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stevesavage
PostPosted: Fri Aug 20, 2021 8:11 pm  Reply with quote



Joined: 13 Apr 2017
Posts: 150

What pressure is safe in older shotguns such as the Ithaca NID or LC Smith? Solid steel barrels and in good shape. Is it necessary or desirable to use low pressure loads in these shotguns? Low pressure being 8500 psi or lower. High pressure toppling out at 11,500 psi. I suspect powder might burn cleaner at higher pressures. Thanks in advance.
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RGuill96971
PostPosted: Fri Aug 20, 2021 9:22 pm  Reply with quote



Joined: 21 Mar 2019
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Location: Texas

I shoot some old ones, hammer guns including LC Smith and I like between 7-8000 psi. I never have a problem, and shoot the low pressure stuff more to save the wood from cracking then anything. Rst loads for the old school are around 8000 psi. The sweet spot is 10,000 psi, for the majority of loads to perform the best from what I have read, but I’m personally not going to shoot those in my old school ones when I can get it done at 7500. Of course what your shooting at, and the distance you wanna shoot at comes into play.
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Byron Whitlock
PostPosted: Fri Aug 20, 2021 9:51 pm  Reply with quote



Joined: 27 Jan 2016
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Low pressure loads are a good idea with any old gun but what causes problems with stocks is recoil. Keeping loads on the light side helps keep recoil down. 7/8ox loads in my LC Smith shoot great and use less of that expensive shot for target shooting and dove and quail hunting.

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revdocdrew
PostPosted: Sat Aug 21, 2021 5:08 am  Reply with quote
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This might be of interest
https://www.shotgunworld.com/bbs/viewtopic.php?f=5&t=366087

Short version. ANY vintage gun needs to be evaluated by a double gun specialist with the interest, equipment (bore scope and wall thickness gauge), and expertise to properly do so.
If the action is tight and barrels have not been modified, are free of defects, and the wall thickness is adequate, use shells that reproduce the ballistics of the loads for which the gun was designed.
It has been well established that turn-ot-the-century load pressures were similar, or even higher, than those of shells today.

That said, Byron is correct. In light of the maybe >120 year old wood it is reasonable to choose lower recoil loads.
OR have the head of the stock glasbedded if you want to shoot heavy turkey or non-tox waterfowl loads.

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FallCreekFan
PostPosted: Sat Aug 21, 2021 9:17 am  Reply with quote



Joined: 30 Sep 2019
Posts: 135
Location: Colorado

Ross Seyfried, a long time contributor to the Double Gun Journal, has an article on low pressure loads for “good guns” in the current issue. This quote from the article gives you the essence of the premise for the article. “…you do not need modern “high velocity” shells to kill birds!”

At the end he confesses that he is “…a “one load guy”; give me one load that works and a few different shot sizes, and I will catch anything that flies.” Without intending that similar end, I find that I’ve arrived at the same place. I shoot almost exclusively a 3/4 oz load at 6200 psi and 1150 fps. All my classic doubles are happy with that load and I’m happy with the results.

(And it does save money on increasingly expensive powder and shot.”
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MSM2019
PostPosted: Sat Aug 21, 2021 9:23 am  Reply with quote



Joined: 04 Mar 2019
Posts: 1819
Location: Central ND

What revdocdrew has posted is absolutely correct.

"Low pressure" loads saving old wood are a fallacy. Chamber pressure is NOT part of the recoil equation. Chamber pressure does not hurt a well maintained older firearm's wood or action.

Recoil is what hurts older wood stocks. So loads that have a light payload and/or lower velocities are what you are looking for when using older shotguns.

I read this in an article written by a ballistician some years ago.......If you wouldn't trust your shotgun to safely handle ammunition with a chamber pressure of 11,500 PSI why would you ever trust it to handle ammunition with a chamber pressure of 7,000 PSI.

Folks somehow 'think' that 7,000 PSI is 'low pressure'. 7,000 PSI is not low pressure. If a shotgun is unsafe, lowering the chamber pressure of the ammo you are using is like putting lipstick on a pig.

Ever see what happens when you knock the valve off a 100+ lb. gas cylinder with 2,500 PSI of compressed gas in it? It becomes a rocket.

Low chamber pressures are a fools paradise.

Have a person that actually knows how to inspect firearms when in doubt of the safety of shooting an older shotgun.

