View Full Version : Shotgun Barrel length and patterning.
09-14-2012, 3:07 AM
Just curious about what you all think about patterning and barrel length in shotguns. By what I can understand barrel length plays a relatively small part nowadays on shot patterning and what really makes the difference is quality of shot and the choke you use, length of forcing cone and quality of barrel. Other than the difference on how they point (long barrel 28" vs short 18"), the slight velocity differences, and sight plane. Shouldn't their patterns be very very close?
I'd assume that the shorter barrels would be slightly larger patterning due to the shots lower velocity as it passes through the choke, and creates a larger pattern as the shot slows (which would happen faster due to lower initial velocity) but other than that, I can't see of a reason why you couldn't use a 20-21 inch interchangeable choke shotgun for bird just as well as a 28-30 inch interchangeable choke shotgun.
09-14-2012, 7:33 AM
Actually, it's been found that the slower the pellets move generally the better and sometimes tighter the patterns become for a given choke. I'm convinced that shooting very high velocity ammo will "blow" a pattern more readily than a slower load with the same payload. Pellet energy and pellet density in the pattern is important too.. When we fire at a pattern board, we only see the 2 dimensional pattern.. but that's not how a shotgun works.. You need to think of the shot pattern as more of a "cloud" in motion.. one reason why being just ahead or just behind a target might get a single bb on target.. where as if you are right in the middle of the cloud the target appears to get crushed.
Generally if the barrel is short but has a screw in choke, it should pattern about the same as a longer barreled gun.. The reason a short barrelled gun patterns wider is due to most "riot type" barrels not having any choke at all which tends to let things spread out faster than if it had say an IC choke installed.
Also it depends on what kind of load you are firing. If you are using a target type powder or load (think wally world promo stuff), these loads are generally using a fast burning powder that will get you up to the target velocity with one good pop. If you are using a heavier load that utilizes a slower burning powder (magnum velocity lead or steel hunting loads), it generally means that the slower burning powder needs some barrel length to get that payload going over a slightly longer presure curve. Put that heavier load in a short barrel and you will likely get dazzling muzzle flash since some of the powder will still be in the burn mode when it exits the shorter barrel. Blue Dot (Slower burning magnum powder) is notorious for blinding muzzle flash in low light conditions. Red Dot (faster target powder) not so much.
09-15-2012, 8:00 PM
That has to be one of the best of the choke/powder/shot/pattern relationship explainations I've ever read, thank you for taking the time to type it up.
09-15-2012, 10:05 PM
Pattern is a function of choke, mainly, then velocity and wad... at least as I see it.
The choke of the gun is the most controlling factor. Like chokes should shoot like patterns regardless of barrel length, but chokes do vary from maker to maker and from gun to gun so there are no absolutes.
As called out above most 'riot barrels' in the 18 to 22 inches of length category are either a Cylinder or Improved Cylinder choke.... that is no choke at all (Cylinder) and very little (Improved Cylinder). This is due, in part, to these barrels typically being used to fire buck or slug. The Improved Cylinder provides just a small amount of constriction, generally, so as to keep pellet deformation to a minimum while exerting some control on the size of the pattern.
Sporting barrels, shooting bird shot loads through tighter chokes or with choke tubes are a different approach. The function of progressively tighter chokes (Light Modified, Modified, Improved Modified, Full, Extra Full, Turkey) is to allow the shot pattern to hold together at longer range. To echo sargenv above, I've found that I get very similar patterns from 24 inch and 28 inch Mossberg sporting barrels using the same choke tubes in both guns. Point of aim / impact can change with length, as it could be expected to, but the patterns do seem to be consistent when I've tried it.
Higher velocity seems to lengthen the shot string, more so than widen it. Powder selection relative to velocity and weight of payload is a key consideration. I generally shoot loads that are 1 ounce of #8 moving at ~1150 feet per second for clays. I get a consistent pattern within the target ring and right on point of aim with my Remington 1100. This combination of load and gun serves me very well at trap and 5 stand sporting clays. The same payload at 1300 feet per second, which I might use for hunting or shooting handicap trap, shoots to a similar point of aim, but the pattern is somewhat more concentrated which tells me that the shot is stringing out more than it's widening.
How the wad interacts with the choke and how much, if any, it allows pellets to be deformed is, I think, the least mitigating factor, but is a factor none the less. Deformed pellets will absolutely widen a pattern.
09-16-2012, 12:11 AM
I can't see of a reason why you couldn't use a 20-21 inch interchangeable choke shotgun for bird just as well as a 28-30 inch interchangeable choke shotgun.
You can use a 20-21" barrel and put birds on the table. The longer barrel is an advantage as you try to shoot targets at longer ranges, 35-50 yards. Point your finger at an object the size of a bird at say 30 yards, now try to point at the same object with you finger 6" closer your eye. Which is easier and more precise?
Longer also balance the gun better which helps to get the gun to mount easier, a smother swing and follow through.
09-24-2012, 5:20 PM
Longer barrel also doesn't hurt in the sense of recoil dampening..a heavy gun and a light gun, all else equal, the heavy gun will feel like it recoils less.. giving the perception of better control and it will also lessen fatigue over many shots/targets..
I also tend to like a 28" bbl since it gives good weight and a tendency to keep in motion, which aids in follow through.. Lots of beginning shotgunners tend to stop the gun which means they are almost always behind the bird when firing or constantly trying to play "catch up" and letting the target get farther away before firing..
One thing that a lot of people lose out on the "net" is that they buy XYZ brand of cheapie ammo but lose out on some of the knowledge that used to be gained by physically reading books on hunting, target shooting, etc.. I am happy that I was able to read up on ballisitics and the internal stuff for many years before the "net" just listed load data and how we got to that point seemed to get "lost". Occasionally I'll re-read some of my older shotshell loading manuals to remind myself of tidbits I may have forgotten about over the years..
Even if you aren't interested in reloading, I'd suggest picking up some of the manuals put out by Ballistic Products for information purposes and how things like lead, steel, bismuth, and some of the exotic shot materials act/react under different situations.. So far I've loaded lead, Steel, and tungsten/iron.. the latter was expensive but still very effective..
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