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Air Gun Home Forum Index » Pistols » Building the wife's 2240 Goto page 1, 2  Next    View previous topic :: View next topic  Building the wife's 2240   Posted: Mon May 02, 2011 5:41 am Sholo Veteran Member Joined: 24 Mar 2011 Posts: 125 Location: Eastern Ontario Hello All! Ya I know it's been done 1000 times before,& yes I've done the search thing (lots of good info, Rsterne is a friggin' wizard)! Just want to make sure I'm headed down the right path.Anyways,the "General" has informed me that I have to build HER 2240 before MY 2250 hpa !? (May as well practise on hers before I go all "McGyver" on mine ,right?) She has no interest in hunting,just plinking/paper punching, so this is my thought process: 2240 will stay 12 grm powerlet @ about 400-425 fps with RVA @ low power 14" barrel from my 2250 conv kit (or should I drop to .177 to save more Co2) Crosman steel breech Clip stock hammer spring and/or drill 1/4-3/8" out of hammer Install RVA (just in case I want to dial it up to "plink" the odd squirrel!) Angle/polish valve exhaust port poly tube transfer port seal Extended bolt probe I'm hoping these few mods will get her a fairly respectable increase in shot count. I didn't post any other mods(trigger,stock etc..) as I am more interested in performance #'s right now. Anything I missed? Any and all advice, good or bad, would be greatly appreciated. Thank-you much - Todd   Posted: Mon May 02, 2011 9:50 am Alstone Moderator & Site Supporter Joined: 01 Mar 2007 Posts: 4139 Location: Linconshire, ENGLAND I don’t think you will save any Co2 by dropping down to .177, if anything it will use more. A power adjuster will make a lot of difference to your shot count, you can adjust it to optimise the co2 usage. The rest of you suggestions will also make a difference when added together. Al _________________   Posted: Mon May 02, 2011 9:54 am rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC For your intended velocity range you don't need to do ANY valve or port work, it's a waste of time.... I hate poly port seals, I've seen more poor ones than good ones (cut crooked, too long, too short) and there is NO performance advantage to a drilled steel transfer port (and you don't need to do that anyway).... You will get more shots in .177 than in .22 no question, especially if you tune to similar velocities.... If you go .177 DO NOT do any valve or port mods.... If you are installing an RVA, you probably won't need to clip the spring, depending on how low you can dial it.... The hammer is hardened and you might have a devil of a time drilling it.... I've never tried, but I can tell you that the outside of the hammer is almost impossible to turn on a lathe even with carbide until you remove the outside 1/16" or so.... Put on the longer barrel, steel breech, and an RVA and leave it alone.... IMO.... with the exception of maybe a longer bolt probe depending on pellet choice.... You probably won't need it if you stick to Crosman, they have a shallow recess in the back.... other pellets need a longer probe to get the skirt past the transfer port.... but again, for your purposes it may be not worth the work.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Mon May 02, 2011 1:05 pm Alstone Moderator & Site Supporter Joined: 01 Mar 2007 Posts: 4139 Location: Linconshire, ENGLAND rsterne wrote: You will get more shots in .177 than in .22 no question, especially if you tune to similar velocities.... If you go .177 DO NOT do any valve or port mods.... If you are installing an RVA, you probably won't need to clip the spring, depending on how low you can dial it.... Bob I've always understood that .177 give less shots per charge than .22, because of the reduced surface area requiring more gas to get it up to speed? Al _________________   Posted: Mon May 02, 2011 3:10 pm Griz Member Joined: 16 Mar 2011 Posts: 36 Location: Colorado Springs, CO Okay, dumb newbie question. What is an RVA? Griz   Posted: Mon May 02, 2011 3:50 pm Alstone Moderator & Site Supporter Joined: 01 Mar 2007 Posts: 4139 Location: Linconshire, ENGLAND Griz wrote: Okay, dumb newbie question. What is an RVA? Griz It's a power adjuster, it alters the pressure on the hammer spring which inturn alters the amount of Co2 released through the valve. Al _________________   Posted: Mon May 02, 2011 5:40 pm rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC HI Al.... I have a "1750" which is a .177 cal 2250 with an 18" barrel and I get over 120 shots at 500+ fps at room temperature.... over 600 FPE from one 12 gram cartidge.... Not only that, the valve is operating in the "self-regulating" range where it is nearly temperature independant.... I have never heard of anyone even approaching 100 shots in .22 cal.... but I could be wrong, of course.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Mon May 02, 2011 6:33 pm Sholo Veteran Member Joined: 24 Mar 2011 Posts: 125 Location: Eastern Ontario Thanks for answering yet another 2240 mod question guys. Rsterne: I was going to angle/polish exhaust port only but seeing as I'm not going for max power, I guess it makes sense not to help air flow-DUHH!! I would like to be roughly 425fps at lowest pwr adj setting(figure out that one on my own-look at me go!!) I will likely drop to .177 to save a bit more (still @ 425fps) Alstone: I can't believe I'm about to *nitpick* with a guy who built a 2240 autoloader , but if co2 pressure is constant(somewhat), @ around 850psi ,and the pellet is lighter, wouldn't it take less co2 to reach 425? Just my opinion, not trying to start an argument or any dissrespect. Thanks again, Todd   Posted: Mon May 02, 2011 9:58 pm rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC The base of the pellet goes up by the square of the caliber.... a .22 cal pellet (actually 0.217") is almost exactly 50% bigger in area than a .177 pellet.... and would therefore receive 50% more force from the same psi.... Scaled up, however, .22 cal pellets are (0.217/0.177)^3 heavier.... ie about 84%.... 