eeb;
If you go back & read my first post on this subject you will find I mentioned that most loose guns were the result of "Wear".
All;
There are several things which need to be borne in mind. Shooting a gun does not "Wear" it loose. "If" a gun is "Shot Loose" it is the result of metal deformation, not Wear.
2nd thing that needs to be borne in mind is that wall thickness has absolutely no bearing upon the forces tending to bend the hinge pin, deform the hook or stretch, bend or crack the frame. Thus in the example of the .22LR in an insert bbl the walls of the inseret containing the radial pressure is what takes care of the bbl, it could be shot from a Barrel made of River Cane. This has no bearing upon the back thrust of the cartridge. In this case one of the major differences is simply the size of the case, thus greatly lessened area for the .22's pressure to push against. 20K psi time .035 SgIn (approx area of the internal .22LR case) = 700 lbs thrust (No account taken of case wall grip). 11K psi times .44 SqIn (approx area of 12ga hull internals) = 4,840 lbs thrust (same conditions). But you "Rightly Say" we are talking of two different loads of differing pressures inside the same hull. It now becomes a lot more complicated. Note carefully though that a lead crusher will not read as high a pressure as a piezo/electric crystal. If the brevity of the pressure cannot compress a "Lead" piston to what it would theoretically be compressed by the pressure read by the PE crystal, it also isn't going to bend the standing breech made of a steel forging to the extent it should theroetically do from that same pressure. The peak of the pressure curve from say Blue Dot powder will be a lot flater than the peak of a Red Dot load for instance. Thus if a load is fired using each powder @ 9K psi for instance the 9K would remain longer with the BD load than the RD one. More metal "Bending, Stretching, Flexing etc would thus occur.
Bottom Line still is if you want to determine which load is most apt to burst yuor chamber, compare the peak pressures. If you want to figure which load will stress the hinge joint, frame, bolts & Stock compare the "Momentum" of the loads. If you compare the recoil using identical wt of gun for all loads the same percentages will be obtained. I did not point this out in my earlier post, but is necessary to keep all on the same level.
Another thing that should be remembered is a lot of these older guns are not as weak as many give them credit for. In my 1913 Lefever catalog the following are all the heaviest loads given for various powders in 12ga with "1¼ Oz Shot"
Black - 3½ drams (Guns over 7lbs)(My 8lb gun with 2 5/8" chambers should qualify here, as no chamber lengths are listed)
Bulk Smokless - 3½ drams by measure
Infalliable - 28 grains (3½ DE)
Walsrode -34grains (3½ DE)
Nobel's Sporting Ballistite - 28grains (3½ DE)
Note these aren't Pussy-Cat loads, & while true they do not exceed 1¼ oz they are well in excess of the above mentioned 3-1 1/8oz load stated as the "Heaviest" load guns of this era were "Designed" for.
No gun wt limitations were given except for black. Apparently Lefever Engineers were not aware of the fact the gun would recoil less with the Black because it burned slower than these other non-progressive smokeless powders.
Last edited by 2-piper; 08/08/09 12:53 AM.
