This article will cover a pcp conversion of the Crosman 2400 (and crosman 2240) using the hipac system. I will not be going over any simple details, as there are several tutorials available that go into great depth on an issue such as disassembly. Rather, I’d rather spend my time telling you about some finer details I had to learn the hard way.

Disclaimer
I honestly do not recommend changing a CO2 gun to use high pressure air. CO2 operates at a relatively low pressure compared to hpa. Asking a low pressure gun to work at triple the pressure is begging for failure. But you can make a functional pcp rifle if you have patience.

If you are trying to save money, stop here and buy something guaranteed to work. You’ll end up spending a ton on parts. If you want to make a rifle that preforms to your exact specifications, just look around and buy something that fits the bill. But if you like tinkering on stuff, you may enjoy the process (and end up with a decent rifle).

Like I said there was a lot of trial and error in my experience, so maybe my instructions will ease the process for you.

Parts needed
Hipac.
This inventive product is made by a guy in Texas in his shop. He stands by it. I was under the impression it was drop in. It wasn’t for me. It took a bit of tinkering before I could get it to stop leaking. But once I figured it out it preformed flawlessly. This method is simpler than assembling your own hpa tube.

Extra valve seals.
You get a few extra from hipac, but order some more. You’ll end up blowing them up in your endeavors.

Benjamin discovery valve stem.
The stock valve stem will work, but the valve stem seal will start leaking in short order. The discovery stem is much sturdier and has additional machining that functions better for hpa.

Benjamin discovery hammer spring.
The stock hammer spring is much to light to overcome the pressure from the hipac. The hipac came with an extra spring, but it was way to stiff for use.

Extra breech screws.
Buy 3 at least. You will damage the stock breech screw during initial disassembly. You’ll probably break a few more down the road, so stock up. When they arrive, cut a slot in the head for easier removal. The hex head is easy to strip out.

Dust cap
Anything will work. It doesn’t have to be fancy. I’m using a marker cap. It just has to do its job. Once you start getting dust in the air resivore start expecting seals to blow.

Aside from that, stock parts can be used from the rifle

Optional parts
Hammer debounce device
This makes air use more efficient thus increasing shot count.

Extra valve
Just in case you want to modify the valve for more efficient air use. Can increase power…allegedly.

Extra valve screws
Several people have secured the valve in place with 2 extra screws (just like the discovery). You’ll have to drill through the tube, and drill and tap the valve to do this. I won’t be doing this with my rifle yet, but I recommend it if you have the equipment and know how. For a 3000psi fill pressure this is necessary.

Saying goodbye

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This is the 2400 before the conversion. As a .22 CO2 carbine, it was an awesome squirrel killer. Alas, it is time “Black Raven” metamorophisize into a high powered .177.

Disassembly
I’m going to skip most details of the disassembly as the process is easy and fairly straightforward. There are a few helpful tips I want to stress:

When you remove the grip frame it’ll look like this:

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Remove the tiny spring and small ball bearing. It’s easy to lose. Put it in a zip lock with other small parts. Nothing else will fall out of the frame. Also, you might as well do a trigger job while the gun is apart. Untouched, the trigger on this rifle is horrendous. By polishing the contact points on the trigger and sear you will have a MUCH smoother pull. By cutting 1 or 2 coils off the trigger spring you’ll have about a 2-3lb pull. This is very important because the heavy pcp hammer spring will increase the trigger pull weight by a few pounds.

Breech screw
This is by far the hardest part. It took my forever to get this thing out – because it strips easily. The only trick that worked for me is this: remove the bolt handle, clamp the breech down, use a slightly oversized hex head, beat it in, turn, and repeat as necessary. It took about 30 minutes with this process, but it did work. After that, I slotted all breech screws with a Dremel tool. With slotted screws breech removal goes from taking half an hour to less than 1 minute.

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The whole disassembly process takes about 15 minutes (minus that pesky breech screw). Now we’re ready to start the conversion.

