Rammed out! Which spring??

[leetrenchard]

Using lockdown time to go through all my airguns not working properly.

Got to my errant Remington Thunderjet, bought this to have a cheap fiddle with gas rams and got what I wanted.

The gun is weak despite me taking it apart for a good clean up and relube. The piston seal is a bit tatty looking but can't find a replacement.

The ram itself is 300mm in length with a diameter of 19mm. Gone through my old springs and found a Weihrauch one that is 19mm o/d and about 255 length.

This has worked with 14mm of slip washers in the piston end, the spring sits on top of the trigger block as its too big to slip into the block as the ram does.

It cocks and fire smoothly, with the ram it was at 645 fps average/7.67 ftlbs with superdomes (.177), with the spring and absolutely minimal preload its at 735 fps/10ftlbs

So, can anybody recommend a spring? needs to be 19 o/d and 300mm or more? hopefully the 19 will fit inside the trigger block and not rest on the top, will make a guide for it when I can borrow a lathe.

[TonyL]

Hi Lee, I'm not au fait with your rifle. Looking briefly at images of it, it looks like it may be based on the Gamo platform, as shared with a few other guns originating from China?

Have a look at the Mainspring Data Thread in the Useful Section. Go to the last page. You'll see an excellent post by Phil Russell giving spring stats of many springs. And also an updated one for Titan springs posted by Pete, "look no hands". Alternatively, you could try Tony Wall at SFS with your required dimensions.

If it is based on the Gamo design, take a look on the Welsh Willy site to get an idea of the spring guide design required.

Hope this helps a little and be sure to shout up for any further help.

P.S.....The stock looks nice on the Thunderjet.

[leetrenchard]

Was coming to similar conclusions on origin of it.

Ordered a titan 006 for it, would be useful to find a spring guide. It does look similar Internally to a meteor Mk7, are they Chinese too?

[TonyL]

Hi Lee, no, the Meteor is not Chinese, but these later Meteors are Gamo based (Gamo now owning BSA).

I like many of the characteristics of the Gamo action. But they are renowned for being very twangy, due to the spring guide being a loose fit on the spring. Usually, to rectify this, one would drive out the guide section that is set into the rear portion of the guide and replace this with one that is a better fit for the spring. So, if you can make your own, that's why I mentioned having a look on the Welsh Willy site to view the design of the guide. If you can't, I don't know if Will (he's a lovely and very helpful chap) would supply you just the guide and top hat? I'm not familiar with the innards of the gas ram version and whether the rear of the action is the same, or if you'll need to first buy the standard type springer guide?

Don't know if anyone on here may have the dimensions for the guide for of you wanted to make one. It's a stepped design and needs to clear the trigger unit / sear arrangement.

Once suitably tweaked this action provides very polite firing manners.

Ooh, just another thought......Lyn Lewington (venoman on here) runs ARC Tuning which specialises in tuning the Remington springers, so he might also be an excellent port of call?

[Neil54]

Your thunder jet is a Chinese copy of the Gamo Hunter series of rifles. SMK XS19, remington pest controller, many crosmans and the Turkish kral devil all use this platform.

I have an old rear spring guide I can give you the dimensions of. I also had two gas ram rifles, one with the ram facing forwards and one with the ram facing rearwards.

[leetrenchard]

That would help.

The trigger is in a cast rear section that pins I to the rear of the cylinder. It has a 19mm hollow in it where the ram/spring guide goes.

So the spring guide would have to have a short 19mm section tapering down to the guide rod to fit in a 19mm o/d spring.