by Tom Gaylord
Writing as B.B. Pelletier
Today’s report is the continuation of a guest blog from reader HiveSeeker about his Crosman 2400KT.
If you’d like to write a guest post for this blog, please email me.
Over to you, HiveSeeker.
The 2400KT CO2 carbine is available exclusively from the Crosman Custom Shop.
This report covers:
• A reminder of the two guns
• Barrel length and velocity
• Can you help? Part 2
• New thoughts on barrel length
Part 5 was going to be the Crosman 2400KT .22 velocity test. However, I’d already reported that this gun delivers almost identical velocities in both .177 and .22. When I stated in Part 4 that barrel length alone does not appear to account for this, a number of questions came up. I’d already researched this and knew why I had drawn that conclusion; but without that information, some blog readers had questions. So, let’s jump ahead to what I had already put together about barrel length and its relationship to velocity before moving on.
A reminder of the two guns
The Sassy Sandy is a target carbine in .177 with 10.10-inch Lothar Walther choked match barrel, black custom shoulder stock, black trigger shoe and black muzzlebrake.
The HiveSeeker is a light-duty small game and pest hunter in .22 with 18-inch barrel, simulated carbon fiber custom shoulder stock, black trigger shoe and black muzzlebrake.
Barrel length and velocity
We’ve mentioned barrel length a couple times already, and we’ll finally address that topic here. A longer barrel means higher velocity because the CO2 has a longer distance over which it can exert pressure on the pellet, generating more speed. We’ve already discussed the .177 Sassy Sandy and .22 HiveSeeker having the same velocity, but that statement is only partly true. With an 18-inch barrel close to twice the length of the 10.10-inch Lothar Walther barrel, the HiveSeeker has a decided advantage. How much? Let’s see if we can find out.
Although I couldn’t get a word out of Crosman on Custom Shop gun velocities, one of their customer service reps did tell me that the velocity difference across all the available barrel lengths was about 50 fps. In my research, I came across B.B.’s blog, How barrel length affects velocity in a CO2 rifle, which showed almost exactly the same result. There, B.B. tested a Quackenbush XL rifle with a removable 7-oz. CO2 reservoir. It started off with a .22-caliber, 20.125-inch Crosman 2200 pneumatic barrel. B.B. cut down that barrel in 1-inch increments as he conducted his test. You’ll want to check out that blog for yourself, but below is B.B.’s velocity table, reproduced with his permission.
I’ve reversed the order of the original table to show velocity gain as the barrel gets longer, rather than velocity loss as the barrel was cut down. Problems cropped up when the barrel was cut down below 13 inches, so the comparison had to stop there.
Velocity increases with barrel length — up to a point. This table is modified from B.B.’s blog, “How barrel length affects velocity in a CO2 rifle.” The data is presented in the reverse of how B.B. presented it. Data is from a Quackenbush XL rifle with a removable 7-oz. CO2 reservoir and .22-caliber, 20.125-inch Crosman 2200 pneumatic barrel.
As you can see, velocity increases with barrel length up to 19 inches, and the maximum increase is 52 fps — just what Crosman Customer Service told me.
But at 20 inches, velocity drops. Once the CO2 has expanded inside the barrel and is no longer under enough pressure to push the pellet faster, friction takes over and the pellet begins slowing down. Further digging revealed the following from one of B.B.’s earliest blogs on the Crosman 2240: “According to tests I ran [on the 2240] with The Airgun Letter, a 24-inch barrel will slow the pellet back down to about where the 10-inch barrel is. A 16-inch barrel would be ideal, and you might see over 500 fps from a stock valve.” (Crosman’s 2240: Are we having fun, yet?) When Rick Eutsler sent B.B. the HiPAC kit for his Crosman 2240 conversion to air, he told B.B. that the 14.50-inch barrel would be the optimum length.
