H&R, Pounds Per Square Inch, and a Face Full of Receiver

Calling all gun freaks who do stupid stuff.

Here's the dilemma.

I have a spare H&R shotgun receiver and a spare 45-70 barrel. I want to mate the two together as the fit is perfect between the two parts.

The listed chamber pressure rating for a 45-70 Trapdoor load is about 17,000 to 27,000PSI.

H&R will install a 44 magnum barrel on a shotgun receiver. A 44 magnum rifle chamber pressure is rated at 25,000 to 35,000 PSI.

Soooooooooo, it seems OK to mount a 45-70 barrel on a shotgun receiver. PSI is PSI is PSI. Right???

I spoke with H&R about this and after 10 minutes of the guy telling me he can't comment for safety reasons, he finally commented and said it would be fine. Either he was telling me the truth or he wanted me off the phone.

Keep in mind that these will be hand loads. 55 grains of H335 under a 300 grain JHP bullet. 2 grains under the starting load of 57 grains and under 17,000 PSI.

There is always the tree and string method of testing too.

Thoughts.

sure...what could happen?

I called a friend who is a Gunsmith by trade and he tells me, the shotgun receivers are treated different than the rifle receivers. H&Rs website says NO also. H&R says rifle to shotgun OK but not shotgun to rifle. I don't believe I would do it. What's the worst thing that can happen ? KABOOM when you shoot it, If you can live with that, Go forth Grasshopper.

Current H&R guns use 2 different receivers - the SB1 and SB2. Basically cast iron SB1 (shotguns and pistol cartridges) and the cast steel SB2 (rifle cartridges).

Older H&R's were all cast iron receivers and included 22 Hornet, 30-30, and 45-70 (i.e., "low pressure" rifle cartridges). I would not be concerned with "Trapdoor loads" on a cast iron receiver.

If you decide to do it, film the test fire for us

airsporter said:

Current H&R guns use 2 different receivers - the SB1 and SB2. Basically cast iron SB1 (shotguns and pistol cartridges) and the cast steel SB2 (rifle cartridges).

Older H&R's were all cast iron receivers and included 22 Hornet, 30-30, and 45-70 (i.e., "low pressure" rifle cartridges). I would not be concerned with "Trapdoor loads" on a cast iron receiver.

Click to expand...

This is my thinking exactly. We are talking about black powder equivalent load data. Sans the 22 Hornet.

I would also wager that even the crappiest H&R shotgun receivers/barrels are stronger than even the best original Trapdoor receivers/barrels.

If a shotgun receiver can't take a 17,000 PSI Trapdoor load then it sure as hell shouldn't be OK with a 35,000 PSI Magnum load.

And the 45-70 case would disperse the pressure over a wider area making it even safer.

Time to look up some really hot shotgun data and see what kind of PSI ratings I come up with. And shotgun barrels have much thinner chamber walls.

As for filming the event, I will keep those who wish to see me eat a shotgun receiver in mind.

Thanks for the input.

iH8DemLibz said:

....And the 45-70 case would disperse the pressure over a wider area making it even safer....

Click to expand...

PSI is definitely PSI, but you now have more SI, so with the same PSI, absolute pressures increase, not decrease. Beware.
.

E.Shell said:

PSI is definitely PSI, but you now have more SI, so with the same PSI, absolute pressures increase, not decrease. Beware.
.

Click to expand...

Damn!

My thinking was more along the lines of Bolt Thrust in relation to the receiver face. I would assume the theory is the same even for a single shot.

Smaller diameter case head imparting more thrust. Contact area being more concentrated.

Larger diameter case head imparting less thrust. Contact area being more spread out.

I do value your opinions and words of caution. Thank you.

iH8DemLibz said:

Damn!

My thinking was more along the lines of Bolt Thrust in relation to the receiver face. I would assume the theory is the same even for a single shot.

Smaller diameter case head imparting more thrust. Contact area being more concentrated.

Larger diameter case head imparting less thrust. Contact area being more spread out.

Click to expand...

I see your point, but would suggest we are mixing apples and beans...

"Contact area being more spread out" is more a concept in which we would see a reduction in pressure if we worked in absolute weight, but not with force characterized by pressure per square inch.

