doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Sherman Bell's pressure testing

This has been referenced many times, so I found the original for posterity. Sorry about the format

Sherman Bell�s pressure testing published in The Double Gun Journal Summer 2002 "Finding Out for Myself, Part VI, Smokeless vs Black", p.19, and summarized in Volume 17: Issue 4, Winter 2006, p. 39


1 1/4 oz. 3 3/4 dram GOEX FFFg Black Powder at 1240 fps and equivalent load Blue Dot
.........................1 inch.................6 inches...............12 inches
BP.......................5900 psi...............4100....................2100
Blue Dot................6000....................4300....................2300

1 1/2 oz. at 1236 fps Blue Dot (weight not stated)
.........................10,000.................4,400...................2000


And the oft cited DuPont mid-1930s pressure curve

For the record: I also am a disciple of the "can't 'splain it but know when I feel it", phase of the moon, voodoo junk science school of shotshell ballistics; possibly related to self treatment of my hopeless flinch with this stuff

So Drew, I hope you can help clarify this. Since pressure = Force / Area, the longer the area along the shotgun barrel that the propellant is dispersed then the lesser the calculated pressure, such as with a slower burning propellant? So Pressure = Mass x Acceleration / Area. So, given the same velocity and payload and since force is the only parameter which relates to recoil, a lower pressure shell really doesen't actually have lesser recoil than a high pressure shell; it only has a lesser perceived recoil because of the character of the 'kick'. Is this correct in your opinion, and does this make any sense? I'm trying to figure out why pressure has nothing to do with recoil. Thanks.

With all the mumbo jumbo from the other post aside, felt recoil to one person might not be the same for the next person shooting the same load, same gun, etc.

It be what it be.

From what I've read and understand a slow burning powder takes longer to reach peak pressure so " felt " recoil will be less. The formula for recoil is : [BwMw+4700Pw}squared/ 64.348Gw
Gw= gun weight in pounds
Bw= weight of ejecta [ shot and wad ] in pounds
Pw= powder weight in pounds
Mv= muzzle velocit
No where is pressure involved. Pressure comes from the burning gas trying to expand against the weight of the wad and shot and the crimp holding it back. Hope this helps - Paul

JWD - yes. Because the shooter is holding the gun, he becomes part of the equation. His weight, build, and height will make a difference to the resistance of the gun going rearward. My small wife looks like a " bobble head " and claims she doesn't feel the recoil. I'm 6' 4" and weigh 235 and do.

In rifles the bullet is touching the rifling and this causes a resistance. In shotgun shells the only resistance is the crimp and makes a big difference in how much pressure is developed.

Bladesmith, I just ran your formula against some guns in my stable. Here were the results:

Subject Gun Subject Load Weight of Ejecta (shot and wad, in pounds) Powder Weight (in pounds) Muzzle Velocity (feet per second) Gun Weight (in pounds) Fealt Recoil
J. Lang 12 Bore B&P F2 Subsound 7/8 ounce, 7.5 shot 0.0546875 0.01171875 1100 6.1875 22.1611455
Army Navy 28 Bore Blackpowder Load, 5/8 ounce, 7.5 shot 0.0390625 0.0078125 1100 7.4375 18.42095423
Perazzi MX-8 12 Bore Remington Handicap Load, 1-1/8 ounce, 7.5 shot, 4 dram eq. 0.075 0.015625 1235 8.875 45.80731919
Browning Citori 20 gauge Lightning Winchester AA 2-3/4" Trap loads, #8 shot, 7/8 ounce load, 2.5 dram eq. 0.0546875 0.009765625 1300 6.56 23.85369398

So putting it this way, an ultralight 12 bore London Best shooting 7/8 ounce 2.5" loads has less kick than a modern Citori 20 gauge shooting a modern load.

Interesting finding, huh?

Also of interest, a big bulky beast of a Perazzi trap gun still kicks 2x as hard as a London gun when the Perazzi is shooting a modern 1-1/8 ounce handicap load compared to the London gun shooting a 7/8 ounce vintage load.

