What are the safe Trapdoor load limits for 45-70?

[tacotime]

Probably an old subject, but what are the safe "trapdoor" limits for the older frames like the Shikari, that are limited to trapdoor loads?

I know the factory Rem 405 gr loads are safe, but what about the usual Winchester 300 grain factory loads off the shelf?  I see these 300's produce significantly higher numbers.  Are the safe in a Shikari, and under trapdoor limits?

Thanks!

[quickdtoo]

The SAAMI maximum average pressure for the 45-70 is 28kpsi which is equal to 28kcup,  so any trapdoor load data you use will work fine, different source use different limits, but the highest is listed by Hodgdon and Hornady at 28kcup, others are lower, any will work. I think your shoulder will tell you differently using the warmer 28kpsi data in the light Shikari tho.  

Tim

[PawPaw]

Winchester doesn't want anyone blowing up a trapdoor with their ammo, so they load it to trapdoor levels.  I think that would be a pretty fair bet with any of the mainstream ammo manufacturers.

I've seen some custom loaders who manufacture ammo beyond trapdoor limits, but they label the ammo as such.  For example, Garrett's Cartridge Co. lists their ammo by rifle type. 

[tacklebury]

My trapdoor loads have been primarily 42gr. Reloader7 with 300 to 350gr. jacketed bullets.  I have successfully loaded it down as low as 34.3 gr.  Still has good accuracy with the FTX or Interlock HP from Hornady. 

[tacotime]

It looks like the specs on the factory 300 gr Win JHP's are about 1800fps and 2180 flbs. Are we safe to say that these numbers should be below Trapdoor limits?  Just wanted to be sure before firing in the Shikari...

Thanks.

[quickdtoo]

The factory Rem loads are trapdoor, you can see what the pressures are by looking at Hodgdon's trapdoor data, 300gr jacketed data runs over 2100fps at 28kcup(28kpsi), equivalent 1800fps data runs 16-22.5kcup, so the Rem 300gr are just fine in the Shikari.

Tim

http://data.hodgdon.com/main_menu.asp

[Chas.]

The SAAMI maximum average pressure for the 45-70 is 28kpsi which is equal to 28kcup...
Tim

This is confusing to me.  I've read that cup and psi are not the same and there's no way to convert from one to the other.  Is 28Kpsi being equal to 28Kcup just a coincidence in this case?  Tell me more.

[quickdtoo]

It's just a coincidence I think, this is from a reloading manual, which one I don't know.

Tim