logo by smgunner

Crosman999's Sheridan

 


  << Previous Topic | Next Topic >>Return to Index  

Some more 2240 chrony results

February 28 2009 at 2:51 PM
  (Login aslap)
Crosman Forum Member
from IP address 71.206.200.66

 
I did a couple of more mods to the gun and got the numbers. The graph shows the temp when each test was done. My attempt at building a power adjuster was, to put it politely, an abject failure. All else seems to move in the right direction. What was very interesting was that after I got done with the last test in .22, I installed a 16" .177 barrel. I was expecting to see velocities way up in the 700's but actually saw the velocity drop into the mid-630 FPS range. This particular barrel only has a 1/8" diameter barrel transfer port hole so I'm guessing that this is simply a choke point. The RSD's when using this barrel were also extremely low (0.5% over a 10 shot group) so that lends a little creedence to the small transfer port hole acting as a regulator, albeit one that doesn't allow much in the way of flow.

It is also no surprise that doing these mods is blowing more and more CO2 out of the barrel. I'm probably contributing more to global warming by doing these tests than most of the third world and I'm sure I'm leaving a carbon footprint that has to be Sasquatch-esque. While I didn't show it here, the final test I did was with a much stonger hammer spring and that got me to 670 FPS on the 24 " barrel at 63F. However, it looks like I was only able to get 12 good shots out of a cart before the velocity started to drop like a stone in the ocean. About the only thing left is to wait until the weather here in Pittsburgh warms up so I can see what happens at higher temps.

Here are the mods and the order in which they were done.

Test 1 is stock valve and springs and running off carts. Barrel and valve milled to seat poly tube transfer port. All tests will use Daisy P-Max WC pellets. Standard bolt.
Test 2 adds extended probe bolt.
Test 3 opens exhaust port on valve and barrel xfer port to 11/64" the ID of the poly tube
Test 4 angles valve exhaust port
Test 5 adds a crude power adjuster = about 1/8" shim behind hammer spring
Test 6 removes crude power adjuster and adds weaker valve spring. Same # of turns, wire dia at .0.35" vs.0.044" stock
Test 7 removes 1/2 of the threads on the valve front
Test 8 re-shapes valve stem in exhaust port area

[linked image]

Tony


 
 Respond to this message   
AuthorReply

(Login aslap)
Crosman Forum Member
71.206.200.66

I don't know why the second 24" appears ...nt

February 28 2009, 2:53 PM 

.

 
 Respond to this message   

(Login aslap)
Crosman Forum Member
71.206.200.66

I know why - just ignore it...nt

February 28 2009, 2:54 PM 

.

 
 Respond to this message   
Lorrin
(Login leel)
Crosman Forum Member
75.71.212.178

I bet that you will see a significant improvement with warmer temps

February 28 2009, 3:37 PM 

You could try leaving the gun in the warm house for a few hours, then take a couple of quick chrony shots to see what happens...

Good luck,
Lorrin

 
 Respond to this message   


(Login twhooper)
Crosman Forum Member
75.53.213.140

Very good that you're doing these tests so precisely...

February 28 2009, 5:16 PM 

again, it appears to show that the single most effective way to increase performance is to use a longer barrel. Then the other mods help incrementally, noting that with the longer barrel, they have a more significant effect.

Now we know more clearly how we will gain the most benefit. I guess I'll be digging around for my stashed 24" barrels, stop doubting the wisdom of my longer barreled pistols and put up with the extra length.

Thanks... keep it up.

LUK

Be Well... Tom
Think as though you LIFE depends on it...IT DOES!
"A fear of weapons is a sign of retarded sexual and emotional maturity." - Sigmund Freud

 
 Respond to this message   

(Login aslap)
Crosman Forum Member
71.206.200.66

Tom, that appears to be the case

February 28 2009, 6:28 PM 

The longer the barrel, the greater the baseline gain and the greater the incremental gains from the common mods. The harder hammer spring I used really jumped the FPS and I need to do some more with that later.

