CIP proof for steel

[harpoonlouis]

In the case of two examples of 3 inch shells you mention the two loads of 36g of steel and 50g of lead represent the same volume of shot trying to squeeze through the choke at the same time. The lead will deform (yield) at a far lower pressure than the steel an so won't cause as high a peak back pressure.

 

I see what you mean about my short explanation above, I should have made the point that a heavier load of the same type of shot means back pressure rises regardless of the type of shot.

 

A harder shot deforms less than a softer shot so back pressures rise with harness of shot.

 

There will be combos where more weight of softer shot produce lower ( acceptable) back pressures than lighter weights of hard shot.

 

Hence the suggestion that you check your shottie, load and choke combo with the manufacturers!

 

What we don't know for sure in this case is why you believe one load to be OK and the other not, was that from the gun maker?

[harpoonlouis]

Oops I meant to add something else because your comment about the steel going out faster reminded me.

 

Loading formulation for steel shells is often different to lead loads and pressures and speeds can be different.

 

Because steel is lower weight it carries less energy at the same velocity than lead. To keep the performance of steel loads up to scratch in terms of killing clays or game the velocity of the shot is often increased to deliver the same energy to the target.

 

So the design of the load also accounts for potentially higherback pressures in your gun

[Guest cookoff013]

my benelli has a different proofmark it has "psf" with "**" directly over the psf.

it is magnum proof, and has 3.5" chamber.

 

it does not have a fleurdelise at all. it is steel proofed, as it is a wildfowling gun.

Edited April 30, 2010 by cookoff013

[harpoonlouis]

Here is a BASC publication of 2001 which makes direct reference to the max 1/2 choke that is mentioned frequently.

 

Note it is only specified in relation to shot sizes over 4mm. The larger the shot size the fewer points of contact there will be across the shot column where the shot can deform and help squeeze through the choke.

 

Cookoff you might want to ead this post http://forums.pigeonwatch.co.uk/forums/ind...?showtopic=6263

 

Looking for proof marks? http://store.bluebookinc.com/Info/PDF/Firearm/Proofmarks.pdf shold be there.

Edited April 30, 2010 by harpoonlouis

[UK fowler]

all very well bringing this old basc data to light but in 2001 they didnt have a clue themselves they did some long range patterning with two 10g shotguns in about 2005 all steel shot putting steel Ts thats 5.1mm through the factory full choke and a briley Xfull Most of the cip maximum shot size -velocity regulations are dated in the eyes of most wildfowlers what CAN be done with steel shot and what IS being done are oceans apart the US leaves us standing when it comes to steel shotshells and aftermarket-RETRO choke tubes .A lot can change in nine years so much so that the old guns are getting left behind thats just a fact of life i have a midlands gun co side by side 3"paper case dowt it will ever see the wash again,sad but true

[Guest cookoff013]

uk fowler,

 

you are right, in america they shoot t shot at geese. but the distance they shoot ! they should be ashamed at themselves.

thats the equivalent of shooting buckshot at geese. Thats just not sane. seriously. throught tight choke too.

 

-cook.