In two shotguns with the same choke, will barrel length play a factor in the patterning of one over the other? I.e., would a 21" barrel with a Modified choke be expected to produce a different pattern density as a 28 or 30" barrel with an identical choke?

Obviously each shotgun may be a law unto itself but for the sake of argument let's assume all else is the same - same load, same exact constriction - in fact consider the same choke tube screwed into two barrels of different length mounted on the same gun. However, given that the longer barrel may produce a higher velocity would that enter into the equation?

I'm guessing the difference in barrel lengths only would not affect the pattern density but wanted to ask since I've never patterned anything with same/same chokes and different barrel lengths.

The choke is what matters, not the barrel length.

I've got a custom, 24 inch choke tube barrel for my old Ithaca 37 that basically patterns the same as my 26 inch Remington 1187. My 28 inch O/U's have as well.
Not quite what you asked, but as much as I can describe. E

Long bbls produce very little if any added velocity in shotguns. Shotgun powders burn really fast, by 21" the shot is pretty well at max speed. Black powder was a different story, which is why it used to be true that long guns shot harder.

You can change pattern density quite a bit just by changing cartridges. A shooter who cares about patterns needs a pattern board, an assortment of cartridges, and a lot of time to count pellet holes.

Some people say not to pattern your gun, though. They say you'll be so discouraged with all the holes in your pattern that it'll ruin your shooting.

If you don't pattern, you have no idea what you're gun is doing. Some people still don't pattern. Maybe it's more fun that way.

There was an article in one of the shotgun mags a few years ago by a shooter who went so far as to test cartridge patterns in 2.75", 3", and 3.5" 12 ga chambers. He used the same choke tubes, and cartridges from the same case, in all 3 guns (his, and two borrowed guns of the same make). Nothing mattered but the choke.

Thanks for all the replies verifying my guess.

Reason for asking is that I did some buckshot testing this spring with an 1100 28" barrel and an IC choke tube then with an 18" cylinder bore barrel in an 870. I used 00, #1 and #4 at 7, 15 and 25 yards.

I was going to buy a 20" barrel that would allow removable chokes so I could try a short barrel with a modified tube to see how those same loads performed but then I thought why? I could just use the 1100 with the 28" barrel and put the modified tube in that and results should be pretty near equal to a 20" tube but wanted to check here first.

The exception is ultra-long barrels. Apparently there's so little pressure from the gas at the muzzle of barrel three feet or more in length that patterns tend to be tighter, because there's less disruption of the shot-cup and shot.

Who is offering shotguns with 36"+ barrels these days?

No factory that I know of, though I would guess Marlin did most recently, with their bolt action shotguns.

The research I'm familiar with was done with custom barrels.

noped

Ok I'm going against the grain on this one. Choke and a clean pollished barrel is 90% of your pattern BUT a long barrel say 28-32" will add a few percent to your over all pattern. Some will say bull$hit and I will say if you just look at it you won't see much difference but if you count pellets and do percentages you will see an increase. Why do you think all the guys that shoot in the NWTF still target championship use long barreled guns. Call rob roberts or kicks or ballistic specialities or anyh other company that specializes in turkey guns and they will tell you the same thing.

But for all practical purposes it won't matter, I'm just splitting hairs. I have also through many pattern sessions descovered guns with larger bores are more consistent with heavy loads and large shot sizes. Shotguns are a funny animal.

IIRC, Hastings (sold through MidwayUSA) a few years back offered a very long screw in barrel extension called a Metro barrel. The main claim-to-fame was that it quieted a 12 ga muzzle blast to around 80 db.

As I always explained to folks in the gun store, the difference between a 28" barrel and a 36" barrel is that you get the exact same pattern eight inches farther away with the long barrel.

In the immortal words of the great Bob Brister, "No."

Do you have a citation for Brister's quote, because I'd like to be able to repeat it. I searched Shotgunning: The Art and the Science but was unable to find any mention of barrel length and patterning.

My take:

A short barrel loses a little bit of velocity, 50-75 fps difference between a 20 and a 28" barrel, total.

A short barrel is definitely louder.

If there is any difference in patterns, it would be caused by the greater gas pressure at the muzzle. If it makes a difference, it is likely so small as only be important to card shooters, where every single pellet matters. Whatever the difference might be I suspect that it would be even less if a ported barrel / choke were used.

IMO the most important difference between short and long barrels is swing characteristics.

.

Briley made for me an adaptor kit to make a Browning BT-99 48-inches long with a 0.060-inch constriction choke. We will go out on a limb and call that a Full choke.

It is quiet to shoot.

.

Yes, barrel length factors in to pattern efficiency. I pattern a bunch of shotguns and while there are many factors to pattern efficiency, bbl length is definitely one of them. I have always experienced better efficiency from longer barrels when using the same chokes. At the same time, you have to look at it from a practical standpoint as well. IE: While a 30" bbl may offer slightly superior patterns over a 24" bbl, the 30" may not be well suited for the task(turkey hunting for example). This is nothing new, browse a few shotgun boards for more on the subject.

A good example of this is by browsing guns at card shoots or a NWTF match.