Question on preload...

[daved]

My gas ram CFX seems to be settlling down finally, seems to be shooting pretty consistently.  But the velocity still isn't what it should be, in fact, it's slipped a little from my last test.  So I think I want to try adding some preload to my gas ram.  My question is, which end should I put the spacers on?  If I do it on the piston end, I effectively increase the piston weight, which could be good or bad.  The CFX uses a pretty heavy tophat to start with, which is no longer in my gun, of course.  And I think the ram weighs the same or less than a spring.  So I'm pretty sure I'm currently "light" compared to stock.  I know that the general rule of thumb is heavy tophat, heavy pellets, and that this can be used to "fine tune" the gun/pellet combo.  I'm not even sure that preloading will help with the ram, but if so, I'm looking for a starting point.  And it's supposed to be rated at 18 fpe, I'm currently doing a little over 14 fpe with Superdomes.  When I first installed the ram, I got 15 fpe from Superdomes.

So any ideas, guys?  Obviously, if it was a regular spring, I wouldn't have much choice in where the spacer(s) would go.  But since I do have a choice, what do you think would be best?  And anyone want to take a guess at how much spaceing to add?  TIA.

Dave

[IJL]

Dave, based entirely on my experience with a Theoben gas ram in a BSA Superstar there is no option to add preload as the length of the rod gives maximum penetration into the ram and will bind if shims are added. On some of the gas rams you can vary the internal pressure with a pump, dont know if you have that type.

Ian

[daved]

Thanks, Ian,

You raise an obvious point, one so obvious I hadn't thought of it :-)!  That said, I don't think the rod is bottoming in the piston yet.  I need to take some measurements, but I'm pretty sure I have some piston stroke I can play with.  The real question is, will it make any difference?  Looks like the only way to find out for sure is try it.

Since mine is a retro fit ram, it doesn't have the adjustable pressure feature that Theoben offers on some of their guns.  Or maybe I should say used to offer, I seem to recall reading recently that they had discontinued that feature.  Thanks for your response, and I'll keep you posted on what I find.

Dave

[IJL]

Dave, further thoughts..............
As I remember the BSA has the body of the gas ram cylinder in the piston, I would assume that as this is an aftermarket ram designed for the for the Superstar that this configuration compensates for the lost weight in the piston with the cylinder.
Regarding shimming, on the BSA there is NO slop to take out bar a gnats wotsit width (thats very little here, we only get very small gnats) but please dont let me stop you looking :)
Also Theoben reckon that if you fit a 177 ram into a 22 then it will be more powerful, cant comment, but that seems to be supported elsewhere.

Ian