Why a rimjam on a 303 is actually a non event

[A-R]

Tried it with commercial PMP brass and it works. I suspect their shape hasn’t changed since they started making 303 ammo.

I think the difference in COL between the FMJ and soft-nosed bullets will also affect this.

[CorditeCrazy]

I think the difference in COL between the FMJ and soft-nosed bullets will also affect this.

Entirely possible. The milsurp was MKVII. The reloaded PMP brass had Hornady RN, the bolt required more force with RN than spitzer Bullets.

[Slamfire]

I have had Chinese 7.62 X 54 R rim jam in several of my Mosin Nagants, and those took "fiddling" to get the upper cartridge to feed. I think I had to push on the stack to get the top cartridge rim to clear the lower, even though, the Mosin Nagant had a cartridge interrupter to prevent rim lock.



I also have had my 375 H&H Magnum, M70 push feed rim jam when shooting 235 grain bullets. The OAL of the cartridge is such that it slides in the magazine with these bullets, and slides enough that the top cartridge was behind the lower. And then, the belt on the belted magnum cartridge locked on the rim of the cartridge below, requiring me to retract the bolt and press down on the cartridge stack to clear the rim lock jam. That only happened at the range, practicing rapid fire with the rifle, but that was enough for me to prefer rim less cartridges if I ever was in a hazardous situation.


As long as I have stacked the cartridges in the proper order in a 303 British magazine, I cannot recall having a rim lock jam, though, I might have. Rimmed cartridges are just so 1880's, and work extremely well in single shot weapons, but based on my experiences with antique rifles, even the belted magnums are best left for collectors and collections if 100% function is important.

[CorditeCrazy]

I tried to set up a rim jam in my 303’s (CLLE, SMLE and No4Mk1). I. General the mag sorted it out own its own, most of the time I could chamber a rimjammed round with a little bit of elbow grease, when seriously locked the thumb press down sorted it out.

I’ve never had an issue with my 375H&H, I’ve loaded 380gr, 300gr, 220gr and 200gr over a range of brands - Barnes, Rhino, Hornady, Impala. Not one issue, also the action is a M98 controlled feed. Perhaps the issue is the short cartridge, are they below spec length? Also it’s a belt not a rim, the belt doesn’t protrude as far a rim.

Yeah rims are very Victorian, but they work fine.

[Slaaibak]

I now like the word Rimjam!

[A-R]

I also have had my 375 H&H Magnum, M70 push feed rim jam when shooting 235 grain bullets. The OAL of the cartridge is such that it slides in the magazine with these bullets, and slides enough that the top cartridge was behind the lower. And then, the belt on the belted magnum cartridge locked on the rim of the cartridge below, requiring me to retract the bolt and press down on the cartridge stack to clear the rim lock jam. That only happened at the range, practicing rapid fire with the rifle, but that was enough for me to prefer rim less cartridges if I ever was in a hazardous situation.

Not disputing your account, but I have tried to get my 375H&H (ZKK602) to rimjam intentionally, by staggering the belts in the mag. No luck. The only thing I accomplished was to load 6 rounds in the mag (+ another in the chamber) and observe them feed perfectly.

[FNBROWNING]

A belted cartridge won't jam in a properly set up action. That being said there is no question in my mind that they are an unnecessary speed bump that impedes slick feeding.They also require a properly set up magazine box.Not that all cartridges don't just that these require more detail.

[vratvark]

If memory serves me right, original military .303 ammo had a bit of a rounded bevel to the forward facing edge of the rim. This would nullify any rim jam as the cartridge will slide over/push the impeding rim down with a bit of applied pressure.

Also, the design and shape of the magazine box will "auto correct" rimjams when the cartridges are pushed down.