whats the appeal of these as a user?
the grip-safety aspect, or something else?
They have a couple of good points deriving from the design and ergonomics- Let's start with accuracy?
Mechanical potential for accuracy: The barrel is FIXED to the frame, unusual in a delayed blowback pistol (or any reasonably light weight pistol over about .380/9mm short energy levels).
No inaccuracy due to sloppy, loose barrel lockup as happens with the various tilting, rotating or roller locking barrel systems- Which MUST have sufficient looseness to unlock properly even when dirty or very cold.
Attempts to tighten up moving barrel locking systems for better accuracy often lead to failures to cycle unless clean, well lubed and fired only in a "shirtsleeve environment". Tightened working parts clearances may lead to ammunition sensitivity, possibly requiring one to install different springs to tune a pistol for different loads. This may be an acceptable tradeoff in a match pistol if you like to tinker but it can get you killed in a carry pistol.
Very little "muzzle flip", a potential for quicker, more accurate follow up shots: The bore axis is very low, closer to in line with your arm than (most) delayed blowback designs which keep recoil springs, disconnecting links & etc. BELOW the barrel and require the breech to drop during recoil as in the Browning system and variants, the sights are also lower compared to this family of pistols.
Cocking lever encourages a uniform grip: You HAVE to hold that lever in, the force required keeps you from "limp wristing" or otherwise being as sloppy with your grip as can easily happen with other styles. Even a 1911 style grip safety won't do this to the extent the squeeze cocker does.
Light trigger: Since you need to squeeze the grip pretty firmly to **** the striker and hold it in at all times to KEEP it cocked, the trigger pull can be quite light yet still "drop safe" compared to some designs that stay cocked when dropped and have the potential to fire when they hit the ground. For example, the infamous NYPD Glock speced for a 16lb. + trigger pull?
A uniform trigger pull whether first or any succeeding shot and a really nice, short trigger reset.
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Safety-
Untrained people who take your gun away from you or get unauthorized access have regularly been shown to be unlikely to shoot (you?) with it immediately afterwards- The manual of arms is not difficult to learn but the cocking lever actuation is unique. As mentioned, a very good thing in a carry pistol.
Also as mentioned, once it leaves your hand, it's decocked in a fraction of a second. Doesn't get more "drop safe" than that.
Much less likely to have a negligent discharge- Two positive actions required to fire from the draw ALWAYS, no leaving this pistol holstered and cocked but not locked.
Plenty of people have got a bullet stripe down their leg or worse from the discharge of a holstered, cocked pistol. The P7 is not prone to this type of negligent discharge yet no extra time or non intuitive finger motions are required to bring the pistol from holstered and uncocked to cocked and ready to fire, only a firmer grip is initily required than most other pistols.
After achieving cocked status, the grip force required to maintain pistol cocked is enough less than initial cocking force not to be fatigueing, but not so much less that you don't have to consciously apply it.
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This pistol was intended to be as carry safe as possible yet allow the users to get off a few ACCURATE shots as QUICKLY as possible. Design goal was achieved.
It is a cary pistol designed for use where accidental discharge or losing control of the weapon are considered to be a greater danger than encounters with multiple armed opponents/other situations requiring one to expend more than one or two magazines.
The P7 was never intended to be used in a pitched battle. It is not a target pistol for long strings of fire, as noted, the gas delay system HEATS UP after a couple of magazines. After several hundred shots with dirty ammo, the gas cylinder will need cleaning which requires a field strip and a scraper tool or, in a pinch, a .270 cal. wire brush.
It is what it is:
"If one is going to carry an underpowered pistol he sould carry the neatest and handiest one available, and that is the H&K P7."
- Jeff Cooper
I wish this system were available in .45ACP but H&K never got past the protype on that caliber.
I have heard that the .45 ACP prototype had a HYDRAULIC BUFFER like an artillery piece, the required ratio beteen gas cylinder and barrel diameters didn't allow a small enough gas cylinder design.