Interesting read by Randy Wakeman :)

SAAMI Shotgun Pressure Specifications


Shotshell Maximum Average Pressure (MAP) in PSI


10 gauge 11,000
12 gauge 11,500 (except 3-1/2 in.)
12 gauge 3 1/2 in.14,000
16 gauge 11,500
20 Gauge 12,000
28 gauge 12,500
.410 Bore 2 1/2 in. 12,500
.410 Bore 3 in. 13,500

Pressure is discussed a great deal in a casual sense, but like most things unseen and unmeasured by most . . . little valuable information is normally imparted.

Lab data does not measure or indicate pressure in your gun. In the case of many factory shotshells, specific pressure is not discussed. In some cases, it cannot be reliably mentioned, as shotshells are marketed on the basis of performance, not SAAMI pressures. Shotshell manufacturing is a very competitive business; some shotshell makers (like rifle cartridge makers) have multiple approved recipies for the same shell-- the "why" is so they can buy and use whatever powder, many of them bulk or proprietary powders, that is found to be the most economical at the time. It could be St. Marks Powder one day, Nexplo the next, and ADI for the next run.

With shotshell chambers varying in length and diameter, exact pressure cannot be predicted. A simple primer change can change pressures by 3000 PSI. My friends at Accurate Powders / Western Powders inform me they have seen 5000 PSI changes just by a primer swap through their test barrels as recorded by radial tranducer.

Peak Pressure has no relationship to shotgun recoil, and so is not part of any free recoil formula. As published by Lyman and other sources: E = 1/2 (Wr / 32) (Wb x MV + 4700 x Wp / 7000 x Wr)squared.

Where E = recoil Energy in ft. lbs., Wr = Weight of rifle in pounds, Wb = Weight of bullet in grains, MV = Muzzle Velocity of bullet in feet-per-second, Wp = Weight of powder in grains.


Pressure, peak or otherwise, does not exist as part of free recoil. It likely won't stop those who think a tiny peak pressure node level equates to recoil, or enjoy speculating that that there is a relationship-- but there is no basis for it, unless we have a brand new branch of physics that attempts to now address it..

Peak Pressure, that always happens inside the shotshell, also has no relationship to pattern quality. Peak Pressure must always follow the base of the wad. When "pressure" is discussed, it invariably means only the peak pressure node that exists for mere fractions of a thousandth of one second. As its existence is so very fleeting, it cannot and does not illustrate the entire pressure curve-- nor even a substantial portion of it. Oberfell, E. D. Lowry, Zutz, Brister, Brindle ... no one familiar with exterior shotshell ballistics has postulated, much less shown, that peak pressure does anything to patterns one way or the other. If you follow the logical continuation of the discussion, a reduction of 3000 PSI must equate to something in pattern percentage. It doesn't, not one percent, and so the entire discussion moots itself in one big hurry. There is also nothing to show that higher peak pressure means more "open" patterns: if it did, every skeet load made would be at the highest MAP pressure possible-- quite obviously. Naturally, they are not. The peak pressure always happens inside the shell, before shot touches the first forcing cone, or the second forcing cone we like to call the "choke."

The bump up in pressure in the "newest" popular chambering, the SAAMI 3-1/2 inch 12 gauge, allows the 3-1/2 in. 12 gauge to effectively obsolete the 10 gauge when used with steel or other no-tox shot not subject to deformation. It allows a payload (or velocity) increase for the gauge beyond what can be had with the old 12 ga. 11,500 PSI MAP limit.

We all like to think of "pass / go" and "good / bad." We also have difficulty accepting that a "pressure number" is a vague one, contingent on our gun, our ambient conditions, and tolerance stack-up. Wad material variances affect pressure, crimp depth affects pressure, hull basewad variances affect pressure, lot-to-lot powder variances affect pressure, lot-to-lot primer variances affect pressure as well. It is a very vague if interesting number, unknown by most shooters in their guns with any precision, and has no effect on recoil, patterns, and assorted other attributes attempted to be associated to the tiny, fleeting little peak pressure node.

IT JUST NEVER ENDS :corn:

http://www.shotgunworld.com/bbs/view...p?f=3&t=209636


http://www.shotgunworld.com/bbs/view...p?f=2&t=184155

Wow, early this morning I risked life and limb. I shot the GH and survived. It seemed to handle the 2 3/4" Winchester Targets 2 3/4 dram, 1 1/8 oz. 1145 fps loads with out a hitch.

