Canadian Airgun Forum

The #1 Community for Airguns in Canada!
It is currently Tue Nov 12, 2019 1:45 pm

All times are UTC - 5 hours


The Canadian Airgun Forums are a place for people to discuss and learn about airguns and the airgunning sport in Canada. There are lots of discussions about airguns, airgun accessories, reviews, modification and repair information, airgun events, field target and free classifieds!

 

You need to register before you can post: click the register link to proceed. Before you register, please read the forum rules. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload your own pictures, and access many other special features. Registration is fast, simple, and absolutely free! To start viewing messages, select the forum that you want to visit from the selection below.








Post new topic Reply to topic  [ 58 posts ]  Go to page 1, 2, 3, 4  Next
Author Message
PostPosted: Mon Jul 27, 2015 3:43 pm 
Offline

Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
Right now with the stock 7-3/4" inch barrel and a clipped stock hammer spring,my 2240 is shooting around 440 fps with Crosman Premier 14.3 gr Domes. How can I get more pellet speed (maybe 50 more)while keeping the gun under 500fps and still keep the same shot count,using the same stock barrel?
Since the gun is wasting Co2,how about using a smaller inside diameter transfer port with a heavier hammer spring with a velocity adjuster??
RWS 11.9 Hobbies shoot roughly 445fps,which is surprising...I thought they would go a lot more?!Thanks,Huck

_________________
Crosman Phantom .22 ...UTG High mount,UTG 3-9x40 Hunter mil-dot scope
Crosman Phantom .22


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 4:14 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
Increasing the port diameter will waste even more CO2.... so will installing a heavier hammer spring.... Once you are blasting unused CO2 out the barrel (and the gun does that already in stock form).... most things that will increase the velocity will also decrease the shot count.... other than shooting in higher temperatures to increase the available pressure.... To get more velocity you need a longer barrel to harness some of the wasted energy of the CO2 that is arriving at the muzzle after Elvis has left the building.... Even using a lighter pellet has little effect, because it arrives at the muzzle sooner, and more CO2 is wasted.... If you do make the ports larger, you can make tiny gains in velocity.... at the expense of decreased shot count.... Once you do that, however, you may be able to reduce the hammer strike to quit wasting as much CO2.... basically the opposite of what you suggested....

The only hope you have of getting more velocity without losing shots.... is to deliver more CO2 over a shorter period of time.... closing the valve just before the pellet leaves the barrel.... More flow for less time....

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!


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 4:23 pm 
Offline

Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
rsterne wrote:
Increasing the port diameter will waste even more CO2.... so will installing a heavier hammer spring.... Once you are blasting unused CO2 out the barrel (and the gun does that already in stock form).... most things that will increase the velocity will also decrease the shot count.... other than shooting in higher temperatures to increase the available pressure.... To get more velocity you need a longer barrel to harness some of the wasted energy of the CO2 that is arriving at the muzzle after Elvis has left the building.... Even using a lighter pellet has little effect, because it arrives at the muzzle sooner, and more CO2 is wasted.... If you do make the ports larger, you can make tiny gains in velocity.... at the expense of decreased shot count.... Once you do that, however, you may be able to reduce the hammer strike to quit wasting as much CO2.... basically the opposite of what you suggested....

The only hope you have of getting more velocity without losing shots.... is to deliver more CO2 over a shorter period of time.... closing the valve just before the pellet leaves the barrel.... More flow for less time....

Bob

Thanks! My original suggestion was using a smaller diameter port(not larger) in conjunction with a heavier hammer spring to stop wasting gas and keeping the same shot count.
How would I go about "The only hope you have of getting more velocity without losing shots.... is to deliver more CO2 over a shorter period of time.... closing the valve just before the pellet leaves the barrel.... More flow for less time...."Thanks,Huck

_________________
Crosman Phantom .22 ...UTG High mount,UTG 3-9x40 Hunter mil-dot scope
Crosman Phantom .22


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 4:35 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
Larger ports to deliver more flow.... then a weaker hammer spring to get the valve to close sooner.... As I said, the opposite of what you suggested....

You can drill the barrel and transfer ports out to 0.161" and the valve port the same, and then round the front corner of the valve port to smooth the flow from the throat into it.... Shorten the hammer spring, and/or install an RVA to reduce the preload....

