Hot loads in older shotguns?

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Gibo

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Got my hands on an old Mossberg 195 12ga bolt action shotgun manufactured between 1955 - 1958.
I want to use it for deer hunting but I'm concerned with what loads these older shotguns can handle does the 1300-1400FPS range sound about right for the upper limit?

My biggest concern is the wood stock cracking the risk of the bolt flying back into my face should be minimal as these Mossbergs were known for being built like tanks.
 
For waterfowl fps can get as high as 1600fps I find it hard to believe they were using that kind of high pressure loads back in the 50's.
 
Gibo said:
For waterfowl fps can get as high as 1600fps I find it hard to believe they were using that kind of high pressure loads back in the 50's.
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Don’t confuse velocity and pressure. The pressure level the shells are producing is the same even with the higher velocity.
 
TimberPig said:
Don’t confuse velocity and pressure. The pressure level the shells are producing is the same even with the higher velocity.
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Really?
So is the pressure across all 12ga 2.75" the same no matter what type of shot/slug used? And is velocity determined by the type of gunpowder used or how many grains is loaded?
 
Go here - https://saami.org/wp-content/upload...Z299.2-Shotshell-2019-Approved-2019-04-23.pdf

About Page 6 - SAAMI sets MAP for 2 3/4" 12 gauge at 11,500 psi - note that various velocities are from 900 fps to 1500 fps, at the same MAP. Shotguns that are /were made to comply with SAAMI standards are made with safety factors sufficient to use all SAAMI compliant ammo, that the firearm was made for. Nothing really prevents a re-loader from using components that result in much higher pressure, or to alter the firearm so that it can no longer handle that level of pressure - cracks, corrosion, packed in dirt that interfere with lock-up, might be examples of the latter. There are several examples in various pressure tested reloading "recipes" that show that substituting some hulls, some primers, some wads or some powders can significantly increase pressure, with about no change to velocity.

Gibo - your statement that 11,500 psi is very low "for ballistics" is true, if you compare to some centre fire that operate in SAAMI range of 60,000 or 65,000 psi - but that 11,500 psi is actually fairly healthy for shotgun - is why shotgun design, lock-up, barrel wall thickness, firing pin size tends to be much "flimsier" (weaker) on shotguns, than on various higher pressure centre fire rifles - not the same demand, at all.

SAAMI is a voluntary organization in USA that most USA arms and ammo makers or sellers follow those standards - so about any one's ammo can be used in about any one's firearm that comply - in Europe, the "sort of" equivalent is C.I.P. who performs a similar function - in not all cases do SAAMI and C.I.P. standards perfectly comply with each other. That I am aware of, certain European countries, like Sweden, have not adopted C.I.P. standards - they generated their own standards, but their end result is to be very similar to C.I.P. - I do not think Canada or USA has done so. Separate, as well, that I am aware of, is NATO, which has it's own testing protocols and standards, as well as the world's various militaries - at least for a time - for example - SAAMI was formed in the mid-1920's (?) - USA military had been making 45-70, 30-40, 30-03, and 30-06 ammunition, (Britain - 303 British; Sweden - 6.5x55; Germany - various 8x57J and 8x57JS; etc.) for many decades prior to SAAMI's existence. I believe the various USA "trench guns" that used 12 gauge shotgun in WWI were firing some sort of shotgun ammo made by someone - well before there were SAAMI standards.
 
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Gibo said:
I saw on https://www.shotgunlife.com/shotguns/tom-roster/important-information-about-shotshell-pressures.html that the max avg pressure for a 12ga 2.75" shotshell is around 11,500psi is there ever a case where store bought ammo will go over this rating? 11,500psi is very low for ballistics so I don't think anything at that pressure should harm the stock or come close to a sheer failure in the locking lug.
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It’s not low for shotguns. It is the max pressure level the barrels are designed to manage. Commercial loads will never go over that except as an extremely rare mistake because liability exposure would be huge. On the other hand,

I have lots of vintage guns designed for much lower pressures than 11,500 psi…and my array of ammunition is tailored to that. I have commercial loads with pressures as low as 5,500 psi.

