doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Correct patterning of a .410

here are a few 410 pattern boards

my superposed new model skeet, 30 yds, 30" circle, 1/2oz #8


410 ugartechea sidelock, left bbl (extra full) 25 yds, 20" circle, 1/2 oz #9

410 ugartechea sidelock, left bbl (extra full) 25 yds, 20" circle, 1/2 oz #7 1/2

410 ugartechea sidelock, rt bbl (mod) 25 yds, 20" circle, 1/2 oz #8

sxsman1 - there is no such thing as "correct patterning." Barrel marks for choke refer to constriction and do not exactly refer to pattern performance. Patterns show the result of a given load in a given gun for a given shot; if you really want to know how a given load performs in a given gun, you will need to average not less than five patterns and ten is better. Counting holes in a circle of some diameter at some distance is a very poor surigate for statistical analysis of the shot distribution, target vital area, and distance of the target. A very pragmatic approach is to first determine the vital area of your target and required number of hits: clays are about 5 sq inches for edge presentation, 10 sq in for quartering, and 15 sq in for face, birds can be approximated by 1 sq inch per oz of weight. Make a circular disc of the correct area (5 sq in = 2 5/8" dia, 10 sq in = 3 9/16" dia, and 15 sq in = 4 3/8" dia). Using the shot size required for penetration of the target and shooting at the most likely distance, use the proper disc to assess the maximum effective diameter of the pattern where the lethal number of hits is likely to fall within the disc. Also, look for holes within the pattern. Shoot the next pattern at five additional yards and compare effective pattern diameters; is the effective diameter of the pattern blooming or withering? Do it agin for another 5 yards out. As you get further away, the pattern effective diameter will first bloom to some maximum and then wither. The effective diameter is still lethal, but the allowable aiming error goes down as the distance increases and the pattern effective diameter withers. Choke effect delays bloom for up to 10 yards or so. Using Cyl as a baseline, each increasing choke effect will have a more distant point where the withering Cyl effective pattern diameter and blooming choked effective pattern diameter cross over. From that point on, the choked pattern will give a larger aiming error allowance. Note that the center of a Cyl pattern will remain effective to some pretty remarkable distances. However, you will approach rifle shot aiming error allowances.

When you reach the distance where you can't be sure of staying within the aiming error allowance, you must increase choke effect, increase shot count, or set a target range limit for yourself. If you are already at full choke, then you must increase the shot count. If the gun is at maximum shot charge and minimum shot size for the target at that range, then you must increase guage.

The above is not "correct," but it will really tell you something for your work.

sxsman1 - OK, you have some interesting patterns to work with. Here is a method that will help you learn something beyond rules of thumb. Pick a target and determine the vital area and the number of hits needed. Find the center of each pattern, mark it , and divide the pattern into eight pie wedges. Make an hole of diameter equal to the vital area in a card. Slide the hole down each of the eight pie wedges (outside in) and mark the center of the hole when you first have a count of needed hits. Average the measurement from the pattern center to each of the eight marked hole centers. this number will give you a good approximation of the effective diameter of the pattern. Repeat this procedure at increasing distance and watch the effective diameter bloom and then wither.

The next question becomes how good a shot are you? Well, you now have a basis for deciding maximum range of shooting.

Those are some great patterns Devrep.
Thank you Rocketman, what I was trying to accomplish, was finding what the choke was by the pattern it produced.
If you had a 12-gauge gun and it put 70% of a shot charge in a 30" circle at 40 yards you would say it had a full choke.
I was trying to find the correct distance and pattern size to find the same thing about a .410.
The method you describe would tell much more about the shooting performance of a gun for sure.
Pete

Dealing with % of shot launched landing within a circle of some diameter at some distance, would you expect an difference among the gauges? Far as I know, patterns are the same size for the same choke effect reguardless of the size hole they come out of. So, would you not expect the % of pellets within a circle at distance to be constant for all gauges for equal choke effect? Obviously, the utility of 70% of a 1/2 oz load (say 70% of 205 = 144 pellets for #8's) is quite different than 70% of a 1 ounce load (say 70% of 410 = 288 pellets of #8's). Even though both have full choke performance of choke effect, they don't have the same capability.

Am I missing something in this question? Trying to help, anyway.

Rocketman
What I think your missing is the tall column of shot being exposed to the abrasive action of the barrel walls as it travels down the barrel, leaving much more of the shot scuffed and flattened on one side or the other thereby effecting its aerodynamics.
Steve

I thought a 1/2 oz .410 was well contained within a shot cup. Not so? If we use your explaination, Rockdoc, are we not actually saying that such shot loads are simply incapable of full choke performance, no matter the choke constriction?

Rocketman, I didn't know what chokes I had in the gun.
Barrels are marked O&C (open and choke) the pattern test was to determine what the chokes actually were.
I could have measured the chokes if I had a bore gauge, but this way I know for sure. (The chokes are, cylinder and full, or skeet in and skeet out.)
Pete

sxsman1 - barring some other explaination, you can take any of the usual combinations of distance/cicle size/% of pellet count and pattern your .410 with it. You just have fewer pellets to count. But, I'm open to other explainations. I just don't see that there is a special circle size/distance for .410's. 30" circle at 40 yards: 70% = Full, 50% = Mod, 40% = IC, and 30% = Cyl/Skt #1, all ranges +/- 5% or so.

Pete;
I posted here on one ocasion some time back that a .410 was patterened in a 20" circle @ 25 yds & was promptly told I knew not whereof I spoke, that a 30" circle was proper, so didn't mention it this time. As you have found patterening in a 30" circle at 25 yds is useless for designating patterns. A 20" circle @ 25yds is proportionate to a 32" circle @ 40 yds, so gives a slight advantage to the .410. Especially prior to the introduction of shot cups etc, it needed all the advantage it could get, but to expect similar percentages in the same 30" circle 15yds closer in is simply out of the question. I suspect the 30" @ 25yds is special patterening for skeet guns, but this should be equally applicable to the "Gauges" as well as to the .410.