GTA

PCP - HPA - C02 Gate => QB-7X Gate -W/Co2 & HPA => : September 19, 2007, 04:04:37 PM

: This Crosman CS 2400 (2250) can be powered 3 different ways
: September 19, 2007, 04:04:37 PM

The short story: I now have a 2250 that can be powered by my choice of bulk Co2, HPA, or Co2 cartridges. I did this by using the stock Crosman valve and a sealed endcap. This isn’t a 40 fpe beast like the last .22 I built, but rather a nice quiet shooter.

The long story:

I bought a Crosman Custom Shop 2400 (2250) this spring with the 24” barrel. I was delighted by the quality of the gun as I received it. The addition of an adjustable trigger and a new breech that had the hold down screw relocated were big plusses in my book. Out of the box, the gun shot between 580 fps – 590 fps and would easily punch one hole groups at 20 yards. I liked the gun so much that I left it in stock form for 5 whole months. I learned at the SC shootout that paintballs at 35 meters were no match for this gun.

The only drawback was that I knew this Co2 powered gun wouldn’t shoot the same in the winter when the temps may drop down into the 30s and 40s. I didn’t want to change the power level of the gun, as it’s so quiet and accurate and a sweet shooter at 11-12 fpe. I knew that if I dropped in a B&A bulk kit and went to HPA, the power would be a bit higher than I wanted with this gun. So I decided to use the stock valve and still convert it to run on bulk Co2 or HPA. But I still wanted the gun to be able to run on Co2 carts……….

I decided that I would use the stock valve and cut an o-ring groove on the valve cap. I would leave the internals stock otherwise. I also had to deal with sealing at the grip frame screw, but that was simple. I did not port the valve or change the springs or transfer port. I simply cut an o-ring groove on the stock valve cap and anchored the valve using two 8-32 screws. I did also sharpen the piercing pin on the valve stem and drill the tiny 1/8” opening in the valve cap out to 5/32”, a tiny mod for more airflow. I hoped that using an endcap from the B&A bulk kit would allow me to use Bulk C02 and HPA without changing the valve. I also wanted to be able to drop in a Co2 cart if needed.

Initial results were good. The gun sealed the first time I put it together (Yeah!). Velocity on Bulk C02 was at 660 fps (at ~80 degrees w/ 14.3 grainers). HPA at 850 psi yielded 710 fps. HPA at 1150 psi yielded 750 fps. Co2 carts with the stock 2250 endcap gave 630 fps. When I swapped to the bulk endcap and dropped in a CO2 CART, velocity climbed to 645 fps, because the Co2 had a bit of an expansion chamber. I will now only use the one bulk endcap; it works fine with co2 carts. The gun shot well, but it was a bit more power than I had aimed for. Plus, I only got 4 good shots on a tube fill of HPA.

I cut 2 coils off the hammer spring. Velocity on C02 carts is now at 610 fps, bulk Co2 does 620 fps (at ~80 degrees w/ 14.3 grainers), 1150 psi HPA does 662 fps all day long with the bottle attached. I don’t plan to leave the bottle attached, but rather fill to 1150 psi and disconnect the tank. The gun has a small reservoir, the 2250 tube. I get 5 consistent shots, with 6 or 7 good ones. Here is a string I shot today, using 14.3 grain Crosman points, from a tube fill of 1150 psi:

664
673
673
673
661
645
620

I think this gun will be a nice rifle for the winter. With 14 fpe muzzle energy and superb accuracy, it will be a good small game hunter as well. It is actually a bit quieter than it was in stock form. I am very happy with this setup. I have done a few guns that’d run on bulk co2 or HPA, but this is the first one that I can drop a 12 gram powerlet into, too! BTW, the gun gets 30+ good shots on a powerlet and 40-50 on a fill with bulk Co2.

I can always swap to a 2260 tube (or add the 22xx tube extension from Bryan and Associates) if I want more shots per fill. And, of course, I could add a HDD. Right now I'm very happy with both the performance and the versatility of this gun.

I may post pics soon, but it looks like a plain Jane 2250 with 24” barrel.

Tim

: Just realized that I had forgot to ask {or can't remember}
: 3n00n September 19, 2007, 06:10:53 PM

How many 12fpeshots were12gram providingbefore the conversion? 366+fpe from a 12gramseems very good efficiency. Also, 14fpe should be plenty of power for 70m shots on bunnies {5fpe+ retained with cp @ 70m}

We'll have to set up a 70m bunny to practice with. (http://www.getphpbb.com/phpbb/images/smiles/a_bravo.gif)

: RE: Just realized that I had forgot to ask {or can't remember}
: September 20, 2007, 06:09:41 AM

It was getting 25 - 30 shots at 11 fpe before I touched it. I think that the expansion chamber offered by allowing the cart to fill the tube may account for the improved efficiency. The mods that I did shouldn't have affected efficiency too much, except maybe clipping the 2 coils off the hammer spring. Pretty cool when stuff works out better than you expected ;-).

Tim