tophat shims

i was thinking about trying tophats shims but you guys haven’t really said what you use. i was thinking neapream washers but getting them on and off would be hard. also o-rings, might work could get them off with a pick. just wondering what and sizes. thanks

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I quit using washers when I went to .25 caliber. I was after max power with less deviation, so I went the “adjust the tophat” route with the .25.

On my valve, I can turn the tophat all the way down to 0.0″ gap. Must have a lot more threads than most. I ended up right around 0.65″, seems to work well with a stock valve.

During my times of adjusting for maximum consistency i have found some stems don’t have enough threads to allow for enough adjustment. This could be a bigger problem in .177 cal. or .20. I found on one valve that even bottomed out it still needed to be tightened down some more. I was at .069 and at .067 was the sweet spot. A paper hole punch and ali cans works well just about the size of the bottom of the tophat. Drill a hole in center and your set.


What you could use are so-called e-clips (I think, because that’s what we call ’em in The Netherlands). See picture. I used them on my Talon SS, because it has a homemade valve stem which is not adjustable. The 4mm e-clip fits perfectly. I used 2 and I have an approximate 1,4mm clearing, which is about .055″ I believe. With a 24″ barrel I shoot JSBs @ 1030 fps (approx. 38 fpe). This is a little fast for these lightweight pellets, but I’ve been having great experiences with them 😉
But it’s getting good accuracy (I’ll shoot some groups when I get the chance) and a lot of shots.


You can use 3/4″ diameter neoprene washers with a .25″ hole in them very easy. Just use a scissors trim it around the hole leaving a tab to grab ahold of. Make it a teardrop shape with the hole in the middle of the fat part.

The rubber washer will stretch over the tophat pretty easy. The tab lets you grab ahold of it to pull it back off.

Adjusting the tophat works too, but I really liked using the washer. With the washer, JSBs would shoot around 985 fps nice and accurate, and Kodiaks shot around 980fps nice and accurate.
With no washer Kodiaks hit 1050fps, and groups opened up quite a bit.
My barrel didn’t like EunJins, but they shot around 980 without the washer, and 875 with one.

For me, best results came with a 0.062″ thick rubber washer, with the tophat set to 0.090″. This left a 0.038″ gap which effectively let my valve work very well without tophat bounce. I could always get 40+ shots very accurate and consistent with this setup.

The thing is, the tophat doesnt have to slam into the brass insert of the valve if you use a rubber washer. If you adjust the tophat too close, you bottom out the tophat on the brass insert when you fire the gun. If you go too far, the tophat will bounce and the valve will slam shut early giving you weak shots.

Properly adjusted, theres no problem without a washer, but I could never keep the grub screws from loosening up once I started messing with them.

I just cant see how that impact can be good for the valve parts. Probably also why the grub screws kept coming loose.

If you are speaking of “shims” to adjust the flow of the valve, there is no need. The tophat is threaded to allow adjustment of the valve.

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