2240 project starts

[Greg Butcher]

While I wait for my Vern grips (can't wait)
And I build out my indoor range area, here's progress so far. I thought I would be doing better than my latest chrono results show. Unless my expectation is off.

so any ideas you have would be welcome.

I figured I should be seeing higher fps.


10.1 crosman barrel
Alchemy longer .22 probe
Alchemy boss rp valve
Alchemy stronger hammer spring
Alchemy big port
Steel breech
Tko 6.5 moderator
Adjustable sear spring
Alchemy Roller trigger

Ran it on the chrono tonight, indoors.
Time between shots, just reload time.
Temp:68 °F
BP: 29.55 inHG
Shots
#     FPS        FT-LBS     PF
20    419        0.00       0.00     
19    426        0.00       0.00     
18    426        0.00       0.00     
17    432        0.00       0.00     
16    437        0.00       0.00     
15    441        0.00       0.00     
14    446        0.00       0.00     
13    446        0.00       0.00     
12    448        0.00       0.00     
11    452        0.00       0.00     
10    457        0.00       0.00     
9     459        0.00       0.00     
8     460        0.00       0.00     
7     467        0.00       0.00     
6     482        0.00       0.00     
5     479        0.00       0.00     
4     482        0.00       0.00     
3     485        0.00       0.00     
2     483        0.00       0.00     
1     495        0.00       0.00     
Average: 456.10
StdDev: 22.63
Min: 419
Max: 495
Spread: 76
True MV: 456.10

[cobalt327]

What pellet?

[Greg Butcher]

What pellet?

Good point
Crosman premier 14.3

[nervoustrigger]

Hi Greg, I just noticed you posted here on GTA.  I will copy/paste from the other forum for others who may be following.

You answered my question about the barrel port perhaps still being at the original diameter.  If so, that's what is choking off the flow and limiting energy.

I could not find the diameter it has from the factory but I looked back at the 2240 barrel I swapped out last year and I had apparently drilled it out to 0.154" (#23 drill).  I want to say it was originally 0.140", same as the stock transfer port. 

So assuming the Alchemy exhaust and transfer port are at least 0.170", you should see a nice gain by enlarging the barrel port to 0.170".  If you go much larger, pellets may get chewed up when being chambered.  Of course be sure to deburr the inside of the hole.

To put it into perspective, going from 0.140" to 0.170" is a 50% increase in area.  That is significant when looking for higher energy.

[Greg Butcher]

Thanks nervoustrigger.

I did indeed find the barrel port was smaller naturally than the boss transfer port. so I opened it up to match the transfer port circa .170. so far it has not made a difference with fps in testing.

A power adjuster is on the list to get to fine tune it, in the meantime I tried it with the stock spring back in, made zero difference oddly.
 just finding it odd these changes made little difference. I would have expected the barrel opening up would have seen a change.

Unless the extended bolt is coming into play here as there is alot of it sitting across that barrel hole.

I was wondering on the additional co2 and 10" barrel. was reading last night that based on timing and the additional volume it may need a longer barrel since the pellet is out before its all done dumping.

Frustrating as I  have a bone stock 2240 sitting here doing the same basic numbers lol.

[nervoustrigger]

Sounds like you are about to find the culprit, if you haven't already done so in the bolt probe. 

For there to have been no difference from enlarging the barrel port, something else is restricting flow.  Like you said, it could be the bolt probe.  I just pulled up a picture of it on Alchemy's site and it does look pretty chunky.  I would turn down the nose to about 0.060" for most of its length, and do a radius blend up to the shoulder for the O-ring.  This picture is of a .177 bolt but it should give you an idea.


Or it could be a misalignment in the valve exhaust, transfer port, and barrel port.  In an ideal world, all 3 would be perfectly concentric.  The Crosman transfer port, with a shoulder on both sides, helps ensure they are aligned.  Based on the picture of the Alchemy transfer port, it looks like it is designed to work in a similar way.  Maybe you can look at it carefully and see how it fits to both the valve and the barrel and see if that is a source of the restriction.

FYI, I considered the possibility of blow by from a leaky transfer port but if that were the case, there still should have been some improvement in velocity when you enlarged the barrel port.  The only counter argument for that I could come up with is that the alignment could have possibly been worse when you reassembled, thus no improvement was seen.  That seems pretty unlikely but I just wanted to mention it for the sake of completeness.  Best not to leave any stone unturned when troubleshooting.

Regarding barrel length, you can certainly expect better performance if you go with a longer one.  The fact you lost no velocity with the stock hammer spring suggests the valve is staying open longer than necessary.  Using the heavier spring will simply harm shot count and make a louder bang when you pull the trigger.

[Greg Butcher]

Thanks, I also pinged David @ alchemy and he confirmed also my thoughts on the performance valve and barrel length. So i am going to have a little play with what you have suggested while i also wait on a longer barrel. I have another 2240 in the works so nothing goes to waste

I also feared the alignment issue with the ports but was pretty anal when putting it together so i think we are good there. no harm in taking it apart and trying again either.

Thanks for all the steers, will see what happens next and report back.

fun stuff.

thanks again.

[nervoustrigger]

No problem, I hope you get it sorted out soon.  It's also good to hear you're having fun with it.