pressure

[lynn deforest]

Which is more likely to cause damage to a gun stock? Chamber pressure or shot weight? It seems to me that pressure affects the metal, but higher shot weights cause more recoil and more stress on the stock.

[Stan Hillis]

I vote for shot weight, and, even though you didn't mention it, velocity. High pressures, while confined to the chambers and first few inches of the barrels, will probably cause the action to shoot loose quicker than lower pressure loads. They should not, however, have much, if any, effect on the stock wood. Some would argue that higher pressures mean that the gases exiting the muzzle will be moving at higher velocity, thus adding more to the total recoil. While I load low pressure loads for my damascus guns, and some older fluid steel doubles, I do so mainly for the barrel's and action's sakes. The lower shot charge weight and velocity of these loads coincidentally help preserve the integrity of the buttstock. Bottom line is: Lower pressure loads with lower velocities and lower shot charge weights will be the best for everything concerning these old guns. And, lo and behold, one just might find that the 1150 fps loads kill just as far and just as dead as the speed demons. Physics demands that they do. Many times they will pattern much better as well. Win, win.

[Twice Barrel]

Stan's conclusions are correct. Recoil is what causes damage to stocks and to a lessor degree the other components of the firearm. Following is the formula to calculate recoil, you will notice that chamber pressure is not a component of the calculation.

Recoil calculation formula
If you're interested in recoil you may calculate it for any gun with the following formula:

E= 1/2(Wr/32)(WbxMv+4700xWp/7000xWr) squared

E= energy in foot pounds
Wr= weight of gun in pounds
Wb= weight of shot and wad
Mv= muzzle velocity in fps
Wp= weight of powder in grains

This does not reflect FELT recoil with a recoil management device but does give accurate energy transfer at a solid butt plate.

Here is a handy link to calculate recoil http://www.10xshooters.com/calculators/ ... ulator.htm
that you can use to check how much of a beating you and your shotgun is taking using various loads.

I shoot 16 gauge guns exclusively so for hunting loads that I will only shoot sparingly I like to keep the recoil below 19 ft lbs. For Clay and other target shooting I prefer to keep recoil below 15 ft lbs but even at those relatively low values I have had old stocks start to show signs of splitting so now I have my Wood Smith glass bed the stock head to the receiver on all of my guns.

[lynn deforest]

I shoot mostly 10z, 1100fps loads, was wondering if there is any advantage to the super low pressure loads that can be made up imr pb, the velocity is the same.
PS, what is the case lenth of a fired 12 gauge roll crimp shell? Is it by any chance less than 2 3/4?

[Twice Barrel]

If you are shooting a Fox, which is an extremely strong gun, there is no advantage to super low pressure loads. Any load in the 9000 to 10,500 psi chamber pressure at your stated velocity is just fine and will be more reliable in cold weather.

I'm not aware of any manufacturer that is currently producing roll crimped 12 gauge ammo. If you find some you will just have to shoot it and measure it.

[Silvers]

I have a different take on several points.

Low pressure shells will help keep the barrel ribs intact; that's a factor that doesn't appear in the formulas but is obvious to anyone who shoots Foxes with a variety of loads. The barrel vibration harmonics are much different with a 5k pressure load as compared with a 10k load. You can feel the difference with your leading hand if you have it ahead of the fore-end.

Regarding shooting shells with IMR PB or IMR 7625 powder that are loaded in the 5-6k pressure range, I fired 2,900 such 12 gage shells in our local winter sporting league and at practice, since January 1 when it started. That was thru 5 different Foxes. Temps here in PA were often just above zero Fahrenheit in the mornings and I deliberately left the shells in the vehicle overnight to be sure they were at ambient temp. I didn't have a single blooper or anything that sounded weak. One morning a friend with an overbored Browning o/u was short of 25 shells and I gave him mine. No bloopers with that gun either. All my loads were with Remington factory wads, not the so-called replacement types. Over the same period my buds using modern competition guns experienced some bloopers using faster powders like IMR 700X, and with replacement wads. Net, I've proven to myself at least that slow powders for lower pressure loads is the way to go for Foxes as long as you are using a good wad.

RST offers a roll crimp 2-3/4" 12 gage shell @ 1-1/16 oz that uses a frangible shot disc. The ones I have are in red paper cases and the shells are cool looking. Silvers

[birdawg]

Frank,
Which primers and cases are you using?
Thanks
Jess

[Silvers]

Remington Gun Club or STS hulls. Remington primers. Rem TGT12S wads for 1 ounce and RXP12 for 1-1/8 ounce. Powder charges were taken straight from the Hodgdon/IMR website for 5-6k pressure loads in the 1100 fps range.

[lynn deforest]

thank you
I used to load 7625 for a grade 2 Flues Ithaca
I will try PB
the gun is a Philly Sterlingworth, stock is not oil soaked or soft, mechanicaly about 90%

[Twice Barrel]

Low pressure shells will help keep the barrel ribs intact; Silvers

Silvers in 50 years of shooting I have never seen the ribs on a Fox, Parker, Lefever, LC Smith, Ithaca NID or any other quality shotgun fail from being shot unless there was a catastrophic failure of one of the barrels and even when barrels have burst or have been seriously bulged most time the ribs have remained firmly attached.

Something is odd RST on catalogs 12 gauge shells being available with roll crimps in 2 1/2 and 2 inch lengths. Must be something they did up special or have discontinued.

[Silvers]

Yes RST currently lists 2-1/2" roll crimp papers with 1-1/16" shot charge. The 2-3/4" ones I have are ~ 2 years old and may be prototypes or now discontinued.

