Playing With my Crosman 1701P

[DRAGON64]

So I started out to clean the 1701P, but ideas just seemed to barrelroll from there.  I started by removing the brach and barrel assembly from the air tube.  It is a nice feature, as the pistol does not need to be degassed to do this.  My main reason for removing the breech assembly was so I could see the transfer port 

The barrel cleaned in two passes with a wet and 2-passes with a dry patch... but the transfer port needed a little attention to.  I took the tranfer port, and modified it by drilling it out to .062" from .04"  I wanted to up the fps of the pistol, which was factory set at 450, adjustable to 550.  I finished my cleaning, and put the pistol back together, here are the numbers:

Filled to 2800 psi, the first shot was 422 fps    But the more I shot, the more the fps climbed, until I ended with a high of 577 fps and a pressure of 1600 psi.  That is an fps spread of 155 fps over 45 shots.  The PSI seemed to hold steady starting at 2000 psi when the pistol was shooting around 560+

Not very scientific right.  It was not meant to be, as I just wanted to see what changes drilling the transfer port made, prior to making further adjustments per the manual.

Here is my lab:


Test subject in the hot seat:


With no adjustments to the pistol other than the tranfer port drilled to 0.062" I achieved the following numbers in a 45-shot string:

Starting fill= 2500 psi

Low# 484.3
high# 583.6
ext spread: 99.3
Avg FPS= 552.98
Avg FPE= 4.03



Next, I made adjustment to the hammer spring and hammer stroke adjustment screws.  I wanted to obtain high fps shots from a higher psi fill.  As seen in the graph above, fps is low at higher psi fills.  Noted in the first shot fired after drilling the transfer port, at 2800 psi the pistol shot a measly 422 fps.  Below I logged a new tune...  I did not erase factory adjustments by begining at zero, instead, I made adjustment s off of the factory settings:

Stroke= 2.5 revolutions CCW from factory
Hammer Spring= 1 revolution CW from factory
2800 psi fill

Low# 609.5
High# 630.4
Ext spread 20 psi (I cheated and rounded the 609.5 up to 610)
Avg FPS= 623.24
Avg FPE= 6.82
24 nice shots



My goal is to reach 8 FPE so that I can use this pistol in pistol field target.  6.82 is a little low, especially since this measurement was taken 12" from the muzzle, and I will need to address targets up to 35-yards away.  More tuning tomorrow, but I believe that I am on the right path.

[quickster47 †]

Excellent information for those of us with 1701P guns or those thinking about getting one.

Carl

[DRAGON64]

I managed a high of 666.6 fps, but the pistol was a bit of an airhog, consuming 1200 psi in 20-shots.  I will need to keep playing, but I believe I am at the limits of this small air tube.

[quickster47 †]

I managed a high of 666.6 fps, but the pistol was a bit of an airhog, consuming 1200 psi in 20-shots.

While that is very good power for the 1701P that 20 shots is almost a killer for making the mods.

Will be interesting to see if you can squeeze some more shots out of it.

Carl

[AZAG]

Nice testing, thanks for sharing.

What pellet are you using?

[DRAGON64]

Nice testing, thanks for sharing.

What pellet are you using?

Crosman Premier Lights from the box.  I am fixing to change over to JSB Domes (8.4gr) and see how they perform, both in fps and accuracy.

[Crosshairs]

Very nice your great post got me thinking to myself should get one. 
                                                Mike

[DRAGON64]

I have only recently begun to play with my 1701P, but I have had it for like a month and a half now...  It is quite accurate right out of the box, but shoots a little slow for what I hope to use it for.  Pricier than a 1377, but it seems to compliment the my Marauder nicely.  I like it!