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Barrel Length vs Velocity


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This was posted by Jason Hinkle over on Subguns. Jason got me into the Saiga market back in 2004 and owns the very first prototype 12" Tromix SBS. He's a pretty colorful guy.......

 

 

Hinkle writes......

 

OK so I finally took most of the shotguns out for a spin on the old Chronograph. What I found is that, basically, those of you chuckleheads with no empirical data who have been yapping your cockholsters about how short barrels on shotguns seriously affect ballistics are fucking wrong. Lots of wrong. Like I said long ago, shotgun powder IS pistol powder- it burns fast and quick, and barrel length doesn't fucking matter that much.

 

I can't .PDF a spreadsheet on this computer so I'll get really slow and dumb like those who talk out their ass about ballistics with no basis in reality and list the average FPS for the shot strings.

 

First, using shitass birdshot- 12 gauge, 2 3/4 inches, 1 oz shot

12" barrel average FPS- 1040

14" barrel average FPS- 1069

18" barrel average FPS- 1114

19.5" barrel average FPS- 1114

20" barrel average FPS- 1108

28" barrel average FPS- 1159

 

Then using Remington 00 Buck-

12" barrel average FPS- 1121

14" barrel average FPS- 1127

18" barrel average FPS- 1216

19.5" barrel average FPS- 1205

20" barrel average FPS- 1182

28" barrel average FPS- 1250

 

Wow- 119-129 FPS velocity loss in 16 inches of barrel. That's devastating. Oh wait- no, it's actually not, it's fucking nothing at all and is actually about the same velocity variation in factory loaded ammo. I will feel as comfortable fucking up a bear using a shotgun with a 12 inch barrel as I would using one with a 28 inch barrel. Those of you clammering over 20 gauge Serbu Super Shortys rather than the biting sting of a 12 gauge to dust up a gravel pit should stick with the shortest of shotshells. I wouldn't want you to drop your purse while shooting.

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hehehehe, Tony, don't hold back, tell us how you really feel ....

 

I don't know what the tacticians would say about loosing 100+ fps, but shotgun is often overkill on stuff/game at close range so I doubt it does matter.

 

BTW, IMO, the ultimate SBS are chamber length. There was a company "little skeeters" (sold out to browning, IIRC) that had chamber inserts that allowed 12ga to chamber 20, 28 and 40. They were the length of the shotty shell, so basically a 0 inch bbl. They were targeted to skeet cometitors (as the name implies), so they had enough umph to break clays at 15 yards, but had to be fast enough not to alter the lead needed on crossing shots too much (or they would never have marketed them).

 

A close second is that pistol that fires both .45 long colt and .410!

 

But a huge thumbs up for testing it with the real deal.

 

BTW, I think the powder burns out 12 - 18 inches (I don't recall). But what this means is that late burn is making very little difference in ballistics.

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Caspian posted some slug data a couple of years ago, and I believe the velocity drop was more than what Hink's test shows here.

 

Here's a chart posted by Jeff Z, writer for Small Arms Review Magazine, note the velocity drop with the 20" barrel in his tests as well.

 

Velchart.jpg

 

Tony

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My data was using slugs @ around 10 feet from the chronograph. i think i only used one slug/barrel length since i didn't have a huge supply of slugs at the time.

 

I had greater drops of velocity, but the final velocity from a 7" barrel was still substantial enough to put an end to the critter on the receiving end.

 

caspian

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My data was using slugs @ around 10 feet from the chronograph. i think i only used one slug/barrel length since i didn't have a huge supply of slugs at the time.

 

I had greater drops of velocity, but the final velocity from a 7" barrel was still substantial enough to put an end to the critter on the receiving end.

 

caspian

 

Caspian,

 

Could we impose on your to re-post your data here in this thread?

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very interesting info, I bet it will be hard convincing the old man ,maybe the old double barrells are 30"

just to improve sighting.

just about the last chart on spread , before everyone gets out their hachsaws

is that with full choke or open

does barrell length affect spread with a full choke ??

 

Pretty tough to do that experiment. A lot of variables affect pellet spread. But the theoretical answer is no, bbl length will not affect pellet spread given the same choke.

 

As you mentioned, most of the "old men" with shotguns are interested in how hard something hits (with choke, how hard does it hit at distance). A longer bbl facilitates a better aimed hit, so it will hit harder. The answer is patterning.

 

One of the things that affects performance is the internal dimensions of the bbl, esp the length of the tapering/choking section. Many hold that if you ONLY need a full choke (i.e. shooting trap from the 26 yard line) the old fixed choke bbls gave a better performance. Screw in chokes force the constriction in a short distance, older bbls did it more gradually.

 

But there aren't many fixed choke models because of the flexibility screw chokes offer, to the most versatile firearm platform on the planet ...

 

But to the question. As long as you were measuring from the muzzles (proper technique) and both were screw choked and nothing funky going on with bbl internals, they should perform the same.

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  • 2 years later...
I find it interesting that a 20inch barrel is not as good as either an 18-19.5-28..... that is an oddity that caught my attention..

 

good info to have though...

 

Yeah, thats wild. I wonder what the physics are that cause the 20" to be like that? Anyone know?

 

 

Small arms Reveiw magazine had the same results with the 20 inch barrel.

 

I don't remember which issue, but I think it was last year. They took a single shot 12 ga and cut the barrel 1 inch at a time and chronographed it all the way down to about 7 inches

Edited by Banshee
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I have one of the 24 in barrels on my first saiga, I was thinking about cutting it down to 20 in. Guess I'll rethink that. So I guess I'll cut it between 18 and 19 inches... Or I could use this as the perfect time to chrono and cut while at the range to give some data.

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