I'd say that the heirarchy of mods is:

Longer barrel

Bigger ports

Reshape valve exhaust

Weaker valve/harder hammer spring

Of course, the poly port mod is good for sealing but that alone doesn't bump the FPS unless the other stuff is done.

I'll do another post when the temps are up.

Thanks for looking!

Tony

 
 Respond to this message   


(Login twhooper)
Crosman Forum Member
75.53.213.140

Hey we're really glad you're doing it...

February 28 2009, 9:25 PM 

helps us, me anyway, to evaluate where to put my time and money to get the best and what the results of my choices will be.

For instance, I can get significantly better performance by adding a 24" barrel to my hunting carbine, but it will handle different, and be harder to case when carried and it won't 'look' the same. So I'll accept the trade off.

And, I'm happy with 12" of barrel on my 2240 even though I planned on a 10" barrel even if it's looks a little odd being so long knowing I get more performance and it still fits in the case.

Just my examples...

LUK

Be Well... Tom
Think as though you LIFE depends on it...IT DOES!
"A fear of weapons is a sign of retarded sexual and emotional maturity." - Sigmund Freud

 
 Respond to this message   


(Login bigbore)
Crosman Forum Member
65.13.53.171

Get the power adj. from Crosman...

February 28 2009, 5:32 PM 

about $20 shipped, money well spent.

Great numbers once again Tony, thanks!



[linked image]


    
This message has been edited by bigbore from IP address 65.13.53.171 on Feb 28, 2009 9:49 PM
This message has been edited by bigbore from IP address 65.13.53.171 on Feb 28, 2009 5:32 PM


 
 Respond to this message   


(Login wydeopenspaces)
Crosman Forum Member
70.191.167.175

Power adjust

February 28 2009, 6:01 PM 

I had looked at the part numbers for the 2300S version's power adjust part...ism that what you're referring to?

 
 Respond to this message   


(Login bigbore)
Crosman Forum Member
65.13.53.171

Yes. nt

February 28 2009, 9:48 PM 



[linked image]

 
 Respond to this message   

(Login aslap)
Crosman Forum Member
71.206.200.66

Opened the hole in the .177 barrel

March 2 2009, 3:53 PM 

To 11/64 and got the same 630 fps. So, the idea that getting more gas in the barrel works best with larger calibers looks true. With the 16" barrel, it looks like 630 is about it in .177 with the way this gun is modded. Temp was 62F.
I wish I would have been thinking because I could have included this .177 barrel right long with the others when I did this.

Tony

 
 Respond to this message   


(Login Biohazardman)
Moderator
76.27.245.57

Nice werq on the graph...

March 2 2009, 10:57 PM 

most of us that have done any tests don't do it so fancy. ;^) The .177 does not need the ports or volume to be as large as the .22 as there is much less barrel volume to fill. Likely in .22 you can let off on the hammer spring a bit and get more shots at near the same velocity? Some if not most of my longer barreled guns get near 10fps more velocity per degree F increase. It's quite a bit and something to remember when people post high velocity numbers.

I used to have a life. But now I have the forum. I am a sick man?

[linked image]

 
 Respond to this message   

(Login aslap)
Crosman Forum Member
69.33.200.6

Right

March 3 2009, 2:14 PM 

At 75F, that .177 might be smokin'!

I have a nice 19" .20 barrel that is currently using a 1/8" transfer port and is a 1320 gun. I think I'm going to put that on the test frame and mess with the ports on that to see what happens. One would expect results just about 1/2 way between .177 and .22.

So you think you have no life? I may have you beat, brother.

Tony

 
 Respond to this message   
Current Topic - Some more 2240 chrony results
  << Previous Topic | Next Topic >>Return to Index  
 Copyright © 1999-2014 Network54. All rights reserved.   Terms of Use   Privacy Statement  

Crosman Corporation 1-800-724-7486