Velocity vs Barrel Length for a Shotgun

slimjim

I had my Mossberg 20 gauge pump at the range this week. At the last tactical shotgun match I felt like I was limited by the 18-inch barrel with no choke. I wanted to try out my 26-inch barrel with modified choke to test the pattern and see what extra velocity I picked up with the additional 8 inches of barrel. Boy, was I surprised by the chrony results. The main advantage of a longer shotgun barrel appears to be mostly sight radius. Has anyone else had experience with this?

________ slug ___ 1oz Shot 7 1/2
18-inch _ 1530 ___ 1060
26-inch _ 1580 ___ 1125

Fireman_DJ

As I understand it, a longer barrel gives a better follow through for shooting game on the run, a better sight radius and a tighter shot pattern (assuming using no chokes on both guns).

I would say the minimal difference is due to the large bore diameter.
The barrel length to diameter ratio doesn't change as much when you have such a large diameter barrel.

Hoping I've done the maths right here.

For a 30 cal rifle
A 18 Inch barrel has a 1 in 60 ratio.
A 26 Inch barrel has a 1 in 86.6 ratio.

For a 12ga,
A 18 Inch barrel has a 1 in 24.6 ratio.
A 26 Inch barrel has a 1 in 35.6 ratio.

In short, for the 30 cal rifle, there's a difference of 20 vs 10 for the shotgun. From that, you can assume that the velocity lose for a shotgun will be half of the lose in a rifle.

Elvis

for the range most shotgun shooting is done at the velocity means bugger all untill you change it by 3-400fps. fireman you are correct about "swing" a long barrel helps to maintain swing through as the weight out there takes more stopping.

slimjim

Thanks, Fireman_DJ. I followed your explaination. I was surprised how little velocity was gained by the extra barrel lenght.

English Mike

Fast powder in shotguns, therefore unlike a rifle, it's all burned before the shot leaves the barrel.

Aloysius

English Mike wrote:

Fast powder in shotguns, therefore unlike a rifle, it's all burned before the shot leaves the barrel.

but not with heavy loads, because then a slow powder is used. And a slow powder + short barrel = firework + lot's of unused powder.

And 1 remark: when you start working with shotgunloads, you should forget everything you know about bullets and cartridges for rifles and handguns. It needs a complete different approach.
Look at the data for shotgun: they give everything: shell, primer, wads, powder and load, even the kind of crimp/closure. Now compare that with rifle-data.

PaulS

You guys are hilarious!
Smokeless powder is completely burned almost before the bullet leaves the case! Even with the slowest powders all the actual burning is done in the first few inches of the barrel. The flash is composed of super-heated carbon and ash. The powder is burnt before pressure peaks - the heat takes time to complete the pressure peak so the bullet is pushed all the way down the barrel.

Gil Martin

Sounds about right. The bigger factor is how the shotgun feels and swings with a specific length barrel. At shotgun ranges, shorter or longer barrels perform about the same. All the best...
Gil

stovepipe

Shotty's use fast powders, small charges and BIG bores, the pressure is way low and no apreciablegains are made by the barrel lentgh thingy like a rifle.

Barrel lentgh in shotty's is all about recoil management, and, allegedly swing through, I guess one's not allowed to swing through with a short tube, so I've read.... just as easy for me to learn both and I'm equally shakey/choppy with either. For blind shooting I'll take a long tube and a heavy gun to mitigate recoil..but for upland? Shorter the better. Ever go out with an 18.5"? It's magic on back-flushers.

I've been on a short barrel gig for a couple years now at least. I dont like long barrel pop-guns, never have and recently sold my last one. And, since I switched to 24" and even sub 21" tubes I'm happier. Let the nay-sayers tell me I'm wrong, I'll pick up all their upland snap-shots and have them in the bag before they even get that 5 foot log to their shoulder.

*flush/POP!* Plop. Stuff....aaaand BEERTHIRTY. Razz

Fireman_DJ

You're allowed to swing through with a short barrel, but it will be your body controlling the smoothness of it.

If your body is able to have that good enough control, then a pat on the back to you. For an older person with the shakes, I'd still recommend a longer barrel.

With a long barrel, the pivot point is at the same location (your body), but there is more weight further out (the distance multiples the effect of the weight) so it is more natural for your body to follow the shotgun.