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!


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 4:46 pm 
Offline

Joined: Tue Oct 13, 2009 1:27 am
Posts: 2514
Location: Vancouver
I'd expect something like larger transfer port, lighter hammer, same spring but with an RVA to fine tune preload until you get the tune you want, and a shortened valve stem to keep the valve opening time shorter would do it. Dump as much CO2 as you can per millisecond but trim the milliseconds it's actually dumping, reducing waste while increasing the effectiveness of the given valve volume of CO2 during that reduced open time. It could make for a number of surgeries as you carefully grind away a little at a time from the valve stem. You may have to elongate the slot in the main tube to allow the hammer to travel further to strike the shorter valve stem. But I've done these sorts of things on my 2240 (using a HiPAC, so not quite the same physics involved with the power supply) and found I was able to dramatically increase efficiency. Sorry but I've not saved exact numbers on anything. I just made a MUCH shorter valve stem out of an old drill bit shank and a nylon bolt for the poppet seal, put in a weaker valve spring so it opens more easily (used a firing pin spring from a Glock 17), and elongated the hammer pin slot perhaps 3/8" so it can go far enough forward without banging into the tube slot end. Went through a lot of open-tweak-close-test cycles before I got the tune I wanted. Then started all over again when I got a Lane regulator into mine as that changed things yet again. But if you're willing and able to fuss enough you ought to be able to trim your CO2 waste down to very little and increase shot count while increasing velocity. If it happens that you go too far on TP size (and barrel port and valve port would need enlarging as well of course) and cross the line, you can always choke it back again with a smaller TP.

Ah, I see Bob's spelled it out. Grinding down a hollowed area in the valve stem in front of your valve's poppet seal will help with flow as well. Anything you can do to reduce restrictions to flow will give you all the gas pressure you need. That's the starting place. After that it's up to you what you do with it. Controlling how much of that available pressure gets dumped behind the pellet is determined by how much weight hits how long a valve stem, how fast, with how much spring strength, length, and preload. Opening out the valve body for the last centimeter helps too, if you have a lathe, carving away some brass behind the part that's threaded together. I just opened mine out as deep as the peaks of the threads, smoothing the inner wall. Not a huge increase in volume but together with everything else it gives a huge range of potential power levels in any of the whole line of 22xx airguns. After that valve stuff working on the hammer train is relatively non-invasive, not so much of a pain to fiddle with until it's just right.


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 5:18 pm 
Offline

Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
Thanks to everyone who commented....I don't want to get too involved with this project,so if I can't get the same shot count as stock by installing smaller transfer ports and changing out hammer springs and trying to gain a few more fps by doing that alone and if not,I will re-install the stock port and leave it alone. Huck

_________________
Crosman Phantom .22 ...UTG High mount,UTG 3-9x40 Hunter mil-dot scope
Crosman Phantom .22


Last edited by Huck on Mon Jul 27, 2015 6:02 pm, edited 1 time in total.

Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 5:19 pm 
Offline
User avatar

Joined: Mon Oct 10, 2011 12:29 pm
Posts: 3110
Location: New Brunswick
I've read that increasing the barrel length will increase the fps but that over 14" it doesn't increase much more. Therefore 14" is ideal.
Is this true?

_________________
Image


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 5:25 pm 
Offline

Joined: Tue Oct 13, 2009 1:27 am
Posts: 2514
Location: Vancouver
Yes. And no. If you're talking about a lower-powered spring-piston or nitro-piston airgun, then yes. If you mean a CO2 or PCP, the longer the barrel the faster the pellet, depending of course on other aspects of tuning which allow a sufficient supply of gas to keep pushing through the full length of the barrel. If on the other hand you've fine tuned your 22xx to be maximally efficient with the stock barrel, getting the maximum shot count and staying legal, then you put a 14" barrel on the thing it is unlikely to shoot much if any faster. Might even slow down due to friction. But very few tuners are actually able to tune that efficiently so a 14" barrel will probably speed things up a bit at least. 18" is definitely faster than 14" given enough air supply. 24" is faster still, again given sufficient air/CO2 to push the pellet all the way out. A springer/nitro can't keep pushing. Once it's done moving it's done pushing the pellet. So there's an optimal barrel length for any given piston airgun. In playing with a couple of barrels for my QB57 I found that cutting down to 10" was too short, I lost a fair bit of velocity. Going to 14" from the stock 16" still cost a little speed, but only a few FPS, no big difference. All depends on the power plant.


