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Joined: Jan 2002
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Sidelock
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Sidelock
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The weight of the shot per square inch to be moved, coupled with higher pressure, shows why deformation is more likely the longer the shot charge is in the bore.
Assuming the same shot charge in, say, a 28 or a .410 vs a 12ga, there's another reason why there may well be more shot deformation in the small bores--although it's less true now than it used to be. That's because of the significant difference in profile between a given shot charge in a small bore (relatively long and skinny) vs in a 12ga (relatively short and fat). Long and skinny = a higher percentage of the pellets in potential contact with the bore vs a lower percentage in a 12. Much of that negated by modern plastic wads, but I expect it still has some effect on deformation. Re Brister's work on shot string, it doesn't show up to any significant extent other than at relatively long range (40 yards or more). But he points out that soft shot (thus more likely to deform) is a contributing factor.
Last edited by L. Brown; 06/06/16 10:43 AM.
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Sidelock
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Sidelock
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Larry;
Area of a circle is proportionate to the square of their diameters while circumference is proportional to their diameter.
Thus if we loaded both a 28ga & a 12ga with shot loads of exactly the same length the 12 ga would have a 75% heavier shot load, but would have only 32% more bore contact, so yes the smaller gauge will have more shot in contact with the bore.
As shot cups have done so much to reduce barrel scrub I did not go into this aspect. Many modern plastic wads also do a better job of cushioning the charge to help reduce shot deformation from setback as well.
These factors along with the development of progressive burning powders is in fact what has made the small bore shotgun a viable option for so much of today's use.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Sidelock
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Sidelock
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There are two possibilities for pellet deformation, barrel scrub aside. One is due to acceleration and the other is due to pellet to pellet contact. Deformation is caused by force per square inch above the pellet material's compressive yield strength. Spherical contact points are very small, so relatively smaller forces will cause an "upset" spot on both spheres. As the upset spots grow and the material work hardens, relatively higher force is required to continue to grow the spots.
IMO, (no, I've not done the math) upset occurs only from pellet to pellet contact and only near max pressure. Pellets are deformed as the pressure passes through max chamber and then deformation stops for the rest of the ride down the barrel. I do not believe there is sufficient acceleration to deform the pellets from MA.
DDA
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Sidelock
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Sidelock
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There are two possibilities for pellet deformation, barrel scrub aside. One is due to acceleration and the other is due to pellet to pellet contact. Deformation is caused by force per square inch above the pellet material's compressive yield strength. Spherical contact points are very small, so relatively smaller forces will cause an "upset" spot on both spheres. As the upset spots grow and the material work hardens, relatively higher force is required to continue to grow the spots.
IMO, (no, I've not done the math) upset occurs only from pellet to pellet contact and only near max pressure. Pellets are deformed as the pressure passes through max chamber and then deformation stops for the rest of the ride down the barrel. I do not believe there is sufficient acceleration to deform the pellets from MA.
DDA Don, doesn't one cause the other? Without acceleration, from standstill to max velocity, you would not have the pellet to pellet deformation, right? Well ..... maybe a tiny bit from passing through choke constriction. SRH
May God bless America and those who defend her.
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Sidelock
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Sidelock
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Larry;
Area of a circle is proportionate to the square of their diameters while circumference is proportional to their diameter.
Thus if we loaded both a 28ga & a 12ga with shot loads of exactly the same length the 12 ga would have a 75% heavier shot load, but would have only 32% more bore contact, so yes the smaller gauge will have more shot in contact with the bore.
As shot cups have done so much to reduce barrel scrub I did not go into this aspect. Many modern plastic wads also do a better job of cushioning the charge to help reduce shot deformation from setback as well.
These factors along with the development of progressive burning powders is in fact what has made the small bore shotgun a viable option for so much of today's use. Very good point at the end, Miller. Combine a good wad with hard shot, and smallbores are likely to throw much better patterns today than they could back in the day.
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Sidelock
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Sidelock
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I've got to agree with Old Colonel and Rocketman. Although it is intuitively appealing, I think the deformation from MA is overstated in most peoples minds. I don't know when "back in the day" was, but I do remember Francis Sell advocating for the 20 gauge in the 1950's and achieving 75-80% 40 yd. patterns using up to 1 1/8 oz in the twenty - no plated shot, no plastic shock absorbing wad, no buffer and no plastic shot cup.
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Sidelock
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Sidelock
Joined: Jan 2006
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Arthur Brisbane to the Syracuse Advertising Men's Club, in March 1911: "Use a picture. It's worth a thousand words." Pellets recovered from mallard at 45 yds. Ed Lowry, "Shot Penetration in Soft Targets", American Rifleman, Oct. 1988 
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Sidelock
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Sidelock
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Seem like a lot of effort to show what everybody already assumes.
Small bores generally deform more shot than larger bores. It seems the ammo maker have been working on this issue for quite some time.
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Sidelock
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Sidelock
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Arthur Brisbane to the Syracuse Advertising Men's Club, in March 1911: "Use a picture. It's worth a thousand words." Pellets recovered from mallard at 45 yds. Ed Lowry, "Shot Penetration in Soft Targets", American Rifleman, Oct. 1988 Do you think the shot was deformed in the barrel or in the duck? My money's primarily on the duck.
Last edited by cpa; 06/06/16 07:57 PM.
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Sidelock
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Sidelock
Joined: Jan 2006
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Dimples = pellet to pellet contact from "set back"
Flat side = bore scrubbing. I believe the load had the Mark 5 polyethylene shot collar.
Deformed/misshapen/impact crater = duck bone
And I could be wrong, but have cleaned a bunch of pheasants.
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