Those familiar with the structure of Double Rifles

[Ray B]

I presume that since a double barrel shotgun is designed for pressures of less than 15K and the double rifles are for cartridges that have pressures three times that amount, that there are some structural differences. I am wondering what makes them stronger. Are the pivot pins and locking blocks larger. Is the frame larger? While the outer dimensions of the barrels my be similar, there is a lot of steel in a ,400" bore around the bore until it reached the outside diameter of a 12 gauge.. So there are two options: The shotgun action is far inferior to the rifle action in strength so would be unworkable for the higher pressures, The other option would be of interest if the action was sufficiently strong, the weak link being the barrels, In that case, a smith could make a set of barrels matching the lockup with the action. A possibly easier rout would be to remove the 12 ga barrels from the action and precisely fit a liner in the barrel. the shotgun barrels were regulated so it is likely that the rifle barrels would be close, the thickness of the barrels, combination of the insert and the original barrel should provide sufficient strength and since the original premise involved sufficient strength for the action, It seem to me that such a project would work.

 

[mark-hunter]

I am not an expert in that sense, but I know there are some makers producing barrel inserts converting shotgun, to rifle.
Also, Brno and Check Zbrojovka were making spare sets of barrels for their guns; O/U shotgun, combination, and O/U rifle.
However to my knowledge, it was not made then in tropical calibers.
Browning B525, was also made as O/U rifle. Not sure in which calibers.

However, your question is very interesting, and I look fwd for experts answers!

 

[rookhawk]

@Ray B the shotgun action and the double rifle action are virtually identical. Back in the day there were improvements to the double rifles as they believed it was making a difference but they were debunked.

Four examples of common double rifle improvements:

-A third bite. (aka the Greener Crossbolt. Many shotguns have it too. It makes no difference empirically)

-An extended tang

-Side clips (barrels mate with the action not on flat surfaces, but on a 45 degree with the idea that the barrels won't blow off the sides of the gun...myth)

-Bolsters under the barrels (again, not much strength value but it helps ID a double rifle)

Most double rifles are built on a frame approximating that of the the 20 bore. You'll often see .410 and 28 bore shotguns that were once double rifles but when gun control hit in 1921 the Brit owners would bore them out so they could keep them even if they had no owned lands. The only reason the latter are heavy is because the tubes needed to be heavy to mate up properly.

Exceptions to all these statements would be when you get to the bore rifles and the 577s and 600s that are built on massive frames.

For 470NE for example, there is little difference. Consider this: The service life of a shotgun is tens of thousands of rounds. That same action can take the few hundred Nitro rifle rounds in equal stride as they both put the same wear and tear on the gun practically speaking.

The biggest area of improvement that you'll note on Double Rifles that is legit is the substantially overbuilt wrist and more materially left at the head of the stock. This is just to withstand the recoil (so the story goes) but is probably to withstand the harsh use and constant dropping of guns that happens in the bush. Shotguns are not nearly so abused by their owners.

20 bore barrels outside diameter is more than sufficient at the breach for a nitro express rifle cartridge. It is the additional wall thickness of the double rifle that contains that pressure in the chamber. The lock up of the Anson & Deeley boxlock or the Holland 7 pin sidelock is absolutely sufficient for the service pressures of most dangerous game cartridges.

 

[rookhawk]

I am not an expert in that sense, but I know there are some makers producing barrel inserts converting shotgun, to rifle.
Also, Brno and Check Zbrojovka were making spare sets of barrels for their guns; O/U shotgun, combination, and O/U rifle.
However to my knowledge, it was not made then in tropical calibers.
Browning B525, was also made as O/U rifle. Not sure in which calibers.

However, your question is very interesting, and I look fwd for experts answers!

The barrel tubes you're mentioning are very common on drillings. You'll see 16 bore drillings with .222, .223 and .22 hornet tubes inserted with great regularity. The restriction on caliber isn't due to action weakness, its due to the available space inside a 16 bore tube of roughly .66". It doesn't leave much room for a durable chamber and a thin wall barrel sleeve to be carried in there and the exterior shotgun barrel provides no structural assistance to the integrity of the tube inside. (it fits loosely so it can be removed with a rubber mallet at will)

So question extrapolated: Could you put a 500 Nitro tube inside a 12 gauge shotgun and go hunting? No. The interior .729" diameter of a shotgun barrel is insufficient to handle the .511" rifle bore, and the less than .218" of room for the barrel liner. It's not enough inner barrel to handle the pressures because again, the shotgun barrel on the outside is not providing any rigidity or value to it.

