The internal difference is the block and how that all works together. The 602/603 both use the newer style block and is a much better design imo. The 600/601 block is still nice though, just a lot more dated by todays standards! The seals are also different between the old and new style block.
Other differences include the ratchet system on the lever, which as you say stops it flying open!
The stock also changed between the 601 and the 602, with the latter having a cleaner silhouette, and it pretty much hasn’t changed since then for the wooden versions! The mounting bolt position does change on the 602 but I’m not sure how far through the production run, all 603s seem to have side bolts front and rear of the action, which again hasn’t changed since!
The 603 is the only one with a stabiliser, or compensator, FWB were late to the game with this as Walther already had one inside the probe of the LGM2. The Stabiliser on the 603 is that odd looking black rod attached near the breech. To be honest I don’t notice the lack of a stabiliser on my 602
A minor detail but the later the gun the more modern the FWB branded diopter is that comes with it!
Slightly obsessed with Single Stroke Pneumatics
Also making stocks over at Daviesbuilt gunstocks.
So i shot the 601 for about a month and ran it over the chrono this evening, all looks about right.
3 x 10 shot strings from cold.
Average speed 593fps with H&N Excite Econ II pellets (7.4grains), 5.78ft/lbs.
1.
Lo 589.5
Hi 596.3
Av 592.2
ES 6.80
Sd 2.44
2.
Lo 591.1
Hi 595.6
Av 593.3
ES 4.47
Sd 1.73
3.
Lo 590.6
Hi 596.8
Av 593.5
ES 6.12
Sd 2.00
Decent pellets could only improve consistency.
I did have the front weight fitted for a while but had to remove it, still felt very unbalanced so last week i cast a few weights for the stock and it feels much better now, i might even want a little more but its ok for now.
288g in the cheekpiece
and another 335g in the stock
Last job was adding a few baffles which turned out great, it's really very quiet now
Does anybody have a 602 or 603 with the dry fire feature ?
Slightly obsessed with Single Stroke Pneumatics
Also making stocks over at Daviesbuilt gunstocks.
I found a drawing for the 603 so i see how the slide fits onto the cocking linkage, i was thinking about attaching a wee rod to the same place on the linkage but coming straight out the bottom and hiding it in the accessory rail.
With the baffles fitted i can cock and fire it's so quiet so dry fire isn't such a priority now but it would be easier not to have to cock it properly every time.
Still undecided on refinishing the stock or not, i was thinking about stripping it and giving it an oil or wax finish with some stippling on the grip, its a bit smooth as is.