Have a 20 ga SxS that's has 2 3/4 chambers. I'd like to lengthen them to 3". Any problems or concerns doing so ?

After asking what make s/b/s it is I'd have these questions.

The first question is why? The second is what is the weight of the gun? The third question is is the action and are the lumps robust enough to stand use if three inch cartridges?

My own thoughts are that it'll go off the face very quickly.

And that if you can't get the job done with a 2 3/4" shell then you are better buying a cheap 12 Bore s/b/s as even with a 2 1/2" chamber it'll give you 1 1/8 oxs of shot and in 2 3/4" 1 1/4 ozs shot.

Last your 2 3/4" 12 Bore will shoot that 1 1/4 ozs better than will any 3" 20 Bore.

I'd urge you not to do the modification.

It's a J.P. Sauer & Sohn. About 5 3/4 lbs. Have a lot of 3" shells and would like a bit more shot in the load. Have a nice 12 , but it is bit heavy.

A nice J P Sauer. I'd leave it as it is at that 5 3/4 lbs. Hold tight indeed! I think it'll spoil the gun and, more to the point, I don't think it'll do the gun any good. IMHO it'll take it off the face and if it's that sort with a top extension and cross bolt it'll be a pain in the backside to re-joint. Or if there's no sentimental value sell it an see if you can get a 3" 20 Bore Winchester s/b/s?

Don’t touch that classic gun. You don’t need 3” for anything. I can’t even remember how many ducks I’ve shot with 2.5” Bismuth from a classic British gun. JP Sauer generally has it right. If anything open up the chokes to no more than IC, but best is CYL.

A 5-3/4 lb 20g SxS with 3" loads will kick the snot out of you. Further, while you might have additional shot in the load, patterns will suffer. I would re-think this idea.

Why would patterns suffer ?

Two reasons. The longer the shot column the more shot in contact with the bore. Therefore it will become abraded and not fly true.

Also the greater the pressure on the base of the shot column when the cartridge is fired. This will deform those shot so they'll not fly true.

So all in all the additional shot payload in your three inch cartridge will offer little benefit compared to a standard 2 3/4" shell if you're using fibre wads and lead shot.

A nice gun like that I would leave alone...you DON'T gain a whole lot of extra whatever with an additional 1/4" of shot...depending...as to the rest, that is conjecture and bias I think...LOTS of ways to mitigate all the suggestions.

I have a OLD Sears 20 ga 2 3/4-3" pump that weighs right at 6#...the difference in MAGNUM shells of both sizes is noticeable both in recoil, range and in killing ability...the 3" does a better job from 40-70 yds...but the recoil is hardly noticeably much different but it does recoil a bit harder.

For the most part I buy the cheapest #7 1/2-8 field loads in the shorter length and a heavier #4-6 loads for the longer one. One is for birds and one is for grey squirrels and such. AND, I reload some #2 shot 3" for larger varmints...I have several 12 ga o/u, pump, semi-auto and ss shotguns to pick from but I just like that 20 and have been shooting it about 50 years.

Buffer material and shot cups pretty much stop deformation but if you use harder copper/steel, etc., shot you can pretty much forget all that "it's been squashed" stuff...and I'm not sure if that's really a problem at all or just something a gun rag writer came up with, although it does happen and there is a modicum of truth in it. Some of those "fly away pellets" have brought down game when I just got it wrong with my job.

Think hard about it...if you want a 3" 20 ga, go buy another shotgun or a larger bore size.

Good Hunting

With your explanation, I’d find a really good gunsmith and ask them.

Pressure wise, 2.75 and 3” shells are the same.

Recoil wise, there is a difference, but as a guy who shoots 3.5” 12 Ga out of a light benelli SBE, that’s relative as well. (And if you look at the insides of my older benelli, you can tell it’s had numerous cases of 3.5” magnum loads fired thru it...)

If the gunsmith thinks the walls are thick enough, and doesn’t think there is a concern with going off face, it’s your gun, and you can do what you want to there. Just know that changing the chamber length can cost you some resale value on a higher grade gun. The extra 1/4” does make a difference with nontoxic shells, like bismuth- even if it doesn’t do much with lead.

I knew the pressure ran the same. Recoil is of no concern. I'd just like a bit more shot with bigger birds. It's a pleasure to carry this gun.

quote:

Originally posted by leemar28:
I knew the pressure ran the same. Recoil is of no concern. I'd just like a bit more shot with bigger birds. It's a pleasure to carry this gun.

Can't even count the number of pheasants and large ducks I killed with 1 and 1/8oz of 6s.

Out of 2 3/4 inch shells I wouldn't bother to re-chamber a fine gun like that.

Let alone the number of smaller ones I have kill with 1oz and 7/8oz loads

I have owned many J P Sauers in several gauges. I am going to guess that if this gun is only 5 lbs 12 oz, it is either a pre war gun or was built immediately after the war when production resumed. I can definitely say that in any case this gun is not made for...not was it proofed for ...magnum pressure. It WILL loosen up or go off face in a relatively short period of time if you use 3" shells. JMHO...

Not sure what "magnum pressure" means. Looking in the Dupont Handloaders guide. It lists Federal 2 3/4 plastic "Hi Power hull's. Loaded with Winchester 209 primers, 22gr SR4756, Rem RP20 wad column, 1 1/8 oz shot for a velocity of 1185 fps @ a chamber pressure of 10900 lup.
The load for a Federal 3" plastic "HighPower" hull. Loaded with Winchester 209 primers,24 gr SR4756,Rem RP20 wad column,1 1/4 oz shot for a velocity of 1155 fps @ a chamber pressure of 10400 lup. In fact looking at the chamber pressures listed for both 2 3/4" VS 3' loads are just about the same ......

quote:

Originally posted by leemar28:
Not sure what "magnum pressure" means. Looking in the Dupont Handloaders guide. It lists Federal 2 3/4 plastic "Hi Power hull's. Loaded with Winchester 209 primers, 22gr SR4756, Rem RP20 wad column, 1 1/8 oz shot for a velocity of 1185 fps @ a chamber pressure of 10900 lup.
The load for a Federal 3" plastic "HighPower" hull. Loaded with Winchester 209 primers,24 gr SR4756,Rem RP20 wad column,1 1/4 oz shot for a velocity of 1155 fps @ a chamber pressure of 10400 lup. In fact looking at the chamber pressures listed for both 2 3/4" VS 3' loads are just about the same ......

Hey, it’s your gun. Do what you want.

As you lengthen the chamber, you push the "weak point" forward into a skinnier part of the barrel ..this is the risk. Rule of thumb you want .100 wall thickness at the beginning of the forcing cone (the weak point). So measure your barrel OD at the 3" point, subtract the chamber ID at that point, divide by 2, and if the answer is less than .100 you should not proceed.

If you do proceed, you should lengthen the forcing cone at the same time to reduce pressure and recoil.

But if you reload, you can squeeze more shot into the shorter shell... shotgun shells were designed back in the BP era when powder was very bulky. With modern powders, you can find a wad that will handle more shot in the same length ctg. So going up to 3" not necessary. Of course, you need to use load data and not invent your own as shotgun pressures are a little touchy.