View Full Version : Shotgun pattern???!!!!

January 29, 2001, 05:36 PM
Could anyone here tell me how to check the pattern on a shotgun? I have two, both purportedly for home defense, 20" bbls, bead sights.

I realize I must fill this inexcusable knowledge void if these lovely pieces are to do me any good in time of need.

Thanks in advance to all who will help this poor ignoramus...

Al Thompson
January 29, 2001, 05:59 PM
Simply put, the pattern of a shotgun is the spread of the pellets. Usually this is expressed in terms of the diameter.

The object is to discern the extreme "footprint" of the shot at a given range. The actual measurement is from the outermost pellet strikes - across the widest part. This gives you a working idea of what to expect at a given range.

Pellet count in a target is also important if your patterning at longer ranges. I.E., if the 00 buck round holds 9 pellets and your getting 7 on the target (humaniod), two pellets are unaccounted for..

For HD, Dave McC has the best plan - measure your extreme engagement distance, add a yard for GP, test your chosen load/gun at that distance. Also check your load at closer distances as the rate of spread is pretty marginal until a few yards out.

Many variables here. Had a pal with a load in his SG that would hold really tight groups out to 35 yards. Cylinder bore. Once he exausted that box of shells, he was never able to duplicate that performance. He shot a bunch of buckshot trying.

Lots of threads on this topic too. Try the search button!


January 29, 2001, 06:13 PM
I noticed Dave using the abbreviation "GP" in that thread, and didn't think to ask what he meant. So now I will. What does "GP" mean?


Al Thompson
January 29, 2001, 07:38 PM
General Purpose (s)



January 29, 2001, 08:07 PM
I've been living a pipe dream for the last ten years thinking I was protecting myself...what is the "extreme engagement distance...?"

and thanks...

January 29, 2001, 11:03 PM
Unless you live in a VERY large home or are under the threat of possible attack by the critters from the Alien movies, I think you're probably fretting a wee bit too actively. ;)

I'm not saying you shouldn't follow Dave McC's ideas, I'm just saying that if you had a home invasion robbery tonight, without reading his post, your SGs would likely work just fine, thankyouverymuch. ;)

'Maximum engagement distance' would be the max range at which you would be trying to pop an intruder in your happy home. Figure out what your defensive plan would be under various scenarios, figure out what the maximum possible range from you to the BG would be...add a yard. Thats your max engagement distance. Now do a search on 'patterning' and test out your SGs with various loads at that distance. Whichever load gives you the tightest pattern is the one you want.


If you are like 99.9999999% of the people out there, your max engagement distance under a home defense scenario will be really really close...so close that the shot doesn't spread much. Which means that you can sleep well knowing that whatever load is in your tube will work perfectly well. This is ballistics, not rocket science. ;)


January 29, 2001, 11:43 PM
K80's sure fire method of patterning your gun!

(read with a grain of salt:))

Go to a paper supply house and buy a roll of kraft paper, preferably 3' wide. Butcher paper or other similar paper will work also.

Gather up the following items; A box cutter knife with fresh blades, a piece of 2 X 4 wood at least 3 ft long, magic marker, or those large stick on target posters sold in gun shops that are round and orange, stapler or tape, wood for a frame, old pallets will do, pencil and 18" of string, Out of the way area where you can shoot without alerting the local constabulary.

Go out to your spot. Build a wood frame or metal frame that will allow you to tape or staple a 3 x 3 foot piece of the paper. Use the box cutter and 2 x 4 to cut off a 3' long piece of the paper. Tape or staple the paper to the frame. Place the orange paster in the middle of the paper, or use the magic marker to draw a target in the center. The target pasters are removable and can be used several times before they are shot up. Use 7 1/2 birdshot for the test.

Step back to a distance that approximates the distance you expect to engage the perp. Load up, raise your SG and fire as quickly as you can after acquiring the target.

Unload, go to the paper, check for the center of the pattern if possible. You may be able to draw a circle around the entire pattern with the pencil and string. Do this several times. This will help you determine the center of your pattern and if your gun shoots where it is aimed. You may have to adjust the distance if you fill up the entire 3 X3 ft of paper. If you do move closer and shoot again.

Shooting at varied distances will tell you what the patterns are at given distances, keep a record and write the distance on each sheet for your records. The size of the pattern may surprise you, and it is very revealing to non shotgunners who have misconceptions about patterns.

