MAx C.U.P. pressure for 1873 springfield trapdoor 45-70

[Superflywimpy]

Looking for loads for my 1873 springfield. I have been shooting 30 grains of IMR 4198 topped with a cast 405 grain .459 lpf which was giving me a speed at the muzzle of about 1350 which is equal to the bp loads ment for the rifle. I looked at the IMR website and found a load I want to try. 46 grains of 4064 ,same bullet . Says velocity is 1534 fps with a CUP pressure of 17900. Does anyone know the max pressure for a Springfield 45-70. I might add the site listed this load for trapdoors only.

 

[bmcgilvray]

I've used a similar load: 31.1 grains of IMR 4198 with a cast lead 405 grain bullet in my Springfield Model 1884 "Trapdoor." It clocks 1441 fps from the long-barreled rifle.

 

[Alk8944]

It is generally considered to be 25,000 PSI Crusher (CUP).

 

[ArchAngelCD]

It is generally considered to be 25,000 PSI Crusher (CUP).

Not to be picky but it's either measured in CUP or PSI but you can't mix the two.

From what I've read the Max pressure recommended for Trap Door 45-70 ammo is 28,000 PSI. The CUP levels are usually a little lower but I have seen loads listed as safe at 28,000 CUP too but you might want to stay below 26,000 CUP.

Lever Guns can go as high as 40,000 CUP.

 

[bmcgilvray]

I have seen a Trap Door with a cracked hinge said to be caused by firing factory .45-70 ammunition. This one is owned by a close family member. Don't know if the ammo really caused it. Don't know if it was a manufacturing defect.

It is reasonable to assume that what was originally a conversion design for adapting Civil War muskets to breach loading cartridge operation wouldn't be immensely strong. The War Department of the era must have really been staffed by a bunch of skin flints to actually order up newly made rifles to the design.

 

[Superflywimpy]

Thanks guys,I'm sure I'll be ok with a 19700 pressure load.

Being 135 years old,there no way in hell I would try any load over 20000 anyway. I really like my springfield and my son would like to have it when I'm gone. So I want to make it last. Anybody that would shoot a box of smokeless 45-70 factory is just asking for trouble. Here is a pic the first time out using a .457 bullet at 200 yrds. I forgot to bring the camera last time out and the results were a whole lot better using bullets sized to .459.I polished out my lee sizing die and I dont think I want to go any bigger than that. I was able to gent them all on the black at 200 using that old springfield. I'll give that 46 gr load of 4064 and post my results next time. Thanks again ....Super.

 

[Jellybean]

I've never loaded for the .45-70, but I have noticed that several of my loading manuals list several different pressure levels for the cartridge, based on what kind of gun it's being fired from.

For the 1873 Trapdoor they suggest keeping the loads under 18,000CUP and list data specifically for it. For 1886 Winchesters and 1895 Marlins they list data for the SAAMI suggested maximum of 28,000CUP, and for the Ruger Nos. 1 and 3, they list data beyond SAAMI max. up to 40,000CUP.

 

[SOFMatchstaff]

I have found that the Lee 405 HB bullet works great in my 1884 Rifle. Cast from 20/1 and loaded with out sizing, hand lubed with SPG or my home grown lube over 31 to 32 grs of 3031 just about equates the trajectory of the sites. If you slug the bore you find its bigger than .459 usually, my rifles(4) all are over .461 and the bores are VG to perfect. Thats where the HB bullet does its work in those wide lands an grooves.

Im in the same climate you are so I dont feel iffy about recomending a load. These old warhorses are to neat to risk with a load that doesnt regulate to the sites just to get a few extra FPS.

You may have noticed that the sites, if un-molested, have a long range battle zero, I got around the close range zero problem by filing a small V in the bottom of the mill cut radii, on the Buffington sight, below the slider and it came very close to the proper setting for 50 to 100yd steel( pigs& chiickens).

If you can find a book by J S & Pat Wolf, Loading Cartridges for the Original 45/70 Rifle and Carbine, its got some interesting info.

 

[Superflywimpy]

I think I'll give it a try.

I am thinking of getting that lee hollow base mold. It should eliminate that problems of the correct size bullet in the trapdoor. I also have a 1985ss marlin that I like to shoot and will get it out again when I have found the right recoil pad. Being such a short rifle and shooting lever loads beats me up nine ways to Sunday. Yet I can take 50 rounds from my springfield trapdoor no problem. Still get a bruise, but the smaller lighter loads just dont kick as hard in a big rifle.

 

[SOFMatchstaff]

1873

OH Yeah, I have the marlin cowboy long octagon barrel and it whacked me smartly until I put a pad on it. I use that same load and bullet in it that works in the 1884, and it likes the 20/1 alloy just fine. thank Ballard for the rifling.

I only made the long bullet mistake once in the 95, had to dis-assemble the gun to unload it. now I stay with the short nose projos in the levergun.. The 200yd rams seem to go down just fine with the 405 at 1300fps. a real chicken flipper too..
I size the bullets closer to bore dia for the 95. I have lots of JHPs but save them for the Ruger No 1, thats a hammer when it goes off at 2000+-..

 

[ArchAngelCD]

For the 1873 Trapdoor they suggest keeping the loads under 18,000CUP and list data specifically for it. For 1886 Winchesters and 1895 Marlins they list data for the SAAMI suggested maximum of 28,000CUP, and for the Ruger Nos. 1 and 3, they list data beyond SAAMI max. up to 40,000CUP.

