A Previously Used, Misbehaving Airgun Is A Great Teacher!
HAM reader Matt Coulter brings us this interesting saga about a previously used, misbehaving airgun that he purchased some time back. Take it away Matt…
In his role as Forest Gump, Tom Hanks spoke these words while sharing a bench waiting for a bus to arrive:
My momma always said, “Life was like a box of chocolates. You never know what you’re gonna get.”
My recent experience trading a few mid-level air rifles for a used .25 caliber Kalibrgun Cricket has been an interesting journey. One, which in many ways, reminds me of this iconic movie…
Below. The view through the SWFA 16×42 SS scope looking at a target positioned at 63 yards.
Allow me say up front that I don’t regret doing this trade for one second, nor do I believe the other party misrepresented anything about the rifle I received in trade.
Consider just how different people’s expectations can be with air rifles and how their intended use defines expectations of how the gun “should” perform.
As far as I can tell, I am at least the third owner of this specific rifle.
Blanka from Kalibrgun.ru has been very helpful and was able to provide me a bit of history regarding this particular rifle. It was originally imported to the US by Airguns of Arizona in the fall of 2014. The person I acquired it from used it specifically as a hunting rifle. As such, this Cricket had come to him from the previous owner having been “power-tuned”.
Houston, We Have a Problem…
I am not a hunter, but I have had the privilege of shooting a variety of Crickets in the past. This means that I have experienced just how accurate these guns can be!
Also, I didn’t have any illusions about some of their shortcomings either; they do have magazines that can be “fiddly” to insert. Furthermore, their bullpup configuration isn’t considered the best choice for backyard-benchrest shooting that I do most often.
But, like other platforms that have been in production for some time (the Hatsan AT44 and Benjamin Marauder come to mind here) the Cricket is well-designed with good track record.
As the previous owner had told me, I found that my new-to-me Cricket was indeed a hard-hitting air gun! It arrived shooting .25 caliber JSBs at a solid 60 Ft/Lbs of energy. I chronographed it achieved this level of power with both 25.4 and 33.4 Grain JSBs.
But there were signs that this was a misbehaving airgun. You see, the chronograph also revealed that these shots were swinging wildly in velocity. Across its 12-shot magazines I was seeing over 100 feet-per-second velocity spreads. Wow!
Below. Here’s an early example of Matt’s tunes as he started to bring the Cricket under control. Now he was at 100 FPS spread across a complete fill, not just one magazine!
These variations simply were not going to work for me in my use of the Cricket as a target gun. Had this been my first PCP, I’m not sure if I would even know where to begin to look in correcting this issue.
Fortunately, I have owned a few PCPs and it began to sink in that getting this gun to perform the way it should is going to be a bit of a journey! Being a regulated gun the Cricket definitely should not be doing performing this way! But with a used, misbehaving airgun, where do you begin in unraveling what’s going on here?
Measurement with the chrony captured the problem.
The sound and feel of the shots led me to suspect mechanical issues were at play here and the gun’s regulator wasn’t necessarily the culprit.
After a few magazines of test shots, I was able to map the sound of these slow shots to what felt like light hammer strikes on the airgun’s firing valve. I also experienced a few occasions where I felt binding when cocking the gun.
Below. Matt recommends photographing EVERYTHING as you work on your airgun. That’s great advice! Here’s he’s testing and measuring the preload on the firing valve after putting an OEM spring back into the Cricket.
With a Little Help from my Friends
So there I was during my Christmas and New Year vacation with a “new-to-me” misbehaving airgun. Fortunately, we have a great online airgun forums where folks are generous with their knowledge!
With help from the forums, I was able to confirm my suspicion that the aftermarket hammer spring adjuster that came with the gun likely was affecting the hammer strike and causing the inconsistent velocities. In addition, I was quickly offered a replacement adjuster that would hopefully take care of this problem!
Fortunately for me, the rifle was sound, seemed to show very good accuracy potential, and I found it very easy to work on. By this time I had some practice breaking it down and reassembling it again!
I felt this hammer spring adjuster replacement gave me hope for a more reliable baseline in my tuning efforts. Moving forward, I had a few simple goals as I learned some of the finer points of this rifle. These goals were to:
1. Stabilize velocity
2. Understand regulator behavior
3. Test accuracy at various velocities
4. Explore efficiency and finer tuning characteristics
With the new hammer spring adjuster stabilizing the huge velocity swings, further chrony testing still showed that I had two more issues to address that were related to velocity.
One issues was a slow increase in pellet speed over the course of the shot string. The second was a very distinct surge in velocity at the very end of the string (when the regulator set pressure was being reached).
The “AHA!” Moment
No amount of hammer spring or regulator adjustments seemed to get me any closer to finding resolution to either of these issues. My “AHA!” moment was when I decided to reseal the gun to correct a slow air leak that had developed.
In doing this resealing, I came across Ernest Rowe’s video showing the valve stem adjustment that this gun is capable of.
Initially, I was dismayed by finding one more variable that I had to test and understand. However, it also became apparent that my valve did NOT have anything like the original spring inside of it!
I have to assume that the “power-tune” my gun had received also included a much weaker spring than that originally fitted to the gun. By this time I was in fairly regular communication with a very skilled tuner who provided me with a couple of OEM springs.
Below. Four 6-shot groups at 50 Yards with JSB 33.4 Grain pellets.
I was quick to install a new spring and made my best guess at how much preload should be applied to it.
This new spring immediately helped with the occasional velocity drops and surge towards the end of the string. However, I lost much of the range of velocity that adjusting the hammer spring typically provided.
I was still seeing a velocity of 855 FPS which was MUCH higher than before – even at the lowest hammer spring tension. And after adding five turns of tension on the hammer spring (in a Cricket these are clockwise turns) the velocity only climbed to 885 or so FPS.
My assumption here is that the firing valve preload was way too light. Time to dump air, disassemble, and add some more preload!
While making multiple changes at the same time generally isn’t a good plan, I went ahead and brought up the regulator pressure to what it was set at when I received the gun (120 bar).
Then I put it back together! Now the velocity range was well over 125 FPS (it could be much more, but I did not feel the need to drop the velocity below 825 FPS (at 3.5 turns of the hammer spring). But perhaps more importantly I was seeing an extreme spread between the high and low velocities of only 12 FPS across 60 shots!
Happily, I am able to report that the gun continues to shoot steady and respond to normal tuning techniques.
I’m able to easily use the external hammer spring adjuster to fine-tune the velocity to determine just how fast any given pellet “wants” to be shot. And these velocities are steady across the entire air fill!
Now I can truly say that had I given up on this rifle and sent it back to the previous owner, I would be so less informed about the inner workings of air guns!
And since my gun safe only houses one air gun, I don’t feel the least bit bad about giving my reborn Cricket – that formerly misbehaving airgun – my FULL attention…
– There is no substitute for having a chronograph in understanding your gun’s behavior.
– When working on a gun, document EVERYTHING with photos! You never know when you will need them!
– Keep notes when testing. Life happens and what you think you will remember often gets lost or forgotten.
– Become active on one (or more) air gun forums! Folks there are simply the best and are so generous with their knowledge and experience.
– When in doubt try to determine the history of your gun and what my have been changed inside of it.
– Resist the urge to change more than one thing at a time (I am not always good at this and regret being this way more often-than-not!).
Matt, thanks for sharing your interesting story and great photographs about your misbehaving airgun with us. Congratulations on your persistence and excellent results!