Cutting Shotgun Barrels

[Mortblanc]

[CharlesHarris]

"The Truth About Buckshot" - American Rifleman Magazine, October, 1982

This article summarized results from firing approximately 500 patterns with Remington "Express" 12-ga. buffered buckshot loads, without shot wrapper from the Model 870 pump shotgun. Firings were conducted by myself, Robert N. Sears and Supervisory Special Agent William F. Vanderpool of the FBI Firearms Unit, at the FBI Academy, Quantico, VA, using test materials provided by the Remington Arms Co.

The article as published was oriented towards deer hunting, rather than home defense, for political reasons. Ten patterns each were fired at 25 and 40 yards, from cylinder bore, improved cylinder (1/4 choke), modified (1/2 choke) and full choked barrels. Cylinder and IC barrels were standard Police and Military Guard and Riot Gun barrels 20 inches long. Modified and full choked barrels were standard sporting barrels of 26" and 28", respectively.

Experimental modified and full choked 20 inch police and military barrels were also tested also, although the results with those were not included in the published article, because of the desire to maintain a "sporting" focus in the published summary. Other than slight, insignificant drop in velocity, results with the shorter, more tightly choked barrels was not materially different from common sporting-length barrels.

The same Remington 870 Wingmaster action was fired repeatedly interchanging the four different barrels.

Patterns were fired against a 48" square plate of AR500 steel 1cm thick, photographed and the oiled pigment rebrushed between shots. Pellet hits were plotted in relation to a clear plastic overlay having a 30" outer circle, positioned after each shot to to contain the greatest number of pellets, the clear patterning template having a 21.2" diameter inner circle, the 30" circle and 21.2 inner ring then being quartered by strung piano wires into eight equal-area fields. The 21.2" inner circle approximates the major torso area of a US Army "E" or FBI “Q” silhouette. Pellets striking inside the inner ring have a greater probability of striking vital organs, whereas those in the fringes outside the inner circle, but still within the 30" outer ring are more likely to cause non-life threatening wounds to the extremities.

A 100% pattern in which all pellets strike within the 30" ring may be ineffective unless the inner circle of the pattern surrounding the aiming point contains three or more pellet hits. The combination of soft buckshot, unbuffered loads and tight chokes increases pellet deformation which results in "doughnut" shaped patterns having weak centers. WW2, Korean and Vietnam-era Army experience indicates that fewer than three pellet hits of 00 buckshot do not produce “instant incapacitation,” unless one or more of those pellets strike vital areas of the head, neck, or chest. With random distribution of as few as three pellets in the 21.2" circle, hitting a vital spot depends on luck and random variations of chance. More hits are better!

A single 00 pellet (.33 inch diameter, weighing 60 grains) at 30 yards has a kinetic energy of about 120 ft.-lbs. Three pellet hits therefore produce 360 ft.-lbs., which approximates the kinetic energy of a single round of .45 cal. Ball ammunition fired from the M1911 service pistol. More than three pellet hits, when their combined effect is distributed over the body, produce greater shock to the nervous and vascular systems and vital organs struck than a single projectile hit having the same kinetic energy.
For law enforcement and military purposes 4 or more hits is considered "adequate" performance, producing a high probability of instant incapacitation. Any shotgun-ammo combination reliably producing 5 hits with 00 buck at realistic combat ranges from 25 to 40 yards is said to provide "good" performance. More than 5 hits is considered "excellent."

The standard Remington Express 9-pellet buffered load of 00 buck with no shot sleeve, fired from an 870 cylinder bore 20" riot gun averages 8.9 hits in the 30" circle and 7.1 in the 21.2" inner ring at 25 yards. This falls off to 7.5 and 3.3 hits at 40 yards.

Repeating the test using a 20-inch improved cylinder barrel, all nine pellets strike in the 30" circle and 8.6 in the 21.2" inner ring at 25 yards. Repeating the test again, at 40 yards, the IC barrel produced 8.0 and 4.4 hits, respectively. For civilian home defense purposes the 20" improved cylinder "Brushmaster" or "Deer" barrels with rifle sights give dependable performance.

For combat use the 12-pellet "short-magnum" load of 00 buck is a better choice in 2-3/4" chambered guns, if you can tolerate additional recoil. Even though the pattern percentages produced are lower, you can expect one additional pellet hit inside the inner ring.

If you wish to maximize pellet count to optimize pattern density, while still having adequate penetration to defeat interior walls or auto glass, the 20-pellet "short magnum" load of No.1 buck is the best choice. No.1 buckshot weigh 40 grains each, producing 103 ft.-lbs. at the muzzle, 69 ft.-lbs. at 30 yards and 61-ft.-lbs. at 40 yards. It takes twice as many pellet hits with No.1 to produce the same kinetic energy as half as many 00, so 6 pellet hits are marginal, 8 hit "adequate" and ten or more "good" performance.

No. 4 buck weigh only 20.7 grains each, and have 81 ft. lbs. of energy per pellet at the muzzle, 45 ft. lbs. at 30 yards and 41 ft. lbs. at 40 yards. Experience has shown that despite excellent pattern density, their penetration is inadequate to reach vital organs if major bones are hit, such as a sternum, rib or defensively positioned arm. The M257 buckshot cartridge with 27 pellets of No.4 is specified only for r interior guard and corrections system use where collateral damage to bystanders must be minimized.

As a general rule, softv lead, unbuffered buckshot spread about 1 inch per 1 yard of distance beyond the muzzle, when fired from a short-barreled cylinder bore police riot gun. Hardened shot assembled in buffered loads containing granulated polyethylene “grex” do better than that. Typical 15-yard patterns on a military silhouette using the Federal Pattern Control 00 buck LE load from a 20" ¼ choke or Improved Cylinder barrel are about 8" in diameter.

