Well I finally a pre-mod baseline for my 1377. I suspect this is fairly typical performance for a stock 1377.
I didn't get any really light pellets, just stuck with medium to heavy. I plan on trying some lite pellets (<7gr) but won't hold up the mods for it.
The pellets that I used were: Beeman Laser, CPHP, Polymag, RWS Superdome, JSB Exact, CPUM, Big Boy, and (because I just couldn't resist) Eun Jin.
Not surprising that the lightest pellets were the fastest but the fpe was pretty similar across the pellet weights for a given number of pumps.
Pellet Beeman Laser 7.1 gr
Shot fps fpe
2 292 1.34
3 350 1.93
4 377 2.24
5 419 2.77
6 430 2.91
7 455 3.26
8 473 3.53
9 487 3.74
10 499 3.93
Pellet CPHP 7.9 gr
Shot fps fpe
2 272 1.30
3 322 1.82
4 356 2.22
5 395 2.74
6 419 3.08
7 429 3.23
8 449 3.54
9 462 3.74
10 474 3.94
Pellet Polymag 8 gr
Shot fps fpe
2 293 1.52
3 326 1.89
4 359 2.29
5 393 2.74
6 413 3.03
7 436 3.38
8 453 3.64
9 468 3.89
10 479 4.08
Pellet RWS Superdome 8.3 gr
Shot fps fpe
2 232 0.99
3 295 1.60
4 341 2.14
5 376 2.61
6 402 2.98
7 417 3.20
8 436 3.50
9 458 3.87
10 473 4.12
Pellet JSB Exact 8.4 gr
Shot fps fpe
2 293 1.60
3 319 1.90
4 364 2.47
5 387 2.79
6 417 3.24
7 447 3.73
8 450 3.78
9 459 3.93
10 468 4.08
Pellet CPUM 10.5 gr
Shot fps fpe
2 235 1.29
3 287 1.92
4 315 2.31
5 346 2.79
6 364 3.09
7 386 3.47
8 389 3.53
9 414 4.00
10 432 4.35
Pellet Big Boy 13 gr
Shot fps fpe
2 216 1.35
3 273 2.15
4 292 2.46
5 320 2.96
6 340 3.34
7 352 3.58
8 368 3.91
9 379 4.15
10 391 4.41
Pellet Eun Jin 16 gr
Shot fps fpe
2 Error
3 233 1.93
4 254 2.29
5 275 2.69
6 297 3.13
7 310 3.41
8 329 3.85
9 336 4.01
10 350 4.35
At these low energies the real issue is which pellet is the most accurate, so I'll be checking this next. I may write up reviews on each pellet as I go, if anyone is interested.
Quotefor a given number of pumps.
Can we assume that would be 10? :)
Cheers,
Quote from: JEBert on August 02, 2011, 06:24:56 AM
Can we assume that would be 10? :)
Cheers,
It was actually reasonably similar from 2-10 pumps, between pellets. I thought so anyway.
OK, My bad. I see that now by the fps. It was under the column Shot and I thought it was shot #2-10 and thought that #1 didn't register on the chrony for some reason.
Cheers,
hummm
numbers look kinda low
most 1377's shoot around 525fps or at least over 500
have you taken the gun apart yet!
do a tissue or powder test
take the tissue put it across the bolt and at the bottom of the breech where the transfer port is
pump a few times shoot no pellet necessary if the tissues moves you have a leak
works the same way with powder
Bummer, i'm missing ~50fps. I did take it apart to do some trigger work and install a steel breech after this testing. I didn't see anything wrong with the transfer port o-ring but I didn't look real close either. I'll do the tissue test and report back.
Just found this. Great post, thanks for the info. I saved the data in a Word file for future reference. I hope you don't mind.
It seems like 5 pumps out of the stock gun approximately equals a CO2 gun of about the same size.
Quote from: JEBert on August 02, 2011, 09:19:02 AM
OK, My bad. I see that now by the fps. It was under the column Shot and I thought it was shot #2-10 and thought that #1 didn't register on the chrony for some reason.
Cheers,
Not sure why I put "Shot" for the first column heading, its a little misleading. It should be "pumps."
Smaug - No problem. I hope its useful information for your moding.
Quote from: 1377x on August 02, 2011, 04:03:14 PM
hummm
numbers look kinda low
most 1377's shoot around 525fps or at least over 500
have you taken the gun apart yet!
do a tissue or powder test
take the tissue put it across the bolt and at the bottom of the breech where the transfer port is
pump a few times shoot no pellet necessary if the tissues moves you have a leak
works the same way with powder
I tried the tissue test and there doesn't seem to be air leaking from the transfer port. Is there another test for missing fps? How can I tell if I am getting efficient pumping (if the piston is getting a good seal on the tube)?
im having the same problem with my 1389
at first i tought it was the breech/barrel set up switched to a steel breech and barrel(phase 3)
still the same fps very low
now im thinking its to much headspace between the piston and valve as for a test i dont have a clue
im going to try some flour on the end of the cup see if it transfers to the valve
Tried the tissue test and had the tissue blown off. Not sure if it is the transfer port or the when the bolt kicks back some after firing.
Quote from: Make MY day on August 22, 2011, 02:50:18 AM
Tried the tissue test and had the tissue blown off. Not sure if it is the transfer port or the when the bolt kicks back some after firing.
what i do is turn the gun on its side lay the tissue aprox.where the transfer port is fire if it flies off there is a leak
then i lay the tissue to the top of the bolt if it blows off there is a leak.just fixed a bolt leak a couple days ago
after doing this test
What did you do to fix the leaks?? On the steel sleeve, which way does the longer end go, Up into the barrel or Down? Checked today again and still getting the tissue blown off both areas. New barrel and bolt.
Quote from: Make MY day on August 23, 2011, 12:49:21 AM
What did you do to fix the leaks?? On the steel sleeve, which way does the longer end go, Up into the barrel or Down? Checked today again and still getting the tissue blown off both areas. New barrel and bolt.
to fix the leaks i put new o-rings in
the sleeve goes big end up
Has anyone come up with an accurate Baseline for the 1377C up to 15-20 pumps???
So I was inspired to do some power mods by this thread:
http://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=3688.msg35888#msg35888 (http://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=3688.msg35888#msg35888)
My goal is to maximize fps at 3 pumps. The following tests were performed with JSB Exact 8.4gn.
Results:
Pumps fps Mod 1 Mod 2 Mod 3 Gain
2 293 293 304 304 11
3 319 338 345 357 38
4 364 376 389 400 36
5 387 400 414 432 45
6 417 428 446 459 42
7 447 447 463 484 37
8 450 458 475 503 53
9 459 462 482 518 59
10 468 482 507 535 67
First column is stock and the other three are mods.
Mod 1 File valve and shim with one washer
Mod 2 File valve and shim with two washers
Mod 3 File valve and shim with one washer and paper, stiffen piston
Just to see what would happen I took it up to 15 pumps.
11 547
12 557
13 560
14 572
15 581
I'm very happy with the results so far. Next up will be a reduced volume valve to get the pressure up faster.
nice numbers!