I just got my “dream gun”, an arsenal-rebuilt Walther P1 from the West German Army (now Re-Unified Germany). As far as I can tell it is the same as a Walther P38 but with an aluminum frame instead of an iron one. Several of us went in together to get a $10 discount from the regular price of $259 and out of the five that we purchased I got the lemon. The way the other four shoot vary from a fantastic 2" group at 25 yards to a still fantastic 3 inches. Mine puts ten shots into a cool 12-inch pattern that looks like the proverbial shotgun blast with 00 buckshot. I swapped my barrel and slide with my buddy’s pistol that does 2-inch groups and it does the 12-inch pattern trick with that frame, too, while my frame with his barrel and slide still does 2-inches, so it is somewhere in my barrel and slide assembly where the problem lies.
These pistols are new with the exception of their frames; the frames were checked over and rebuilt with new steel inserts installed in them. New barrel, slide, trigger assembly, etc. I checked the sights and the barrel-to-slide lock-up to see if anything was loose, but the barely-noticeable slack between the barrel and slide when they are locked together in no way would cause a foot worth of inaccuracy at 75 feet. I did the geometry calculations and found that for that to happen, the slop would have to be a whopping 1/16-inch of wiggle and play to cause that much trouble. I checked the play with a dial indicator and it is .015”, which gives a theoretical 2-inch group at 75 feet. That is what the other P1 I shot has!
I slugged the bore and found that it has a 0.358” groove diameter with 0.348” land diameter, the groove diameter being two-thousandths over the 0.355”-0.356” that the 9mm Parabellum is supposed to run. I don’t know how much effect that has on accuracy since I quite often run 0.356” boolits in my three Smith & Wesson .357s and they don’t go nuts spraying shotgun type patterns. With boolits that are 0.002” undersize for my Smith & Wessons, the groups do open up very noticeably to double the size, but they only open up one or two inches at 25 yards, they don’t increase to a whopping 14-inches! The same goes for my rifles, I run 0.308" boolits in my 0.312" bore Mosin-Nagants and they go from 2-inch groups to four or so inches at 100-yards, not to 48" groups that is the equivalent of what this Walther P1 does!
The cartridges that cause the most trouble are store-bought 115-grain full metal jacket round nose Winchesters. Because I am waiting for a Lee 0.356” 124-grain truncated cone mould to arrive, I bought some already cast boolits to get started reloading with real boolits for my P1. Those boolits shoot a much more realistic group, ten shots making only a 10-inch shotgun-like pattern instead of the abysmal 12-inch group. I have been loading them with 5-grains of Unique, which is the only pistol powder I have right now here where I am. I also re-crowned the barrel; I cut it back about 0.003” with a large 60° lathe center drill to clear any small nicks and dents at the end of the bore and then went in with a #2 Morse Taper reamer and cut an additional slight chamfer a few more thousandths to clean up the ends of the land tops. Doing the re-crowning got things down to a more reasonable 9-inches at 75-feet! The bore is just as pretty as can be, being brand new fresh cut with a mirror shine. When I slugged the bore the lead slug pushed down through the barrel nice and smooooooth, no hang-ups or tight spots at all. Of course I have a few guns with crappy sewer pipe bores that are pretty good shooters, too. Go figure!
I also just bought a new Cz85B (same as a Cz75 but with ambidextrous controls) and it is one of the finest 9mm Parabellum autoloader pistols I have ever shot, right up there with that OTHER Walther P1 that does 2-inch groups at 75-feet and my Browning High Power. My Cz85B does 4.25-inch groups at 75 feet with store bought ammo and with the 115-grain cast ammo loaded with 5-grains Unique it does an honest 2.5-inches! It feels good, to. That is important. My new Walther P1 has got the "feels good" part just fine, IT JUST DOESN’T SHOOT!
I’m out of tricks that I know how to do, what should I look at next to turn this Walther P1 back into my dream gun instead of the rotten nightmare it is right now?