Beeman R9 with Vortek center-latching air piston: Part 4
by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- Important discovery!
- JSB Exact
- Test restructure
- Predator Polymag
- H&N Field Target Trophy
- H&N Baracuda
- Crosman Premier
- Benjamin Cylindrical
- Velocity comparison
- Retest of JSB Exacts
- Cocking effort
- Going forward
- Testing new designs
Today I will test the Vortek Center-Latching Air Piston in the Beeman R9, with the pressure set at 50 bar, which is 725.19 psi. This is the highest pressure to which I have set the unit, so today’s velocities should be the fastest we will see.
Before we begin today’s test, a remark made by reader GunFun1 to the last report triggered some unplanned testing that revealed some surprising results. He was concerned by my remark that some spring-piston guns (and that is EXACTLY what this center latching unit is) need a “wake up” shot when they are first fired. I have seen this with perhaps half of the springers I have tested over the years. Here is what he asked me.
“BB , Maybe next time you shoot the gun after it has set all that time. Do about 4 or 5 shots over the chrony and see if velocity is low on the first shot.
I’m guessing it will be ok but something to look for.”
So, the day after the last test (which was the day he posted that comment) I chronographed the rifle again with Crosman Premier pellets. I got different numbers, so I chronographed the rifle again a week later and the results were even different from those. Let me show you.
Crosman Premier .20 caliber pellets
Average in Part 3……..One day later……..One week later
528 f.p.s……..………….508 f.p.s……………419 f.p.s.
27 lbs………………….didn’t record…………..21 lbs
I didn’t answer GunFun’s question with this impromptu test, but I did uncover an issue. You may recall that in Part 3 I pressurized the CLU to 500 psi. That was far below the minimum recommended by Vortek, and I knew it. They really didn’t give me a lower limit, though we did discuss 600 psi as being very low. I was testing the limits of the unit by what I did. I wanted to know how light I could make the cocking effort, to see how tame the R9 could become. Well, it looks like I went too far.
I went so low in pressure that the CLU leaked air slowly. The internal pressure apparently wasn’t enough to shut the valve all the way. It didn’t affect that first day’s testing, but it wasn’t going to hold pressure where it was. At least that is what I think happened. At any rate, I need to conduct another low-pressure test. This time I will go to 600 psi and we’ll see if that will hold. I will also do the test GunFun1 asked for, but I’ll report on it next time. I will explain what I mean in detail at the end of this report.
I disassembled the R9, removed the unit, repressurized it to 50 bar (725 psi) and assembled the rifle again. All of this took me 30 minutes.
Now, let’s see what this pressure gives us.
Shooting JSB Exacts the rifle started out with three powerful detonations. The velocities were 847, 778 and 913 f.p.s. Shot 4 was not a detonation and registered 699 f.p.s. Shot 5 registered 659 f.p.s. and was the start of the 10-shot string that I recorded. The average for that string was 650 f.p.s., and the spread ranged from 643 to 659 f.p.s. Lest you think I started recording too soon, shot number 8 in this string was 658 f.p.s. As it turns out, though, I think I did start too soon and I will address that in a bit.
In the first velocity test (found in Part 2) this pellet averaged 689 f.p.s. with a 21 f.p.s. spread. The spread this time was 16 f.p.s. At this point in the testing I was stumped, however, at the end of the report I will discuss everything in detail.
It is possible that the CLU requires a break-in period. We are also assuming that the gauge on my hand pump is exact and repeatable. But it might not be — especially at this very low air pressure (725 psi is on the low end of a gauge designed to read to more than 4,500 psi).
I think a restructure of the test is in order. What GunFun1 suggested now makes more sense than what I have been doing. For the next report I will first rerun a small portion of this test with the rifle exactly as it is today. I won’t do anything to it.
I will also shoot another string of JSB pellets at the end of today’s test, to see if the velocity has changed over the course of the few shots in the test. For now, however, today’s test will continue as planned.
Predator Polymag hollowpoints averaged 632 f.p.s. with a 27 f.p.s. spread (614 to 641 f.p.s.) In the first test they averaged 672 f.p.s. with a 16 f.p.s. spread (662 to 678 f.p.s.).
H&N Field Target Trophy
H&N Field Target Trophy pellets averaged 721 f.p.s. with an 8 f.p.s. spread (718 to 726 f.p.s.). In the first test they averaged 763 f.p.s. with a 9 f.p.s. spread (758 to 767 f.p.s.).
The H&N Baracuda pellet averaged 641 f.p.s. with an 11 f.p.s. spread (637 to 648 f.p.s.). In the first test they averaged 676 f.p.s with a 9 f.p.s. spread (669 to 678 f.p.s.).
The obsolete .20 caliber Crosman Premier pellet averaged 627 f.p.s. with a 14 f.p.s. spread (618 to 632 f.p.s.). In the first test they averaged 662 f.p.s, with a 15 f.p.s. spread (654 to 669 f.p.s.).
The Benjamin Cylindrical pellet fits the R9 breech very loose. Most of them fall into the breech by one-eighth inch, or so. In this test they averaged 605 f.p.s. with a 42 f.p.s. spread (576 to 618 f.p.s.). In the first test they averaged 642 f.p.s. with a 46 f.p.s. spread (620 to 666 f.p.s.).
Here are today’s velocities compared to the first test’s velocities.
Retest of JSB Exacts
At this point, I retested the JSB Exacts. This time 10 shots gave an average of 639 f.p.s. with a 16 f.p.s. spread (631 to 647 f.p.s.) I think 639 is enough slower than the first time (650) that something is happening. I would like to believe the CLU is settling down after being adjusted, but I will address that in the discussion that follows.
I noticed as I shot the gun today that it was cocking much easier than I expected. On the bathroom scale the R9 now cocks with 30 lbs. of effort. You will remember that in the first test, when (I thought) the CLU was pressurized to 675 psi, the rifle cocked with 36 lbs. of effort.
Obviously this test is not developing as expected. If the pressure in the CLU is higher, shouldn’t the velocity also be faster? Several things could be happening.
1. The CLU I am testing could have developed a leak.
2. My hand pump gauge could be reading wrong.
3. I might have read the gauge wrong for the first test — which now seems very likely.
4 What Ben Taylor once warned me about has happened. I have exceeded the operating pressure range of the CLU and the velocity is dropping. If the cocking effort was higher today than in the first test I could believe that, but it’s lower, so I think this is not very likely.
Here’s what I plan to do. I will retest the rifle in one week without doing anything to the rifle. I only need to test a single pellet of the 6 that are in this test, plus I need to retest the cocking effort. If one pellet is significantly slower, they all will be. I plan to retest the rifle with JSB pellets, since I tested them twice today. I will use the second average velocity of 639 f.p.s. as the baseline. That assumes the CLU does need a break-in period. If the retest comes out within a few f.p.s. of 639 with this pellet, I will say we can rule out any leakage. That being said, I still think the last test at 500 psi was too low for the unit.
Once I’ve done this, I will know what the next step should be.
Testing new designs
The CLU is a brand new product and I am no doubt testing it in some ways that Vortek never did. You are watching me test the unit step-by-step. Some folks understand this, once it is explained, but some don’t. They feel that, if something is in writing it should be the final result, and everything should have been done before the blog was published. If I worked that way I might be able to publish one blog a week. The rest of the time I would be testing.
My way of writing allows you to watch behind the curtain, and sometimes you will see stuff that the rest of the world never sees. Don’t form any opinions about the CLU — yet. Let me conduct the next test and we will see where that takes us.