Now, don’t forget, while load size and velocity don’t have a direct linear connection to pressure, they do directly affect recoil. And excessive recoil is the most likely culprit in the wood cracking.
 
Modern loads and pressures in NA really began with Winchester's SuperX powder, introduced in 1922. That was followed in 1926 by the establishment of SAAMI spec standards. So basically any American made gun subsequent to 1926 was designed for what we would now consider modern loads and pressures. The exception to that is it took a few years for the widespread adoption of 2 3/4" chambers. Fire a SAAMI spec 12 gauge 2 3/4" shell in a 2 1/2" chamber and you are bumping the pressure up in the range of 500-800 psi. Higher amounts in smaller gauges.
 
My Mossberg 195 is not that old compared to the stuff in your collection and I see that SAAMI introduced their ammo standardization near the 30's so my 50's era firearm should have no issue with 11,500 psi.

I am more fearful of the walnut stock cracking under high velocity slugs. I was hoping to turn it into a slug gun for white tail deer as it was even advertised as being able to take both rifled and non-rifled slugs but seeing how modern rifled slugs can easily hit 1800+fps I worry the amount of recoil will crack the stock.
 
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Gibo said:
My Mossberg 195 is not that old compared to the stuff in your collection and I see that SAAMI introduced their ammo standardization near the 30's so my 50's era firearm should have no issue with 11,500 psi.

I am more fearful of the walnut stock cracking under high velocity slugs. I was hoping to turn it into a slug gun for white tail deer as it was even advertised as being able to take both rifled and non-rifled slugs but seeing how modern rifled slugs can easily hit 1800+psi I worry the amount of recoil will crack the stock.
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So if that is your concern (reasonable) there is a way to minimize that likelihood. Stocks typically crack under heavy loads because as the wood ages, it shrinks ever so slightly. And as it shrinks, it pulls away from the various contact points with the action. Those contact points need to be tight against each other to smoothly transfer the forces of recoil. The most common way to solve this is to glass bed the action into the wood. That involves building up an epoxy layer where the contacts points are and then sanding the epoxy back down for an exact fit. Done properly it's a perfect and stable fit and not at all visible when the gun is assembled. It's a relatively common procedure on vintage SxS.
 
I am not familiar with shotguns like canvasback appears to be, but his explanation in Post #17 is about exactly the same why so many splits are seen on wrists of mauser rifle stocks - the gun was originally built with a recoil ledge that was fitted and would transfer the recoil from the metal parts to the wood stock - at that place, ONLY. After some years of soaking in gun oil - that wood might have gone soft and punky - or was never fitted properly in the first place - or the moisture content in the wood changed - the recoil transfer moves to some other surface that was never designed to handle that, and cracks are the result. Cracks in a wood stock almost always the result of wood gone punky (soft) in the area designed to accept recoil (often "oil soaked"), the wood has gained or lost moisture and changed shape, or was never properly fitted to start with.
 
Your concern about the recoil level might be towards a correct issue - most "recoil calculators" that I looked at consider velocity of the "projectile", velocity of the exhausting gases, etc. but I do not recall any that consider "breech pressure" as part of a recoil calculation. I could be corrected about that, though. It comes down to the fit of the wood stock to the metal - if that wood is "solid enough" for the service, and if it still "fits" like it should.

Until some time ago, I had a Winchester Model 70 in 375 H&H that was made at the factory with "two" recoil lugs - one was up on the barrel - was apparently not an uncommon thing on various "big boomers" to give more surface area to transfer that recoil pulse to the wood stock, without breaking it. And I suspect that perfect bearing on both is required - hard to imagine how that can work, if only one of those lugs is bearing on the wood stock, and the other is not.
 
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canvasback said:
The most common way to solve this is to glass bed the action into the wood.
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Seems like the best thing do do, will disassemble the gun later and see how the action fits in it's cut out.
Are there any clear signs to show the action is no longer fitted properly in the stock?
 
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