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 8:28 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
Shortening the valve stem will increase the dwell not reduce it, because you will increase the hammer travel, and hence it's energy and momentum.... so the hammer hits the valve stem harder and opens it further and for a longer time.... While the stem sticks out of the valve nearly 5/16", you only need to open the valve about 1/16" to flow all the CO2 you can use in an 8" barrel.... A stock 2240 valve, with stock springs, opens about 3/32".... Because the stem can move 1/4" before the valve spring goes coil bound, people assume that is how far the valve opens, but it isn't even close to that.... The hammer stops and reverses long before it even approaches the back of the valve....

I'm not saying that there isn't some combination of a shorter stem and lighter valve spring that won't work.... just that reducing the hammer spring preload by cutting the spring or reducing the preload is all you need to do.... If you want to go to the trouble of drastically lightening the hammer and changing a whole bunch of other things you may gain more shots.... but it's a lot of tuning for a small gain, when the major one can be made with a simple reduction in spring preload or length....

The tune you want involves two changes in opposite directions.... Bigger, smoother, more efficient ports to increase the power.... and then a much weaker hammer strike to open the valve less to conserve CO2 instead of blowing it out the barrel.... Sorry, Huck, but your original idea to reduce the flow and hit the valve harder is in the wrong direction....

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!


Top
 Profile  
 
PostPosted: Mon Jul 27, 2015 8:53 pm 
Offline

Joined: Tue Oct 13, 2009 1:27 am
Posts: 2514
Location: Vancouver
Well I was meaning a considerable reduction in hammer mass. The stock 2240 Crosman hammer is far too heavy, even for high power applications. Seems designed to waste gas. Carving away a bunch of steel from the sides with a grinder is probably a good idea no matter what else you do to the power train. When I went to regulated pressure at 800psi I ground off a further 10% of the hammer steel or so as my goal was to maximize shot count. The hammer is down to about 60% of its original mass, and combined with a relatively weak spring, cut fairly short, with very little preload and the short stem and elongated hammer travel I'm getting what I was after. But it is all quite the balancing act. A bit at a time, here and there, lots of notes and time at the Chrony, and you will learn a lot about tuning.


Top
 Profile  
 
PostPosted: Fri Jul 31, 2015 7:51 pm 
Offline

Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
rsterne wrote:
Shortening the valve stem will increase the dwell not reduce it, because you will increase the hammer travel, and hence it's energy and momentum.... so the hammer hits the valve stem harder and opens it further and for a longer time.... While the stem sticks out of the valve nearly 5/16", you only need to open the valve about 1/16" to flow all the CO2 you can use in an 8" barrel.... A stock 2240 valve, with stock springs, opens about 3/32".... Because the stem can move 1/4" before the valve spring goes coil bound, people assume that is how far the valve opens, but it isn't even close to that.... The hammer stops and reverses long before it even approaches the back of the valve....

I'm not saying that there isn't some combination of a shorter stem and lighter valve spring that won't work.... just that reducing the hammer spring preload by cutting the spring or reducing the preload is all you need to do.... If you want to go to the trouble of drastically lightening the hammer and changing a whole bunch of other things you may gain more shots.... but it's a lot of tuning for a small gain, when the major one can be made with a simple reduction in spring preload or length....

The tune you want involves two changes in opposite directions.... Bigger, smoother, more efficient ports to increase the power.... and then a much weaker hammer strike to open the valve less to conserve CO2 instead of blowing it out the barrel.... Sorry, Huck, but your original idea to reduce the flow and hit the valve harder is in the wrong direction....

