Reloading and short chambers
 

This is a subject I posted in another forum but thought it would be a good one to pose here.

I am not trying to put anyone down but looking for an open discussion on the subject of shooting longer shells in short chambers of older shotguns. For years I have read of this practice being done.

1. Is this practice reasonable with low pressure loads?
2. Would a steady diet of longer shells in shorter chambers, rather low pressure or not, cause an older shotgun's action to loosen.
3. If one reloads for an older (shooter not collectible) shotgun, would it be acceptable to lengthen the forcing cone and shoot low pressure 2 3/4 shells.

An article in "Gun Reports" by Russell Corbitt addresses some of this. Article

Dick

In all of the articles I have read on the subject, the answer was always 'Yes, pressure increases slightly'. Would the pressure increase to the point of peeling open a composite or fluid steel barrel? That was always the part where the author/researcher bowed out. I suppose it is a liability issue like some one asking on the forum if their gun is safe to shoot. We all agree that the person should have them looked at by a qualified individual. I suppose the guys writing short chamber articles don't want to be held liable. I would think that if pressure increases, the rearward thrust on the breechface would increase, along with forward thrust on the hook. I dunno. I will watch this thread, too. Cheers!

"Common knowledge" says that shooting 2 3/4" shells in chambers designed for 2 1/2" shells will cause an average increase in pressure of maybe as much as 150 psi.

Pretty small pressure increase when dealing with low pressure shells I would think. :corn:

It is not the pressure one has to worry about. It is the increased recoil! I do not know exactly why but it is true...

From 12006 "16 Ga. Gun Talk" Topic

ITHACA CHAMBERS -- The last Flues period catalogue (1925) states -- "Unless otherwise ordered Ithaca 28 Gauge and 20 Gauge guns are chambered for the standard 2 1/2 inch shell, 16 Gauge and 12 Gauge for the standard 2 3/4 inch shell and 10 Gauge for the standard 2 7/8 inch shell. Longer chambers are furnished if ordered on new guns without extra charge, but it should be remembered that shells of standard length do not give quite as good results in chambers which are longer than the shells and it should be remembered that extra long shells are more expensive and it is much harder to find a dealer who carries extra long shells in stock."

In the published book "The Parker Story, the Remington vintage specification sheets on pages 164 to 169 call for a chamber 1/8-inch shorter than the shell for which it is intended. I have a 1930-vintage VH-grade 0-frame 20-gauge and its chambers are 2 3/8 inches intended for the old 2 1/2 inch shells, eight years after the 20-gauge Super-X shell was introduced in a 2 3/4 inch case!!"

American Rifleman: "And here's the reason why better patterns resulted from slightly overlength shells in short chambers (or chambers marked 2 3/4" that weren't really that long): Remember that we're talking the pre-WWII days, paper cases and felt or cork wads, no plastic shotcups. One reason for pellet deformation back in those days is that the unprotected pellets would slam into the walls of the forcing cone when the gun was fired. However, if the paper case mouth opened into the forcing cone, the mouth of the shell itself afforded some protection to the shot charge, on its initial contact with the bore. Tests established that slightly shorter chambers resulted in tighter patterns. Some trap shooters even when so far as to shoot 3" shells in 2 3/4" guns. Today, of course, with plastic hulls and wads, there's no longer any pattern benefit to shooting longer shells in short chambers, because the wad itself does a much better job of protecting the shot."
__________________

Richard, that American Rifleman article is interesting. That is the first time I heard of that theory!

Ah, it sounds like a very good theory. I have a Parker 10ga with 2 5/8 chambers. It has about a .020 "step", so for that reason I cut shells. If it had the regular forcing cone I'd just shoot the longer shells. As to shooting shorter shells in longer chambers you'd get some blow-by and pressure loss. I've read that chambers of old were shorter so the cushion wad would still have some in the shell as the front was at the end of the forcing cone; thus giving a good seal. Paul

Paul, my 10 gauge 1879 Lifter is configured like yours. I have a 'cheesy' inside divider and managed a crude measurement of .809" about 2" forward of the chamber. There is an imperceptible jump from the chamber to the bore. The chokes measure .790"-ish (I don't have the figures at my desk). I questioned the bore size, but have been informed that Parker bores, at that time, were not always consistent with any set standard. I will re-check my measurements this evening. I am preparing to chase the Ruffies this morning with my RBL. Cheers!

Mark, I have a 12ga Parker with .742 bores. Some of the more knowledgeable on this board have stated that Parkers before certain serial numbers had larger than standard bores. I have a 11ga Claybrough with .765 bores. The chambers almost took 10ga shells so I opened them up enough to take 10 to 12ga Gaugemates. Paul