To answer Lynn's question, a fired 12 gage 2-3/4" Peters Victor roll crimp shell measures 2.705". In comparison a fired Federal paper folded crimp shell of modern manufacture measures 2.740". I measured two random shells; there may be a slight difference from hull to hull. Silvers

[Twice Barrel]

To answer Lynn's question, a fired 12 gage 2-3/4" Peters Victor roll crimp shell measures 2.705". In comparison a fired Federal paper folded crimp shell of modern manufacture measures 2.740". I measured two random shells; there may be a slight difference from hull to hull. Silvers

In either case there is no need to be concerned as the chamber pressures will only increas by 300 to 400 psi between 2 5/8 and 2 3/4 inch hulls. IF he is choosing the PB load he will be developing only 1/2 of the SAAMI 13,500 psi limit for chamber pressure.

[Silvers]

I'm pretty sure the current SAAMI service pressure limit for 2-3/4" 12 gage is 11,500 psi measured at 1" from the breech face, not 13,500. That's using modern transducer technology.

Something for readers to keep in mind when shooting Foxes and other vintage side by sides: Service pressure max in 1905 when Foxes with low carbon steel frames were first made, was "3 to 3-1/2 tons in warmer months" = ~ 7,000 psi max by older measurement methods. By 1929 the service pressure max had increased to 10,000 psi undoubtedly due to the use of progressive burning powders, and higher tensile alloy steels in shotgun barrels and frames.

The very best advice anyone can give you is to shoot shells loaded to pressures that were standard when your gun was made. For those interested, I keep my 12 gage Fox loads < 7,000 psi per the modern references, and I shoot them in early or later Foxes. Also FYI, RST generally keeps their shells below 7,000 psi, and some offerings are well below that number.

Silvers

[Twice Barrel]

I'm pretty sure the current SAAMI service pressure limit for 2-3/4" 12 gage is 11,500 psi measured at 1" from the breech face, not 13,500. That's using modern transducer technology.


The very best advice anyone can give you is to shoot shells loaded to pressures that were standard when your gun was made. For those interested, I keep my 12 gage Fox loads < 7,000 psi per the modern references, and I shoot them in early or later Foxes. Also FYI, RST generally keeps their shells below 7,000 psi, and some offerings are well below that number.

Silvers

Sorry about the misprint on the SAAMI chamber pressure I knew I should have had a second cup of coffee.

Silvers I must disagree with you on the low chamber pressures that you are expousing for folks to use. If people would only shoot sub 7000 psi loads they would be limited to RST, Sub sonic and hand loads using slow burning powders and would not be able to use any modern Winchester, Remington or Federal hunting or standard target ammunition. There has been a long running disagreement about what causes the most damage to vintage gun, high chamber pressures or heavy recoil. After reading Sherman Bell's exhaustive work on the effects of high chamber pressures on Damascus barrels (and actions) I think there is much more to be said about excessive recoil being the culprit. Bell was repeatedly shooting rounds that were equivalent to one and a half proof loads through barrels that had severe pitting and the barrels and actions continued to function. I am not advocating shooting loads in excess of SAAMI standard but there is no reason not to shoot modern ammunition that falls within SAAMI standards with moderate shot charges (7/8th ounce for 20 gauge, 1 ounce for 16 gauge and 1 1/4 ounce for 10 and 12 gauge) at moderate velocities (sub 1200 fps) in vintage double guns that are in sound condition.

[Silvers]

Mr. Twice, this might be a debatable point over dinner but in fact the professional engineers and ballisticians (and yes, lawyers) at the Big Three shotshell companies all concur that modern 11,500 psi shotshells should not be used in anything but modern firearms. To quote from a Remington box: "SAFETY WARNING ... use only in modern firearms in good condition designed for this gauge and length". No Fox shotgun can be considered modern, the oldest ones were made 105 years ago and the newest ones about 65 years ago.

You've made reference to Mr. Sherman Bell for whom I have the greatest respect. I've followed his writings in the DGJ and am familiar with his research with vintage side by sides to include pressure transducers for testing cartridges, and overload/destructive testing using factory proof shells loaded to 18,000 psi. If you have the DGJ Winter 2006 edition, you might refer to page 37 - 3rd paragraph up from the bottom, where Mr. Bell himself states "I recommend that you use loads that develop pressure similar to the ammunition that was available back when your gun was newly made. This makes sense for any firearm of any era ...... " Shotshells loaded to the current SAAMI max of 11,500 psi were not in use when any Fox shotgun was made. If anyone has read a quote from Mr. Bell stating that vintage SxS shotguns are OK for a steady diet of current SAAMI max pressure shells, please reference the DGJ issue and page here.

Practically speaking I'll add that I participate in many of the vintage side by side shoots in the east and I almost never see shooters using modern factory shotshells. Virtually everyone is using RST or similar brands marketed especially for vintage double guns, or are using their own handloads to low pressures.

Have Fox shotguns been used with every factory load known to man? Yep, they sure have. People shot whatever the local hardware store had in stock. And it's a tribute to the excellent Ansley Fox design that his guns held up and gave long service without problems. However I personally attribute this practice of shooting anything including short magnums to those I've seen that are off the face on the right or both barrels, or that have dead sounding barrels and/or loose ribs.

It's a free country and anyone can stuff whatever shell he wants to in his Fox or Parker, etc. But in net it's good to keep in mind that the professionals who make modern shells print a warning on the shell boxes. And most of the dedicated vintage SxS shooters I see do heed that advice.

Silvers