Naturally, Butch Searcy and many others can take a 20 bore shotgun and make new barrels in 500NE, regulate and away you go. Nothing wrong with a 20 bore frame for a DG rifle structurally speaking.

 

[Velo Dog]

Hello Double Rifle Enthusiasts,

My first double rifle was a Merkel side by side in .375 H&H that, I had purchased brand new in the box.
Other than the specific rifle barrels plus, a pound or two of lead, added to the interior of the butt stock, to counter-balance the heavier rifle muzzles, it appeared identical to Merkel's 20 gauge side by side shotguns, in every way.

Incidentally, one of my friends here has a book entitled something like; "Building Double Rifles On Shotgun Actions", or words to that affect.
He also bought a lathe and upon retiring one of these years, intends to try his hand at building himself a double rifle from a Brno side by side shotgun.
He has not settled on the specific cartridge yet but, is leaning toward the .400 NE Jeffery (450/400 3" NE).
Whichever one he settles on, it will be none of the high pressure, severe bottle neck cartridges of present day.

Also, I have fired a .450 NE that was built on a shotgun action.
It went "bang" just fine and I hit what I shooting at for the very few shots I tried it with.
I think it was originally a JP Sauer 12 bore prior to ?
Matt85 ended up buying it from another member here (AKMike).

Some shotgun actions are apparently better suited for conversion to rifles than others are (robust moving parts, three locking feature, aka: "bites" is preferred and very important is quality of steel / proper heat treating when the action was made in the first place).
It is my impression, right wrong or arguable either way that, there is no inexpensive way to own a top quality double rifle.
By the time you have an EXPERT double rifle maker (few and far between in today's world) build up a rifle on some shotgun action, you will have so much money into it that, you probably could have bought a 2nd hand Heym, or a new Merkel, Krieghoff for about the same amount of money.

Cal Pappas is in fact a world authority on double rifles although, he is not one to speak of himself in that way.
We are fortunate to have him on this forum and I would definitely consult him, prior to buying someone's home made double rifle.

JJ Perodeau, of: www.champlinarms.com in Enid Oklahoma is an expert double rifle Gunsmith and no doubt can PROPERLY build such rifles on shotgun actions.
However, again the cost might be substantial.
But spending money is way better than losing an eye or a few fingers, from firing some mess, built at "Joe Buzzard's Snow Mobile Repair & Gunsmithing".

Cheers,
Velo Dog.

 

[Luis Almeida]

The barrel tubes you're mentioning are very common on drillings. You'll see 16 bore drillings with .222, .223 and .22 hornet tubes inserted with great regularity. The restriction on caliber isn't due to action weakness, its due to the available space inside a 16 bore tube of roughly .66". It doesn't leave much room for a durable chamber and a thin wall barrel sleeve to be carried in there and the exterior shotgun barrel provides no structural assistance to the integrity of the tube inside. (it fits loosely so it can be removed with a rubber mallet at will)

So question extrapolated: Could you put a 500 Nitro tube inside a 12 gauge shotgun and go hunting? No. The interior .729" diameter of a shotgun barrel is insufficient to handle the .511" rifle bore, and the less than .218" of room for the barrel liner. It's not enough inner barrel to handle the pressures because again, the shotgun barrel on the outside is not providing any rigidity or value to it.

Naturally, Butch Searcy and many others can take a 20 bore shotgun and make new barrels in 500NE, regulate and away you go. Nothing wrong with a 20 bore frame for a DG rifle structurally speaking.

So how can you tell if a shotgun action can handle a rifle caliber? Is there any information on the technical data of the manufacturer of the gun that can give a clue on that? Like the stoeger double defense shotgun? The reason I'm asking that it's because I'm from Brazil, and here imported guns can reach extreme values, and no hunting rifles are made here, for example a friend had his cz 500 rifle, in 458 lott caliber, valued and sold for around 7 thousand dollars, so if a local hunter spends even 4 thousand dollars to a local gunsmith do that here, it would be a good saving. Local authorities do not even allow to import barrels or inserts.