I never knew!

[Howler]

That air rifle bedding could be so important.. Was trying to tune my cayden (adjust hammer spring) to the H&N 23gr slugs. When I started, they was shooting 760 FPS which isn't bad! But I was going to try for 800 FPS. Took the rifle out of the stock for easy access to the adjustment & much to my surprise managed to getting the velocity up to 845 FPS. However, when I placed it back in the stock & run it over the chrony again,
it was only getting 785 FPS.. This isn't bad at all IMO, but I couldn't figure why such a drop just from simply fastening it back in the stock?? I used a 22 K hornet case cut off to just meet the pillar on the bottom of the stock & glued it using J.B. After it dried, it was just slightly to high & was causing the action to rock. So, with no way to cut it down, I improvised & took the cutter from my case trimmer with the appropriate mandrel & cut it down fairly quick to just match the surface. Long story short, didn't fix the probem! Place a small tripled piece of aluminum foil just in front of the action screw & the velocity went up. I assume the stock was putting pressure on the reserve?? Any other opinions??

Thanks,Robert

[Tommyzgunz]

Havng owned both rimfire and air rifles i have to wonder how much bedding and stock screw torque may matter with airguns.there is no doubt that pillar/bedding rmfires as well as experimenting with various in/lbs in fhe stock screw torque makes huge differences with many .22lr rifles. I woudn't be surprised if torque settings also affected specific airguns  to make a difference when removing a stock then re_tightening the stock screw at a different torque than was previously. I did post a question about it as i was curious a while back but the post didn't really go anywhere as far as many people experimenting with it.

[CableStop]

Were you shooting it out of the stock at first?  I don't entirely know what you mean by "pillar" either so it's hard for me to understand how you glued that .22 casing in.  I would try going back to the way you were shooting it before and see if that increases velocity again, it may just be the hammer spring and valve settling too, especially if the gun is new.

[Howler]

Answer a couple questions #1- It's obviously been doing this since I've owned the rifle! Just didn't notice it until I went to get the most from this specific slug.  #2- Setting the hammer spring out of the stock of course! easy access that way! otherwise you have to remove the stock every time to make a adjustment.

FWIW, You can buy pillars for bedding! I simply made mine from a 22 K hornet case trimmed to the appropriate length, drilled thru the primer hole & case web so the action screw would slide thru it & JB welded it in place. Why?? to keep from stressing the wood under torque, but to also attempt to stop what was bending/stressing the action/air reservoir.

[Greg_E]

I'm only sort of grasping this, can you post some pictures?

[Howler]

I could have! but I have no intension of taking it back out of the stock until I get more Jb weld ( & time) to properly bed. I'll post pics than..

[Greg_E]

OK, thanks, I can wait.

[cosmic]

My guess is a weakening hammer spring or it hung up some when tuning.. Could be the hammer binding also hammer adjuster backing out....  I would take it back out and adjust your hammer tension for what you want the speed to be, and fix with some blue or purple loctite..Still can't figure out why bedding would have anything to do with it...
   POI I can see but velocity not so much...
   Maybe try the stock loose on the rifle and slowly torque it in stages and record the results.. I say it is some mechanical issue..

[AlanMcD]

Honestly, I don't think it could be from poor bedding of the action in the stock.  What you describe is a loss of about 15% of the total energy of the gun.  In the distant past, I did a bunch of tuning on Marauders and I found that if I let them just sort of "float" in the stock and not be secured that could lead to a shift in average speed, but it was under 10 fps or so.  In fact, I bet if you put the action on a block of ice and let it slide reward on the shot you would not see much more than that . . . .

But since something is clearly happening, I'll offer this - but do know I have no experience with the Cayden.  If there is a significant change in air flow in and around the tube around the hammer as it fires, this could have such an effect.  Marauders have an air hole at the rear of the action, and if you put your thumb over it on the shot the gun will lose quite a bit of energy.  I'd look for something like that, or maybe something actually causing an interference with the hammer in the tube (maybe the bedding is so bad that the tube is bending when you tighten down the stock?).  It has to be more than just a loose or sloppy fit in the stock . . .

That is just a massive amount of lost energy

[kbstingwing]

my guess is that the poppet or the hammer is touching the end of the stock mount screw, I had a Gauntlet poppet get stuck from an over tightened stock mount screw, I ground the end of the screw and only tightened it snuggly, that solved the problem.