I have the Mil Thunder 5 (as seen in my avatar) chambered in .45 Colt/.410 Bore. It has an interchangeable (read: same OD) cylinder chambered for .45-70 Gov't, made from the exact same alloy (4140 Chrome/Molybendum Steel).

The argument is this: Since the .45-70 is a larger round (it tapers to the same size as a .45 Colt), then the .45 Colt cylinder can withstand at least as much pressure as the one chambered for .45-70.

Please include reasons with any answer, as I would like to learn more about this subject and would like to apply your reasons to other questions I have swimming around.

You may have a problem. 45/70 is 0.458". .45 Long Colt is 0.452".

All other things being equal, wall thickness of the cylinder and material strength dictate pressure handling.

In your argument, the case volumes are not equal, so the pressure handling is not an apples to apples comparison.

You would need to evaluate each individually. My feeling is that the one with more meat between the chambers will win, but case volume still has to be considered.

Jeremy

Based on your dimensions, your LC cylinder can hold at least as much pressure as your 45-70 one. (probably more since it is thicker walls. Look up some hot loads for the Ruger; the pressures are way above those for the 45-70. Having said that, I do not know the actual strength of your cylinder. Your case volumes and bullet diameters are irrelevant with regard to how much pressure your cylinder will take, but if you are using your 45-70 as a base line, then your 45LC will take at least as much.

For starters your 410/45LC cylinder is going to have a lot of freebore when using the 45LC because it's chambered for the 410 shotshell. That reduces pressure for the 45LC. What most seem to forget is that the brass case is a "gasket" to seal off the breech end of whatever it is fired in. A gasket has to be tightly supported. Think of a car engine's head gasket. Firearms that shoot high pressure rounds, such as the Freedom Amrs in 454 Casul, have very tight chambers to support the case. I have many firearms chambered for the 45LC, including both revolvers and rifles, and some of them have such "fat" chambers that even moderately hot loads really "bulge" the cases in front of the solid web. If pressed to real high pressures it's possible the case could rupture. That's one reason Freedom Arms tightly chamber their firearm.

I think your hand will give out before reaching the pressure limit for the 45-70.

What is it you are trying to accomplish?

Let's quantify what pressures he is shooting for. Maybe a pun. The SAAMI pressure for a 45-70 is 28K psi. Factory 45 LC loads are 14K.Linebaugh loads for Rugers (not current ones) go at 32K. So, making the assumption that your cylinder is made the same as your 45-70 one, then it will also take LC loads of the same pressure. I do not know the dimensions of your chamber; that will enter into the equation as outlined in previous post.

I would call the manufacturer for this info, and not rely on any "educated guesses" from the internet forums, Period! Having said that, I will say that the weakest link in six shot revolvers is the lock bolt notches. Your revolver appears to be a five shooter, thus the lock bolt notches are in between the cylinders instead of directly under them, hence the six shot weakness. This may add some strength, but the walls on this particular model don't seem to be very thick. You really just need to Contact the manufacturer!

Thanks for the replies.

Reason I'm asking is that since the chamber on my cylinder is 3-1/8" long, I could use a longer case in the cartridge family to work up a large black powder load for it.

I figure that this pistol would have been the ultimate cowboy gun if it were invented then, so I should have some fun with cowboy propellants in it.

You should have said you wanted to use black powder; a case full of that won't generate anywhere near the SAAMI pressure limit of 28K. Go for it. And be prepared for a very large boom and lots of smoke. I use a Walker Colt for Cowboy shooting at least on one stage just to get everyone's attention.

quote:

I figure that this pistol would have been the ultimate cowboy gun if it were invented then, so I should have some fun with cowboy propellants in it.

You did not say black powder. You said propellants. I think you have a very bad idea.

If you want a cowboy pistol shoot it as is with 45 Colt ammo. Those other ideas may get you hurt.

I would shoot them as is with smokeless round and not worry about velocity or pressure. If you go blackpowder then you have not only really clean your gun but your brass cases as well.

Wrong barrel diameter. Bad idea. Call maker and verify.

This is a Darwin moment.

Wait minute... I re-read your OP; "Interchangeable cylinder"? I thought you had a 45-70 revolver and wanted to use hot 45LC loads in another cylinder.
What is your barrel groove diameter?
Do not shoot .458 bullets from a .452 bore.
For SR4759, he did say "black powder".

Apparently they made some of those with dual cylinders. I hope they made some effort in safety
firing of the larger diameter 45-70 bullet. I don't have an opportunity to examine one to see if they choked the 45-70 cylinder or just made the barrel with bore for the 45-70 bullet.

An any rate they were a company now out of business in a little town not far from me in TN. Not to insult you but they aren't a "top of the line" revolver. Charter Arms later came out with an almost identical revolver.

I would definitively only shoot the low pressure factory rounds from it and not mess with it. Preferably sell it off for a better firearm.

Hey everyone, thanks again for the replies.

I do indeed intend to use black powder or pyrodex, which for my purposes is the same. I'm not sure about the bore/barrel diameter, but since I do not presently own the 45-70 cylinder, it's either just right or too big for the .452 bullets I send down it.

SmokinJ, do you suggest only factory loads only because it is not top of the line, or because my reasoning is flawed? And by factory loads are you excluding the hotter Ruger/ TC loads?