I checked the load data on the Hodgdon site and they have 3 categories for the 45-70 as you mentioned. They list data for the Trapdoor up to 28,000 CUP, data for leverguns up to 40,000 CUP and modern rifle data goes all the way up to 50,000 CUP. Are you sure the limits for a Trapdoor are only 18,000 CUP? I have never loaded that low.

 

[Jellybean]

ArchAnglelCD, Lyman and Accurate both gave the max of 18,000 CUP for the Trapdoors.

Speer said their data doesn't exceed 21,000 CUP, which is the maximum average pressure of black powder loads they tested, Hornady states their data doesn't exceed 25,000 CUP, but since their data doesn't include pressures it's hard to say exactly how much they actually used.

Hornady also goes with the 40,000 and 50,000 CUPs too, but the 40,000 is not listed for any lever action, it is only for the modern Marlin model 1895 and not for antiques or modern replicas of antiques.

Hodgdon has lost a lot of points with me over the last 10-15 years and I don't take anything they say as gospel without checking with other sources first.

 

[ArchAngelCD]

Jellybean,
Thanks for the information...

 

[Alk8944]

Not to be picky but it's either measured in CUP or PSI but you can't mix the two.

From what I've read the Max pressure recommended for Trap Door 45-70 ammo is 28,000 PSI. The CUP levels are usually a little lower but I have seen loads listed as safe at 28,000 CUP too but you might want to stay below 26,000 CUP.

Lever Guns can go as high as 40,000 CUP.

In this case you can because when the standard was established the method of testing was strictly by Lead or Copper crusher equipment and it was expressed in PSI, not CUP. That is why the notation of (Crusher) was included. Only after absoluyte testing methods were developed that directly measured in PSIG did the CUP/LUP designation even come to be. So, in the last Ice Age when a load was shown to develop 25,000 PSI by the crusher method it was shown that way. This does not mean that PSI(Crusher), means the same as PSIG, it doesn't. It just means you don't understand the old method of pressure notation.

Jellybean's comment about the, I assume, current Lyman and Accurate manuals showing 18,000 CUP as the limit for Trapdoors is, no doubt, correct in todays manuals, although it is highly unlikely they are still using the crusher method as it is extremely expensive and time consuming compared to Piezo and Strain Guage measuring methods. If a side-by-side comparison of the two methods were ever made it is likely that 18,000 PSIG and 25,000 PSI (Crusher) are equivalent, whether you express it as PSI (Crusher) or CUP makes absoluely no difference as they are two methods of expressing exactly the same thing.

Now do you understand what was meant by PSI(Crusher)? You do understand the difference between PSI and PSIG, don't you?

 

[ArchAngelCD]

Now do you understand what was meant by PSI(Crusher)? You do understand the difference between PSI and PSIG, don't you?

I always understood what you mean but you are the only guy I've seen to use the notation PSI when talking about CUP. Like I said, I understood you but there are a lot of new reloaders lurking here and reading these posts who might be confused by you mixing the two notations in the same pressure value.

 

[Opie]

How about Black Powder?

Use a case full of FFg. Don't leave an air space between the powder and the bullet. No problems with over pressure.

I followed the instructions in Wolf's book for my 1892 vintage Model 1888. I got better results with black than I did with any smokeless powder.

Rifle clean up is usually easier with my black powder cartridge rifles than with my modern rifles shooting jacketed bullets. Case clean up takes a little more work, though.

I get a lot of satisfaction shooting trapdoors, rolling blocks, and Sharps rifles the same way it was done 120+ years ago.

 

[Bryan Austin]

I know this is an old topic but many of the replies are comical at best.

SAAMI lists both CUP and PIS for several cartridges. As said, CUP and PSI are the results of two different measuring methods.

For example, for the 44-40 the max CUP is 13,000 and the max PSI is 11,000.

For the 45-70, it just so happens that both psi and cup is the same for the max recommended pressure...28,000psi/28,000cup. This does not mean the two are linier from a low pressure on up.

On a side note, max pressure recommended for the 45-70-405 Trapdoor Springfield is said to be between 18,000cup and 25,000cup depending who you talk to.

 

[bmcgilvray]

Chiming in again after12 plus years.

I'm still shooting the Trapdoor I have here to a limited extent. It is liking IMR 4198 in 31 grain charge weights under 400 grain cast bullets. The load seems mild in the rifle. "Seems" is a really scientific term so work up to any load in your rifle ... if you can find any IMR 4198 to buy.

 

[DWalt]

CUP and PSI are not synonymous. CUP (copper crusher method) can be considered as being somewhat of an average peak chamber pressure estimate rather than producing an accurate instantaneous peak pressure measurement. It dates back well into the 19th Century. For quite a few years, the ammunition manufacturers have been using a piezoelectric gauge which does allow precise measurement of an instantaneous peak pressure in PSI. SAAMI still recognizes CUP, but in fact there is probably no ballistics laboratory on earth today that still measures chamber pressures by using copper crushers. It is an obsolete technology which is comparable to attempting to tell accurate time with a sundial. Even though there is really no reliable way to convert CUP to PSI, or vice versa, you can assume that the actual instantaneous peak chamber pressure in PSI will be around 20-25% greater than the corresponding CUP measurement for the same load. There is indeed a correlation between the two, i.e., a high CUP indicates a high PSI, but the difference between the measurements taken using the two methods side by side has considerable variability depending on test conditions.

Another advantage of the piezoelectric gauge is that is far faster than using copper crushers. You can probably make 100 piezo gauge measurements in the time it takes to make one copper crusher measurement. There are many time-wasting operations to be performed in using copper crushers, and nearly none using piezo gauges.