Trapdoor Springfield Safe 45-70 Loads using Unique? Max trapdoor safe PSI?

[Jim Watson]

As shown in recent actual pressure-trace data -- now shown to be another one of those settled science facts . . .
that warn't so settled
(Post #20)



.

That leads me to an article on .44-40 which is an entirely different cat.

 

[Charlie98]

Sorry... I missed your last question. It's 18000 PSI for BP equivalent loads.

postscript from Buffalo Bore, re SAAMI:

We believe that SAAMI got it wrong with the 45-70 govt. cartridges, to state
that 28,000 CUP is OK to fire in trapdoor actions. We believe you can
damage the basic 1873 Trapdoor action (regardless of vintage) with loads
that exceed 20,000 CUP. We are not stating that you definitely will damage
Trapdoor actions with ammo that runs 28,000 CUP, but we know that it can
happen, so while this ammo is operating at or under the SAAMI limit of
28,000 CUP, we warn against using it in the 1873 Trapdoor Springfield
action or modern reproductions thereof.

So take care.... These are people who have to put their mouth where their money is...


,

I actually answered the OP's question back on the first page, but it isn't the answer he wants to hear.

 

[Remington1911]

I guess you missed the part where I said 18K is the general smokeless limit for a vintage Trapdoor. And, yes, I understand there is conflicting data (and opinions, including mine...) on this. The limited amount of research I've done in the past day or so, based on this question, leads me to rethink my position on running smokeless in something like a Trapdoor, but the general consensus was to limit the loads to 18K PSI.





I would have to question your comments, however. I posted 2 loads... the 15grn Unique load, and my 30grn IMR4198 load, both under the same 405grn cast bullet, for roughly the same velocity. The 15grn Unique load peaks faster and then drops quickly, but at nearly 25K PSI, where the IMR4198 load, while holding the pressure longer, only peaks at roughly 15K PSI. I'm not a metallurgist... but explain to me why a much higher pressure is advantageous over a lower one, even if it's drawn out?

The reason I would shy away from those two powders is the margin of error with each of them. Not really any other reason.

Be it right or stupid, one of the things I look at is what is the range between min and max loads. If one has a wide range but uses more powder I will go to that one over one that has a more narrow range but uses less......but it is not a hard and fast rule. I forgot yesterday to look, but my trapdoor uses a VV powder, and as I recall it is quite a narrow range, but I really liked the pressures stated. I did a quick and dirty check against quick load and the numbers are in the same ball park, so I went there. It was not my first choice and it was not till some digging did I see the pressures and I thought, I like that. I really want as low as I can get and still have an acceptable (to me) group. Like the other poster said, these are some old rifles, and metal does not last forever, and metal under stress like a gun.....well in the article linked up the term used something to the effect of life span of the rifle.

So it is really not something specific to the pressure of the powder, just the range....but again not a hard fast rule. I don't remember everything I tried but I think several on his list I did try, but not any "hand gun" powders.....that is a bit too much for me.

 

[MEHavey]

https://www.thehighroad.org/index.p...e-max-trapdoor-safe-psi.912823/#post-12470666

That leads me to an article on .44-40 which is an entirely different cat.

For BP/BPCR purposes, it's absolutely relevant to the discussion here.
BP rise times are much faster than previously ascribed to "settled science"

Still.... for Trapdoor purposes ... stick w/ BuffBore recommendations.


.

 

[Jim Watson]

BP rise times are much faster than previously ascribed to "settled science"

Right, otherwise it wouldn't have been much use for mining, pre-Nobel.

I have been suspicious of the usual post "Your Grandpa's Gun isn't RATED for smokeless."
Well, Grandpa's Gun is very likely second or third quality, not very durable with anything, and smokeless then was not as consistent as smokeless now. David Chioine said he was seeing more top breaks with loose latches which he ascribed to smokeless powder but I blame more on them simply being SHOT as they were dug out of bureau drawers and maybe even taken out to play SASS.

 

[Remington1911]

Right, otherwise it wouldn't have been much use for mining, pre-Nobel.

I have been suspicious of the usual post "Your Grandpa's Gun isn't RATED for smokeless."
Well, Grandpa's Gun is very likely second or third quality, not very durable with anything, and smokeless then was not as consistent as smokeless now. David Chioine said he was seeing more top breaks with loose latches which he ascribed to smokeless powder but I blame more on them simply being SHOT as they were dug out of bureau drawers and maybe even taken out to play SASS.

One reason I load this stuff as light as possible, and that SASS stuff is pretty light. Never played that game but watched it, there is zero recoil, very light loads.

 

[Jim Watson]

I allus loaded .44-40, .44 Russian, and Special to factory equivalent. Usually shot factory .38 S&W in the side matches but did reload some even a bit over for my Legal Defender conversion.

My only BP shooting is in single shots; real Winchester and Japanese Browning copy.

 

[Charlie98]

So it is really not something specific to the pressure of the powder, just the range....but again not a hard fast rule. I don't remember everything I tried but I think several on his list I did try, but not any "hand gun" powders.....that is a bit too much for me.

Ok... I think I'm understanding you right.

