I only recently learned that some of the SuperUltraCrazyLights came in 3".

A few years ago, I would have wanted an Ithaca that shot 3" shells, too. But then I had some experiences:

16 gauge guns weigh 6 pounds and shoot 1 1/8 ounce loads easy peasy. Just get a 16.

I started shooting 1 1/4 ounce pheasant loads in my fixed breech guns. But then started shooting 1 ounce loads in my 16. At the end of a season, I couldn't see one disadvantage to the one ounce load.

Our last month was cut short because the dog was injured. He ran onto a sharp stick. He's okay now.
In that last month, that's when I go to my 12 gauge pheasant whompin' loads. I would only want to light those off in a nice soft SemiAuto. Ow.

For grouse and bunnies, an ounce is a bit heavy handed.

Now I've started shooting Sporting Clays with a 20 gauge and 1 ounce loads. The standard is 12 gauge 1 1/8 ounce. Know what? I shoot better with the 20 because it fits me better.

Long story short: anything I want to shoot I can shoot with 1 ounce. Or 7/8.

As for technicalities... the Ithaca has an all steel receiver. They would have to forge a new receiver for the longer shells. That would add weight to a shotgun prized for light weight. And they already make a 16.

 

I ran into your post searching 20 gauge model 37 things, and while it doesn't address my question I do have a 3 inch answer to your 2 3/4" gun.

Lyman data (from that complete reloading manual compilation sold in big box stores) lists a reload for 20 gauge Federal Plastic Target Shell with paper basewad with 1 1/8 oz of shot, 23.0 grains of Blue Dot, a Rem SP20 wad (which are back in production, btw) at 1175 fps and 10,900 psi. I put a box together for a 20 gauge shooter before we agreed she might as well shoot a light 12 gauge load. Hope it's useful to you, though.

 

I suspect the only difference between early production ULT and late samples is the barrel. The last ones will not be marked Ulrafeatherlight or Featherlight for that matter, but it will have 3" chamber. It will fire and cycle 3"shells perfectly, but for obvious reasons I would not use lot of magnum loads through such light gun.
I prefer these because to modern hunter VR, choke tubes, 3" chamber matter, therefore, guns with those features sell faster for better money.
The bottom line is if ejection port of your shotgun is 72mm it will cycle, fire, and eject empty 3" case. The standard receiver ejection port is 1/4" shorter and will not eject empty 3" case.

 

Ejection port? I didn't understand what you're saying, so I pushed a 3" fired shell into my 2 3/4" 20 gauge Model 37.

It took a little oomph, because the chamber isn't cut for a 3 inch shell.

Pulling the forearm back, the shell stuck firm in the gun. The lifter was pressing on the shell to be ejected. It was stuck fast.

The problem isn't the ejector port- it could milled all the way into the trigger group. That's not the problem

One cant' push the bolt back 3" because the lifters' swing, encounters the stuck shell, and prevent the action from cycling about 1/4" before the end of the shell is freed from the rearmost part of the chamber.

My conclusion is that the design would need to be changed so the lifter activates 1/4" later.

To get the 3" shell out? Pierce it with a sharp Exacto blade and make incision. Insert needle nose pliers and pull.

Mine is from 1954.

 

Many many parts are different between the 2 3/4" versions vs the 3" versions. Hammers, receiver, forearm and slide. There are other differences. As has been noted, a 3" shell will feed into a 2 3/4" receiver that has a 3" barrel on it, but can't eject as the shell gets pulled reward and is supposed to pivot downward.

A fired 2 3/4" shell is about 3" long, that is why a 3" unfired shell will feed.

The changes to allow a 3" shell were for the most part, forward of the trigger group. You just can't mill the ejection port back to the trigger group. They added 1/4 forward, allowing for the shell to clear the barrel and pivot on its arc to eject.

Trigger guards are the same, hammer is different.

Here are pictures of a 3" and a 2 3/4" hammer. I stole the pics of eBay and converted to jpg's. Credit to the folks selling these.

A person can go onto IthacaGuns website and look at the internal parts (where available) and see the ones that are specified for 3" guns vs all guns (gauge specific where appropriate of course).

 

All I'm saying is if ejection port opening is 72mm and the barrel has 3" chamber the gun will cycle, fire and eject 3" shell. Yes, there are other part differences, but there is no need to take the gun down to find out one has a gun with longer receiver. If you own such Ultra do not shoot 3" shells through it. I fired two 3" shells, it was not pleasant. It is old design where bolt locks into the receiver in this case into light alloy receiver. Modern designs lock bolt into barrel extension.
The 3" shell isn't needed for smaller upland birds, but 3" marking is big selling point especially in 20ga.
It's important to check and spec the gun before purchase. For example, in late 80s I bought new Ithaca pump 2 barrel field set (parkerized, walnut no checkering on wood, grooved front). Both barrels had 3" chambers, but the gun would not eject 3" shells after it was fired, so markings on the barrels are not indicative of function.

