pattern count variability from shot to shot???

[Mild Bill]

How much variability do folks normally find in pattern counts, say for instance if we were to shoot 5 shots of the the same load, cleaning the barrel to the same amount of "clean" you choice on what that is, but the same for each shot,

what would we expect for a range/ variation in shot hits within the 10 inch circle?

[FttFttVroom!]

Provided the pellet counts are the same from shell to shell and you were able to replicate the shooting conditions shot to shot EXACTLY (all very hard to do without the most stringent guidelines and measurements) you still would have to assume at least a small amount of variation.  That's why I'm a follower or the "more is better" school of thought when it comes to how many pellets I can put into the 10" at 40 yds.

Say, for instance, you are using a load that gets you the minimum 100 hits.....wanna hope you can do that EVERY time, regardless of temp, wind, humidity, shooting form/stance, shell quality...etc the list goes on.....
or do you hedge your bets with a load that will throw 200+?

[HuntSource]

I've found it's relatively small for the circumstances you've described here. I just did a quick calculation of three, five-round sessions in the Excel workbook where I keep my shot data. I took the number of pellets in a 10" ring at 40yd and divided it by the estimated number of pellets in the load. Then, I subtracted the highest percentage from the lowest percentage from that session to get an extreme variation. The extreme variations were 4.7%, 5.8%, and 6.9%. I didn't do a standard deviation.

In essence, I don't' see much variation in pattern density found shooting back-to-back shots and cleaning the barrel between each shot. However, I do see significant variations in pattern density with big differences in air density and to a lesser degree wind. I've seen swings of 20-30+% comparing the same load with one shot on a windy day when the air temp is near freezing and the other shot a hot, humid, still day like you get in the dog days of summer.

That's why I scratch my head a bit when some compare a different lots of ammo and opine how much worse one is than the other. Sure, those variations do exist. However, many times it clear that the lots were being compared on different days, even different seasons. The only way to really compare quality there is to shot them back-to-back on the same day.

[Mild Bill]

I do a lot of farm crop trials as part of my job, and so I am familiar with variability, statistics, average etc. 

I was/ am curious as to what we might look at as a reasonable range of expectations.

Very good points brought out by both replies so far.  That weather conditions have a big impact, so we should make comparisons in as similar of weather as we can.

Also in order to be good sportsman we should strive to find and use a combination that errors on the side of making sure we send enough shot into the target zone to make quick and humane harvests of the birds we enjoy hunting so much.

Looks like around a 5 to 6% variation is somewhat typical for all other conditions being as close to constant as possible. according to the results so far.

[HuntSource]

While I keep data logs, I mainly adhere to KISS approach. In short, I only use loads that will yield 100 in the 10" at my desired max range on the worst conditions for patterns I might expect in the field. That's why I go to the bench in late winter on clear, cold, windy days when the humidity is low. It makes a difference. I have a stash of Hevi-13, 12ga, 3", #7s that averages just under 290 @ 40yd when the weather is right, but will only do about 190 when it's bad for patterning. On a percentage basis, I've found it's true with my #6 loads too.

[jasperjet]

huntsource can you elaborate on your set up for the 3 inch 7's

[HuntSource]

huntsource can you elaborate on your set up for the 3 inch 7's

Sure, I have two rigs. Both are Benelli Vincis with Aimpoint T1 Micros. One's a 24" Steadygrip model and the other is a conventional stock with a 28" barrel. The choke of note is a Rhino .660". Patterns between the guns are essentially indistinguishable, but I'm citing patterns out of the SG here. I'm now shooting a Jeb's .665" quite a bit too. It moves a few pellets out of the 10" into the 15". I like it a bit better with the #7s.

[Rapscallion Vermilion]

This is an interesting thread.  I agree with HuntSource on planning for your worst patterns.

I ran some simulated pattern sequences with the tools on this site (fun to play with)
http://www.shotgun-insight.com

For a setup that would average 145 in the 10" circle, here are two example runs of 10 shots each.

137 145 153 148 139 157 131 135 150 148

131 136 134 145 146 141 145 133 158 160

At least for these two sample sequences, about 2 shots out of 10 are about 10% from the mean.   Doing some real long sequences (less than 40), I found as low as 124 and as high as 172.  And this is all for an ideal situation where each shot is identical, other than for the statistics of the pattern.

-Rap