Short mag length and 178-gr A-Max jump

[Fred_C_Dobbs]

So I'm working up a load for this .308 FN PBR and I have a dilemma with magazine length. The two OEM mags will support seating about 0.020" off the lands but the one OE mag won't go any less than 0.060".

Is the 178-gr A-Max tolerant enough of that much jump that you'd go with 0.060" and forget about the rest? Or would you go to the trouble to test it at the shorter OAL, knowing that that would mean you'd end up spending another $50 for a third OEM magazine?

The OE mag (L) has a different follower retention system from the OEM mags (R):

The OE's follower retention gizmo works better but also takes up about 0.040" more of the internal length of the magazine. The spring in the OE also is about 3x as strong as the one in the OEMs (~6 lbs vs ~2 lbs).

I've shot 155-gr Scenars from that short magazine but they don't seem to care how much jump there is.

Here's another view:

These bullets' relative positions make it appear the internal length is the same but, trust me, it's a trick of the camera angle.

 

[ChrisGarrett]

Re: Short mag length and 178-gr A-Max jump

I'd fiddle with both COALs. If you find the longer COAL shoots better, use that magazine when you go shooting.

If the shorter (longer jumps) COAL shoots better, there's your answer. Only you can tell us how they both shoot in your weapon.

I have loaded up some 178 AMAX and jumped them, some, but it's really too small a sample size for me to yield any insight, to you.

Chris

 

[blklabs]

Re: Short mag length and 178-gr A-Max jump

Amax will jump well. I used to load my ltr at 2.8". I never measured it but would assume its 2.9"+ to the lands. Load the shorter coal and shoot it and if it works then your done.