shotgun chamber and pressure question

Vincent Phipson · Apr 2, 2017

An interesting question came up in the shop the other day.

All else being equal, would a 2 3/4" shotshell have the same or lower chamber pressure when fired in a 3" chamber?

Thoughts anyone?

CalG · Apr 2, 2017

Same

There is not a significance difference in the chamber geometries associated with the shell case opening on discharge.

Might be "some" difference, but less than shot to shot variations due to load and powder burn.

trevj · Apr 3, 2017

If the loads were supposed to have the same (equal) pressures, as loaded, then that is what they would have, as the pressure is really working against the crimped or rolled portion of the case, and bringing the mass of the shot column up to speed.

I would expect, if a 1/4 extra inch of chamber length was going to make a difference of any discernible nature, that the differences between the chambering and barrel dimensions of the various makers would play a much larger role than we hear about.

Cheers
Trev

GGaskill · Apr 3, 2017

Most standard shotgun powders are so fast burning that the peak pressure may be before the shot leaves the mouth of the shell (don't know this for sure, just a speculation.) The forcing cone of the 2 3/4" chamber is a 1/4" closer to the shell than the 3" chamber and that will be the next resistance point. So my guess is the short shell in the long chamber will have slightly lower pressure but it won't change the ballistics very much.

OldSquier · Apr 5, 2017

GGaskill said:
Most standard shotgun powders are so fast burning that the peak pressure may be before the shot leaves the mouth of the shell (don't know this for sure, just a speculation.) The forcing cone of the 2 3/4" chamber is a 1/4" closer to the shell than the 3" chamber and that will be the next resistance point. So my guess is the short shell in the long chamber will have slightly lower pressure but it won't change the ballistics very much.

Pressures are, as has been said, slightly lower, but not enough to matter.

Squire

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shotgun chamber and pressure question

Vincent Phipson

Aluminum

CalG

Diamond

trevj

Titanium

GGaskill

Titanium

OldSquier

Aluminum

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