Velocity Adjuster

[ejackyou]

New to forum and gun, 2240, just starting to hop it up a bit, with longer barrel, steel breech,
next on my list is a rear velocity adjuster and new spring. But, I've heard that the rear velocity adjuster
does little for performance, more for looks, the stronger spring is what actually makes any improvement?
Any advice? Any other simple mods to improve performance?

[DaveB50]

The stronger spring makes more power yes, but the VA lets you fine tune for more consistent power/accuracy.

[ejackyou]

Thanks, makes sense.

[BillK]

I like the Rear Velocity Adjuster (RVA) because I don't always want to shoot at full + power & have a bolt that is hard to pull back to cock.  Probably 90% of my shooting is at less than full + power.

[ejackyou]

If the Spring that comes with most velocity adjusters is stronger, doesn't the gun have more power than stock,
even when the adjuster is backed out all the way?

[ped]

at co2 pressure no point fitting a stronger spring as all you'll do is waste gas
better using the std spring with about a 4mm shim
ped

[crossliner]

at co2 pressure no point fitting a stronger spring as all you'll do is waste gas
better using the std spring with about a 4mm shim
ped

Herr Ped is right..Even half an mm will greatly decrease/increase velocity..These are the hammer spring washers on my Air Arms








The brass one w/c I had made has a flange thinner by half an mm and when I installed it the velocity dropped from 920fps w/ 18g JSBs  to 880 something.

[BillK]

ped is quite right about wasting gas.  A full power valve with a heavy spring will probably even waste gas with a 24" barrel.  It would take many shots over the crony to determine where the best setting of the RVA is.

Most RVAs do not come with a spring.  The Crosman RVA comes with a softer spring (blue) so that it will give you more shots at a lower FPS.  The Crosman RVA has less adjustment than most of the aftermarket RVAs.  Therefore the softer spring.  It allows you to lessen the FPS but not increase them.
A good RVA will allow you to increase the (OEM) spring tension to the point that the gun won't cock and decrease the tension so that you will be shooting in the 300s (FPS).  This is all done with the OEM Crosman spring.  A heavier spring is not needed.
Many RVAs incorporate a "spring guide" on the adjusting screw.  Crosman includes a separate spring guide with their unit.  The spring guide makes the spring use all its tension to push the hammer forward and not to the side as it is released.  It won't let the spring get crimped up.
This explanation probably will cause more questions, as expected, and corrections from others, as expected. 
More info the better......

[crossliner]

Also stiffer hammer spring means harder trigger pull if you don't have that 1701P trigger kit upgrade. I myself do not see the need for too much power it's accuracy that I am after for the most..


http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,13470.msg176995.html#msg176995


About 3 weeks ago I was able to do this out to 45 yards..






If your Crosman is in carbine form cheek weld is of utmost importance...





You are Canadian right?

[T191032]

"But, I've heard that the rear velocity adjuster does little for performance, more for looks, "

Never thought my Mellon Velocity Adjusters were for Looks, at least till I started tinkering and added the extra nut to keep the adjuster in place once I found the "sweet spot".   

[Davio]

A couple of observations:

Adding a spring guide with a base will itself add to spring tension. But, adding a spring guide (with or without a PA) can present a problem sometimes (especially when breeches and rear sights are changed / removed as well) when the rear breech screw is too long and pushes into the guide and spring.

My PA's will most definitely increase to coil bind that can then be backed away from. The rest of the "recipe" is a slightly shortened stock spring with guide so that I reach coil bind at or near the end of the full in adjustment (at the expense of CO2 usage but max fps), then the full out gives close to or max tension release (to conserve at the expense of fps).  I also prefer to put a weaker spring in the valve (do this first, actually) when I am really after power (besides valve, porting, blah blah).

Now on a pumper, I'll shorten the check to relax valve spring tension without a spring change. Makes pumping easier (for a few anyway) and valve stays open longer for larger dump. <ADDED LATER>  Also adds a very wee bit of compression chamber volume as well.

It's all a balancing act.

[ejackyou]

Wish I could take advantage of Your expertise
Why can't You ship parts to Canada?

[Gippeto]

What makes you think that airgun mod parts are not available in Canada?

RVA is (JMO) of VERY limited value as a performance mod on a stock barreled 2240. They make more sense (again JMO) on airguns using AIR...where pressure (and thus valve opening forces) is more of a variable.  I do like light valve springs in a pumper...lowers the cracking pressure of the check valve.

Could be that some folks over estimate the amount of resistance to opening that comes from a valve spring...closing force too for that matter. A quick calculation using available pressure and surface area at the effective sealing diameter of the head and the effective surface area at the valve stem bore tells the tale.

.340" head (unsure if this is correct for a stock 22xx valve...I have used it in a build though) @850psi is 77 lbs force.

3/16" stem @ 850psi is ~23.5 lbs force trying to close the valve during the shot cycle.

Either is considerably more force than available from the valve springs commonly in use by Crosman.

Al

[Davio]

Wish I could take advantage of Your expertise
Why can't You ship parts to Canada?

It is ebay that does not allow air gun purchases from outside the US. 

I ship to Canada and UK all the time. Go to the website www.alchemyairwerks.com and see the international inquiry page.

[ejackyou]

That's awesome news, I'll be $hopping buy!