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RGuill96971
PostPosted: Sat Aug 21, 2021 3:48 pm  Reply with quote



Joined: 21 Mar 2019
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Mark:
Help me out here. I agree recoil is what cracks stocks. Recoil with 11,000 psi should be more then a load with say 9000 psi?
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FlyChamps
PostPosted: Sat Aug 21, 2021 4:39 pm  Reply with quote
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RGuill96971 wrote:
Mark:
Help me out here. I agree recoil is what cracks stocks. Recoil with 11,000 psi should be more then a load with say 9000 psi?


Absolutely wrong.

Recoil is a function of the weight of the gun, weight of the ejecta (powder, wad & shot) and velocity. Pressure has nothing to do with recoil.

If you look at the linked recoil calculator and explanation you''ll not find pressure in either the calculator or explanation because recoil is not related to pressure.

http://www.omahamarian.org/trap/shotshellenergy.html
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Swampy16
PostPosted: Sat Aug 21, 2021 5:41 pm  Reply with quote



Joined: 17 Oct 2019
Posts: 453
Location: New Jersey

Any vintage gun you plan on shooting any volume with should have the stock head glassed like revdocdrew said. I had both my vintage clays guns done and have never had a problem with thousands of rounds fired.
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RGuill96971
PostPosted: Sat Aug 21, 2021 6:11 pm  Reply with quote



Joined: 21 Mar 2019
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Location: Texas

Flychamps:

I picked 2 loads off Hodgdon, using the recoil calculator link you provided.

#1 1oz
19.6 gr clays
7 lbs gun
leave 33 as wad (both loads use same wad)
1235 fps

#2 .875 7/8 oz
19.7 gr clays
7lbs gun
33 wad
1275 fps

loads are very close and only .1 grain of powder and the difference between 7/8 oz and an 1oz isn't to many bb's
recoil 20.5 recoil 17.6
pressure 8900 psi pressure 7300 psi
I shoot a lot of auto 5 and a low pressure load does not cycle that long recoil very well, and yes I have read many articles that say pressure has nothing to do with recoil. That 7300 psi load may cycle the auto 5, but the bolt will move to the rear very slow. the shell may or may not eject. The 8900 psi will eject with no problem. The felt recoil between the two loads is noticeable, so by these numbers the higher pressure load has more recoil.
Any comments welcome
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MSM2019
PostPosted: Sat Aug 21, 2021 8:54 pm  Reply with quote



Joined: 04 Mar 2019
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Location: Central ND

You must understand that the recoil equation is not a guess or an opinion. The recoil equation comes directly from SAAMI. Who is SAAMI? SAAMI is NOT a separate faction that oversees the US ammo and gun manufacturers.

SAAMI is a group of US manufacturers (and some foreign manufacturers) that decide how NEW ammunition is to be tested and what the dimensions are so that it fits and is safe in firearms for a particular cartridge. They do this by consensus using their combined engineering and manufacturing knowledge. So if you disagree with their recoil equation........really?

I do not know who actually came up with the online recoil calculators but many are very close to what you would get if you used the SAAMI recoil equation.

In any case, chamber pressure has nothing to do with the actual recoil figure. We are not talking felt recoil which also has nothing to do with chamber pressure. That is entirely a 6" between the ears issue.

As far as one load functioning a recoil action and another load with lower pressure that won't, but both loads have the same velocity. You must chronograph the loads using the shotgun in question. You cannot base a conclusion on reloading data. You have to base it off how each load performs in that particular shotgun.

Reloading data shows how a certain load performed in a test barrel mounted in a universal receiver. It doesn't always work out the same when you test it in your shotgun. Barrel length and choke will/can change velocity figures. As will how the cartridge was actually assembled. Did you actually throw the full amount of shot? Did you substitute a wad? What is the actual crimp depth? Was the wad firmly seated on the powder or do you let the crimp seat the wad on the powder? Clone wads maybe a safe swap but that doesn't always mean an equal swap. Then there is the famous....well it goes bang so that is good enough. It very well might be good enough for consistent ballistics, but not good enough to cycle your shotgun......and the list goes on.

At any rate chamber pressure gets blamed for problems that have nothing to do with chamber pressure. Recoil is just one.

The real problem with chamber pressure is that many reloaders are afraid of it and most do not understand it. 11,500 PSI is not a cliff to fall off. 8,000 PSI is not any safer than 11,000 PSI.


