hope it was corrected, but shall check and advise.

Thanks again.

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Android Ballistics App at http://www.xplat.net/


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crshelton
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Re: donor shotguns? [Re: crshelton]
      #339068 - 15/03/20 09:58 AM

Hello again 4seventy,

I have just read the section on page 9 dealing with the German 16 gauge shotgun and have the book open to that page.
The author references the Standard Directory of Proof Marks as stating the action was made in East Germany after 1950 and was proofed at 13,000+ psi. He plugged that pressure into the formula using the .819 head diameter and found the pressure against the standing breech to be 10,530 pounds during proofing.

It seems to me the error you referenced being in Edition 1 was corrected in Edition 2. At least I can not find the error in Edition 2.

Thank you for pointing out the Edition 1 error and helping me to check Edition 2 for the error.

For what it is worth, I have read this Edition 2 of this book more than once and found it to be well written and very well proofed with respect to grammar and spelling. After working with you on this issue, I am given hope that it was also well proofed with respect to technical content.

Thanks again and Best Regards.
CRS

--------------------
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Android Ballistics App at http://www.xplat.net/


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4seventyModerator
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Re: donor shotguns? [Re: crshelton]
      #339095 - 16/03/20 09:34 AM

Hi crshelton,
Thank you for posting the info from the 2nd edition of this book.

It's interesting to note that the author has reduced the claimed proof pressure which was printed in the 1st edition by a large amount.
1st edition-32,000+psi.
2nd edition-13,000+psi.

That's a step in the right direction.

However, when calculating the force against the breech, he has still made the same mistake as in the 1st edition.

He has again used the case head DIAMETER when he should have used case head AREA in square inches. {.515 sq in}

His 2nd edition (incorrect) calculation using case head DIAMETER of breech thrust resulted in 10,530 pounds force against the breech.

Using case head area, would result in the considerably lower figure of 6,695 pounds force against the breech.

His figure of 10,530 is approx 50% higher than 6,695!

As I mentioned before, despite the math errors concerning proof pressures and breech thrust calculations, the book does contain some very good ideas on how a shotgun to double rifle conversion can be done.

Cheers
4seventy


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