Vectan powder?

[Guest cookoff013]

The object of any wad is not solely, but primarily to provide a gas seal, yes? the actual gas seal is (or should be!) made at the point

where the wad (in this example a card OP wad) sits on top of the powder, so any part of the wad column (of similar type/weight) above this

OP card(assuming the gas seals integrity holds) should thusfar, in theory have no impact on pressure on ignition!

 

I can see when a plastic wad starts to compress (on ignition) into the voids between the wad cup and the gas seal will have some

effect.

 

But I am talking about the same weight of a given powder (AS) under a similar width solid card OP wad (the gas seal!) under a solid fibre

wad, the same primer in the same structure/type (Reifenhauser) case (whatever its length) the same shot load (28g) all held in by a

6 point crimp closure.....I still can't see where the case length should make any difference?

 

so let me get this right?

you expect the pressure to stay constant? while you change the available volume for it to expand into before the crimp gives? (ie change the case length).

 

i`m under the understanding that the different wads have different compressability and different volumes.

 

thats one of the issues with steel, as its larger volume / oz, and that compression section is completely smaller.

[sitsinhedges]

My understanding is that all wads are compressible even fibre ones and the greater the distance between the powder and the shot the more compressibility there will be within that space all other things being equal, and that this will largely express itself by way of lower breech pressures. Even lead shot has compressibility when compared to steel. Maybe it wont be enough to matter going from 70 to 67mm in an average load but it might if say going from 70 to 65mm in a cartridge that is already quite hot.

[panoma1]

If you have two identical new Cheddite 12g cartridge cases one 2 1/2" the other 2 3/4" both primed with cx2000 and filled with 21grains of

AS powder with a 4mm card OP wad followed by a 19mm fibre wad, surely the area for the gasses to expand would be the same? any extra or loss of pressure would be dictated by the resistance to the cartridges contents (longer/shorter wad column) exiting the case and travelling up

the barrel? the weight of the shot charge being the same shouldn't affect pressure? should it?

Any resultant increase in pressure caused by a longer wad column could be mitigated by filler wads with a smaller diameter above the correct diameter 19mm fibre wad? couldn't it?

 

On ignition the charge exits the cartridge case (which is retained in the chamber so is unable to expand laterally) and enters the gun

barrel proper which replaces the cartridge tube in retaining the gas pressure in order to maintain the velocity of the payload as it travels up the barrel (the barrel is a continuation of the cartridge case!)

 

I genuinely can't get my head around longer case same ingredients more/less pressure!!

[roughshooter]

I think we can be a little anal when reloading sometimes.

I believe that a softish 28g lead load that it put into a slightly shorter case with a slight;y shorter wad will make hardly any difference.

Most data has a 10% safety margin and if we are looking at As and the C&G data actually calls for 24gr of powder then we are already dropping 3 gr of powder off a proofed load.

 

I really do not see an issue with these lead loads. The old shooting times reloading book has a whole chapter on cartridge development but in todays society we are too frightened to vary the data even slightly.

I would hasten to add that lead is one thing but Steel is totally another

Just my thoughts

Graham