14.3 gr. compared to 7.8 gr. for example (83%).... You are accelerating an 84% heavier pellet with a 50% greater force.... leading to a velocity of about 18.5% less, in theory, in the same barrel length.... As an example, a D-34 shoots about 850 fps in .177.... and should in theory shoot about 693 fps in .22 cal.... just about exactly what it does in real life.... However, if you look at the energy, the .22 cal D-34 at 693 fps (14.3 gr.) would be 15.3 FPE.... while the .177 cal D-34 at 850 fps (7.8 gr.) would be 12.5 FPE.... That is why .22 cal guns typically produce more energy from the same powerplant.... but a lower velocity.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Tue May 03, 2011 4:58 am Sholo Veteran Member Joined: 24 Mar 2011 Posts: 125 Location: Eastern Ontario rsterne wrote: The base of the pellet goes up by the square of the caliber.... a .22 cal pellet (actually 0.217") is almost exactly 50% bigger in area than a .177 pellet.... and would therefore receive 50% more force from the same psi.... Scaled up, however, .22 cal pellets are (0.217/0.177)^3 heavier.... ie about 84%.... 14.3 gr. compared to 7.8 gr. for example (83%).... You are accelerating an 84% heavier pellet with a 50% greater force.... leading to a velocity of about 18.5% less, in theory, in the same barrel length.... As an example, a D-34 shoots about 850 fps in .177.... and should in theory shoot about 693 fps in .22 cal.... just about exactly what it does in real life.... However, if you look at the energy, the .22 cal D-34 at 693 fps (14.3 gr.) would be 15.3 FPE.... while the .177 cal D-34 at 850 fps (7.8 gr.) would be 12.5 FPE.... That is why .22 cal guns typically produce more energy from the same powerplant.... but a lower velocity.... Bob Like I said in my original post, a friggin' wizard!!! _________________ Cheers, Todd   Posted: Tue May 03, 2011 5:20 am Alstone Moderator & Site Supporter Joined: 01 Mar 2007 Posts: 4139 Location: Linconshire, ENGLAND Hi Bob, it’s just that over here in the UK with a 12 flb limit most people find that they have a lower shot count using the same rifle in .177 cal as against a .22. The only data for this is looking through post for UK forums and people being surprised by it. The basic calculation is the same but the physics seem to be different. But this is for rifles not pistols which with a shorter barrel may perform different? Al _________________   Posted: Tue May 03, 2011 9:50 am rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC 12 FPE is a pretty significant target for .177 using CO2.... I can well believe that it would be pretty difficult (and therefore wasteful of CO2) to reach in the smaller caliber.... I stated that .177 was more economical "especially if you tune to similar velocities".... That would not likely apply if you were tuning to similar energies.... for the reasons I gave above.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Fri May 20, 2011 4:56 am Sholo Veteran Member Joined: 24 Mar 2011 Posts: 125 Location: Eastern Ontario Finally got her gun back together the other day.Didn't actually do that much to it- 14" barrel,spring guide on trigger spring,steel breech,made a trigger shoe,polished hammer and trigger/sear.(Thanks for the parts Eric!) I didn't do any valve mods as I'm trying to get her more shots per powerlet.When I took a few shots over my new chrony,I was surprised to see Co2 cloud still coming out the end of the barrel with a stock valve. I have not clipped hammer spring/installed RVA yet,just some preliminary test shots (Highest-554.7,low-526.4 after 20 shots) I'm sure (hope) once I clip hammer spring so fps is around 425, Co2 cloud will disappear and shot count will go up. _________________ Cheers, Todd   Posted: Fri May 20, 2011 9:47 am AirGunEric Site Admin Joined: 20 Jan 2007 Posts: 6929 Location: "Out There" Sholo wrote: ...surprised to see Co2 cloud still coming out the end of the barrel with a stock valve. The stock valve- for some unknown reason, got some sort of online reputation (by of course, people who really didn't do any significant testing, or sellers of expensive aftermarket valves) as being "not all it could be" in respect to gas flow- which, as time and experimentation by many many people- was essentially untrue. The stock valve, unmodified needs a 24" .22 barrel in front of it before even beginning to fall behind- all these hogging-out and 'porting' activities people seem to amuse themselves with do very little but waste alot more Co2 for very little extra power. My point is- don't worry about the valve- as you have indicated, it makes more sense to reduce Co2 flow and try to conserve gas (this is especially true in a stock 2240 with the 7.5" barrel- it essentially throws Co2 away). _________________ ` I'd say "I care." But I'd be lying. Canadian Airgun Supplier: http://www.scopesandammo.com/storefront   Posted: Fri May 20, 2011 10:00 am rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC One thing I forgot to mention.... If you dial an RVA low enough.... or clip too much off the hammer spring.... the hammer hit won't be strong enough to pierce the cartridge.... It's an easy fix, though.... Drill the end cap (or the RVA screw) through with a 9/64" drill and insert a (removable) 1/8" rod through the hole to rest on the back of the piston.... With the gun uncocked and a new cartridge in place, pull the trigger and tap on the end of the rod to pierce the cartridge.... then remove the rod and start shooting.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count! 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