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Alliance Hobby 36 S ARCH AVE UNIT 2283
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Aluminum Flat Top Valve & Piston Kit
For Crosman 1322 1377 2289 P1322 P1377

MAY 2021 UPDATE: The piston now features two o-rings for better compression. Looks a lot more professional, too.

MAY 2021 UPDATE x2: A solid brass piston is now available. It's fancier. It's heavier. It's bling that only you know is inside...?

  • The Flat Top upgrades are immensely popular with Crosman pumper enthusiasts. The idea is that by giving the gun a larger air reservoir, you can do more work per pump, resulting in the same shot velocity with FEWER pumps. Or, increase velocity with the same number of pumps over OEM.
  • You can buy just the Flat Top Valve, just the Piston or the Complete Kit.
  • Note that you should not install just a Flat Piston with an OEM valve. The gun won't cock completely and will be useless.
  • You can, however, install just the Valve.
  • But the smart move is to install the complete kit.
  • Want even more mods? Consider the Flat Man's Pack, which is the Flat Top Kit + Power Spring + Max Flow Bushing.
  • The Flat Top Valve is an OEM Crosman valve that has been heavily modified.
  • First, we put it on the mill and angle the exhaust so the escaping air doesn't have to make a hard bend.
  • After that, we straighten up the exhaust hole with a nice six-fluted bit.
  • Then, we flatten the face to allow more air to be pressurized per pump.
  • Finally, we remove as many machining marks as we can to make a perfectly smooth exterior.
  • And, of course, the valve is cleaned and polished prior to reassembly with BRAND NEW o-rings.

  • This is the Flat Top Piston. It is 7075 aluminum milled from scratch.

This is the older single o-ring style. All shipments will feature double o-ring pistons as shown below.

  • And here is the complete kit.

Older single o-ring style.

  • Here is the kit with the brass piston.

Flat Top Kit

Flat Top BRASS Piston Kit

Flat Top Valve Only

You can buy just the FT Valve or Piston for specific use purposes, but understand
you're on your own with that purchase. They're not designed to be used separately.

Flat Top Aluminum Piston Only

Flat Top BRASS Piston Only