Crosman Challenger PCP target rifle.
How we fix them today (Part 1 to this report)
Part 2
This report covers:
- History of the Challenger tune
- More to it
- Conserving pellets
- Thank heaven…
- Start
- Two observations
- Adjust striker
- Adjust striker again
- Third striker adjustment
- Shot count
- Where does that leave us?
- Summary
Today I’ll adjust the velocity of the Crosman Challenger to get it shooting where I want. Where I want it is around 560 f.p.s. with an 7.8(ish)-grain target pellet.
History of the Challenger tune
In 2009 the H&N Finale Match High Speed pellet (7.87-grains) that’s now obsolete averaged 545 f.p.s. in this rifle. In 2020 the same pellet averaged 565 f.p.s. The spread in 2020 was 15 f.p.s. Of course in the recent overhaul I changed the firing valve, so it’s a whole new ballgame.
More to it
There is more to this test than just velocity. In 2009 the shot count for the Finale Match High Speed pellet was 116 shots on a 2000 psi fill. In 2020 the shot count was 110.
Conserving pellets
Obviously I need to shoot a lot of shots to test this rifle. After adjusting the velocity to where I want it I will shoot a string of blank (no pellet) shots, followed by a shot for record. If I get to shot 100 I will shoot each shot after that with a pellet.
Is this a legitimate test? Yes, it is because I told you what I’m doing. You may feel that a blank shot may not use as much air because the pellet isn’t in the barrel to hold the firing valve open. I would agree. I just don’t want to waste these pellets that I can no longer get because they are the baseline pellet for this rifle.
Thank heaven…
… for that overhaul video! Back in 2009 I thought that adjusting the striker length longer would increase velocity, but I now know it does just the opposite. It gives the hammer a longer run before striking the firing valve stem and that pushes the valve open a little longer, allowing a little more air to escape.
This time I will adjust any gross velocity changes (10+ f.p.s.) with the striker length and any fine changes (-10 f.p.s.) with the hammer spring adjustment). Let me show you what I’m referring to.
Start
The rifle was filled after the overhaul and was still holding at just under 2000 psi — maybe 1950 psi? So I shot a first string of 10.
Shot…….Vel
1………….378
2………….441
3………….did not register
4………….463
5………….467
6………….473
7………….481
8………….472
9………….479
10………..475
Two observations
I saw two things from this string. First, the rifle needed a lot of adjustment to get up to my 560 f.p.s. goal. But second, I felt a LARGE puff of air from the action on each shot. There is always a puff with each shot but this one is too large. Apparently I did not install that transfer port seal as well as I should have. We’ll see, but if I can get at least 40 good shots from a fill I’m leaving things where they are, because that transfer port seal is very difficult to install.
Adjust striker
I now adjusted the striker length by one full turn counterclockwise. That gave me this.
Shot…….Vel
1………….522
2………….517
3………….507
Just like in the overhaul video, one turn doesn’t adjust that much. Let’s do another.
Adjust striker again
Another full turn counterclockwise gave me this.
Shot…….Vel
1………….533
2………….530
3………….540
Third striker adjustment
This time I turned the striker adjustment two full turns counterclockwise. That’s a total of four turns from the start. And I got this.
Shot…….Vel
1………….555
2………….569
3………….556
4………….553
5………….571
6………….559
7………….566
8………….566
9………….567
10………..554
The average for this string is 566 f.p.s. I would have accepted that if we weren’t learning how this process works, but we are so now I dialed the hammer spring tension back (counterclockwise) one-half turn. It is FAR more difficult to determine how far back you dial the hammer spring because the knob is knurled with no reference point, plus it’s in a place that’s hard to access. So I just guessed at what I was doing. Then I shot another five shots.
Shot…….Vel
1………….546
2………….547
3………….544
4………….541
5………….544
Okay, apparently I went the wrong way. So I dialed the hammer spring knob clockwise 1-1/2 turns. What did that do?
Shot…….Vel
1………….537
2………….533
3………….537
4………….540
5………….543
Now I wondered if so much air had escaped from the bad transfer port seal that I was off the power curve. So I cranked the striker adjustment another full turn, which makes five fill turns from the start. I now got a velocity average for ten shots of 558 f.p.s. No, the power is where it is supposed to be.
Shot count
At this point in the test I had fired the rifle a total of 46 times. So now I started shooting blanks and recording pellet velocities every ten shots.
Shot…….Vel
50………..560
60………..549
70………..547
80………..540
It seemed the velocity was falling, so I shot another five pellets, one after another, to see.
Shot…….Vel
81………..534
82………..531
83………..536
84………..532
85………..526
Yep, the rifle has fallen off the power curve. So I refilled it to 2,000 psi using the G9 hand pump and then shot another string of five.
Shot…….Vel
1………….564
2………….559
3………….563
4………….564
5………….556
I would say the rifle has returned to where it was after this fill. You can argue that I had cranked the striker another turn shorter, but it has either bottomed out or for some other reason the last adjustment doesn’t seem to have affected the velocity that much.
Where does that leave us?
As far as I’m concerned, this rifle is ready to be tested for accuracy. I don’t like the strong puff of air on every shot, but if I hold my shots to 40 per fill the rifle should be okay.
Will I fix the transfer port seal? I will if I can find where someone addresses how to make that seal work. It is a bit of work to get to that seal, but if I had a feeling I could do it better, I would.
Summary
This test reveals the absolute need for a chronograph. I wouldn’t have been able to do today’s tests or adjustments without one.
Tom,
That is a finicky part to seal properly. I can imagine Bubba putting some silicone caulk to ensure the seal is good.