[Midnitemo]

Does length of barrel play much of a part or is it all in the choking? I ask because 24 inch is the minimum permitted barrel length here on a shotgun certificate....have 24 inch cylinder bore pump a 27.25 side by side 1/4 and 1/2 choke and 28 inch over & under 1/4 and 1/2.

[Mortblanc]

The gun that fired that 95% pattern with 8 pellets in the center circle was my 20" turkey barrel using a standard 12ga Mossberg full choke tube. I was using that barrel because it has a scope and makes aiming more precise for this work.

I showed the results of those two tubes due to the general presence of full chokes and its drastic comparison to cylinder bore.

I was also shooting a Remington 870 having a 28" barrel with screw in choke tubes and did not see any difference in pattern density when compared to my 20" barrel with equal choke rating. I do not have a full set of tubes for the Remington so all the math I did was using the Mossberg, for which I have an entire set of tubes from cylinder to xtra-full.

I also shot 1/4 and 1/2 chokes and the practical difference is more dependent on weather than choke rating. Only a 5% difference in pattern count on the industry standard. On one target I got a tighter pattern with the IC choke than the 1/2 choke gave me. I shot the modified just as a puff of wind hit and got a scattered pattern.

I must say that screw in choke tubes are the best of all possible worlds. If I am not getting good performance from the choke I can cure the problem with a new $20 choke tube rather than a new gun or expensive barrel work.

After reading the material GH posted I look at the results of my test and consider the options. My #4 buck is .24 caliber and 40 grains traveling at 1275 fps. That is the same as a .22 long rifle slug and people will argue that a .22 is "adequate" all day long. Energy is the same, penetration is the same. Only one difference.

Just imagine 16 of them hitting you from head to crouch, at the same instant?

[Midnitemo]

no 4 buck is not readily available of the shelf here but I do have a couple of boxes of AAA in the cabinet which I have used for fox control in the past... just thinking about getting a load that covers all bases , a general purpose load of sorts , thinking AAA or BB perhaps....00 buck is a great load but overkill in some circumstances with a fair chance of not connecting at all with a smaller target....thoughts?......have stocked up on 30 and 32 gram no5 and no6 as my hunting cartridge.....I guess I'm looking for a cartridge with the widest application possible.

[Mortblanc]

Think about what you are saying Mo.

Yes 00 is overkill in some circumstances and there might be a chance of missing small game with it.

Do not use it for small game!

00 buck is excellent for its intended application, which is larger targets. That is why they call it BUCKSHOT !

Your box of AAA is an excellent compromise for varmint control. it is slightly bigger than BB which is what we used over here on coyotes. You have 45 pellets in a one ounce load and my #4B has 18.

I chose the #4 buckshot as a load that does cover all bases for medium and big game and defense. My main concern was to have a shot size that offered enough pellets to make the choke obviously effective. I also found a #4 buckshot mold, which casts 18 shot at a time, on sale.

However, selection of shot size is part of versatility of the shotgun. One should have a few rounds of 00 buck in the cabinet, just in case, as well as some AAA along with the normal #5, #7 1/2 and #8 for normal use.

The targets I show are for comparison of CHOKE and it's influence on the effectiveness of the shot once it arrives at the target.

Since the weather just made testing possible this week I have not had time to do much with the larger buckshot sizes. Being able to cast my own buckshot for reloading has made testing much cheaper. I can reload the buckshot loads cheaper than my standard game loads and test all I please.

I have learned a great deal I had not learned from 55 years of hunting and field shooting. Having a set of choke tubes that all fit the same barrel eliminates all of the variables I had ever encountered in my testing. I know that the test results are the effect of the choke constriction and not the individual barrel.

[Midnitemo]

I have stocked up on 00 buck /no5 and no6 shot for ground game am a bit short on clay rounds(next purchase) which I would use for flighting game , when I do buy I tend to buy 7.5's as I prefer the extra kinetic energy rather than more pellets in the air....I'm thinking of a round that can do most things competently rather than having a mix in my bandolier/gun bag...specifically I'm thinking bug out bag,curently a box 00 and the rest 2 inch 26gram no6 shot(low weight/cube)

[Mortblanc]

One of the things I recognized immediately upon viewing the targets was that any amount of choke in the barrel vastly improved the performance of the larger shot size!

I only showed the full choke and cylinder bores, but even the 1/4 choke barrel made a great improvement on pattern performance over the open choke.

I also have now tested 5 different open choke barrels and have not had more than 35% pattern from even the best. 4 of the 5 gave 25% pattern or less. That means that in a one ounce load of #8 shot 300 of the pellets are scattered to the winds and only 100 pellets land anywhere near where the bead is pointed.

Keep your chokes boys! They are effective controls on the efficiency of the gun you are shooting. Much more important that barrel length or rounds in a magazine.

In a SHTF situation if I look across an open space and see a man with a sawed off shotgun I am going to assume that I am relatively safe at 70 yards and not worry at 100 yards. If that same man has a long barreled gun that I believe might have a full choke I am not exposing myself even at the 100 yard range.

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There is not going to be an all around do everything shotgun round. There is no sense in even going there.

[Steve]

[CharlesHarris]

In modern hammer forged shotgun barrels, the choke is formed within the last 5cm or so at the muzzle, so if you shorten the barrel by cutting off more than that amount, it is safe to presume that all of the original choke is gone, leaving you with a plain cylinder bore.

If you measure the interior constriction behind the muzzle with ball gages of various diameters, you can determine where the choke taper begins, and cut off less of the muzzle to remove some of the choke, but not all of it.