Reassembling the rifle with new parts
This process is again, easy and straightforward. So many details are omitted here.

Organize parts
You will no longer need the factory hammer spring and CO2 endcap, so store them away somewhere where they can’t accidentally get reinstalled.

Valve prep
Disassemble the stock valve. Remove the factory valve stem and replace it with the Discovery valve stem. Remove the CO2 valve seal and install the Hipac seal. The valve is now ready to be installed.

Reinstall everything as normal. I’d recommend applying a thin layer of sealant (caulk…whatever you have on hand) around the transfer port. You’d be surprised how much air can escape from underneath the breech. This eliminates this possibility, adding more consistency.

Lastly, install the hipac. This first time, I had to crank down to stop it from leaking. This time -hand tight- no leaks up to 2100psi. Surprising, as the last attempt caused a two day cussing spell.

The Completed Rifle

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I’m sure you’re wondering how much something like this would cost. For the rifle and hipac, it’s about $200. Add a scope of your choice and a pump. You can get pumps for as low as $100, but they add dust and a significant amount of water to air resivore. Compare that to a Benjamin Discovery- quality rifle and pump for about $450. It does cost more, but you’ll spend more time shooting and less time throwing things.

I do want to add that this attempt went much smoother. The rifle was reassembled, filled, and successfully test fired in less than an hour. Didn’t even cuss.

What can it do?
The rifle was filled to 2800psi and shot over the chronograph with 7.9gr Crosman premiers:

Created: 05-07-2016 05:35:32 PM
Description: Crosman 2400 cphp 7.9
Notes 1: 2800psi
Notes 2:
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 7.900
Temp: N/A
BP: N/A
Shots
#     FPS        FT-LBS     PF
23    896        14.09      7.08
22    905        14.37      7.15
21    915        14.69      7.23
20    921        14.88      7.28
19    925        15.01      7.31
18    931        15.21      7.35
17    942        15.57      7.44
16    948        15.77      7.49
15    952        15.90      7.52
14    958        16.10      7.57
13    958        16.10      7.57
12    969        16.47      7.66
11    974        16.64      7.69
10    981        16.88      7.75
9     980        16.85      7.74
8     979        16.82      7.73
7     965        16.34      7.62
6     973        16.61      7.69
5     964        16.30      7.62
4     965        16.34      7.62
3     ERROR 3
2     943        15.60      7.45
1     896        14.09      7.08
Average: 947.27
StdDev: 27.44
Min: 896
Max: 981
Spread: 85
True MV: 947.60
Shots/sec: 0.09
Group Size (IN): 0.00

Hammer debounce device
When I shot the rifle, it sounded like it was firing a 3 shot burst, so I ordered a hdd from Airguns of Arizona. This tiny chunk of plastic set me back $30. It did it’s job, reducing air used per shot. After about 30 shots it broke completely. I called AoA to ask about returns or refunds, as this tiny, junky, piece of plastic set me back $30. They wouldn’t help me out at all. Great service…

Accuracy

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About half an inch at 20 yards. Average size. Not bad for pellets I had laying around.

Summary
I was hesitant to attempt this again, as the first time was non stop frustration. This time was different. I’ve been shooting this for about a week now and have yet to have a failure, other than the hammer debounce device. The rifle is a loud as a .22 short and the effects of hammer bounce are noticeable. I’ll eat my words later, but I am impressed with the outcome. It shoots well, fills quickly, and has been a rewarding experience.

Update 5-5-16
Rifle is still going strong. Using a 2800psi fill. The 3 shot burst noise goes away, and it still shoots well.

Update 10-26-16

I filled the rifle up and found it wouldn’t hold air. The valve was drilled, tapped and secured in place with extra scope ring screws. New valve seal installed.

Update 11-15-16

Seal failure. CO2 valve assembly reinstalled. No longer using HPA.

Gratuitous glamour shots

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