-
Legacy Member
7.62x54r rim design
Does anybody know why the back side of the rim is beveled on this cartridge? I suppose it's to help it feed onto the bolt face, but I don't really know if that's the case. I can't off hand think of any other major cartridge that's made this way?
Information
|
Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current. |
|
-
-
07-21-2016 08:21 PM
# ADS
Friends and Sponsors
-
Advisory Panel
Perhaps for the extractor to cam over?
-
Thank You to browningautorifle For This Useful Post:
-
-
-
Thank You to jmoore For This Useful Post:
-
FREE MEMBER
NO Posting or PM's Allowed
It is quite likely that the Russians used the 8mm Lebel cartridge (8x54R) as a reference for their 7.62x54R round. Thus they lightly beveled the head of the cartridge in the same manner. The question is probably more correct if one asks why the French beveled the head of the 8mm Lebel cartridge. Of course that leads into the fact that the 8mm Lebel was a necked down cartridge based on the 11mm Gras cartridge. So the beveled head rim comes from it ultimately.
Anyway, the Gras and Lebel cartridges were designed for use in a tubular magazine and the tapered rim likely had to do with more reliable feeding in this case. In the French rifles the tubular magazine is a bit tricky in how it operates and feeds fresh rounds to shoot into the chamber.
-
Legacy Member
change-ver in design of 7,62x54R case head
The bevel head rim design was adopted in 1930 by the SovietsAttachment 76282Attachment 76283Attachment 76284
photos show some early Russian 7,62x54R mm cartridges
-
The Following 2 Members Say Thank You to RCS For This Useful Post:
-
FREE MEMBER
NO Posting or PM's Allowed
I think that browningautorifle has a point. The extractor would more easily slip over the beveled rim on the cartridge when single hand feeding a round into the rifle. So that may really be the reason.
-
Legacy Member
Originally Posted by
earlwb
I think that
browningautorifle has a point. The extractor would more easily slip over the beveled rim on the cartridge when single hand feeding a round into the rifle. So that may really be the reason.
Yeah, this reason does seem to make the most sense. It does beg the question,though, if it's such a good idea (and I think it is), why didn't everybody do it? One would think that a gun designed for the rigors of combat would use every trick available that might make it more reliable.
-
-
-
Thank You to Parashooter For This Useful Post:
-
Advisory Panel
Originally Posted by
bob4wd
I can't off hand think of any other major cartridge that's made this way?
There was a large family of European BPCR cartridges that originated with the epochal Mauser "A" base design from ca. 1871. They all had bevelled rims to help the extractor slip over the rim. In the 1st generation cartridge rifles, the engagement relied on the springiness of the extractor itself, so "Snap" is an unlucky word, as that is exactly what some old extractors have done, and replacements are "hens' teeth" parts to find. A "family tree" would look something like:
M1871---M71/84---11 mm Kropatschek and derivatives
..........---Gras 1874 ---Lebel 1886---Mosin-Nagant 1891
There were many civil versions: 9,5x47R etc. Most were bolt-action rifles with a hook-like extractor that had to pass over the rim to engage. Block-action rifles (Sharps, Rolling Blocks, Martini...) had extractors that sat in front of the rim, and thus did not have to slip over it.
Last edited by Patrick Chadwick; 09-20-2016 at 05:10 PM.
-
-
Legacy Member
You also have the considerations of MGs that used that cartridge like the DP-28, a beveled cartridge probaby was the best fit that worked for all.
-