Convert a H & A falling block shotgun to a centerfire rifle ?

[jedman]

I was thinking of using a old Hopkins & Allen falling block shotgun and relining the barrel to make a centerfire rifle in a lower pressure round like a 38/40 or 44/40.  Has anyone out there done this or seen one of the old H & A shotguns converted to a rifle ?                    Thanks,    Jed

[Nobade]

Sure, it works fine. You may need to turn down the tip of the firing pin and bush the hole, and I would only shoot it with black powder and not that new kind of nitro based stuff. I probably wouldn't ever sell it, just in case somebody else thought they'd like to hot rod it and end up wearing it. I would certainly not chamber it for any modern high pressure cartridge! Track of the Wolf has barrel liners in a wide variety of sizes for a good price.

I've been looking for an old H&A small frame .410 shotgun to do this to. Someday I hope to find one for a good price, make a very light weight tip up 32 S&W or something similar.

[Rangr44]

Good advice.

JMO, but I don't think the shotgun actions received the same heat treating that rifles did.

I would even go so far as to mark the new barrel: "FOR BLACK POWDER ONLY".

[gunnut69]

The real problem is the frame isn't made of steel, it's made of cast iron! This stuff will shatter if overstressed.. You may get by with the practice using black powder only but it's not a good idea. Also I'm refering to the falling block actions only. The rifles they made that resemble the Stevens rifles are in truth rolling block rifles and their diminutive size makes any changes such as you suggest very dangerous. They could be made into very nice rifles chambered to 22 rimfire rounds but in the rolling block variation absolutely no magnums...

[trotterlg]

If you do the calculations you will find that the bolt thrust (breach face thrust) is less in some of the small diameter CF rounds than it is with a 12 gauge.  This is due to the area of the case head, so the load on the frame may be less with full up loaded 357 Mag than with the shotgun.  I have done several conversions of H&R shotgun barrels to pistol rounds, two to 32 H&R Mag and two to 30 carbine.  I have one ready for a 5mm RF necked down to .14 and one ready to shoot in 17 Fireball.  I would only shoot the 17 Fireball on a SB2 frame, but H&R is using the shotgun frames with some of their pistol cartridges now from the factory.  Do the math and see what you think.  Larry

[jedman]

Thanks for the ideas and your opinions, As for doing the math to find the bolt thrust ? I have not seen a formula to do this.
I have converted 3 H&R shotgun barrels to centerfire wildcat s of my own design by what I referred to as relining the barrel
I did not use a thin wall barrel liner, I used take off rifle barrels that have a large enough muzzle diameter and turn them to fit the shotgun bore closely and leave a good sized rim at the breech. I have only fired them on SB 2 frames and have not had any problems with them at all.  I did not know that the H & A shotgun frames were cast iron but they have a lot of mass and thought I would ask the question if anyone has done a conversion on them before. I was thinking of using Modern nitro powder loads but stick to a old rimmed low pressure cartridge but if it is not going to be safe then I will look elsewhere .
                            Thanks guys,  Jed

[trotterlg]

Take the raidus of the cartridge head (half the diameter of the cartridge) (not counting the rim) squared times pi (3.1416) and multiply it by the PSI rating of the cartridge.  I think you will find a .223 gererates less load than a 12 gauge shotgun does.  This is distributed over less area of the breach face, but the load on the frame will be less according to my math.  Larry

[gunnut69]

First H&R does high pressure rounds but not in their old cast iron actions. The new made versions are cast steel and that's a whole different animal. There are more things to consider than bolt thrust on the breach face, especially with the hinge actions.. The H&A action refered to were falling blocks but were cast iron. While they may work for a while they are not likely to last long and their failure may be dangerous. Also note JEDMAN was asking about a Hopkins&Allan built shotgun action likely 75 years old. They were produced in rifle calibers such as 38-55 but those were much less litigious times. Also less safety conscious times.

[John Traveler]

This discussion of relining shotgun barrels to a small rifle caliber reminds me of the most interesting conversion I've seen. 

It was an old double barreled shotgun action with barrels relined to .223 Remington.  The first few shots seemed to work fine until the action became impossible to open.  Examination showed that the .223 caseheads had PENETRATED the breech face, punching neat round holes into the cast iron.

Those breech thrust calculations work just fine IF you are dealing with if your action is made from cast iron, all bets are off!  The yield strength of old cast iron actions is somewhere around the proof pressures of many small smokeless rounds.

[Rangr44]

[but the load on the frame will be less according to my math.  Larry]

'Kinda reminds me, of when a teacher asked "Johnny", how to spell "crocodile".

"K - R - O - C - O - D - I - L - E", spells Johnny.

"That's not right", said the teacher.

Then Johnny said: "Maybe not, but that's how I spell it".   

[jedman]

Back around 1984 I built a 45/70 double rifle on a Union Armera ? sidelock 12 ga. side by side shotgun. I asked alot of questions about doing this conversion and was refered to a guy some where around Oklahoma City, cant remember his name but he had a British accent.  He was suppose to be a good authority on such things and after a couple of phone calls he told me to try it, he even sent me un-drilled firing pin bushings that fit the breech face of my gun for free. The way I built it was I cut the barrels off about 2 3/4 from the breech end, took the monoblock and bored the two chambers parallel, turned a coupl;e of barrel blanks, chambered them, then silver soldered them into the monoblock. Then made a rib and fit it to the barrels and with a jig I made to keep the barrels inline I soldered in the rib and a muzzle support piece.
 To make a long story shorter, when I first fired it the gun was secured in a wood cradle and clamped onto a heavy picnic table and I pulled the triggers with a 50 foot long string while I was hiding around the corner of a barn. I started with Trapdoor level loads at first and worked up loads a little hotter until I was at close to Ruger levels, l stopped at 54 grs. of R-7 with 300 gr.jacketed Hornadys. For the hunting I have done with it I never shoot more than 50 grs.of R-7. I now have fired it enough to shoot up several pounds of powder and have shot many different bullets out of it up to 500 grain cast.
Thru all the shooting even with the HOT loads I have not seen any pressure signs and it has never failed to eject the spent cases, something I can't claim about the H&R handi's with auto ejectors. Anyway I assume the frame on my double rifle is cast iron also, so maybe I should take out the side locks and give it a carefull inspection for any unseen cracks or whatever ?
I just never get tired of playin with these type of prodjects.                  Jed