Bill, that isn’t a sissy load as I found out last evening. I was using that same load with #8 shot (ones I have pictured) I sent a big old groundhog into the promised land from about 20 to 25 paces away. That hog reacted as if hit by a 45-70. I was very impressed to say the least. Those old 30” full and full choke barrels hold a tight reach out there and get’m pattern. :)

Mike, pardon me for being stupid, but what is a maximum average? I wonder if I fell asleep in college math classes.

Bill, I'm surprised you are here to tell the tale. No unraveling of the damascus barrel, no shrapnel, all fingers still? I suspect that a 1 1/8oz 2 3/4 dre load with larger shot could actually kill a pheasant. I know, all the Golden Pheasant and Black Swarm and $15 a box manufacturers don't think so, but maybe I'll try it again this season.

Did I mention the Benelli auto that blew the barrel midsection? Yep, a buddy sent me the photo. His brother slipped a 20ga shell into a 12ga barrel by accident. Proof positive that Benelli barrels should not be shot.

Yes, 1 1/4oz at 3 1/4 dre, which is a stouter load than I care to shoot. Now that is a heavy load, and Parker made damascus 12ga's up until, what's the last one found, 1927? Parker marked them Overload Proved.

LOL Bruce, you got me brother, I have no idea. :)
The more I look into this Damascus barrel and pressure thing,
the more confused I’m getting. :coffee: My eyeballs are starting to bleed
and I have started on the second roll of duck tape around my head. :rotf:
I’m beginning to truly think this whole thing was indeed invented
by the big gun and ammo. manufactures to sell new guns and super
duper 4” magnum hit the moon shotshells. :rolleyes:

I think Mr. Bell showed that damascus barrels are pretty safe. That known, why does everyone say shoot low pressure loads ? Because we don't want to shoot the action loose and to show some respect to 100+ year old guns. It's better to be safe than sorry. I keep my loads under 7000 psi. One thing not discussed was low pressure means less deformation of shot = better patterns. Paul

Randy Wakefield's recommendation to have damascus barrels x-rayed or other NDI ( non destructive testing) procedure to find cracks was particularly strange. These are composite barrels, not homogenous, and all an x-ray shows is thousands of little lines from the iron and steel ribands that will look like cracks. So I suspect he is recommending something that he has never done or read the reports of being done on damascus barrels.

In response to Paul's comment, I don't know who everyone is, but I use the Parker shot and dram loads for the gauge, gun weight and period of manufacture as my guideline for shooting factory hunting loads in fluid or composite barrels and then back off at least in shot load for clays shooting. When I reload for clays shooting, I use moderate burn rate powders because I don't want the gun or my shoulder to get whacked. I don't specifically pursue low pressure loads, nor do many other people I know.

I suppose its also best for preservation of my vintage sports car to never drive it above 60 mph, but I like to know that I can, and every once in a while, I like to drive it to its capabilities, which in truth are greater than my personal comfort zone.

I've been pondering the safe to shoot Damascus question for some time. It seemed almost a silly question after awhile. Many English guns show current nitro proof stamps. Many people still are shooting guns without those proof stamps.

The people that seem to be in they are bombs waiting to go off crowd mostly are working from a friend of a friend point of view.

My GH Damascus was manufactured in 1924. I have feeling that Parker after 50 plus years would know by then if there was some inherent problem with Damascus and twist barrels. I doubt the first owner of my Parker spent a lot of time searching out "low pressure" loads. Likely he or she wandered down to the local hardware store and bought whatever 2 3/4" shell they could find with the preferred shot size.

When I bought my GH I bought it to shoot. The bores were excellent and untouched by a hone. The wall thickness was as it should be. There are no dents dings or pits. The barrels are on face. There are no cracks in the stock. I would have considered all of those things when deciding if a gun was safe to shoot no matter fluid steel or Damascus. My GH is a good sound gun. I'll shoot as God and Parker Bros. intended. I’ll keep it in proper working order and pay attention for possible barrel obstructions just like I would any other firearm.

In my job i do get to see plenty of shotguns with split, damaged barrels. We had a new 870 with a pretty good split and no more more choke tube brought back just the other day. A little mud will do that as the youngman learned.

Okay that was my ramble for the day. Now it is time to get ready and go to work. I have guns to photograph.