High pressure shot load in a rifle

[Jessesky]

Okay, call me crazy. This is a theory, but would it work?

Since rifles can handle much higher pressures than shotguns. Would it be possible to rebarrel a 45-70 to a smoothbore and load shot over something similar to a gas check instead of a wad to keep the pressure and get shot moving in the 2200fps range?

 

[ridgerunner1965]

hmmm kind of a 410 magnum?

im not sure but there may be a reason that shotgun loads have not progressed in velocity as rifles have.

I think pushing a shot charge that fast may just not be lead to good patterning of the shot. if you had a shot wad that could stand up to that pressure it mite not open easily keeping the shot too close together for it to be used as a shotgun really.

if using some kind of over powder card regardless of what its made of would leave the shot in contact with the barrel. lead moving that fast may lead the barrel badly.

also you really need a shot charge of 5/8ths of a oz, at least to be effective on game. that would take up a lot of room possibly in the case and not allow for enough powder to push it that fast? but that is just my conjecture.

I would think a good patterning high pressure/velocity shotgun would be just the ticket for waterfowl. which makes me think if it could be done it would been done already.

 

[Dudedog]

Canister in smooth bore cannons seemed to work well for it's intended use.......

would think a good patterning high pressure/velocity shotgun would be just the ticket for waterfowl. which makes me think if it could be done it would been done already.

Yep, I agree.

I would speculate that due to needing a heavier barrel for higher pressures barrel/gun weight might be an issue. Case length can only be so long so that affects your shot charge.
Ok so you can have say 1/2-5/8 ounce of shot from a "super 410" at say 2200fps or 1 3/8 oz of shot from a 12 gauge at 1300.
(and I should mention 2 1/4 oz from a 3.5" 10 gauge at about 1250, that makes my shoulder sore thinking about it, but sore shoulders do get better)
Seems like the trade for more shot at lower vels is what has won out for a long time now.
Other wise you would see "super 410s" on the market if they worked better.

Should it work, yes, better than a 12 gauge probably not.

 

[Nature Boy]

I have a bolt action 20ga that in inherited from my great uncle. Likey around 100 years old. Not exactly what your talking about but close conceptually

 

[ATLDave]

Aerodynamics are not gentle to spherical objects at supersonic speed. You can ramp up the initial speed, but shot pellets are going to decelerate rapidly. And the supersonic shock waves/transonic transition is going to wreak havoc on the pattern.

Here is an article about the ballistics of spherical objects (including shot pellets and muzzle-loader balls) at supersonic speeds. https://www.sciencedirect.com/science/article/pii/S2214914717301459#fig1

Here's a drag curve graph from that article:



Notice how high the drag gets and stays? Compare that with drag curves for rifle-bullet-shaped projectiles:



Note that the scales on the left are not the same. The bullet scale show tops out at 0.7 drag, while the spherical object chart runs up to 1.2.

What does this mean? Extremely rapid decay of speed for spherical objects driven to supersonic speeds. This chart purports to show what happens to #6 shot launched at 1400 fps:



Notice that the pellets are back down below 1000 fps at 20 yards. They are slamming on the brakes!

A decidedly-subsonic example may help illustrate. Have you ever thrown a ping-pong ball? You can throw it as hard as you want, but it sort of has a built in speed-limit... you can exceed that velocity, but it is going to slow down very hard until it gets back to that speed. You can have Mike Foltynewicz throwing a ping pong ball in a game of catch with you, and if you are standing more than a few feet away, the balls he throws to you and the ones you throw to him will be caught at close to the same velocity.... even if he's starting his out 40 mph harder.

So, in answer to your question, there is no internal ballistics reason in terms of gun design that one cannot build a gun of shoulder-able weight that would throw pellets at 2200 fps. However, there is no external ballistics reason to want to do that. You would dramatically increase the recoil and you wouldn't really get pellets flying much faster... and your pattern would probably be much worse at long distances (which would presumably be the place where you'd most want to use such a gun) than a conventional-velocity shotgun.

Note that this is why anti-aircraft guns are not big shotguns... they are firing single projectiles (rapidly, but only one at a time) that get to the vicinity of the target and then explode.

 

[rsrocket1]

I think the deformation of the soft lead pellets against each other at those pressures are also going to ruin the pattern. At an acceleration heading to 13-1400 fps, target load patterns start to deteriorate. I would think an acceleration going toward 2100 fps will flatten the shot at the bottom of the stack.