Bulk-fill from 12-gram cartridges: Part 2
by B.B. Pelletier
Guy’s winning photo. He says it’s a “great gun and very realistic feel!”
This report is getting convoluted. I’m reporting a device I found at the 2011 Roanoke Airgun Expo that allows the use of 12-gram CO2 cartridges to fill Crosman bulk-fill guns, but I used the Crosman model 114 rifle that already had two reports from 2009 before it broke and had to be resealed. So, the report is really about how this bulk-fill device operates on a Crosman model 114 rifle, but the performance of the rifle is also being examined.
Confused? Well, I will try to keep it simple from this point. Today, we’ll look at the velocity you can expect from a Crosman 114 when it is filled by this device.
The Crosman 114 is a .22-caliber, single-shot rifle from the early 1950s. The new bulk-fill device allows you to shoot it with minimal additional equipment.
Mike Reames, the inventor of the device, told me the CO2 in a 12-gram cartridge would not transfer entirely to the gun, so I should expect some gas loss when I disconnected it. There was a loss of gas as he said, so one of the things I want to determine is how many shots can be expected when the gun is charged this way.
When the gas and liquid flows into the rifle during charging, the CO2 reservoir cools immediately. That’s caused by the liquid CO2 flashing to gas as it enters the reservoir. When it does, it absorbs some of the heat of its surroundings — in this case, the metal reservoir tube.
One way to maximize the fill is to cool the gun before filling. When the CO2 enters, it encounters cooler surroundings; and when it flashes to gas, the pressure of the gas is lower. Since the CO2 cartridge is warm in comparison, it’ll have higher pressure and will push more gas and liquid into the gun. This is an old bulk-fill trick that I’ll try to see what difference it makes — if any.
Velocity with a regular fill
First, I filled the rifle in the normal fashion (i.e., at room temperature). The first pellet I tried was the Crosman Premier. As I test the gun, you must keep in mind that Rick Willnecker, who resealed it, has a policy that he will only return a vintage airgun to its specified power. While there are other repair stations that will soup up the powerplant, you can expect Rick to repair the gun so it will shoot like it did when it was new.
Crosman Premiers averaged 535 f.p.s. The spread went from 531 to 539 f.p.s., so a tight 8 foot-second spread. I have owned one other 114 that shot the same pellet 15-20 f.p.s. faster, so this is well within the ballpark.
Next, I tried RWS Hobby pellets. They averaged 549 f.p.s., but that number isn’t a good one. Because after only three shots, I could see the power drop in the traditional fall-off that happens after all the CO2 liquid has turned to gas. So, the rifle had come to the end of its useful charge. You can look at it in several ways, depending on what you’re doing with the gun, but there were anywhere from 13 to 20 good shots on a fill. If you were just plinking, that might stretch to 30 shots.
The first three Hobbys went 563, 558 and 558 f.p.s., respectively. The next one dropped to 551, which is still okay; but after that, each successive shot went slower. After shooting the string of 10 Hobbys, I fired a Crosman Premier pellet and got 499 f.p.s., so the rifle is definitely off the power curve.
The fill from a 12-gram cartridge is from 20 to 30 good shots. Compare that to 50-70 good shots that you will get when the gun is filled by a large bulk tank. I’ve always used the 10-oz. Crosman tank, so that’s what I’m using to get this number.
It’s time to chill the rifle and check the fill afterward. I placed the rifle in a chest freezer and left it in there for about an hour.
Let me caution you that what I am doing is considered dangerous if you don’t know what you’re doing. I know that the entire contents of a 12-gram CO2 cartridge cannot possibly overfill this rifle’s reservoir; but if I filled the chilled gun from a normal bulk tank, it could easily be overfilled. The consequences of overfilling an airgun like the 114 that has no pressure release device is that if the gun gets too warm, the gas pressure inside can build to the point that the brass reservoir blows apart in a catastrophic failure. That happens because the cold gun accepts too much liquid CO2; and when it warms up, the liquid has nowhere to go. The gun needs space for the liquid to become gas, to relieve the pressure, which is how it normally operates. If you fill at room temperature, the physical properties of CO2 will take care of stopping the fill at the right spot for you; but a chilled gun will continue to accept more liquid than it should.
However, in this case, the quantity of liquid inside a 12-gram cartridge is less than the gun is built to hold, so all that should happen is that more of the liquid goes into the reservoir. The test for that is to see how many good shots we then get from a fill.
After taking the rifle from the freezer, a layer of frost formed on all the metal parts. The fill was far more complete this time, with just a small puff of gas as the device was disconnected. However, the gun was now very cold and would not perform well until it returned to room temperature, so more waiting.
Two hours later, I shot strings with both Premiers and Hobbys. The first string of five Premiers averaged 515 f.p.s., and I thought something had gone wrong. It ranged from 498 to 522 f.p.s. But right after it, I shot the first string of five Hobbys and they averaged 570 f.p.s., which is where they should be. They ranged from 568 to 574 f.p.s. Next was the second string of five Premiers, which averaged 530 f.p.s., so they were now in the ballpark. The range went from 524 to 534 f.p.s. Then a second string of Hobbys averaged 567 f.p.s. with a range from 564 to 571 f.p.s. That’s the first 20 shots from the gun, and all are good except for a couple at the start.
Another string of five Premiers averaged 523 f.p.s., taking the total to 25 good shots on this fill. However, I could see the power tapering off within this string, which ranged from 519 to 528 f.p.s. From that point on, the velocity fell off in a straight line, which indicates the liquid is used up. So, filling this way extracts everything the CO2 cartridge has to give, which is about 25 good shots. If you were just plinking in the yard, there are probably 10 more useful shots in the gun.
The 114 action
When the Crosman 114 was selling new, I was still a kid who knew nothing about genuine bolt-action firearms. If I’d ever seen a 114 back then, I would have thought it was a conventional bolt-action because that’s what it looks like. However, it’s far from conventional.
A bolt-action firearm has lugs to engage the receiver and lock the bolt closed against the thousands of pounds of force the cartridge puts on it. The 114 bolt hasn’t got any lugs. Instead, a single metal stud engages an inclined plane at the rear of the action to push the bolt forward as the handle is turned down. At the front of the bolt, a hemispherical enlargement mates with a socket in the breech. Contact between these two metal surfaces, controlled by how hard the bolt is pushing forward, seals the breech against gas loss.
This 98 Mauser (firearm) bolt has two lugs at the front that pull the bolt forward and lock it to the receiver.
The 114 breech. There’s a lot to see in this picture. First, notice the enlarged bolt face that mates with the breech to seal gas behind the pellet. The pin on the rear of the bolt below the handle fits into a socket with an inclined plane to push the bolt forward tightly. The knurled wheel beneath the bolt is the power adjuster that all these bulk-fill guns have; and note the rear peep sight that I’ll use for the accuracy test.
The 114 trigger is single-stage and quite hard in the factory form. That can be altered with careful gunsmithing, but nothing can ever make it a great trigger. The simple design mitigates against it.
The safety is a standard crossblock pin that’s set into the stock. Punch in from the left to put the rifle on safe and from the right for fire. Back in the ’50s, this was a very common type of safety on inexpensive guns.
Now that I know the characteristics of the gun and how many shots I can expect, it’s time to test accuracy. I’ll use the peep sight that came with the rifle for this.
As far as the bulk-fill adapter goes, I have to say that it has fulfilled all expectations. In fact, I’m surprised that it works as well as it does — especially when the gun is cooled first. I don’t know if Pyramyd Air will ever carry it. If you want one, contact Mike Reames directly.