by B.B. Pelletier

Part 1
Part 2

Velocity test, part 2
Today, we’re going to adjust the power of the Crosman Silhouette PCP pistol. This is a second velocity test for this gun. Before adjusting, I read the owner’s manual, which in this case provides a lot of very instructional information about this procedure.

I learned that the fill pressure of the pistol is also adjustable, and the factory sets it at 2,900 psi and not 3,000. While the difference between 2900 and 3000 may seem small to you, look at the shot string I fired in Part 2 and notice that it took at least five shots to get up on the power curve when I filled the gun to 3,000. Son of a gun! Maybe Crosman knows what they’re doing, and maybe we should be reading these manuals before shooting the airguns. And, when I say “we,” I mean me.

Variable fill pressure
According to the manual, you can adjust the gun to operate on a fill of 2,500 psi, all the way up to a fill of 3,000 psi. This is achieved by adjusting two separate things. The first is the hammer-spring tension and the second is the hammer-stroke length. These work together to control the force of the impact on the valve stem as well as the dwell time that the valve remains open.

Delicate balance
However, as the air pressure inside the reservoir increases, the pressure that closes the valve changes, as well, so that also affects the length of time the valve remains open. What I’m saying is that there is not a straightforward adjustment. It’s a balancing act between the fill pressure, the length of the hammer stroke and the tension on the hammer spring. You have to use a chronograph to adjust the gun–ther’s no way around it. Without a chronograph, you’re just guessing.

Crosman even provides you with a simple chart of the effects of adjusting both adjustments. Cutting to the bottom line, a long hammer stroke and heavy spring tension will boost the required fill pressure as high as it will go and give you the most powerful shots the pistol is capable of. Coincidentally, it will also give the greatest number of powerful shots that can be gotten from the pistol. Since that’s all I’m after in today’s report, that’s what I did. Before I move on to the test, a word to everyone who has an interest in this pistol.

Get to know your airgun
Crosman has given us something rather unique in the Silhouette PCP. They have given us these two adjustments so we can adjust the gun to do exactly what we want to do. That’s not common, and we need to take a moment to appreciate it.

When I worked at AirForce Airguns, we used to get questions all the time about what power adjustment wheel setting should someone use to shoot such-and-such a pellet and a velocity of X f.p.s. Well, heck, how should we know? How would anyone know who did not have that individual gun and a chronograph to do the necessary testing? Yet, these same people would get on the forums and trade their favorite power wheel setting back and forth as though they were precious formulae or something.

Here’s a partial score: Cleveland 3.

Doesn’t tell you very much, does it? Well, the adjustment of the Silhouette PCP is going to be very similar to that. It’s an individual thing. Each gun is unique and each responds to adjustment in a slightly different way. If this is a gun you see in your future, plan on getting a chronograph to go with it, or plan on not adjusting the gun.

On to testing
This test will be different than most because I’ll be adjusting the gun as I go. Whenever I make a change, I will note it and then continue with the string. I used the Crosman Premier 7.9-grain pellet.

For the first shot, I adjusted the gun following Crosman’s instructions to the letter. The hammer-spring preload was adjusted to the max, and the stroke was adjusted as long as possible. The gun was filled to 3,000 psi and these shots resulted.

Shot…Velocity
1……….416
2……….422
3……….414
4……….417
5……….423
6……….425
7……….422

At this point, I realized that the gun wasn’t set up to give me what I was after, which was maximum velocity, so something had to change. I turned the hammer-stroke adjustment in, which is contrary to what Crosman says to do.

8……….456
9……….461

This was working, so I turned the stroke-adjustment screw in some more.

10………470

More in.

11………492

More in.

12………504

More in.

13………497
14………503
15………502

At this point, I figured the hammer stroke was adjusted as well as it could be. Since the hammer-spring tension was supposed to be at the max, I turned the adjuster off a little.

16………489
17………484

Then, I put the tension back where it had been.

18………501
19………502
20………496

At this point, I adjusted the stroke back out four turns.

21………468

Then, two turns back in.

22………488

All the way in (two more turns).

23………500
24………499
25………495

The remaining pressure in the gun was 2,300 psi according to the onboard gauge.

26………502
27………498

Then, I shot two Crosman High Velocity Super Sonic pellets to see what the maximum velocity would be.

28………622
29………619

Then, I switched back to Premier lites.

30………492
31………498
32………498
33………498
34………Did not register
35………499
36………494
37………493
38………491
39………491
40………489
41………486
42………487
43………490
44………481
45………481
46………478
47………477
48………470
49………469
50………465
51………463

That’s my report. With Premier lites, I got just over 500 f.p.s. With High Velocity hollowpoints–about 620.

The adjusting is easy but a chronograph is an absolute necessity, and I hope my report demonstrates why.