Handload Pressure Indicators on Old SS Rifles

[jschluter]

I'm getting ready to load 45-70 for an 1874 Sharps using the "weak action" loadings for SR4759 & 5744 and 405 gr lead bullets. This means I'll be using the conservative 18000 CUP limit, even tho' the original equipment loads ran closer to 28000 CUP. So what do I look for as a pressure indicator in these low pressure loads? Is this even a concern? Max loads in the tables indicates the 18000 CUP limit, but is this enough to show up as a flattened/loose primer or swollen case just above the web? Wouldn't think so. I'm asking because there is considerable discrepancy between expert sources on the max/min loads for powders and the related pressures and velocities. I'd like to have an indicator to watch for as I play work up with these loads.

[montana_charlie]

Max loads in the tables indicates the 18000 CUP limit, but is this enough to show up as a flattened/loose primer or swollen case just above the web? Wouldn't think so.

I don't think so, either. If 28,000 won't flatten a primer I don't see why 18,000 would.

I think the pressure signs that will be your guide in this application would be splits or ruptures in the barrel and breech area.

The way to avoid those, in 'old single shot guns' is to stay within the maximums in that lower range of loads.

CM

[Roundball]

Lyman's load data for AC 5744 in 45-70 appears to be heavy in my rifle even with starting loads. My experience with this data is to be very conservative. Finally decided to use black powder in even good replicas and especially in original rifles.

[Chicken Thief]

There is no such thing as pressure signs to depend on before you pass @60,000psi and the base of the case starts to expand and flow.

[jschluter]

Thanks for the responses. In looking at a number of forum discussions and talking with SS gun shooters, I felt Lyman ran on the hot side. I found a number of loadings in the 19.5 to 23 gr. range for 5744 and 405 gr bullets-below the min in Lyman's loadings. And I agree that some real pressure will be required to get the expansion in the fired case above the web. A burst barrel/action from a rolling/forging defect is not a consideration in loading data. These are hidden defects. The loading data considers the lower strength and possibly lower ductility, higher inclusion content, etc. of the older metallurgical practices. And a heaping load of conservatism to cover unknowns.

[GabbyM]

Comparing published loads to yours over a chronograph is about as close as you’ll get.
I’d have far more faith in newer publications using a strain gage instead of the old copper crusher pellets. When you reach a listed velocity with a given powder you can assume you are close to listed PSI. I have presumed that to be close enough not to be blowing up or stretching guns. Generally speaking there is no free ride. If your loads are running over the Chrony faster than published you are running higher than published pressure.

[GabbyM]

Thanks for the responses. In looking at a number of forum discussions and talking with SS gun shooters, I felt Lyman ran on the hot side. I found a number of loadings in the 19.5 to 23 gr. range for 5744 and 405 gr bullets-below the min in Lyman's loadings. And I agree that some real pressure will be required to get the expansion in the fired case above the web. A burst barrel/action from a rolling/forging defect is not a consideration in loading data. These are hidden defects. The loading data considers the lower strength and possibly lower ductility, higher inclusion content, etc. of the older metallurgical practices. And a heaping load of conservatism to cover unknowns.

Granted I’m a conservative. Thus from my point of view loads that will not damage any sound rifle of a given design are good. If you are dealing with a modern reproduction. I’d look to the manufacturer for guidance on load pressure.

[NickSS]

Is your 1874 Sharps an original or a reproduction? Italian reproductions are tested for a max working pressure of 27500 PSI in the italian proof houses which means they are proofed at higher levels. I also have asked both Shiloh and C sharps and their rifles will handle loads even hotter. The 18000 psi loads in the manuals are for trapdoors which are far weaker than the original sharps actions. I do not load my guns with hot loads and mostly use black powder in them as I like the smoke and boom of that stuff. However, an excellent accurate load for 5744 is 27 gr with a 405 gr bullet and it closely duplicates my BP loads for velocity.

