Load data question

[Smcx]

I have the lyman 49th. They list a max charge of unique with a 230gr TMJ .45acp at 6.6gr with a velocity of 825.

The question is, with a listed pressure of only 15,800 CUP, why stop at 6.6gr? The 700x max load is 17,900 and bullseye is 17,100

Any ideas?

 

[LUTNIT]

Does the Unique fill the case with that charge? It could be that any more powder will compress the charge and cause the max pressure to increase dangerously.
Some powders can get weird above a certain pressure as well but Unique isn't really one of them.

*edit*
The Alliant site lists 6.5gr as a max charge for a 230gr TMJ and Unique. They don't list pressures though.

 

[OldDude]

One explanation I've read is that the pressure with a heavier load shows more variation, so some individual loads would be over the max pressure. What that tells me is that the load in question has a higher variation between individual shots. Some shots may be safe, but you could get the one that is way over maximum.

Stan

 

[VICIOUS]

HI; I found some of lymans load with UNIQUE to be too darn hot. I load closer to the start loads and find that plenty hot enough.

 

[bigedp51]

The Lyman manual uses a universal receiver and a pressure test barrel with a chamber and bore cut to minimum dimensions and the max load of Unique is 6.6

The Speer manual uses a SIG 220 for its testing with the same bullet and powder and lists the max load at 6.5 grains.

"TMJ" is a plated bullet and these two manuals are very close in loading data, my guess would be load density/case volume, meaning how full the case is with that specific powder.

 

[farmboy108]

If the bullet speeds are all about the same go with the low pressure load if the gun will cycle.