Even though I've tried them, and actually had some decent results with them, I'm not a big fan of pistol powders in the .45-70... with the possible exception of TrailBoss, because it's an oddity. Even 2400 and IMR4227, although I've worked with IMR4227 in .30 cast loads and it works quite well there. In the .45-70, under a 405grn bullet and IMR4198, there is about a 7grn range, 30grn-37grns, between a 1300fps, and an estimated 1600fps (in my rifle) and before it hits 25K PSI. I don't see myself getting in trouble with that, nor, honestly, going over 34grns or so.

 

[MEHavey]

with the possible exception of TrailBoss,

FWIW: Trailboss is extremely fast-rise/spikey.
(you didn't really expect this to be easy, did you?)

 

[Charlie98]

FWIW: Trailboss is extremely fast-rise/spikey.
(you didn't really expect this to be easy, did you?)

Because of it's bulky, case-filling properties, I consider it an exception. One of the problems I have with pistol powders in a big case like the .45-70 is all the air space. TB mitigates some of that... but, yes, at the end of the day it's a very fast pistol powder. I also know it does NOT like to be compressed. TB does, however, remain the lone pistol powder Hodgdon provides data for with Trappy-level .45-70 loads. I'll bet a dollar to a donut that Remington1911 doesn't use it there... it has a 1grn range from start to max!

No, I don't use TrailBoss... and probably a good thing, since it's not currently available.

 

[Tall]

I really like Unique powder in revolver rounds. It's just not appropriate in big rifle cases. For less than the cost of a box of shells you can buy a pound of any of the more appropriate rifle powders that will be more accurate and far less pressure on your nice old rifle.

 

[applefish123]

Alright here's chrono data for future reference for those who might seek to use Unique in a 45-70 at trapdoor safe pressures.

Original trapdoor with 32.5" barrel. 5 shots each.

405gr powder coated 13 BHN - OAL 2.540"

• 11gr - QL PSI: 15250 - QL FPS: 1120 Actual FPS: 1043 - SD: 7
• 12gr - QL PSI: 17600 - QL FPS: 1176 - Actual FPS: 1110 - SD: 12
• 13gr - QL PSI: 19800 - QL FPS: 1226 - Actual FPS: 1164 - SD: 9

300 gr powder coated 13 BHN - OAL 2.390"

• 12gr - QL PSI: 13150- QL FPS: 1322 - Actual FPS: 1237 - SD: 6
• 13gr - QL PSI: 15100 - QL FPS: 1381 - Actual FPS: 1304 - SD: 7
• 14gr - QL PSI: 17100 - QL FPS: 1440 - Actual FPS: 1363 - SD: 7
• 15gr - QL PSI: 19200 - QL FPS: 1494 - Actual FPS: 1434 - SD: 3

Pretty nice getting single digit standard deviations with unique!
All extreme spreads <20 fps, except for the 12 gr 405 load which had extreme spread of 26

The 11gr 405 load is a nice subsonic plinking load. All the 300 gr loads are light and have little recoil. The ~19,000 PSI loads worked fine in my rifle, but if you want to play it safe then stick with with the 17,000 PSI and below loads.

These loads are considered trapdoor safe according to the older Lyman manuals (44, 45, and 46), and comfortably 15-25% below the max loads recommended in them (15 gr of Unique on a 385 or 405).

 

[applefish123]

FWIW: Trailboss is extremely fast-rise/spikey.

This -- I'm very glad there's someone who understands interior ballistics on this forum!

Because of it's bulky, case-filling properties, I consider it an exception. One of the problems I have with pistol powders in a big case like the .45-70 is all the air space. TB mitigates some of that... but, yes, at the end of the day it's a very fast pistol powder. I also know it does NOT like to be compressed. TB does, however, remain the lone pistol powder Hodgdon provides data for with Trappy-level .45-70 loads. I'll bet a dollar to a donut that Remington1911 doesn't use it there... it has a 1grn range from start to max!

Trailboss is way way worse than unique for genuine blackpowder-era antiques because it has a burn rate betwee VV N310 and N320, putting it on par with bullseye or titegroup. So compared to a slower powder like Unique (similar to VV N330) you max out pressures much faster before achieving a desired velocity. But at the same time you are tricked into believing you're safe because the low velocity gives you very little recoil.

 

[entropy]

Do you know why Lyman would include hot loads in their early handbooks, but now only advises a max of 18,000 CUP in their most recent editions?

Lawyers.

 

[Charlie98]

Pretty nice getting single digit standard deviations with unique!
All extreme spreads <20 fps, except for the 12 gr 405 load which had extreme spread of 26

Very likely because it burns completely (100%) in about the first 2" of barrel. I had very much the same results with IMR4227 in the .348WCF... single-digit SD's, even when compared to IMR4198. I can only put that down to the burn characteristics.

Trailboss is way way worse than unique for genuine blackpowder-era antiques because it has a burn rate betwee VV N310 and N320, putting it on par with bullseye or titegroup.

No, I got it. As I also mentioned, I don't use TrailBoss because, at the end of the day, it is a very fast pistol powder. I don't even like TiteGroup in pistols... ...let alone reduced velocity rifle, TB would be the same for me. I understand it's purpose (bulky Cowboy loads,) but that's not really in my wheelhouse, so to speak. I was surprised to find the difference between start and max was only 1g...