Pressure Changes in .410ga loads

cpileri

Question: If one were to change NOTHING in a shotgun load (410ga) but the pellet charge, what would happen to the pressures?i.e no change in wad, powder, seating depth, crimp, etc. Just opened up a load and removed 1/2 an ounce of shot, and re-loaded different sized shot for a greater total weight: the velocity would go down sure, but would the pressure change?

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bfair

Chamber pressure would be extremely minimal.A change in the wad seating pressure and the amount of wadding would have a greater effect on chamber pressure.

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Home of the Blue Angels, P'colaSemper Paratus

timbroman

I would have thought the weight of the .410 charge of #4 shot would weigh the same as the charge of #9 shot. No?

cpileri

Here's the change exactly: open a factory load and dump out the 11/16 oz (302 gr) of No.6 shot, replace with 4x .375cal lead balls (84gr each= 336gr total) then re-crimp.The additional 34gr of shot weight will slow velocity, ok.Will the increase in weight/drop in velocity balance out the change in pressure?Obviously, a heavier shot load at the same or higher velocity will give higher pressure. So I'm asking if nothing but the weight were changed, would the pressure remain the same?

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bfair

Weight changes pressure. I am wondering what you want to do with the load. When those 4 pellets scatter who knows where they will go when the pattern opens. Why not just buy some rifled slugs or some #4 shot (largest factory 410 load). A 2 1/2" has 1/2oz of shot and a 3" has 11/16. Regardless of shot size.

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Home of the Blue Angels, P'colaSemper Paratus

roundball

I've reloaded for 20 years...including 12, 20, 28, & 410 for trap & skeet shooting;Any time the weight of a projectile is increased, whether its shot, or a bullet, there will be a pressure increase;The reason is that the heavier projectile will take miliseconds longer to get moving down the barrel, and in this brief instant, as the gunpowder is burning and creating rapidily expanding gases, the pressure will increase higher than it would have for a lighter load; Once he projectile begins moving away from the chamber and down the barrel, the increasing space within the barrel itself becomes an extension of the chamber and the expanding gases have more and more space to expand so the pressure begins dropping. In your example, the question is whether or not the extra 34 grns weight is significant enough to make a difference. Probably not, "but for the record, always follow official publshed reloading data".

roundball

TIMBROMAN:The same 1/2oz physical measure of #4 shot and #9 shot in a 2.5" 410 have different weights;The "1/2oz" is a physical measure, but if you weighed the two examples above, you'd find that the #6's would weigh more than the #4's;The reason is that the smaller shot size you use, the more of them that will fit into the shotgun shell because they are smaller, and they nestle together better, filling up dead air space with more pellets than a larger size pellet like #4's.