Effective Patterning

Oh Technoid can you shine some light my way re a week ends patterning.

I have used up two rolls of table party roll paper patterning various shells and Browning chokes, then started over again with Briley chokes.

I bought a Browning special trap 12 Gauge a few months ago and began to pattern it with the factory chokes, bad move, wasted lots of time and shells, OK I suppose if your happy with 71% maximum patterns at 40 yards with full. The Browning XFull turkey choke should be renamed the DODO because I don’t think it exists so hard to get hold of.

I got good patterns at 30 yards with the factory imp/mod tube but that top tube was a problem.

What to do. I decided to buy some Briley’s, (smart move) and start all over again. I got XFull / Full / LFull / IMod / Mod / LMod, patterning this lot I found the cartridge that shot outstandingly in this gun, is the Lyalvale Express 7.5 28 Gram load lead , (we shoot lead down under not steel).

I suppose that’s why the factory chokes are a bit loose. English cartridge. I have shot just about everything I could get here through this gun and consider that the best loads on paper is the above (preferred) and Ennio Matterelli 7.5 28 Gram lead (but kicks twice as hard as the Express & twice as dirty). Italian Cartridge.

Our competition over here allows maximum 28 Gram loads for trap MMMMM.

Briley choke conclusions.

Top Barrel @ 40 Yards. After screwing in the XFull I ended up getting 84% patterns with both loads (other loads culled) but blown high right POI (point of impact shifted 8 inches) I think it was trying to tell me, “too tight”.

Screwing in the Full I got again 84% patterns but this time very even and dead on POI. The LFull was held in reserve.

Bottom barrel @ 30 Yards I inserted a L/Mod into the barrel and got 82% from both loads. They both looked good but the Express seemed a little better positioned, POI dead on POA (point of Aim).

I hesitated to go any further, because the daylight was growing very dim by this stage so I rolled up all my paper and wired the boot closed and headed home to query the pattern master on Tuesday.

My questions are. What is the magical optimum % figure in consideration of a loads print on the old fashioned 30″ circle at 30 Yards and 40 yards given the above scenario.

Is 84% at 40 Yards & 82% at 30 Yards too tight / loose or MMMM. I can tighten the bottom up some more but the top looks really good.

Can you impart thy wisdom unto the bidding I have done.

Has Glenn very nearly got it made or have I tightened things up maybe a bit too much. I feel confidence building, looking possibly for a junior technoid patterning merit badge.

Many thanks.


Dear Glen,

Sorry not to have replied sooner, but I was down in Argentina shooting duck. How strange to see the Southern Cross and not the Big Dipper in the pre-dawn sky.

I use a series of Gaussian distributions to predict maximum effective patterns at any given range. I use an average count of a 3 pellet strike on a 7 square inch surface (edge on target, not “trap” view where it is tipped up slightly). An average of 3 pellets hitting is mathematically the same of an 85% chance of a two pellet strike. This seemed to me to be a pretty good outer limit.

Rest assured that none of my formulae/programs/better ideas are original. I have borrowed liberally from Warren Johnson (“Choke Chooser” slide care), Ed Lowrey (Winchester ballistician), as well as Brister, Giblin, Brindle, Thomas and everyone else who knows more about this stuff than I do (and that is most of them).

Using these criteria for a 28 gram load of #7.5s, you will maximize your effective pattern size if you can achieve a 95% pattern in a 30″ circle at the distance at which you are taking the target, but it 30, 40 or 50 yards. You can go as low as 80% and still get virtually the same performance. Your effective pattern will be just a bit over 18″ with anything from an 80% to a 99% pattern, but it falls off either side of that.

Bottom line: to maximize your pattern on a standard edge on clay at any distance, you need at least 80% of your pattern in a 30″ circle at that distance. More, up to 95%, is better, but not much.

As soon as you change the angle of the target to show more area, the numbers change radically, but I always like to pattern on a worst case scenario.

Best regards,

Bruce Buck
Shotgun Report’s Technoid
(Often in error, never in doubt.)

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