Trapdoor strength DIFFERENCES??

[Jim]

Just received my latest “Rifle” magazine . . . .
Includes a lengthy article by Brian Pearce on TD’s . . . .

In it, he states that the Model 1884 was an improvement in strength over the Model 1873.
“ . . . .It (the M’73) was replaced by the improved U.S. Model 1884 trapdoor that boasted of stronger breech and allowed ammunition pressures to be increased from 20,000 to 25,000 pounds. . . .”

This is the first I’ve heard of any strength differences . . . .I thought they are ALL the same weak actions, across the various models. (Except the late “positive cam” versions, and those used in/for the development of the 30/40 Krag cartridge.)

What say, ye learned ones . . . .any strength differences?

[Dick Hosmer]

Haven't read the article so cannot address any possible nuances, and I have no idea what he is considering to be his base "1873", but my thinking would be along these lines:

(1) The block arch was filled in, circa 1877
(2) The receiver and block were increased in width and bulk at 96300, in late 1878
(3) There was a constant, even if VERY gradual, improvement in steel quality over the years.
(4) "Model 1884" is kind of a ringer, because NOTHING (barring point 3, which is not exact) is different between a late 1873, and an "1884" except the rear sight and the marking - and that only when they got around to changing it, some as late as 1887!

That all said, whether there is, or is not, a 5,000PSI difference, given my choice of a shooter between rifles 45389 and 406794, I would, unquestionably, take the latter EVERY time!

[Tony Beck]

One other change Dick, Springfield increased the gas escape reliefs between the breechblock and receiver. I doubt that would increase the strength, but what would happen with the early actions was when a case head split, the gasses would flow back under the cut away arch in the block and lift it since the gas escapes could be insufficient to vent off the gas if the case really let go. With the filled arch and large gas escape cuts this couldn't happen, so when a case head let go the action was less likely to blow open. With the advent of solid head ammo this problem was greatly reduced.

[Dick Hosmer]

Good point, Tony, and the difference in vent area IS significant! The old TD is probably stronger than given credit for, but, with modern rifles available, why take the chance? Speaking of which, I picked up a Ruger #1 Lyman Centennial, probably 35-40 years ago when Mid-South had their big remainder sale. I've never shot it, and defintely need to do so before I shuffle off . . .