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 Post subject: 2240 Velocities
PostPosted: Sun Jan 12, 2014 12:24 am 
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Location: Coalmont BC
I decided it was time I did a bit of work on the humble 2240.... I got a new one, took it apart and cleaned it, put on a Crosman steel breech, and an RVA (rear velocity adjuster aka hammer spring preload adjuster), dropped in a CO2 cartridge, and got out the Chrony.... Using the stock 8" barrel I tried five RVA settings; stock, 1 and 2 turns more preload, and then 1 and 2 turns less.... I didn't have enough threads to reduce the preload further.... I then repeated the process with a 14" barrel and a 24" barrel.... All barrels had stock barrel ports, and a stock 0.140" transfer port was used for all the .22 cal testing.... Then I fitted a 24" Lothar Walther barrel in .25 cal (using a poly port) and ran them one more time.... The testing was done shooting only about 1 shot per minute at 67*F, and here are the results....

Image

When I did the test with the 8" barrel I wondered if I had enough travel, as the velocity was NOT affected at all by the change in preload.... However with the 14" barrel fitted there was a slight drop at 2 turns out, and with the 24" barrel, it was pronounced, nearly 20 fps.... With the .25 cal barrel the velocity started to drop at 1 turn out, and it was down about 20 fps at 2 turns out.... What does this tell you?.... Well, at typical room temperature, the hammer strike in a 2240 is too strong, so it's wasting CO2 for a start, particularly with a stock barrel.... With a 14" barrel, which is capable of using the CO2 more efficiently, the velocity is still on a plateau until the preload is reduced by 1/8", where it is just starting to drop.... It's not until you use a 24" barrel that you reallly start to see a drop in velocity with the preload backed out 1/8".... This is in perfect agreeement with theory, by the way, and if you look at the velocities, you will see that the longer the barrel, the more power, even with a stock valve and porting.... If you modify the gun, that difference will become even more pronounced....

I thought the test with the .25 cal barrel was quite interesting.... First of all, it shows that with a stock 2240 and a 24" barrel, the gun is pretty much shooting at 450 fps with 25. gr. JSB Kings.... In fact, when I tested the gun with 20 gr. H&N FTT's one shot was over 500 fps.... Now if you used a "proper" length pistol barrel, that velocity would drop, of course, but I found it quite surprising that a stock valve and porting could deliver that much power in .25 cal.... In case you're wondering, the gun was returned to non-PAL specs right after the testing....

The fact that the hammer spring preload on a stock 2240 is too great at this temperature means a couple of things.... First of all, that is the reason the 2240 is a gas hog, particulary with the 8" barrel.... Secondly, this likely wouldn't apply at a higher temperature.... If you were shooting on an 80-90*F day, not only would you get more velocity, but the point at which the velocity starts to drop would move to higher preload settings.... However, it also means that by reducing the preload from stock, you can tune the gun to shoot the same velocity at normal temperatures, and the velocity won't increase as much in high temperatures.... If you can accept detuning the gun a bit from it's stock power, you can get to the point where the velocity will actually DECREASE in high temperatures, and NOT DECREASE as much in low temperatures.... This is because the valve can be made to self-regulate just like the way a PCP does....

Next I plan to do some lift measurements to see how far the valve is opening at various RVA settings....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 7:44 am 
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Location: Central West River Nova Scotia
Very interesting result,s Bob. I have an RVA coming for mine and plan to test it using the "slingshot" hammer. Both with the HiPac and Co2. I'll post the result,s, naturally. Also it might be prudent to test various size transfer port,s.

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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 11:23 am 
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You hear so much about guys fitting an RVA and cranking in it or fitting a stronger hammer spring.... Yes, it makes the gun louder and uses more CO2.... but at room temp it adds NOTHIING with stock ports.... Go the other way and get more shots per cart. at the same velocity, IMO.... Nothing new here, just time to post some solid data for the noob's....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 11:28 am 
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good stuff ones again Bob thanks :wink:

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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 2:13 pm 
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This morning I got a chance to make some lift measurements on this 2240, which is stock other than a 14" barrel, steel breech, and RVA (PA).... I added a small, light piece of tubing inside the spring, protruding through a hole in the RVA adjusting screw, and carrying an O-ring so that I can measure the lift.... The rod moves with the hammer (it is captured between the inner end of the spring and hammer) and the gap between the O-ring and the end of the adjuster equals the lift of the valve....

