"The sliding weight thing seems to me to be susceptible to malfunction from sources of inertia other than recoil"
Unless it's at the moment of discharge (i.e. a muzzle up landing) the return spring will keep the action forward, same as every other reciprocating design. To be honest, a hesitation lock is probably less grip-sensitive than true locked breech patterns simply due to the initial uncoupled state of the recoiling mass and frame. Keep in mind the bolt thrust force absolutely dwarfs anything else out there besides perhaps an MRI scanner
Now, an inertia locked action like the Benelli, I wholeheartedly agree. I had a Franchi I12 (cheap version) that I could "stiff arm" and short stroke with weaker skeet shells; pretty lame (well, that and I could hit anything with it
). More importantly, it had the slowest cycling action I've ever heard of, and shook and danced while you tried to get back on target; also lame.
"Benelli B76 might be close to what you are talking about."
Not quite, I think this one is a basic delayed blowback, muck like the MP5 but with a single camming part instead of two opposed rollers. Cool gun, and there's one on Gunbroker if anyone's interested
"Kriss?"
I don't think there's any actual delay going on in that one, so it's just a comically over-thought blowback gun with a weird layout; no locked breech.
"Remington Model 51, Remington R51, and SIG MKMO SMG all use the Pederson Hesitation Lock."
Kewl. Didn't know the MKMO used it as well (all I knew was it had some sort of delayed blowback, but there are few details)
Part of the problem in classifying the Pedersen is that it is
not a blowback of any sort. The pressure is gone before the bolt is cammed up; the lack of dirt in my R51 after a session is proof of that, if anything is. Not to mention the fact that even reduced breech pressure would be enough to cause horrific galling of the lug surfaces as they slid over each other (the edges would be rounded/peened immediately). Rather, the Pedersen is closer to the primer actuated system that was initially slated for the Garand; initial breech pressure directly bears on a rearward surface, moving it a short distance before stopping, and imparting momentum to open the action after a brief delay in which pressure can abate.
It's not really a 'recoil operated' gun, since the initial energy is transferred by free blowback, but the way the breech locks and delays its opening is identical. It's more like a hybrid of recoil and blowback systems than delayed blowback. Unlike every other common pistol design currently out there, it really isn't directly comparable. That is to say, it is without compare
I think the OP's idea is an interesting one. The trick to doing rifle rounds, is the headspace conundrum; the Pedersen hesitation is powered by extremely sloppy headspace
, which is a much bigger problem in high pressure rifle rounds than 9mm's. This is why primer actuation was pursued, since headspace could remain fixed while the primer set back a hair, with no risk of case head failure. But it may be possible, who knows, that an AR15 with an extra .01" or so of headspace gap could safely fire, while kicking the BCG back hard enough to cycle reliably. No a reloader's preferred action, I suspect, but then neither is delayed blowback w/ fluted chambers, and G3 owners manage to get by
A rebated-head cartridge like 50AE with a lubed casing could
rule with a Pedersen action, since it could function like a miniature Oerlikon cannon; Extract the required distance to power the action while fully pressurized, with no consequences for case stretch/failure whatsoever since the chamber is perfectly cylindrical
One last thing to mention about the Pedersen action, is a mere theory of mine. I have not run the numbers, since I lack a PHD in impact mechanics/analysis as well as internal ballistics, but I suspect the initial stutter greatly reduces the bolt thrust seen by the locking surfaces. While the bolt may pick up inertia from the bolt thrust, its velocity is greatly reduced by the slide (whose mass does not bear into the locking surfaces). However, in that initial shift, the chamber volume expands enormously from the bullet and bolt displacement, so pressures are
far lower than peak (at least for small case pistol rounds).
Now, the bolt still impacts the frame, and there are high stresses involved there, but what little I know of that science indicates that the relative hardness of the materials greatly moderates the pressure, and that in this case it is compressive and more easily withstood by the lugs. My suspicion is that this 'peak pressure dampening effect' is why the R51 can fire regular and +P ammo with an aluminum locking surface the size of
one 1911 lug without peening or setback (abrasive wear, that's another story; but my lug has shown no damage from applied loads)
TCB