Bob

I have just been doing some thinking and if I shortened the valve stem 1/16",will I still need to elongate the slot in the tube for the hammer pin? Will this modification,along with a lighter/shorter hammer spring bump up the speed a little,using the 8" barrel? Thanks,Huck

_________________
Crosman Phantom .22 ...UTG High mount,UTG 3-9x40 Hunter mil-dot scope
Crosman Phantom .22


Top
 Profile  
 
PostPosted: Fri Jul 31, 2015 9:34 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
1/16" is about where the hammer pin may start to contact the back of the bolt or the front of the cocking slot.... However if you also reduce the hammer spring preload at the same time, that will only be an issue if you dry fire the gun with no CO2 pressure in it....

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!


Top
 Profile  
 
PostPosted: Sat Aug 01, 2015 7:08 am 
Offline

Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
rsterne wrote:
1/16" is about where the hammer pin may start to contact the back of the bolt or the front of the cocking slot.... However if you also reduce the hammer spring preload at the same time, that will only be an issue if you dry fire the gun with no CO2 pressure in it....

Bob

Thanks! Huck

_________________
Crosman Phantom .22 ...UTG High mount,UTG 3-9x40 Hunter mil-dot scope
Crosman Phantom .22


Top
 Profile  
 
PostPosted: Sat Aug 01, 2015 6:52 pm 
Offline

Joined: Wed Feb 11, 2015 3:16 pm
Posts: 304
Location: Ontario,Canada
GerardSamija wrote:
I'd expect something like larger transfer port, lighter hammer, same spring but with an RVA to fine tune preload until you get the tune you want, and a shortened valve stem to keep the valve opening time shorter would do it. Dump as much CO2 as you can per millisecond but trim the milliseconds it's actually dumping, reducing waste while increasing the effectiveness of the given valve volume of CO2 during that reduced open time. It could make for a number of surgeries as you carefully grind away a little at a time from the valve stem. You may have to elongate the slot in the main tube to allow the hammer to travel further to strike the shorter valve stem. But I've done these sorts of things on my 2240 (using a HiPAC, so not quite the same physics involved with the power supply) and found I was able to dramatically increase efficiency. Sorry but I've not saved exact numbers on anything. I just made a MUCH shorter valve stem out of an old drill bit shank and a nylon bolt for the poppet seal, put in a weaker valve spring so it opens more easily (used a firing pin spring from a Glock 17), and elongated the hammer pin slot perhaps 3/8" so it can go far enough forward without banging into the tube slot end. Went through a lot of open-tweak-close-test cycles before I got the tune I wanted. Then started all over again when I got a Lane regulator into mine as that changed things yet again. But if you're willing and able to fuss enough you ought to be able to trim your CO2 waste down to very little and increase shot count while increasing velocity. If it happens that you go too far on TP size (and barrel port and valve port would need enlarging as well of course) and cross the line, you can always choke it back again with a smaller TP.

Ah, I see Bob's spelled it out. Grinding down a hollowed area in the valve stem in front of your valve's poppet seal will help with flow as well. Anything you can do to reduce restrictions to flow will give you all the gas pressure you need. That's the starting place. After that it's up to you what you do with it. Controlling how much of that available pressure gets dumped behind the pellet is determined by how much weight hits how long a valve stem, how fast, with how much spring strength, length, and preload. Opening out the valve body for the last centimeter helps too, if you have a lathe, carving away some brass behind the part that's threaded together. I just opened mine out as deep as the peaks of the threads, smoothing the inner wall. Not a huge increase in volume but together with everything else it gives a huge range of potential power levels in any of the whole line of 22xx airguns. After that valve stuff working on the hammer train is relatively non-invasive, not so much of a pain to fiddle with until it's just right.

Hi:
Regarding your suggestion for a lighter hammer...right now I am using a 1701-P hammer which weighs 1.9oz....how much do I need to grind off for optimum effect in this particular case? I would rather try that first,before I get into shortening the valve stem and elongating the hammer pin slot....at least for now. Thanks,Huck

_________________
Crosman Phantom .22 ...UTG High mount,UTG 3-9x40 Hunter mil-dot scope
Crosman Phantom .22


Top
 Profile  
 
PostPosted: Sat Aug 01, 2015 8:24 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
You can remove half the weight of the hammer to good effect....

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!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 58 posts ]  Go to page 1, 2, 3, 4  Next

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
News News Site map Site map SitemapIndex SitemapIndex RSS Feed RSS Feed Channel list Channel list

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group

phpBB SEO