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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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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.

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John aka NitroX

...
Govt get out of our lives NOW!
"I love the smell of cordite in the morning."
"A Sharp spear needs no polish"

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

I have the second edition only.

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