20 ga. Chamber length

[Drew Hause]

As a victim of a K through post-grad education in the great State of Missouri, this works for me
http://www.omahamarian.org/trap/shotshellenergy.html

35 ft/lbs is more than 1 3/8 oz. 3 3/4 Dr. Eq. (1295 fps) in an 8# gun at 32.6 ft/lbs

And BTW: my aforementioned 2 3/8" chambered 20g had a crack in the wrist that required repair

[Southpaw]

Originally Posted by Drew Hause

As a victim of a K through post-grad education in the great State of Missouri, this works for me
http://www.omahamarian.org/trap/shotshellenergy.html

35 ft/lbs is more than 1 3/8 oz. 3 3/4 Dr. Eq. (1295 fps) in an 8# gun at 32.6 ft/lbs

And BTW: my aforementioned 2 3/8" chambered 20g had a crack in the wrist that required repair

I like it. Good stuff. I did not see your free calculator. Btw sorry to hear about the 20 broken at the wrist. Do you know why it broke. I saw a gun with a broken wrist after a fall, not certain I have heard of a broken wrist on a shotgun from just recoil.

I found a recoil calculator that was on a rifle webpage and then had to to convert ounces to grains and drams to grains. I think I came out about the same as yours but I also played with 2 3/4 drams of powder for a 1 ounce load and foot pounds went up. As follows is exercise I went thru. Will put same variables in the link you provided to see if its different. Lots of variables to consider to get different outcomes.


Okay. I found a shooters recoil formula. Calculator is setup for rifles but it should calculate out the same. Had to convert grains to drams and ounces of powder and shot. I ounce of shot is 437.5 grains and 2.5 drams of powder is 68.36 grains of powder. Looking at Bruce's table for my 16 Gauge I used a 7lb weight for the gun. With these inputs it calculates out at 32.85 foot lbs for the federal load.

Since I/we don't know how much powder is used in the RST loads then its hard to calculate the differences. But its an interesting point. If the charges are all the same just put in 1200 fps for the RST loads and keep then recoil energy goes up to 34.4 lbs. Then the recoil energy is less for the Federals by 2 lbs, thereabout. That is only about 4.5% difference and maybe negligible due to certain vagaries.

For giggles went and calculated what an 8 pound 12 gauge would produce at 1200 fps, 3.5 drams 1 1/8 ounce load. That recoil is 45 lbs. That is a 28% increase. If gun frame is about the same on a 12 to 16 gauge Parker and assuming wood is about same thickness, that is about 10 or more extra pounds being exerted on the stock. That might be the difference in whether old american walnut splitting out, or not.

http://www.shooterscalculator.com/recoil-calculator.php

[Kensal Rise]

More than one factor effects the felt recoil of a gun. Chamber length is one of them. In relation to the cartridge length, of course. If the mouth of a case restricts the passage of the charge into the forcing cone and barrel proper, it will contribute to felt recoil. But not by much.

Other factors include the LOADING. Which, in the case of most commercial ammunition is fairly "stiff." Each firm has its own idea of a good 20-bore load.

Gun weight is another factor. So is stock configuration. Buttstock "plate" or pad. Shooting style, etc.

However, I've fired thousands upon thousands of handloaded 3/4 oz. 20-bore loads in 2 3/4-inch cases/2 1/2 -inch chambers with perfect comfort and results. But that's just me...

[Drew Hause]

Bruce has previously made the point that some factory 20g cases are shorter than 2 3/4"

Estate (Federal) 2 5/8"; Fiocchi 2 11/16"; Nobel Sport 2 3/4"; Winchester 2 5/8"; Winchester Universal 2 9/16"; Remington Gun Club 2 11/16"



If the case mouth looks like the one on left, it's a problem in YOUR gun



A summary of “Long Shells in Short Chambers”, by Sherman Bell with technical assistance from Tom Armbrust in “Finding Out for Myself” Part V, Double Gun Journal, Winter 2001 is about 1/3 way down here. This was a PRESSURE, not RECOIL study
https://docs.google.com/document/d/1...vwLYc-kGA/edit

[James L. Martin]

Here are 2 20ga hulls , a Fed top gun at .610 and a new style Win AA at .608 .I load the AA hulls with 7/8 oz for hunting in my 2 1/2 chamber Parkers and LC Smith. The AA hulls with a polywad works great for those full choke guns.

[Harold Pickens]

Bruce has demonstrated this with pictures before. Win AA's are not 2 3/4". Put them next to an RST shell and they are just barely longer. This is not the case for all shells as Cheddite shells such as Herters are markedly longer than the AA's. Rem 20's are similar to the AA's, I dont know about Federals.
I shoot factory AA's and Rem thru my Parker 20 fluid steel 20's, but most of the time am shooting 3/4 oz AA reloads and they are really sweet to shoot. I cut down Herters 20's to 2 1/2" and have scaveged RST 20's, so lately have been loading them esp for my older damascus guns such as my Manton 20 hammer gun.

[Heff]

In the picture Drew posted with various spent shells lined up is a good illustration of varying lengths of shell casings. If you were to add another line on the board at 2 3/8", wouldn't that make you pucker just a bit

[Dean Romig]

I should have made the point earlier that the majority of "off the shelf" ammo makers load their shell to the charge necessary to fully cycle the semi-autos out there today, which are primarily inertia operated... but even the gas operated semi-autos require a minimum of pressure to operate properly.





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[Southpaw]

Hey Drew;

Maybe missing something. I just put in the variables you mentioned in the calculator you linked to. Sorry could't resist since you are from the "Show me" state. I put in 1.375 ounces of shot, 1295 fps, 8 lb gun, 33 grains for the wad just showed up in calculator, then put in 102.5393 grains of powder which is equivalent to 3.75 drams of powder. I came up with 67.4 foot pounds of recoil energy, not 32.6 lbs.

I could be wrong but 1 dram of powder is suppose to equal 27.344 grains of powder. That maybe the variable that is messing up. 3.75 times 27.34 equals 102.5393

Also my original calculator based on rifles did not account for wad weight, which might add to recoil a tiny bit.

[StubTwist]

I think your issue is the table is for smokeless which is measured by weight. BP is by volume.

27 grains is equal to 1 dram of black powder.

102 grains of smokeless in a shell you can pretty much expect a grenade to go off.