Thread: Seating depth dilemma

Originally Posted by mopheadrob

Starting out loading for my Model 7 7mmWSM. Projectile of choice is 150gr. ABLR.

Measured the max. cartridge base to ogive length for my chamber using the split-neck case method and got 2.305”. That seems really long - the factory Precision Hunters are 2.185” CBTO and they’re too long for my magazine.

Until measuring, I thought the PH’s were too long for the chamber as well because the bolt is really stiff to close on them. I assumed I was jamming them into the lands, because I don’t get that with Fed Fusions or PowerShoks.

Back to the ABLRs…To fit the mag I’d need to seat them to 2.175” CBTO. That’s 0.130” jump. Seems way too much to me. I could single-feed until I can get the magazine modified…

I was planning to start at 0.040”, so 2.265” CBTO. That puts only 0.265” of bearing surface in the neck though, so I need to add 0.020” to achieve the rule-of-thumb of at least the calibre.

Where do the forum gurus think I should start? 0.060” jump, 0.130” or somewhere in between?

Greetings mopheadrob,
I have a Remington 700 Sendero in 7mm SAUM that I regrettably have not done much with. I have measured the cartridge overall length for a number of projectiles with them touching the rifling. Max to seat in the mag is 71mm.

Remington corelokt 150 grain. Crush length 72mm. Jump 1mm
Hornady 139 grain Interlock. Crush length 72.25mm. Jump 1.25mm
Hornady 139 grain SST. Crush length 73.5mm. Jump 2.5mm.
Speer145 grain SP. Crush length 74.5mm. Jump 3.5mm.
Hornady 162 AMax. Crush 75mm. Jump 4mm.
Nosler LRAB 150 grain. Crush 76.2mm. Jump 5.2mm.

I note that the ogive is barely out of the case mouth when seated to mag length with the LRAB in your rifle and has minimal seating depth when loaded close to the rifling. Lengthening the mag will only fix one of these problems. Perhaps a different projectile could be considered depending on the use you have for the rifle.
Regards Grandpamac.