pressure effects of shot type

[Rick Losey]

when I reload, I follow published loads very carefully, but there is one thing that doesn't make sense to me. (well, one thing about reloading that is)

You can look at two loads with the same hull, powder charge, wad and load weight but see difference in the pressure because one listing is lead and one is non-tox - lets say - Nice Shot. Researching Nice Shot it says you can use any lead load recipe but according to what I see on reloading boards the pressure seems to increase by about 500 PSI, not a barrel buster but still an increase.

now - to me -an ounce and a quarter payload is and ounce and quarter so I have a little trouble understanding the reason. Is it just a variation in the testing process of the different load? Or is it just that they know the 1 1/4 load of different materials as thrown by reloader bushings is volume based is not a true weight?

remember the old question- which is heavier - a pound of feathers or a pound of lead?? That is what this sounds like.

[Mark Ouellette]

Young's Modulus explains that everything is a spring. Lead gives a little upon ignition of the primer and subsequent rapid burning of the powder. It then "springs" back to its original shape. Nice Shot gives less than lead, and steel gives much less so.

Elasticity of solid materials explains why a bridge or tall building sways in the wind without cracking or bending. The more elastic something is the more it will change shape momentarily and then return to its original shape.

As part of the ejecta, the more something gives the less peak pressure will be produced. Different plastic wads also vary in how much peak pressure they contribute to.

[John Campbell]

The relative "spring" of lead substitutes also impacts pressure at the choke. i.e., its easier to squeeze lead through a cone than steel or Nice Shot. And resistance equals pressure.

[Pete Lester]

Researching Nice Shot it says you can use any lead load recipe but according to what I see on reloading boards the pressure seems to increase by about 500 PSI, not a barrel buster but still an increase.


Nice Shot or Ecotungsten raises the pressure from a published lead recipe by 1500 psi, not 500.

This information comes from Nice shot but they bury it in the comments section of their reloading blog.

" Big Dan said...
I'll try to answer both posts at once.
Starting with Jay,
Nice Shot works excellent and kills with the lethalness of lead. I suggest not trying velocities above 1300 FPS. because of setback increasing pressure and I have not seen many loads for lead above this anyway. There is no need for steel shot wads or components using Nice Shot either. I do not know what you consider long range for geese but I've been using 1-1/8 oz of #2 Nice Shot @ 1250 FPS. and knocking geese dead at 50 yards.


As for Bismuth weighing in at 9.6g/cc is lighter than Nice Shots 10.2g/cc. Bismuth also gets a little lighter if alloyed with tin to keep it from shattering. The hardness is 14.0~16.0 Brinell. A little harder than magnum lead shot. Hevi-shot (12 g/cc) has some outstanding performance but many of us either can't/don't want to shoot the load through our barrels. As for what sets Nice Shot above the other shot types is its ability to be used with older or finer shotguns, lead loading data and components as long as you stay 1500 psi under maximum pressure for the gauge you are loading for.
"

http://ecotungsten-niceshot.blogspot.com/

[Rick Losey]

Thank you very much gentlemen.

I knew there would be a reason and that there would be folks here that would know it.

And Pete, thank you for the correction, that makes a big difference

[Mark Ouellette]

Rick,

The amount of total energy used to produce the same velocity, in the same bore diameter, for the same mass of the ejecta (weight of powder, weight of wad, and weight of payload) will be the same. What we are most concerned with is the peak pressure developed.

The elasticity of lead spreads out the total pressure so that less peak pressure in produced. Think of this like a gas operated autoloading shotgun that "spreads" out the recoil over a longer period of time making the recoil or "kick" seem less. The total energy of the recoil over time is the same for a gass gun as for a fixed breach. The gas gun just doesn't kick as much at once!

Mark

[Eldon Goddard]

This is a great topic. With leads low yield stress it is also likely permanently deforming (beyond the elastic range) absorbing more energy then steel. A super elastic material like nitinol can be greatly deformed and still return to its original shape. To bad it is very expensive it would make for an interesting material for shot.

[Mark Ouellette]

[quote=Eldon Goddard;108432]
With leads low yield stress it is also likely permanently deforming (beyond the elastic range) absorbing more energy then steel.

Eldon,

Great point! That is why we now use "Hard, Chilled, or Magnum" shot! Certainly even hard shot deforms a little but not so much as to turn into flying pancakes! :)

Mark