"Not recommended for barrels longer than 10 in. "

[milktree]

I'm looking at Speer #14.

In the 124gr 9mm section there's a comment for Accurate No. 7 that says,
“Not recommended for barrels longer than 10"”

Any idea why it says that? No. 7 is the slowest powder Accurate recommends for 9mm, so I'd think it would work *best* in a longer barrel.

What am I missing?

 

[DW357]

I'm looking at Speer #14.

In the 124gr 9mm section there's a comment for Accurate No. 7 that says,
“Not recommended for barrels longer than 10"”

Any idea why it says that? No. 7 is the slowest powder Accurate recommends for 9mm, so I'd think it would work *best* in a longer barrel.

What am I missing?

Hmm yeah i would think it would work well in a 10". Weird.

 

[drgrant]

I'm going to make a wild, but not entirely out of the realm of plausibility guess.... when they tested it in long barrels, because the burn duration or "dwell time" is longer, somehow, the peak pressures may have rose to a dangerous level? I mean it makes sense, you shoot a bullet out of a 5" gun it is going to take less time, however tiny, than a 10"+ barrel. So in the shorter gun the overpressure event is impossible because of the "race condition" of sorts, the bullet is long gone before the powder is finished burning. The other thing is too, Speer doesn't usually put milquetoast grade loads in their manual, so you might see a unique scenario where this warning only appears in their manual because their max charge is probably higher.


-Mike

 

[jpm]

^this. Its similar to the warning about undercharging your cartridge because it will explode. The pressure has to go somewhere, and if the bullet prevents it getting out the end of the barrel, its gonna go somewhere else that you don't want it going!

 

[nutsym16]

Sum people just do not like PPC