W231 in 9mm...volume concerns

[8shot]

I'm having outstanding accuracy with Bayou 138 gr BNWC in my &W 986 9mm revolver. Bullets are sized at .356 and the revolver has a Walter 1-10 barrel.

Been loading them "long" (see pic) but need to seat them deeper (pic) RE: double action drag. The case is nearly full with the deeper seat, not compressed but full.

Are there concerns with W231 (3.7gr) case volume?

[JimB..]

That’s a big reduction in case capacity, pressure will be much higher in the shorter loads unless you reduced the powder charge.
You need to work up a new load.

[P Flados]

Giving actual COALs would have been helpful.

I ran some Quickload (QL) stuff with wild guesses for COAL.

Seated long at 1.105", a 141 gr Lyman 358495 wadcutter has a seating depth of 0.229". With 3.7 of 231, QL predicts a medium 9mm load with 22,301 psi. Velocity would be around 938 fps from a 5" autoloader.

Seated short at 1.00", a Lyman 358495 has a seating depth of 0.334". With 3.7 of 231, QL says the case will be 98% full. QL predicts a nasty 40,392 psi.

Dropping down to 3.2 gr of 231 gets the load back down to a more reasonable 28,392 psi with a similar velocity to the original long load, 924 fps.

[beemer]

That is a big change. Anytime I change the seating depth that much on a handgun I reduce the charge and work back up. Just a few tenths of a grain can mean the difference in a semi-auto ejecting or not, know you have a revolver but the pressure change still applies. I use W231 some loads, it is fast burning and small changes make a difference.

I have no facts and figures but there is no use taking a chance with a fine revolver, not even mention eyes and fingers.