Image

This allows direct measurement of the lift on each shot, all you do is reset it by pushing the O-ring against the adjusting screw before cocking the gun.... The piece of aluminum tubing I used weighs less than 2 grams (~3% of the hammer weight), so has virtually no effect, providing it slides easily through the adjusting screw and the O-ring isn't too snug a fit.... I adjusted the RVA to coil bind, which turns out to be 6 turns in from stock, and measured the velocity and lift at every 2 turns of adjustment, with the following results....

Image

This is exactly as expected, and although I didn't measure the CO2 use (yet), it should pretty much follow the lift curve.... I'll expend 2 CO2 cartridges, one at maximum preload and the other at stock, recording the shot strings, just to show you how wasteful excessive hammer strike is....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 6:29 pm 
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Joined: Sun Jul 01, 2012 4:25 pm
Posts: 199
Location: HRM N.S.
Thanks Bob, as always great info, i will watch this thread for your results on gas usage.
BTW, I modded my first 2240 for my son as an Xmas gift this year, after the usual custom trigger, sights, grips etc. he wanted it shooting just sub 500. I started with heavier springs and the results were poor. Ya i got higher FPS, but the gun was a real gas pig, and much harder to cock, resulting in adjustments on the sear & trigger to accommodate the heavier springs, making it very harsh to shoot. I started again from stock and polished the hammer, turned down the bolt probe tip, and added a very light booster spring inside of the stock spring, in the end it was shooting 475-485FPS and was back to its normal usability. I am happy with these results as is my son. Now to apply this knowledge to my next project a 2250 conversion.
Regards


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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 6:37 pm 
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Here are three shot strings with the same setup as above, a stock 2240 with 14" barrel, RVA, and steel breech.... Pellets were as above, 14.3 gr. JSB Express, with three preload settings, 6 turns in from stock (just shy of coil bind), stock, and 2 turns out from stock (the minimum I can get with this adjuster).... I shot one shot every 30 seconds, and judging by the shot strings, that was a bit too fast, causing cooling that dropped the velocity and shot count.... One shot per minute would be better.... I also weighed the CO2 cartridges before and after and calculated the weight of CO2 in each....

Image

Your brain can pretty much fill in the two strings I didn't shoot, at 4 and 2 turns in.... Counting all shots above 300 fps they would be about 38 and 43 shots, respectively.... There are a couple of interesting things to note.... At the maximum setting, the first half-dozen shots DID show a bit higher velocity, but they were accompanied by a spray of liquid CO2 that was very visible, as were the first 2-3 shots when the preload was set stock (not as much liquid, but noticable).... I think what is happening is that the dwell is long enough that when the cartridge is full, some of the liquid creeps along the sides of the piercing pin into the valve and is blown out the barrel.... It gives a small boost to the velocity, but is VERY wasteful of CO2.... Interestingly, when the preload was set 2 turns OUT from stock, the first shots didn't show that boost (or spray)....

At maximum preload, the velocity pretty much just keeps dropping with every shot.... After the first 8 shots, the velocity is LESS than what you would get with a stock setup, when shooting every 30 seconds.... On the other hand, with the preload 2 turns (1/8") out from stock, the velocity is much steadier, matching or exceeding the stock setting from shot 4 onwards.... I also calculated the average velocity, average and total FPE, and FPE from every gram of CO2, as follows....

Image

There appears to ba a slight advantage to using maximum preload, but remember that it is a short string and the first few shots are extracting a bit of extra power from liquid CO2, so it's not as good as it looks.... One glance at the total FPE generated by a single CO2 cartridge really tells the story.... I'll make note of one thing here.... A few years ago I made a 1750 (.177 cal) with an 18" barrel, detuned it to stay right around 500 fps, with a short hammer stroke and light preload, so that the valve was self-regulating from 35*F to 75*F within about 30 fps.... It got over 140 shots totalling over 600 FPE, setting a record for the most FPE from a single CO2 cartridge that AFAIK, still stands today....

Hopefully this information will keep people from trying to get more power from a 22XX by leaning on the hammer spring.... I will say one thing, without a Chrony you would think you had a powerhouse by doing that.... The gun is much louder, and the CO2 spraying out gives the impression of more power.... The results from a short barrel will be even more disappointing....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Sun Jan 12, 2014 11:05 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8986
Location: Coalmont BC
I just calculated out an interesting tid-bit of information.... If you expand 12 gr. of CO2 to STP it occupies 400 CI.... So, if the gun makes 400 FPE on a cart., that works out to 1.00 FPE/CI, an interesting way to compare it to HPA....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Mon Jan 13, 2014 12:11 am 
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Joined: Sun Jul 15, 2012 10:49 am
Posts: 6029
Location: Victoria, BC and Clarkston, WA
rangerll wrote:
Thanks Bob, as always great info, i will watch this thread for your results on gas usage.
BTW, I modded my first 2240 for my son as an Xmas gift this year, after the usual custom trigger, sights, grips etc. he wanted it shooting just sub 500. I started with heavier springs and the results were poor. Ya i got higher FPS, but the gun was a real gas pig, and much harder to cock, resulting in adjustments on the sear & trigger to accommodate the heavier springs, making it very harsh to shoot. I started again from stock and polished the hammer, turned down the bolt probe tip, and added a very light booster spring inside of the stock spring, in the end it was shooting 475-485FPS and was back to its normal usability. I am happy with these results as is my son. Now to apply this knowledge to my next project a 2250 conversion.
Regards