 

All I'm saying is if ejection port opening is 72mm and the barrel has 3" chamber the gun will cycle, fire and eject 3" shell.

Yes, because that is the size of the 3" shell versions. I just measured and the design change was to add .200 to the front of the receiver. 72mm = 2.834 inches. The early 50's I just checked measures 2.634 inches. So .200 difference. I also verified the ejection port of a MAG-87xxx I have. It measures 72mm / 2.831 (manufacturing tolerances here).

The definitive answer is if the ejection port measures 72mm / 2.834 (ish) then it is a 3" receiver, regardless of what barrel is on it.

To really twist things up, a 2 3/4" chamber will pattern better than a 3" chamber. My buddy is/was a gunsmith who specialized in building turkey shoot guns. Up to and including the race guns that will blow the middle right out of turkey shoot targets. He says that for TS's that specify stock guns only, to get a 2 3/4" gun.

 

This is all great information, right up until we start talking about chamber and "pattern better." Sorry, I am calling "baloney."

First of all: define what a "better pattern is.
The pattern shown on paper is a roughly random gaussian distribution of holes in a radial pattern. Random. Gaussian distribution. Radial.

Folks have been selling extended forcing cones for decades, claiming 'better pattern' but no comparison of patterns has ever shown a "better" pattern. A better pattern would have a kurtosis closer to 1.0. A spreader wad increases the kurtosiis: that is, we don't want a concentration of pellets in the center, we want an even distribution over a whole circle.

Studies by Fabarm and Beretta show that smooth transitions from shell to free-bore to choke result in higher velocities and reduced shot string. But it's a system: you can't simply fix one part of the barrel and get results.

You can't just slap a racing exhaust on your truck and expect any performance increase at all, except by blind luck. It's a tuned system.

Okay. Off my soap box.

What makes a Model 37 Ultralight unique from Winchester Model 12, Remington Wingmaster, and Browning BPS?
1. It weighs A LOT LESS. Enough to matter to your wrist after a 4 mile hike.
2. It has many fewer parts than the Model 12.
3. It's easier to clean the magazine tube than a Wingmaster, although a Wingmaster is easier to clean the bolt.

All are nice pump shotguns, but when it comes to a field-carry shotgun, light weight is king. It's the defining feature of the Model 37.

The more I hunt, the more I realize that a good shot hits and a bad shot misses.

Shooting Sporting Clays lately, the standard is 1 1/8 ounce payloads. I shoot for fun. I can shoot 12 gauge 1 1/4 ounce target loads. I can shoot 1 ounce 20 gauge loads. I seem to score better with the 20 gauge. Gun fit beats 1/4 ounce of lead.

This 3" shell thing? Yes, nice if I want to go duck hunting because I need the room for steel shot. Sorry, duck hunters don't walk all day, they sit all morning. A lightweight shotgun isn't an advantage.

Yes, I am still going to use 3" 1 1/4 ounce shells on late season pheasants. Maybe even 1 3/8 ounce. But until December, I used 1 ounce last year and had more birds in the bag than ever. (I hunt 3 times a week.)

I guess it's just like lots of life these days: all down to marketing. "You gotta have 3 inches!"

The good news: I can pick up excellent 2 3/4" shotguns for much less than their value to me!

ps. If you want better pattern, use better shells. And the crazy tightest pattern I have ever seen comes from my 16 gauge polychoke. I really need to take photos and write it up!

 

The slide on a 3" gun is longer by roughly 1/4" . If you put a 2 3/4 inch slide on a 3 inch gun it won't eject anything.

 

This is all great information, right up until we start talking about chamber and "pattern better." Sorry, I am calling "baloney.

He made LOTS AND LOTS AND LOTS of money building turkey shoot guns. How many have you built ? In this case, I am blatantly going to tell you that you don't know what you are talking about.

He built guns using seamless tubing to rebarrel actions, created stepped chokes to deform the wad and cause it to stay with the shot column.

I think he knows what he is talking about.

When you shoot a 2 3/4" in a 3" chamber, due to the forces the column starts to expand and then is crammed back down when it hits the forcing cone. Some as with a long through BPCR rifle and the slug starts to expand and then in crammed back to size when it hits the rifling.

That is how you get deformed pellets. Would you notice it shooting at clay targets, rabbits birds etc? No. When you are shooting at the little "X", yes.

On a turkey shoot gun, you want a more consistent, condensed pattern, especially going through a fixed full choke when one pellet can spell the difference between the pot of money and nothing.

 

I agree gunsmiths made "LOTS AND LOTS AND LOTS of money" with chamber reaming. But the barrel is a system.

 

For turkey shoots shorter chambers are better.