Pretty remarkable, isn't it? A really heavy 12 bore still kicks 2x as much as a really light 12 bore? It goes to show that weight of the gun isn't a big factor in the formula, it really comes down to the huge difference between light loads and heavy loads. I doubt as many people would shoot 1-1/8 ounce loads over 7/8 ounce loads if they knew that it was putting about 2x as much wear and tear on their beloved double with each trigger pull.

Bro. Buzz - not ducking an answer, but needed my lunch dose of Finley

As a victim of a State of Missouri public education, here's the non-deep thinking version.

1.Recoil is measured per Paul's formula and http://www.handloads.com/calc/recoil.asp

2. Perceived or 'felt' recoil is almost impossible to define. Good science is reproducible and measurable and there is no 'pain-o-meter' because pain is entirely subjective. One can measure the difference in perceived pain OF an individual but not BETWEEN individuals. One person may rate the recoil of the same shell and gun as a 7 and the next a 4.
And perceived pain is highly variable and dependent on multiple external and internal physiologic factors ie. pain seems worse at night when there are fewer external stimuli. One's assessment of recoil when shooting a record Kudu vs.sighting in the .375 is entirely different. 'Felt' recoil may differ based on too much coffee that morning or too much alcohol the night before, fatigue, sleep (and other human needs ) deprivation, stress, or anxiety. And stock design/gun fit/muzzle jump contribute significantly.

3. 12g loads with more shot/more powder/more fps have BOTH more pressure AND more recoil, but are unrelated.

12 gauge 7/8 oz. at 1280 fps 7.5 pound shotgun = 12.7 ft/lbs of free recoil
12 gauge 1 oz. at 1180 fps, (2 3/4 Dram) 7.5 pound shotgun = 17.3 ft/lbs of free recoil
12 gauge 1 1/8 oz. at 1200 fps, (3 Dram) 7.5 pound shotgun = 23.0 ft/lbs of free recoil

3 Dr. Eq. 1 1/8 oz. Winchester Trap Load at 1,202 fps - 9,600 psi
AA Xtra-Lite 1 oz WAAL12 at 1189 fps - 8000 psi
AA 'Low noise Low recoil' 15/16 oz. at 980 fps - 6,200 psi

4. Loads through a smaller tube have more pressure. A 1/2 ounce .410 load at 1200 fps has a higher pressure than a 7/8 oz. 12g load at 1200 fps; but in a gun with the same weight, much less recoil.

5. Recoil pads absorb foot-pounds of energy and lengthen the duration of recoil, thereby diminshing perceived recoil.

6. The movement of the bolt against the spring in autoloaders does the same thing.

7. Compression of the base wad in the B&P Gordon System hull is suppose to do the same thing.

8. 'Slow burning' powder is suppose to lengthen duration of recoil.

9. Leo probably 'feels' less recoil, and moves alot less in response, than pencil neck geeks like myself. Same force however.



BTW: I frequently flinch trying to 'click' my mouse, but haven't resorted to a "release mouse" yet
"Flinch", "yips" in golfers, and a host of other movement disorders are now classified as a 'Task Specific Dystonia'
http://www.wemove.org/dys/dys_flimb.html
http://www.imakenews.com/wemovenews/e_article000394359.cfm?x=b11,0,w
The problem has ended the careers of some professional golfers and musicians. Aynsley Smith PhD, Director of Sports Pyschology and Sports Medicine Research at the Mayo Clinic, Rochester, and Dr. Charles Adler of the Mayo Clinic, Scottsdale have researched the problem extensively http://www.radiology.medscape.com/viewarticle/411176
Michael Keyes, M.D. discussed the 'Yips' on p. 28 of the Sept. 05' Shotguns Sports

I hope I live long enough to wear out a Perazzi shooting sporting with 1 1/8 oz. loads. If I do I'll buy me another'n. Don't think it's gonna happen.

There are lots of presentations in sporting that 7/8 oz. will break 100% of the time. Heck, MOST side by side tournaments and charity shoots can be straighted with 7/8 oz. loads. But there are some major tournaments that I don't believe can be.

SRH