Would like to see your conversion Ranger!

Nice work again Bob! Can you share the dimensions of your plastic port hose? Al(Gippeto) gave me some when I bout the .25 barrel from him but haven't tried it yet!

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-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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 Post subject: Re: 2240 Velocities
PostPosted: Mon Jan 13, 2014 11:32 am 
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The Poly Tubing I have is 1/4" OD x 0.161" ID.... nothing special.... If you look around you MAY be able to find some that is 3/16 ID, but unless you make the barrel port the same, and grind out the valve you won't notice any difference....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Mon Jan 13, 2014 9:36 pm 
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Location: Canada
Rick,

The tube is marked as being .170" id x 1/4" od. Transfer port was drilled #19 (.166").

Al


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 Post subject: Re: 2240 Velocities
PostPosted: Mon Jan 13, 2014 10:02 pm 
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I've been thinking about the possibility of an extended valve to fit in a 2250 tube for some time, and the work I did over the last couple of days was to establish a baseline for this experiment.... I was wondering what would happen if I increased the valve volume, and since a 2250 tube is 1.6" longer than a 2240 tube, I simply made a 1.6" long extension to fit in the middle of the valve and lengthened the piercing pin by that amount.... Here are the parts....

Image

The extension has a small pocket milled in the bottom to miss the front trigger mounting screw.... Above that, back to the valve seat, the extension is drilled 3/8" ID, and in front of that it is drilled 33/64" and the front part is tapped 9/16"-18NF.... The spring seat is just like in the original valve front, except the air passage is 17/64", and the male threads are shortened to 0.30", and the same is done on the valve front (originally they were 0.50" long).... These changes basically triple the volume inside the valve to about 5 cc.... The piercing pin was also lengthened 1.6" with a pointed piece of 1/8" piano wire, joined to the old pin (which was ground flat on the end) with a sleeve of 1/8" ID brass hobby tubing 1" long and glued in place with shaft retainer.... Here is the assembled valve....

Image

The original spring was used, and the original poppet (except for the longer piercing pin).... plus 2 of the original size O-rings.... The valve just drops into the 2250 tube and is secured by the single 6-40 screw on the bottom as per the original setup.... You simply drop in a CO2 cartridge and use the original 2240 CO2 cap to hold it in place.... Cock the gun and fire it to pierce the cartridge, exactly as per the original....

Before disassembling the gun to fit the new valve in a 2250 tube, I installed a new RVA.... I got a Crosman power adjuster from the Challenger, which uses a 24 TPI screw instead of the 16 TPI one I had.... In addition, it has longer travel, and I lengthened it even more by drilling out 3/16" of the threads on the inside to allow the hammer spring to move back further.... It now has 18 turns of travel (3/4") from coil bind to the minimum setting.... Since the adjuster was new, I did a few tests to correlate the previous information to the positions of the new adjuster, then stripped the parts out of the 2240 tube and reassembled them into the 2250 tube, but using the extended valve.... I dropped in a new cartridge and started testing by checking to see not only if and how much the velocity changed, but how that change related to the new RVA.... Here is the results of that initial testing....

Image

The black line is the 2240 with the original valve, and you can see that 12 turns out is where the velocity starts to decline, above that it plateaus.... With the new, extended valve (blue line), the plateau is moved 3 turns to the left (more preload), and the exciting part is that the velocity increased 55 fps.... That is an 11% increase in velocity and a 23% increase in FPE - JUST from the new valve, with no other changes.... In .25 cal, the difference is even greater.... The plateau also shifted 3 turns to the left, and the velocity increased 65 fps (15%), increasing the FPE by 31%.... That's a BIG increase in power from just increasing the valve volume.... I was hoping to see an increase, but I'm overjoyed to see it so dramatic.... Now it was time to shoot a string with the .25 cal and see what I got.... I loaded a new cartridge, shot three shots just to confirm the velocity results at 3, 5, and 7 turns out on the preload, set the adjuster to 9 turns out, and shot one shot per minute until the velocity dropped to 300 fps....