A somewhat longer barrel also seems to perform well, as I found with my 2400KT — though I think a different factory valve may also be helping. You’ll recall that the Crosman Outdoorsman 2250XE also happens to have an 18-inch barrel. When B.B. tested that particular gun, he said, “First, because it has an 18-inch barrel instead of just a 10-inch barrel, you get optimum performance from each CO2 cartridge. However, there’s a point of diminishing returns, which happens to be somewhere around 16 and 18 inches of barrel. After that, the pellet loses some velocity from friction. So, the barrel length on this carbine is anything but an afterthought!” (Crosman Outdoorsman 2250XE_Part 1). In the barrel-length-and-velocity blog, Crosman confirmed that 18 inches was optimum for a 2250. B.B. also concluded that 14 inches would probably be the optimal limit for a CO2 .177 barrel.
To summarize, all my data indicates that the 18-inch barrel is giving the HiveSeeker .22 about a 50 fps advantage over the 10.10-inch barrel on the Sassy Sandy .177. This isn’t enough to explain why the .177 has the same velocity as the .22.
Can you help? Part 2
What you just read was written as Part 6, almost verbatim. At this point, I was planning to discuss the different 2400KT stock velocities contributed by the blog readers and, perhaps, draw some more concrete conclusions about .177 and .22 velocities in this gun. I’d already scoured several Crosman modding forums before starting this blog; but while modded velocity data abounded, the stock velocity data was scarce and contradictory. I would still like comparative stock velocities for the 2400KT. If you can supply it, please remember to mention barrel length and pellet weight. If you’re actually throwing your gun back on the chronograph, please use pellets close to 7.9 grains in .177 and 14.3 grains in .22. Thanks in advance!
New thoughts on barrel length
Part 4’s comments made me do more thinking about why I got similar velocities in the .177 and .22 2400KT. Barrel length is a major factor. But with both the manufacturer and actual field testing indicating that the maximum velocity spread for a CO2 gun is about 50 fps across all barrel lengths, a longer barrel is simply not enough to make a .22 shoot just as fast as a .177. When we compared the Browning 800 Express, we saw a velocity difference of more than 200 fps between .177 and .22. I won’t compare a springer to a CO2 gun any further here, but I definitely expect a .177 to shoot a lot more than 50 fps faster than a .22! If that’s as much velocity as can be accounted for by a longer barrel, I’m forced to conclude that something more is going on with the 2400KT.
I already mentioned that, when looking at the Crosman Outdoorsman 2250XE, B.B. commented that a 14-inch barrel would probably be the optimal limit for a .177 CO2 gun. If that’s true, then velocity would start to fall off with a .177 barrel longer than 14 inches. The maximum velocity increase would be limited to only about 4 inches of added barrel length — not 8 inches — for the 10.10-inch .177 barrel. In other words, the 8-inch disparity in barrel length between my .177 and .22 2400KTs may be making even less of a difference than the 50 fps we’ve attributed to it so far.
The question remains: What’s going on with that .177? Blog reader Buldawg76 mentioned one fact I hadn’t considered — that the .177 Lothar Walther is a choked barrel. I already knew that, but didn’t consider the possibility that choking might actually slow down the pellet — dropping velocity a little closer to what I might expect from a .22. That’s one possibility that a comparison with the standard (unchoked) 10.10-inch Crosman .177 barrel might confirm. A related possibility I’d already considered was that Crosman might assemble differently a pistol ordered with the Lothar Walther barrel, perhaps with a different valve, in order to create a match gun with optimally stable (and also lower) pellet velocity. Again, someone with stock 2400KT velocities from a shorter .177 Crosman barrel might be able to provide an answer.
Before we wrap up today’s blog, I’d like to note that most of the questions that arose from Part 4 were related to much higher barrel-length velocity increases on modded guns. I’ll simply state that a CO2 2400 that’s been converted to air, valve-swapped, and then pressurized to 3,000 psi is no longer a CO2 2400. Please feel free to share your modded velocity data. For direct comparison to the unmodified Crosman 2400KT CO2 Carbine that’s the topic of this blog, please stay with similarly unmodified pistols.
So, this was our detour on the way to Part 6. We still have unanswered questions, but I hope the blog readers better understand how I arrived at the conclusions I did. Next, we’ll conduct the Crosman 2400KT .22 velocity test, which will be less puzzling and a lot more interesting!