If you weigh 175# and you wear size 11 shoes, you will exert a force of "X" pounds per square inch as you stand. Slip on a pair of snowshoes and you will spread out your contact area and so cut your force down to a fraction of "X" pounds per square inch, which is exactly how snowshoes work to keep you (almost) on top of the snow. So, in this context, you would be correct to state that increasing surface area does indeed reduce force per unit of surface area and so reduces point loading.

Conversely, when we are working with a defined force already quantified in pounds per square inch, it means we have this force present in this quantity for every square inch and thus it is additive. Increasing the contact area will increase available force. If we have a working pressure of 17,000 psi and our sample surface area is .5 square inches, you will enjoy 17,000 pounds x .5 thrust value in this area. If you have an area of 1 square inch, then you will enjoy 17,000 pounds x 1.0 thrust value on this area. 2 square inches would be the same: 17,000 pounds x 2.0 would be the total force exerted on this area.

The critical stress point is where the load is concentrated on the far side of the pivot pin, which resists the barrel's desire to separate from the breech face. How much pressure we put on this is approximated by total case head thrust divided by the surface area of the pin contact (adjusted for vector as we work around the pin radius).

My wild ass guess, with regard to why H&R doesn't put the .45-70 on the shotgun frame, is that once chambered thus, it is probably only a matter of time before somebody hot rods it with loads for an 1895 or a Ruger #1. If loads could be counted on to stay under 27,000 psi, it's probably not a lot different than the .44 Mag with regard to case head thrust...**IF**

So... do you feel lucky? I mean "really lucky?".

You could always do the string/tire method and proof it, then measure headspace to assess possible damage, but know that cast iron will usually just let go without stretching and if any previous round damages the receiver's structural integrity, the next shot could be THE catastrophic failure that changes your life.

Now the pin/frame stress does make much more sense.

The area of a real rifle receiver has more strength where the pin passes through the receiver.

I can see failure/stretch there before seeing at the breech end.

Since I like my digits and the shape of my skull the way they are, I will send out one of my rifles and have a 45-70 fitted to it.

Better safe than sorry.

Google Graybeard Outdoors forum and scroll down to the H&R section. Probably the foremost experianced/enthusiasts on the web when it comes to NEF/H&R firearms.

Their Frequently Asked Questions/Information section has volumns of information. Much experimenting and fabrication has been done by several members.

Placing rifle barrels on shotgun frames has been discussed on many occasions at that site.

Quicktdo is the moderator. He has such knowledge about the little single shots that you would think he has an "in" with H&R.


Eddie

I have nothing to add, but...

No comment from BradMacc82?!?!?!

Mr H said:

I have nothing to add, but...

No comment from BradMacc82?!?!?!

Click to expand...

Who do you think was holding iH8's beer...

What E. Shell said about all the theory of Bolt Thrust vs Chamber Pressure.

BUT .... The answer the OP was looking for depends on the vintage of his H&R frame.

Yes , with the current regieme , there are SB-1 and SB-2 frames.

But in the evolution before the current regieme , there were "high strength" frames and "low strength" frames. If you knew the origional chambering , it told you what you had, otherwise not obvious , and the factory had to look up s/n . But the telling part is in addition to pistol cals , .30-30 and .45-70 were built upon the *LOW* strength frames, with the *High Strength* frames being used for '06 class ctgs.

At the time H&R refered to the .45-70's as being suitable for then factory loads , and any loads listed as suitable for Trapdoors. Anecdotal evidence points to them being slightly stronger than T/C Contender.

After mating the 45-70 barrel to 5 rifle receivers, I found a suitable match for it.

Again, thanks for all the advice.

OP, just a suggestion.

Instead of using H-335 and a 300 grain boolit, in your .45-70 loads, consider the 405 grain hardcast boolit and Reloader 7 (aka/ RL-7).

Before I started loading for my 1895G and 1895CB, I read a LOT of information/data on the cartridge.

Reloader 7 gave lower pressures for comparable velocities, and very good accuracy.

40.0 grains of RL-7 and a 405 gr. LWNGC boolit (Cast Performance is what I use) yields about 1660 fps and is very easy on the shoulder.
IF I had enough "catridges" loaded, I could shoot these all day long.

Stepping up to 42.5 grains gets painful after 5 shots. Ten shots, and I'm done for the day!

Here's a very good article on loading for the .45-70, and where I got the above loading data.

http://www.realguns.com/archives/117.htm