doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Needing Low Pressure load for 12 Ga AA

Ok, Got it, thanks. So, is it a significant advantage, as far as effects on wood, to use the lower psi load? Or, is it insignificant? One oz. seems to be a suitable standard for shot amount, especially for shooting trap at the longer distances. Would the higher psi load be more effective for that purpose, with it's higher FPS? Given that both loads are at or below the 8,000 PSI pressures of the black powder loads that the guns were designed for? I get a little "Anal" about this stuff, especially when I show up at the range and someone sees my guns and begins preaching "Anti Damascus" mythology to me. I like to have very specific information for my response.

Recoil can best be related to Newton's third law of motion (for each action there is an equal and opposite reaction).

The formula for calculating recoil is:
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 in grains
Mv= muzzle velocity in fps
Wp= weight of powder in grains

You will notice that chamber pressure is not a component of the recoil calculation and is only marginally related to Mv in that for a given load a higher chamber pressure will most generally result in a higher Mv.

Ok, I understand this, even with my Liberal Arts education. Now, do you have a suggestion as to how I can present that to a 75 year-old farmer who only completed the eighth grade?

I'm kind'a kidding, My usual explanation about black powder equivalency is usually adequate. But not always..

Wb must be in pounds, I guess?

Guns are proof tested to a certain psi level. Stock is not attached. So pressure, in and of itself, isn't the real culprit where wood is concerned. Moderate recoil is best for wood, and you get moderate recoil by keeping the velocity moderate and using lighter shot charges. Pressure comes into play where barrels are concerned. Too much pressure and a thin spot in the barrel, not too far from the chambers where the pressure is still high, can do bad things. That being said, most catastrophic failures (burst barrels) are due to obstructions and not pressure. If you have good barrel wall thickness, you're not very likely to blow a barrel even with a shell that approaches proof load pressure. And that is significantly higher than standard service pressure for the loads we shoot. If you somehow manage to double charge a load, that could do it. There's also the possibility of accelerating gun wear by shooting loads which, while not high enough to burst the barrels, exceed the service pressure for which the gun was designed. But as long as you stay within the pressure parameters for which the gun was designed, you should be in good shape as far as pressure goes. Assuming, of course, a gun in appropriate shootable condition.

There are several recoil calculators on the web.

As others have stated, recoil is dependent only on ejecta mass and velocity. Note that there is no place to input peak pressure as it is irrelevant.

This is an extreme example that illustrates why one shouldn't merely guess at recoil. Some would be quick to assume that the recoil in a 6 lb SxS would be more severe with a 1 &1/4 ounce load than with a 1 ounce load and often that would be the case. But not necessarily. Since both velocity and mass are the major factors, it's necessary to know both. Pushed fast enough, a 1 ounce load can recil more heavily than a 1 & 1/4 ounce load....



I like the above calculator ( http://www.handloads.com/calc/recoil.asp )because it lets me compare 2 loads side-by-side. The numbers I used are from data published in Lyman's 3rd edition.

The foot-lbs of recoil energy begin to make sense when I correlate the input values to real-world situations. I know that I can tolerate 300+ target loads in a day, provide they are 1 ounce @ 1250fps. I also know that 1 ounce @1300 fps would be objectionable. In my 8.5 lb O/U, that's a difference of only 2 ft/lbs, 14 versus 16.

I know I can shoot 200+ in a day with my 6.5lb 20ga SxS with no ill effects. Not surprisingly, 7/8 ounce @1175 generates....14 ft/lbs.

I know that 1 &1/4 ounce @ 1260fps is about the most I want shoot through my 12ga, 7.5lb 12ga bird gun. That's 25 ft/lbs. No wonder then that when I use my 6.5 lb 20ga for late winter pheasants I'm OK with a second barrel load of 1 &1/8 ounce of #5 @ 1175fps...that's only 22 ft/lbs.

All weights are in grains unless otherwise noted. I will update the formula to make sure that this is clear in the future.

Well speaking as a 70 year old with a few more miles than the average Iowa farmer of about the same age you are probably wasting their time trying to change their minds. God love them and accept them as the are, misinformed by years of misinformation from ammunition companies, half assed gun experts that inhabit some gun clubs or proclaim themselves experts because that got an article published in a well known but notably slanted Outdoor magazine looking for a sensation article to titillate the masses.

I think I'm making progress. Next time I intend to lay out a selection of the old girls for them to ogle at and even shoot if they want to. Most have never had the chance to really look at or shoot Damascus Parkers, LCs, Bakers, Stevens, English hammerguns, etc. I'm trying to develop an interest to start up an Eastern Iowa/Western Illinois Vintagers chapter.

No question that "experts" in print can be wrong. I recently read--from one of the "experts"--that once you have a pressure figure in bars (as stamped on British guns until recently), then all you have to do is multiply x 14.5 and you have psi; therefore comparing "apples to apples" with pressure figures for American guns. Well, in order to compare apples to apples, you have to make sure that none of the apples are oranges. Although the British proofhouses converted from crushers to transducers to measure pressure in the 1990's, they continued to use the old bar figures (850 bar was standard proof) AS MEASURED BY CRUSHERS as their proofmark. (They finally dropped all proofmarks expressing pressure as a number in 2006, replacing them with STD for standard pressure, SUP for superior pressure.) And when you have a pressure figure in bars as measured by the old crusher system, you can't convert it to a psi equivalent by multiplying x 14.5. You end up with LUP (lead units of pressure, still seen in some reloading charts) and not psi when you're dealing with measurements taken with lead crushers. The mathematical formula will not magically convert those crusher bar oranges to psi apples.