Oh, just for the record, I've got a IAC 12g lever action with a 20" barrel waiting for me at my local gun shop. (Pump actions require a high class of license which the common people like me can't get. But LEVER action, that's completely different right??? Stupid Australian firearm laws that make no sense.) I also have a nice long SxS. Not easy to use a long barrel for shooting from inside the car (spotlighting rabbits).

chambered221

PaulS wrote:

You guys are hilarious!
Smokeless powder is completely burned almost before the bullet leaves the case! Even with the slowest powders all the actual burning is done in the first few inches of the barrel. The flash is composed of super-heated carbon and ash. The powder is burnt before pressure peaks - the heat takes time to complete the pressure peak so the bullet is pushed all the way down the barrel.

Yup ....what he said !!!

Slim, here's something else that might surprise you..... the velocity gain with the scatter shot was mostly a result of the modified choke in the 26" barrel.
Do some testing with a barrel that has screw in chokes and you'll see what I mean. The tighter the choke the more velocity you gain.
The velocity listed on a box of factory shells is with a full choke.

As far as barrel length it is simply a matter of preference....... to a point !!!
I will not argue that some people seem to shoot better with a longer one and some with a shorter one.
But the fact of the matter is it's been proven that a longer barrel will prevail in competition.
Trap is usually shot with barrels from 30-34 inches, skeet started out with a 26" being the norm but today 28-30" are the most popular, sporting clays and live bird shoots are most ofter shot with 30" barrels.

stovepipe

Oooh- DJ, post some shots of that lever gun!

SxS- you can have a nice long tube w/o a longer OAL due to that lack of action. Smoother swing and less muzzle flip, win-win!

No doubt in my mind a longer tube, to a point, can swing smoother and follow-up is more on due to reduced muzzle jump. I've swung on a lot of multiples and it's just too much for a small person like me to handle long tubes on a SA/pump...on a fixed breech/break open it's different, the gun is all tube and the OAL is much less. But I dont shoot break-actions so, the shorter the better for meeeeeeee!

Fireman_DJ

In Aust due to our laws most shotguns are double barrels.
I put money down to secure this lever action because of fears they may stop importing them. Customs keep giving them grief because it's a loop hole.

I really should take all my guns out for a photo shoot. Maybe a group shot.
I don't have many, only nine (the IAC will make it ten).

inthedark

I was taught bead, butt, beak,boom!
The instructor at the skeet range watched me fire about 5 rounds and said 'You are a rifle shooter'
After an afternoon of shooting clays he suggested that stick to rifles.
I still am not a good shotgunner, but I'm getting better.
Follow through is my biggest problem. Along with not enough practice.

stovepipe

Bustin' clays is fun. It's repeatable.

Wingshooting is a rush. Never the same exact shot twice.

Both have the basics in common- break on the beak, follow through, keep the head down or miss- regardless of what you are shooting.

I say if one's shooting for scores and wants the edge they think, or actually does, a particular firearm will give them? More power to them!

Competiton breeds very fine points- e.g.: long LIGHT back-bored tubes, heavy butts, rounded pads, compact forends that place the weak hand fingers in line with the strong hand's, adjustable combs, cast-off stocks, etc. All that can help and whats the harm, it's nice to have a nice gun! Who don't droll over a Perrazzi or a Kreighof. But when one reaches this point they are probably bordering on being really really serious about getting super consistent and automatic and eliminating any variables, including mental ones.

All of it takes a back seat to fit and feel though. Lots and LOTS of folks pay big $$ for a gun that dont fit or or one they dont close their eyes, mount and swing to see how it feels from the inside, from the gut. Then, open their eyes and see where it's pointng. They follow the mags and others. Not their gut. Then trade it in when they don't shoot a clean course.

I also say if one think's the gun is holding your scores back they are wrong, it's all mental with shotgunning, 100% mental. Guys were killing it in double-trap and skeet long before I came along.....with field pumps!

But, back on topic, barrel lentgh aint got much to do with velocity/effectiveness on game on a shotty. And, since I have to carry mine for miles and snap shoot while I walk on crossing and back flushing stuff I want the fastest handling gun I can get and for me that means a super light, short tube shotty. I'll deal with the recoil at dinner time.