Now you may not believe my post, that is fine.

Have a good weekend. Mine started out right with an 1" of rain yesterday. Hopefully we will get more tomorrow. Been over a month since we had any.


Last edited by MSM2019 on Sun Aug 22, 2021 9:16 am; edited 3 times in total

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FlyChamps
PostPosted: Sun Aug 22, 2021 8:30 am  Reply with quote
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RGuill96971 wrote:
Flychamps:

I picked 2 loads off Hodgdon, using the recoil calculator link you provided.

#1 1oz
19.6 gr clays
7 lbs gun
leave 33 as wad (both loads use same wad)
1235 fps

#2 .875 7/8 oz
19.7 gr clays
7lbs gun
33 wad
1275 fps

loads are very close and only .1 grain of powder and the difference between 7/8 oz and an 1oz isn't to many bb's
recoil 20.5 recoil 17.6
pressure 8900 psi pressure 7300 psi
I shoot a lot of auto 5 and a low pressure load does not cycle that long recoil very well, and yes I have read many articles that say pressure has nothing to do with recoil. That 7300 psi load may cycle the auto 5, but the bolt will move to the rear very slow. the shell may or may not eject. The 8900 psi will eject with no problem. The felt recoil between the two loads is noticeable, so by these numbers the higher pressure load has more recoil.
Any comments welcome



The Newtonian physics of recoil is simple - every action has an equal and opposite reaction - and pressure is not part of it. The only factors are the mass and velocity of the ejecta (shot, wad & powder) and the resistance to the movement (weight of the gun). You are comparing apples and oranges - your first load is 1 ounce and the second is 7/8 ounce, therefore, they are not comparable.

The old Auto 5 is a long-recoil gun - it's the greater recoil of the 1 ounce load, not the pressure that causes the gun to function better with the 20.5 foot pound loads.
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MaximumSmoke
PostPosted: Sun Aug 22, 2021 9:16 am  Reply with quote
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Lots of good truths here. Thanks MSM2019 and RevDocDrew. Remember, the "recoil calculation" determines total recoil energy. That is not the same as recoil force, which is a complicated thing that the shooter feels.

Lets mention pressure now. Pressure inside the barrel during a gunshot is a function of time. It starts from zero, quickly peaks after ignition and dies away as the projectile moves down the barrel. No doubt you have all seen this in "pressure traces" for gunshots. The 1 inch from breech face measurement point has been arbitrarily chosen to capture the peak pressure. By "arbitrarily", I certainly don't mean willy-nilly. Experience has shown the 1 inch point is quite a good one for comparison, even though the actual peak might occur a little before or after that point. The pressures shown in reloading data are those at the 1 inch point and roughly correspond to the peak. The purpose of that data is all about design for barrel strength and comparisons of loads that likely will not over stress a given barrel design. In barrel design, barrel wall thicknesses are usually quite substantial at the breech and slightly down-bore, to cover the area where the highest pressures exist. Certainly barrel wall thicknesses taper down for weight reasons and their materials can be overstressed at any point, but with practical barrel profiles, most barrels are further from their stress limits as one goes down the barrel. Obviously there have been notable failures due to dimensional anomalies, material unsuitabilities and especially condition, not to mention obstructions.

Now lets talk about how velocity is accumulated. The pressure in the barrel acts on the area of the barrel to create force -- pressure times area equals force -- pounds per square inch times square inches gives pounds force. Since pressure is a function of time, then so is the force created by it -- i.e. the force starts at zero, rises to a peak and then drops off as the projectile moves ultimately out of the barrel. You might remember from your physics class the F=ma expression -- force equals mass times acceleration. Rearranging this gives acceleration equals force divided by mass. If the force and mass are constant, so also will be the acceleration, and it will be easy to calculate the resulting velocity by multiplying the acceleration times the time it is applied -- accel in ft per second per second, times time in seconds gives velocity in ft/sec. However, as explained above, pressure in the barrel rises and then falls as the projectile moves down the barrel, and hence the force behind the projectile, and thereby the acceleration of that projectile is not constant, which makes the calculation of velocity more complicated. Without getting too far into the land of Newton's physics, and integral calculus, muzzle velocity is proportional to the area under that pressure vs. time curve.

