What The Heck!?

[BDS]

So I'm shooting my 1377 carbine with FT piston & valve, extended probe, etc, etc. Great gun and chrony's about 640 fps at 9 pumps with CPLs. I decide to also shoot a recent purchase PC77 bought at Walmart, stock gun except for 2289 pump arm and a thorough cleaning and lube etc. I'm shooting some 1-1/2" dia steel discs that stand up in my pellet trap. The carbine is whacking e'm at 5 pumps as usual and they go flying. Then, I pump up the PC77 5 times and let e'r rip... WHACK  , the steel disc really goes flying and the sound of the pellet smashing into the 3/16" thick steel disc is louder than the 1377 carbine! What the heck!? 

OK, let's try this some more, maybe I just hit it dead center? maybe I pumped 8 times? So 5 pumps go into the pistol and again, that target goes flying with a more pronounced whack.

So out comes the chrony, I gotta know whats happening here.

5 pumps each, CPLs in both guns from the same tin, 5 shots over chrony;

1377 carbine fps: 458, 462, 458, 466, 461..

PC77 fps: 477, 479, 488, 483, 480 ...what!?

OK, I gotta see what the PC77 does at 8 pumps... 622, 620, 628, 618, 623 !!! 

So, I'm happy but bewildered. The PC77 seemed harder to pump than normal when it was brand new but, it doesn't seem all that different now than my other pumpers after I shot the first 100 or so pellets thru it a few weeks ago. Or maybe it is but, I'm just used to it? Or did I just get the best set of parts with the best deburr job and assembly and the stars were aligned with the Mayan sun god at just the right time etc?

Gotta go run some 6, 8 and 10 pump chrony tests next... this is crazy, isn't it?

[PC77]

Congrats on your pc it's a keeper for sure. I wonder what it is going to do pumped up all the way?
pc

[breakfastchef]

I hear that every once in a while when the moons align and geo-magnetic polarity is just right, an outstanding shooter leaves the production line. You should be thrilled!

[BDS]

Ya this one is a keeper alright, I just finished modifying the front sight on her, put one of those little fiber optic shotgun bead sites on her (red inner w/ green outer ring). Just cut down the stock sight about 1/4" and super-glued the bead sight on after filing the base of it flat and shiny to hold some glue.

I love these guns, and this one was only $49 on sale at Wallyworld a few weeks back.


Here's the sight, pic enlarged, it's about .030 wider than the Crosman sight base but fits quite well fore and aft...

[airguns100]

That could be a number of things.. My guess is your PC77 is new, holding and expelling air more efficiently, or your check valve could be a mm longer in your PC77, reducing air space in your valve, your 1377 is just getting a tiny bit worn.  Either way, it sounds like your having a great time pulverizing those disks.  lol.   

[airguns100]

Have fun. 

[BDS]

Oh ya, and the discs are 4340 hardened steel from work, they even hold up to .22 rimfires!

[BigErn]

Is this the pc77 you got me for Christmas Brian? 

[Tater]

Here are my numbers using Chronoconnect on my PC77. The 5 pump numbers are really close to yours but mine at ten pumps is WAY less than yours. Thought that was interesting.

Edit - Details from my previous post:  "I ran a test today and here are the results tape measured to 27' with the phone exactly half way in between. I used a 1377 (no power mods except a 12" barrel), CPHP 7.9's and did two 5 shot strings:

5 pumps"

FPS                          FtLb.
459                                   3.7
459                                   3.7
454                                   3.6
459                                   3.7
457                                   3.7

10 pumps

549                                   5.3
540                                   5.1
545                                   5.2
546                                   5.2
535                                   5.0

[BDS]

Is this the pc77 you got me for Christmas Brian? 

Yup, this is the one, Xmas 2020 right? 

[1377x]

i would not take that one apart until a problem happens.shooting to good to mess with it