I have the formula for mag box dimensions for particular cases, but are they the same for rimmed cases...is there a different formula or different way of building magazine boxes for rimmed cases?

Roger

There is no formula. They are slanted for and aft and wider in the rear. Not rocket surgery. I'll look in Speed's book and see if the gives any dimensions. Find an original and copy it.

Below is the formula part of an article I have on magazine box setup....would this change because of the rim? I can't copy an existing one because one doesn't exist. I am trying to make a better box for my 9.3x74r P14. Would such a box have to have ribs like the original 303 box?



Roger

So I am assuming you have an unaltered P14 mag box and want to make it feed better. I'm thinking the rear of the box is OK since the rim diameters are real close. The issue may be the forward guide rib. It was designed to push against the much shorter .303 case neck/bullet to keep the round pointed at the chamber mouth. In your case, the rib is pressing against the case body. This may guide the round too far left or right depending on which side is feeding. Reducing the guide rib height may allow the round to center.

I can tell you that that formula is unnecessary; I have stuffed too many 9.3x62s in 7.65, 8mm, and 30-06 magazines to know that. Meaning built them and they function perfectly.
As for the 9.3x74R; just take the P14 mag and make it longer.
Don't try to over complicate it.

quote:

Originally posted by yumastepside:
Below is the formula part of an article I have on magazine box setup....would this change because of the rim? I can't copy an existing one because one doesn't exist. I am trying to make a better box for my 9.3x74r P14. Would such a box have to have ribs like the original 303 box?



Roger

An easy way...Grab three cases to form a triangle, measure from the base to the top of the triangle..yep you can add a little, to that measurement.... Or not. (Ted Blackburn method)

Thanks to all for the info, I'll give it a go!

Roger

A few no-holds-barred comments on rifle functionality from the late Don Heath - magazine dimensions included

https://www.africahunting.com/...oficiency-exam.2604/

Dan good read from someone who's been there. I personally have nightmare's about a rifle I built failing to function with a resulting injury.

And I see Soooo... much crappy advice here and on other forums about a half assed fix...I'll vomit the next time I read "Just use a stronger magazine spring"

Further one must note that proper magazine dimensions are only a beginning to proper functioning...You still have a long ways to go

Thanks Baxter for the info, and yes Duane, there is more to feeding than the mag box but I have your booklet on feeding, so I feel fairly confident ....and no! that was not a suck up Tom.

Roger