Some people draw a 30" circle around the pattern and count the pellets inside and out, there are charts available to tell you what choke should produce which percentage at given distances. More important, this will tell you if your gun shoots where it is aimed.

Some ranges have a pattern board, usually a metal plate that is witewashed and which will display the shot pattern. This is a PITA to determing shot percentages, but is good for checking aiming point. With the paper you have a permanent record, or extra lining for the bottom of the parrot cage:)

Remember, this is my method, take it for what it is worth, but it has revealed many things to me about my shotguns.

Geoff Ross

Dave McC
January 30, 2001, 07:58 AM
Patterning serves two purposes, both crucial to proper performance.

First,it tells us the spread of the pattern at a given distance with a given load. The others have pretty much covered this well, and it sounds like Geoff spends time teaching newbies. Good explanation, Geoff, and kudoes.

Second, it tells us if the weapon/load/shooter combo is shooting where it's looking. Many do not at first try. Patterning is the empirical check, and the way to rectify any glitches.

"Serious" shotguns are aimed, sometimes aimed very fast, but aimed nonetheless.Patterning, and then correcting by changing stock fit, moving sights, etc, means one can put the payload where it counts the most.

And knowing that the weapon will hit where it's supposed to if we do OUR part of the job adds that confidence factor.

A coupla minor tips and so on...

First,Geoff mentions an 18" piece of string. I prefer a 15" piece, giving a 30" circle instead of a 36". The larger is good for clay games, but I like a deeper density when the target is animate, and possibly inimical.If lots of shot are landing outside that 30" circle, go to a tighter tube or move closer and repeat.

Second, you've taken your first shot at the patterning target and most of your shot landed higher than the aiming point, and a bit left. IOW, the center of the pattern is high/left of the POA.Repeat shots show the same.

This tells you what adjustments need to be made, if any.

And, considering the extreme short ranges we're talking about here, it would take a lot of deviation to make a real difference. Still, one should know where the shot will hit.

So, let's say we've got a nice tight 8-10" pattern at the longestshotposs +3 feet distance, centered just over the aiming point. Huzzah!! But are we done?

Nope, now back off to say, 25 yards and note just how wide the pattern is and whether the same sight pic means the same POI( Point Of Impact). If so, and it's probably going to be close, now you're done and have some idea of the pattern spread from YOUR gun/load combo.

Hope this helps...

January 30, 2001, 08:42 AM
Lets see...Hmmm 18 X2 =36, 15X2 =30. Guess I should learn to add and multiply. A 36" circle on a 3 X 3' paper would be kind of difficult. Yep 15" is correct this will give you a 30" circle and is the standard most gunwriters use in measuring patterns!

Now if I could only count the shot holes without someone interrupting me! 356...357 what... the phone is ringing, grrrr.

An hour later...259, 260, 261. oh drat, the doorbell is ringing.

Next day, 324, 325, ... what...oh the garbge has to be put out, grumble grumble.

A week later, 297, 298, 299 (I need new glasses, and some aspirin)

a 30" circle is indeed the correct measurement, so a 15" string would work. thats what I get for counting all those shot holes!

Geoff Ross

January 30, 2001, 08:43 AM
OOps... this is really starting to get to me.:)
Double post again.

[Edited by K80Geoff on 01-30-2001 at 12:59 PM]

Dave McC
January 30, 2001, 03:41 PM
Geoff, it's starting to sound like work, isn't it(G)?...

Counting holes never was my idea of fun. I kinda split things up into quadrants and look to see if one seems to have many more/less holes than the others. But then again, I don't fret about making 100 straight.

Dave R
January 30, 2001, 05:03 PM
Practical example of the virtues of patterning. I have a Mossy 835. Which choke tube gives me best performance with buckshot? IC/Modified/Full?

I went the range and shot 24" circles (biggest I could hang on their hanger) at 25 yards. That's the range length, and probably farthest I would shoot buckshot in a self-defense setting.

Result? The Modified choke gave tighter patterns than either IC or full. So that's what stays in my gun. YMMV.

Dave McC
January 31, 2001, 08:08 AM
Exactly, Dave. Now you KNOW, and can proceed accordingly.

" The more we know about the situation, the better chances of winning"-OSS Founder Wm Donovan....