quote:

Originally posted by LHeym500:
This is purely an academic question given we all agree 50 fps does not make any difference.
The full load for the 450/400 either 3 or 3 1/4 is often cited at 60 grains cordite. The tropical load begin 55.

Ok, the point of the tropical load was pressure in India and Africa would increase driving velocity up. This increase in pressure could cause sticky extraction or harm regulation due to the increase in velocity. I have read that barrels in England would be regulated apart (less velocity and pressure), so that when they reached India, Africa, or wherever climate factors re would increase pressure and velocity bring the barrels in regulation. Therefore, is it not safe to assume if the tropical load the climate conditions would increase pressure and velocity back to the ballistics of the 60 grain load in the field (comparing cordite to cordite).

Theoretically, your assumption with respect to increased temperature creating increased pressure / velocity has validity.
I am not aware of the 55gr guns being regulated apart, not saying it was not done, just not aware of it.
That said , simply apart ,may not work, low and apart might work.
In general, the 55 gr 3 1/4" load was a lighter loading for a 60gr 3 1/4" proofed gun to be used in a hot climate.

Now what if we had a 60 grain 450/400 3 1/4 rifle and for whatever reason better powder or good wheather the ammo stays consistent. Would not the 60 grain load in the bigger case produce less pressure, velocity, fps than a 55 grain load in the smaller 3 inch case?

A 60gr 3 1/4" load creating less pressure than a 55gr load in a 3 1/4" case, absolutely.

A 60gr 3 1/4" load generating less pressure than a 55r in a 3" case , probably.

Thus, are we wrong in assuming that 3 inch 55 grain rifles are of weaker or inferior proof to their 450/400 3 1/4 inch cousins. Either rifle proofed either way is safe for the 400 grain 2100 60 grain cordite equivalent load.

Though technically if proofed at a slightly lower pressure, I would not consider the guns inferior;
nor presumably would a 60gr load damage the rifle.
That said, shooting a 60gr load would not be an "approved load", as it would be "above" proof of that particular rifle.

quote:

Originally posted by Clan_Colla:
A 60gr 3 1/4" load creating less pressure than a 55gr load in a 3 1/4" case, absolutely.

quote:

Originally posted by sambarman338:

quote:

Originally posted by Clan_Colla:
A 60gr 3 1/4" load creating less pressure than a 55gr load in a 3 1/4" case, absolutely.

Not sure I'm with you on this. Could you explain it more fully?

quote:

Originally posted by Huvius:
I'm not sure that the 3" to 3-1/4" is a very good comparison as the differential in length is all in the neck.
Likely, both cases with the same bullet and powder charge will render the very same pressures and ballistics.

quote:

Originally posted by Clan_Colla:

It is the reverse of course-

It should have been -

A 55gr 3 1/4" load creating LESS pressure than a 60gr load in a 3 1/4" case, absolutely.
Or
A 60gr 3 1/4" load creating MORE pressure than a 55gr load in a 3 1/4" case, absolutely.