Impressions of the K100 Grand Power
AltBlis,
I like rotating barrel locking mechanisms a lot. I think it makes the gun more accurate by design. We are at the point in handgun development where only small things separate the good from the great, so details now matter.
The first thing that jumped out at me about the K100, is there is no locking block. The barrel extension implements the interface between the barrel and the frame. This could be considered a feature of elegant design, as simplicity is usually better. However, an emerging notion of engineering is to purposely design in a weak point/failure mode so you know what will fail first. This has been very important in helicopter design, where random failure has very bad results. The Beretta design uses what should be considered a disposable locking block which is made with a softer steel. They choose which part should wear, the locking block and not the barrel extension. The K100 people like to go on about how everything is harder than everything else, but this is not a feature, it is a flaw. Good design chooses which wear surface or feature is intended to fail, and which should never fail. In Beretta's case the part that fails, as is usually the case in good design, is very easy to replace, cheap and should therefore be considered a consumable.
The 2nd thing that I noticed about the K100 is the very large area of the barrel extension that implements the "cam" and interfaces with the cross-pin. This is an invitation to grit and sand since that interface needs to be oiled or greased. If you think about it further you realized that only the edges of that very wide, flat ribbon are going to bear force when turning. In time this means its edges will wear and will wear groves into the cross-pin. Actually, the design could be improved a lot by just cutting a 2-3mm deep groove/channel out of the middle of the cam ribbon and leaving only the edges. This would act like rain grooves in a tire and give grit and debris a way to get out from between the cross-pin interface.
The 3rd thing I noticed is that to work the barrel has to be held down onto the cross-pin. SO what is holding the barrel down? It has to be the slide. This puts a vertical force vector on the slide that must be borne by the slide rails and frame's rail interface. That is a force vector that is entirely unnecessary, and is non-existent in the Beretta designs, which use a cam and "pin" (the pin is not round, as if it were there would be very little surface area between the round pin and barrel extension's cam slot. By making it "square" and angling it correctly they get the same interface area that would require a pin over an inch in around.) The pin stands up from the barrel extension and is flanked by barrel interfaces fore and aft which have small debris wiper slots cut in them. This means the pin and cam are, to some degree, self-cleaning. The bearing load is also quite high between the pin and cam, so it will aggressively remove debris from the interface. (I am using Krytox pure Teflon grease on this because of the high bearing loads) My take is the lock is pretty much unstoppable and should prove to be extremely reliable. The tests done by the new Canadian border guard seem to have proved this. In general, I think the K100 is still suffering from the influence of Soviet "bigger is always better" mindset and is therefore big when smart would serve its interests better.
The Beretta also harnesses the rifling torque to help unlock the action. The rifling is 6 right, which imparts a counter-clockwise torque on the barrel, and if you inspect the cam slot it turns counter-clockwise when unlocking. Pretty clever! I can't determine from photos if the K100 does this or not. It could certainly change the rifling or cam twist to do so if it doesn't currently, but until I know I give the advantage to Beretta.
The recoil spring on the K100 is not captured, and does not extend all the way to the mag well like the PX4. This makes it a harder recoiling gun. You may think that having a recoil spring that is completely captured by its guide, and seated an inch into the transfer block at one end and slide hole at the other is a small matter, but imagine you are trying to field strip and fix a gun in conditions like those during the sandstorms of OIF, where vis is about a foot and if you drop something it will disappear into brown talc-like sand. In fact, it is not possible to assemble the PX4 improperly from a field-stripped level take-down. That is a very nice feature if you are issuing the weapon to thousands of people with who knows what skill levels.
Finally, the K100 is bragging about the K100 having been tested to 150,000 rounds. Well, as a competition shooter I might find that of interest, but even then a $25 locking block easily solves the problem and can be done at the range in 90 seconds. I should also note that this was not independent testing that was done, and testing done by the mfg is about worthless as an indicator of anything.
What I do like about it is the squared off trigger guard, general slide shape, and weight. If you just can't carry another 10-12 oz around all day then by all means keep your bladder empty, don't render your PDW ineffective by removing weight critical for the control of the weapon. In short, if the K100 underwent testing by the US DOD or some such agency, then I would be more receptive. I think it is an interesting design, one I could easily improve on as suggested here, but I still think Beretta did a better job considering all the requirements. I don't hate the gun, and think it is interesting and likely better than an M9, but I still think a Cougar/PX4 is a better design - especially if they would just make an M9 length barrel for it like the .45 ACP version.