12 v 20 pattern

[ammo.crafter]

Does a modified choke from a 12 ga give the same pattern and desity as a modified choke in a 20ga?

Or would a modified 12ga equal the pattern of a cylinder bore in a 20ga?

Assume, of course the same weight load and shot size and velocity.

 

[Bones]

If I remember right, the chokes are measured by percentage of shot inside a 30" circle. If I right, 1 1/8 oz [same size] of shot form ether a 12 or 20 will be the same.

 

[Tombstonejim]

Well I am going to say tht you can not make those kind assumptions. Every gun patterns different. Here are three patterns I did last friday. the Benelli is a 20ga super sport and the citori is a 12 ga. Notice the Benelli patterns much tighter than the citori. both with IC choke.

 

[oneounceload]

The same choke will deliver the same pattern (theoretically). Mod is Mod; however, since bore diameters and loads are different, density might be different, but the spread should be the same

 

[mwar410]

I think everything patterns differently. There is too many variances in loads to have the densities and patterns the same. I shoot a briley tubed gun, you would almost have to assume that the tubes and chokes are about as matched as you can get. The 28 always seems to have better density than the 20.

 

[darkgael]

pattern

This is an idea that was on my mind recently. Theoretically, patterns fired from different gauge guns will open at the same rate, about one inch per yard for a FC and about two inches per yard for a Cyl. choke.
But....I was wondering....if I shoot a one ounce load from a Cyl. choked 12 ga, the shot emerges from a barrel that is nominally .730" (.715"?). Fire an ounce load through a Cyl choked 20 ga. and that one ounce of shot emerges from a barrel that is .620" in diameter, that is tighter than a Turkey choke on a 12 gauge. Wouldn't that affect the rate that the one ounce opened?

 

[ammo.crafter]

.

That's what I was thinking. Same choke on a 12 cannot deliver the same density of a 20. The barrel of the 20 is narrower than the 12.
So, is there a way to find what choke in a 12 and a 20 that delivers the same pattern?

 

[zippy13]

Obviously, it you have two different loads like a 7/8-oz 20-ga and a 1 1/8-oz 12-ga they both can't shoot the same size shot with the same density at the same diameter circle at the same yardage.

Let's use #9 shot in an example: the 12-ga load will have approximately 654 individual pellets and about 512 for the 20-ga. Let's assume all of the 12-ga pellets are uniformly distributed in a 30-in circle. With an area of about 707 sq.in. that gives a density of about .925 pellets/sq.in. If the 20-ga uniformly distributes its pellets in the same circle, the density will be .724 pellets/sq.in. If you want want the same density as the 12-ga, then the 20-ga circle needs to be reduced to 474 sq.in., or about 25-inches. If you're using a .410-bore with 292 pellets, then for a .952 pellets/sq.in. density, the circle reduces to 278 sq.in., or about 19-inches.

Competitive Skeet shooters who are familiar with shooting #9 shot in 4-guns are quite aware that a .410's "sweet-spot" is about 2/3 that of a 12-ga. and the numbers seem to support them.

Here's a chart of Briley's choke sizes:

[SIZE=-2]Graphic credit: Briley.com
[/SIZE]

 

[oneounceload]

This is an idea that was on my mind recently. Theoretically, patterns fired from different gauge guns will open at the same rate, about one inch per yard for a FC and about two inches per yard for a Cyl. choke.
But....I was wondering....if I shoot a one ounce load from a Cyl. choked 12 ga, the shot emerges from a barrel that is nominally .730" (.715"?). Fire an ounce load through a Cyl choked 20 ga. and that one ounce of shot emerges from a barrel that is .620" in diameter, that is tighter than a Turkey choke on a 12 gauge. Wouldn't that affect the rate that the one ounce opened?

What you'll get is a longer shot string from the 20. "Ideal" loads for each - 3/4 in 28, 7/8 in 20, 1 in 16 and 1-1/8 in 12 should all have the same pattern and shot string when fired through identical chokes. The difference will be the density of the pattern, which is why you see folks "choking up" with smaller gauges at longer distances. What a 12 does at a certain distance with a certain load and choke might require you go one choke tighter with a 20 or 28 to achieve the same density, albeit in a smaller pattern.

The pattern board, while not perfect, can give a decent 2-D view of what is happening.

 

[BigJimP]

There are subtle differences - ( that competition shooters can fuss over - and we argue about this stuff at my club all the time / but in general) ...:

... a 1oz load from a 12ga and a 20ga will give you identical patterns.

....if you choosed to shoot 7/8 oz loads from a 12ga and a 20ga - they are basically the same pattern as well....

experienced competiton shooters - get into all kinds of discussions about hard shot, reclaimed shot, different wads, how many times you reload a hull, different powders, different primers ...shot string length ...what is the perfect patterning load from a 12ga ( 1 oz, 7/8 oz, 1 1/8oz ...) ....and how all that affects patterns ...( and I love these discussions ) ...but we also bore a lot of guys that were just asking "simple questions" ....

 

[zippy13]

…but we also bore a lot of guys that were just asking "simple questions" ….

Amen!
Many the newbie has unwittingly opened Pandora's Box with a seemingly simple question at this forum.

 

[BigJimP]

He's probably a reloader ( with his name ...) so we'll see - he may really want a technical answer ??

I usually assume guys want the "real answer" --- but when their eyes glaze over ...I know I went too far ....and I know the look / because my wife has the same look ...when I discuss a detail on a gun with her. ( she just asks what I'm working on to be nice / and didn't really want a long answer ...let alone why ...)

 

[44 AMP]

Density? not certain what you mean.

Chokes come down to us from the ages, from the days of lead shot, card/fiber wads, paper hulls and no plastic shot cups.

A certain choke was whatever constiction it took to achieve a certain percentage of pellets in a 30inch circle at 40 yds. I don't recall the numbers, except for 12ga, full choke meant 70% in the circle.

My Grandfather's rule for checking a full choke gun (in the shop) was to see if a dime would balance in the muzzle. Full choke 12ga, made before modern ammo, it will. New made gun today, the dime will fall through.

While you get results from the pattern board, when comparing different gauges, they are slightly misleading. This is because the board catches all the shot, and not just the fraction of the pattern that a bird enounters when it intersects the shot string.

While you can shoot the same weight of shot in 12 & 20, the amount of pellets on the plane of the bird (at the instant of impact) is less, due to the smaller gun's longer shot string.

 

[zippy13]

Ideally, we would be patterning in 3-D and would be able to define the effective shot string with some meaningful method. Until then, we're pretty much stuck with the old "how many pellets in the pocket" based on a 2-D paper pattern and knowing that we're generally ignorant of the specific shot string dynamics. An experienced comp shooter can often tell a lot more by how the targets break than by how the paper patterns.