Siraniko
BB
“This test reveals the absolute need for a chronograph.”
For a tuning guy it is a must have.
Guys, yesterday I got a present from our friends – a top condition Diana 25D. This is so much fun to shoot, amazing.
tomek,
That definitely a very far cry from what is usually available to most people. Wood and steel with minimal plastic. I can just imagine you smiling as you shoot it.
Siraniko
Siraniko,
This is similar to HW30S. You can’t stop shooting it. Old school.
EDIT: there is no plastic.
tomek,
Now THAT is really Old School!
Siraniko
Tomek, please tell us all about it. If it is a D version, I would expect the trigger to be plastic with two small adjustment screws in front of it. What is the date of manufacture?
tomek,
I am officially jealous.
RR,
It was a big surprise for me – it came out of nowhere. Our friends bought a house and there were many things there. They found this rifle and immediately thought of me (they know how bad I am). Yesterday they called me and I said, “WAIT FOR ME!”
This is the 25D S model. I checked it again and noticed that it has these two adjustment screws. The trigger is made of metal. I can’t find any serial numbers on it, I don’t know how old it is but it should be pretty old. It’s all made of metal and wood. After I applied some oil and grease, the ECON II pellet now has a stable 532 FPS. It is very accurate. This Old School a bit of recoil and great trigger. I will not touch those srews 🙂 It was just like a rainbow when you down yesterday! 🙂
Along the left side of the tube, does it have a stamp that says “Made in [West] Germany” and a date stamp showing month and year of manufacture? Perhaps the stock is hiding it. Congratulations on the find!
Roamin, you’re a genius! I couldn’t see it.
This is 1978. Amazing.
Not a genius. I have had quite a few Diana’s come to stay at Roman Greco’s Institute for Airgun Appreciation (RR, emphasis on Appreciation ;o) ), RGIAA.
I can’t wait to tell you guys about my most recent PERMANENT resident.
Roamin…. “my most recent PERMANENT resident” – holy moly!!!! Tell all about it. NOW.
tomek,
I already know the answer, but if you should go insane, there is a home for that Diana here at RidgeRunner’s Home For Wayward Airguns. 😉
RR,
I will go soon, so please take care of all my metal rods around of a column of air. 😛
I would gather your detuned 34 is just as nice…just a bit longer.
Maybe. By the way, it has found a new home. How do you think I acquired the Gamo?
You traded a classic Diana 34 tuned by the Godfather himself for a Gamo? I’m speechless!
RG,
Yeah, I understand what you are saying. I wanted to see where Gamo was now. It is not like I do not have some very fine “old gals” hanging around here. There are a couple of REAL nice ones I have not even talked about yet. It is not that I am likely going to miss that 34 much and just maybe she will start an “old gal” collection there.
I actually replied to you both Guys under RR’s post.
The sound of break and cock is just so damn “stable” – did they do some noise quality improvement in those days?… I have lost the rest of my faith in the newest technology.
tomek,
Most of my “collection” is old school. I am not impressed by much of what I see these days.
A toast to “old school” and old curmudgeons too! That is an incredible find, tomek. FM shakes his head though, at the thought of, “who leaves behind a beauty like Diana?” But as it worked out to your benefit and Diana’s, toast that too. To this day FM does not forget leaving behind his toy Civil War cork-ball shooting musket when his family moved; he was eleven at the time. The family that moved to the former home included a boy about FM’s age, as he subsequently found out. As far as the new kid on the block was concerned, it was “finders, keepers.”
At least little FM hung on to the companion percussion cap pistol that came with the musket. Still have it – and there was no plastic used in manufacture. 🙂
Let’s raise our glasses!
This is really getting interesting. B.B. Thanks for the peek over your shoulder as you struggle with the overhaul. I don’t think I could leave that seal alone. I would feel compelled to start over and try to get it to seal properly. Perhaps emailing the author of the YouTube video for advice? He may have some tips for you. Good luck. Can’t wait for the next installment.
As RG states, I for one could not leave that transfer port seal alone.
Would liberally smearing that seal with a suitable lubricant and s-l-o-w-l-y carrying out the tricky procedure maybe do the trick?, asks FM The Unready To Take On Such A Task.
Basil,
I doubt it. The seal already wants to squirt out from its location.
BB
B.B.,
Back a decade or so ago the Crosman Green Forum had all your answers. The breech (Receiver) on your rifle is from the 22XX family and Transfer Ports (TP) were often replaced with refrigerator ice maker water tubing cut to the correct custom length with an Xacto knife or razorblade to improve the TP sealing at hpa pressures rather than the much lower CO2 pressure level. Crosman seems to have never gotten the TP issue fixed since i hear the puff of air complaints frequently. The ice maker tubing takes a bit of try fitting but does work well.
shootski
shootski,
Thank you for this.
BB
BB, I am guessing that you followed the video steps closely. So this probably isn’t the problem. However, I noticed that he took considerable time and effort to adjust the barrel so that it was “parallel” and floated in the band closest to the muzzle. I had a similar problem (large puff of air leaking during the shot) on the Crosman 3622 rifle. I also noticed that the bolt didn’t turn down all the way. It turned out that all I needed to do was adjust the barrel slightly by twisting it. Problem solved.
Elmer,
I never loosened the barrel, but yours is the first good suggestion I’ve had. I need to look into it deeper and I will probably still run an accuracy test first, but thank you.
BB
Going from memory, I believe he (after a couple of tries to align things) loosened up the two barrel set screws in order to help align the port items. Then slowly and methodically tightened the various set screws while aligning the barrel with the bands, etc.
Elmer,
I will review the video when I can. Thanks,
BB