Defensive Shotgun Patterning: Deconstructing the one inch per yard myth

Sage advice?

We can’t even begin to count the amount of times we’ve read, been told or heard someone say that shotgun patterns spread about 1″ per yard after exiting the barrel.  The old adage predicts, if a shooter is 10-yards from his target, the pattern will be 10″ and 15″ at 15-yards and so on.  Typically, this discussion is framed around defensive use of the shotgun with a relatively short 18-20″ barrel and some sort of defensive load like the ubiquitous 00 buck.

Having this not match our experience,  we decided to head to the range and see what typical spreads we would encounter.  For this exercise, we used a series of 5-barrels listed below and Winchester Super-X 105-203-098, non-plated buckshot provided by Brownells.  We selected this full power, 1325 fps, 2 3/4″ load because we have found that the tactical and reduced recoil loads on the market pattern tighter then non premium buck and thought this load would provide a better representation of what the typical defensive shotgun owner would encounter.

Winchester unplated buckshot

Winchester unplated buckshot

Test barrels were all 18″ in length and described below:

  1. Rifleshooter.com back bored & lengthened forcing cone barrel (back bored until reamer was flush with muzzle)
  2. Vang Comp Custom Barrel
  3. Remington Factory Improved Cylinder
  4. Remington Factory Cylinder
  5. Rifleshooter.com back bored and forcing cone lengthened 2″ from muzzle
7 Yards (counter clockwise from bottom left) Vang Comp, Rem Cylinder, Back Bored, Back Bored 2" from muzzle, Rem IC

7-Yards (counterclockwise from bottom left) Vang Comp, Rem Cylinder, Back Bored, Back Bored 2″ from muzzle, Rem IC.  Note that none of the guns shot even close to a 7″ pattern at 7-yards.

15 yards: (Clockwise from bottom left) Back bored, Rem Cylinder, Vang Comp, Back Bored 2" from muzzle, Rem Improved Cylinder

15-yards: (clockwise from bottom left) Back bored, Rem Cylinder, Vang Comp, Back Bored 2″ from muzzle, Rem Improved Cylinder.  Note, only the barrel back bored 2″ from the muzzle was 15″ at 15-yards.  The other 4 barrels were significantly tighter.

20 yards: (counter clockwise from bottom left) Rem Cylinder, Vang Comp, Back Bored, Rem Improved Clylinder, Back Bored 2" from muzzle

20-yards: (counterclockwise from bottom left) Rem Cylinder, Vang Comp, Back Bored, Rem Improved Cylinder, Back Bored 2″ from muzzle.  Note, with the exception of the barrel back bored 2″ short of the muzzle, the barrels did not pattern close to 20″ at 20-yards.

 

Results

We measured the extreme spread of each pattern and recorded the results below in inches:

Barrel 7 yards 15 yards 20 yards Avg spread per yard
Back Bored 2 5 ¼ 7 .35”
Vang Comp 1 ¾ 7 7 ¼ .36”
Remington IC 5 10 7/8 11 ½ .58”
Remington Cyl 3 ¼ 9 1/8 12 .60”
Back bored 2” from muzzle 4 ¼ 15 ¾ 19 ¼ .96”

 

The 20-yard pattern size was divided by 20 to estimate the average spread per yard of the pattern in inches.  Results for this calculation ranged from .35″ to .96″. Barrels at each end of this range represented modifications to stock configurations one would normally encounter in the defensive shotgun market.  The results for the two unmodified barrels, the Remington Improved Cylinder and Cylinder, showed an average spread of .58″ and .60″ respectively.

While the barrel we had back bored 2″ short from the muzzle fit the 1″ per yard tale, it should be noted that we intentionally back bored it short as part of our testing protocol from another article.  When examining stock barrels, the spread was approximately half of the anecdotal 1″ per yard spread.

So what does all this mean?

Pattern your gun.  Next time you wonder how your defensive shotgun patterns, take it out and shoot it with your favorite load at different distances.  Normally, we shoot 7, 15 and 20-yards for T and E, but we do shoot buck at shorter and longer ranges on occasion.  If you haven’t done so, do it; and next time you hear someone tell the 1″ per yard myth, make sure you set them straight.

Resources:

For more information on shotgun projects check out our “project guns” page.  For shotgun accessories and ammunition, check out Brownells.