[bigted]

I'm getting ready to load 45-70 for an 1874 Sharps using the "weak action" loadings for SR4759 & 5744 and 405 gr lead bullets. This means I'll be using the conservative 18000 CUP limit, even tho' the original equipment loads ran closer to 28000 CUP. So what do I look for as a pressure indicator in these low pressure loads? Is this even a concern? Max loads in the tables indicates the 18000 CUP limit, but is this enough to show up as a flattened/loose primer or swollen case just above the web? Wouldn't think so. I'm asking because there is considerable discrepancy between expert sources on the max/min loads for powders and the related pressures and velocities. I'd like to have an indicator to watch for as I play work up with these loads.

so a question for ya but first id say welcome to the forum. you will find an abundance of info here and some sarcasm from time to time but generally this is a "HOMEY" place to hang out.

id like to hear about the "original loads running closer to 28,000 cup" statement. I have always figured that the "origanal" bp loads came nowhere close to this kinda preassure. where do you glean this number from with blackpowder loads please?

I am on the conservative side with my rollingblock and hesitate to use even the currently acceptable 5744 in very small doses ... but have loaded them such...but im in the blackpowder camp with my "original" firearms and am coming round the corner ,,,finally with acceptable repeatability with the old powder. id rather not say how long it has taken me to arrive at acceptable accuracy...[still got a long way to go but it shows real promise now]...with my bp cartridge chambered rifles and revolvers. I glean most of my info and suggestions from the members here as well as the mediator's.

thanks for the question

Ted

[jschluter]

The 28000 CUP (psi) number shows up as the SAAMI max., but I found an arsenal value for the original rifle load in Wolf's book on loading for the original Trapdoor, in the NOTE on pg. 130. The pressure range bracketed the 28K number and I thought it might have been the basis of the SAAMI number. I've seen this number somewhere else but I won't live long enough to go back thru all my loading books and find the reference. BUT that said, I have no plans to use anywhere near that pressure in my vintage Sharps. I'll use 1300 fps as my maximum velocity, although I am one of those poor souls that doesn't have a chrono. But my original question arose because I've found data on similar loadings with pressures varying by as much as 3000 psi, as well as similar pressure ratings with 4759 or 5744 powder weights varying by 2.5-3 grains. The initial test run will be 4759 & 5744 from 19-23 grains. I'm looking for a 100 yd load that is easy on my arthritic shoulder. But as I move to higher loads, I was curious if there was a reliable indicator of pressures approaching the 18K max. in the 1874 Sharps-sticky action, hard extraction, etc. Next step will be light loads with the faster powders and lighter bullets. And, incidentally, thanks for the welcome and your response. My father spent years trying to make lead bullets work in this rifle-jacketed loads shot very well. I'm taking up the torch now since life is not frustrating enough already!

[EDG]

>>>I was curious if there was a reliable indicator of pressures approaching the 18K max.<<<
No nothing that you can see. There is no black and white indicator of pressure. You will have to trust the data.

The pressure you are planning to use will not even burn all the powder granules.

[jschluter]

I agree with you about the Lyman load data since I have been comparing multiple sources for loadings, but what happened to make you feel the loads were heavy for your gun? Did the case or the gun give you some indicator of too much pressure?

[jschluter]

I expect some residue in the barrel with these loads. I'm using a hard crimp and a negative jump (~0.010") to help the burn condition. I'll take the accurate load rather than the cleanest one to preserve my arthritic shoulder so I'd rather not work up to a max load. But time (and a lot of tries) will tell. Thanks for the comments.

[MikeS]

If this is an old original Sharps, and not a modern reproduction, why not play it safe, and load it with the powder it was designed for, black powder? Using BP there's much less chance of making a load that would be unsafe for the rifle, and with modern non-corrosive primers the BP loads are nowhere near as corrosive as they were before. That's assuming real BP, not one of the substitute powders, as some of them (pyrodex comes to mind) are far more corrosive than real BP. I have an old rolling block 45-70 that I only load with BP, and it shoots it great.

[JimP.]

AA 5744 powder has been the best powder for me. 26.0 grs and a 500 gr bullet from the SAECO 883 mold makes my Buff Classic a very accurate rifle. I use the same load in my 1873 Springfield Infantry rifle and it likes the load too. I will admit using a slip on limbsaver recoil pad really tames these rifles and makes them fun to shoot. JimP.