Now you can see that if the pressure peak is reduced or moved around somehow, and muzzle velocity is the same, the pressures somewhere else along the barrel will have to be greater, since having the same muzzle velocity for a projectile of the same mass means the area under the pressure curve must be the same. Also, the muzzle energy is a function of muzzle velocity, and recoil energy is a function of muzzle velocity. Simplistically, muzzle energy of the projectile is equal to one half the product of it's mass times the square of its velocity. Recoil energy, on the other hand is a momentum thing -- the old action-reation thing that says the mass of the gun times its velocity equals the mass of the projectile and its velocity. So the velocity of the gun in free recoil equals the velocity of the projectile times the mass of the projectile divided by the mass of the gun -- i.e. the velocities of the gun and the projectile are in proportion to their masses. From the one half mass of the gun times the square of it's free recoil velocity one can calculate its free recoil energy. This is the figure you see for recoil calculations and comparisons. It's units are energy -- foot-pounds. Keep in mind this is free recoil energy, which means the gun is not restrained at all. If you could fire the gun in free space, the gun would move off in a constant velocity opposite that of the projectile and in inverse proportion to the masses of the gun and the shot. If you suspended the gun on a pendulum that would hold it horizontal, and fired it, the height to which the recoil would swing the gun, times the mass of the gun (ft-pounds) would equal the free recoil energy. I just want you to understand that total free recoil energy, while a true figure of the energy the gun holder or gun mounting system must resist, it is not a definite indicator of the forces a shooter feels.

The above explanation is also quite simplistic, as the recoil energy calculation is complicated by the mass of the "other" ejecta when a gun fires, such as any wads, etc, and most importantly, the powder gases which move at super to hyper sonic velocities as they emerge (hopefully behind the projectile). Their energy must be accounted for, and the recoil estimation formulas vary a bit in how they treat that, but they generally do a good enough job of it.

Now about "felt" recoil. Certainly reduction of peak forces in the barrel make a difference in the force vs. time the gun produces on a recoil absorbing system. A shooter is a recoil absorbing system. Actual sensation of recoil forces or the quantification thereof by the shooter are masked by quite a few physical facts, though. A physical model of the body can be made by breaking it up into a chain or assembly of mass and damping elements, and with modern tools all the forces can be calculated . . . but for what case? As you can imagine, there is a lot of variation in individual build, body position and technique. Some folks might be more rigid; some like a bowl of jell-o. And where is the gun held or supported? I can think of 4 places of contact -- shoulder, cheek and two hands, but exactly how tightly is it connected at any point? And to what? Bone? Tissues of what type? Where is the recoil energy going? What proportion goes to hands, cheek and shoulder, etc. These complications make felt recoil a very conjectural thing. Perceptions of recoil differences can be inaccurate or indistinct. When a person subscribes to a theory he likes but cannot have a hope to actually verify, he often turns to speculation. However, as with all sporting equipment, what fits for feels good or sounds good is good for that individual. A lot of it is a matter of taste. As the Greeks have said, de gustibus non est disputandum -- effectively "matters of taste should not be disputed".

I would caution folks not to get too carried away with felt recoil thoughts, and instead stick to fundamentals. Recoil? If you want more comfortable shooting, use a sensible gun mount technique, get a good gun fit and a decent recoil pad. Want to take it easier on yourself, your gun barrel and your wood? Shoot a lighter projectile. Peak pressures for your ammo? No real effect on you or the gun's wood. Peak pressures do mean something to your barrel, though. However, a perusal of data published from modern day tests with black powder guns might give you some pause if you think internal ballistics required to produce given external ballistics with black powders is much different than with appropriate smokeless powders.

Cheers!
Tony
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MSM2019
PostPosted: Sun Aug 22, 2021 9:39 am  Reply with quote



Joined: 04 Mar 2019
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1/8 of an ounce of shot seems to be a small amount and in the big scheme it is a very light weight. When talking internal and external shotshell ballistics it is a fairly large difference.

When making a comparison such as this, when cycling a recoil operated semi-auto is the goal, you have to match shotshell payload and velocity so that you are comparing apples to apples.

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Builder
PostPosted: Sun Aug 22, 2021 3:21 pm  Reply with quote



Joined: 21 Mar 2013
Posts: 111
Location: Northern New Jersey

Thank you Tony! Great explanation. It sure brought back my college physics. Been a long time.

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