Image

You can see the first three shots, mirroring the velocities in the above graph, and then the string at 9 turns out beginning on shot #4.... One thing became obvious during this, and the first cartridge I shot using the new valve, and that was how stable the velocity was.... Admittedly, part of the level shot string is from shooting every 60 seconds instead of every 30, but there is no question that the larger valve not only increased the performance a lot, but decreased the shot-to-shot variation as well.... Including all 28 shots, the average velocity was 466 fps (12.35 FPE), extracting 28.1 FPE from each gram of CO2 (nearly as good as the best results yesterday in .22 cal) and the efficiency worked out to 0.84 FPE/CI.... If you looked at only shots 4 - 23 (ie 20 shots), the average was 476 fps (12.8 FPE) with only a 19 fpe ES (4%).... and the efficiency would have been higher as well....

I'm extremely pleased with these results.... I've never seen anyone make a valve extension to stretch a 22XX valve to fit into a 2250 tube before, and when you consider the big improvement in performance WITH OTHERWISE STOCK VALVE AND PORTING, this may have the potential to unleash more performance on CO2 when combined with other modifications.... The idea I had, which seems to have been proven, was that by using a larger valve, the pressure drop inside the valve during the shot will be less, increasing the AVERAGE pressure during the shot cycle.... The fact that more preload was required to reach the velocity plateau is proof that indeed that happened.... The piercing pin nearly blocks the inlet to the valve completely, so all we have to work with is the volume inside the valve.... The only other alternative is to go to a bulk fill arrangement and increase the diameter of the valve inlet, but that brings another set of problems.... the major one being that if you raise the muzzle on a bulk fill gun, the valve fills with liquid CO2, resulting in inconsistent velocities and a horrendous increase in CO2 consumption as the cloud of liquid blows out the barrel.... If you stored this gun with the muzzle up, I suppose this could happen, but the clearance between the piercing pin and the hole in the valve front is so small that it would take a while.... I think this is an excellent way to get (nearly?) bulk-fill performance and still be able to use the 12 gr. cartridges....

The fact that the .25 cal responded even more to the extended valve than the .22 cal makes perfect sense.... The bore volume (for the same barrel length) is 33 % greater, so it NEEDS a bigger valve anyway.... In fact, I hope to be able to use this greatly increased valve size to experiment with even larger calibers, building a 3050 and maybe even a 3550.... I wonder how large I can go on caliber and still get a pistol that shoots over 400 fps on CO2 ?.... Sean and I have the barrels available, in .300 cal and .357, designed for the new JSB pellets.... The 25" rifle barrels are just begging to be cut in half and tried on a CO2 pistol with the new extended valve....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Mon Jan 13, 2014 10:30 pm 
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Fascinating! One thing I have been wondering is if it is possible to get away from the solid piercing pin. On my low power 177 gun the spring is too weak to reliably break the seal, so when I replace the co2 I have to manually pierce the cartridge by running a screwdriver through the rva and giving the back of the hammer a smack. It's workable but a bit of a nuisance. It would be nice if I could replace the piercing pin with a hollow point like those used in most of the BB co2 guns, but I'm guessing the length would be critical to avoid wasting too much co2 while the cap was tightened. And there would be the increased risk of liquid co2 getting in the valve as you mentioned, but I think I could live with that. I haven't looked at the 2240 valve in too much detail, but I imagine that a hollow piercing pin could be threaded to screw into the valve front, and the original pin cut off short to provide clearance.

Jim


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 Post subject: Re: 2240 Velocities
PostPosted: Mon Jan 13, 2014 11:44 pm 
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Location: Coalmont BC
I'm sure you could do it, it would be a bit of a fiddle to get the length just right, and of course you have to provide a passage for the CO2 into the valve.... not sure how a "hollow piercing pin" would work.... The valve isn't sealed into the tube, so as you mention if you don't get everything just right, you will lose some CO2 (maybe all of it).... Don't most guns that have a piercing pin seal around the outside of the neck of the cartridge instead of on the end, so that the seal occurs before the piercing?.... You can cut the original piercing pin right off flush with the head of the poppet, that is done on bulk-fill conversions....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: 2240 Velocities
PostPosted: Tue Jan 14, 2014 12:00 am 
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Location: Canada
EHF....Something along these lines perhaps? Unfortunately the fellow who makes them refuses to ship to Canada. :roll:

Called a "Pro top"

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Al


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