What is the correct or preferred FWB 300S piston buffer shape?

I ordered a breach seal and piston buffer for my FWB 300S and the buffer that came has a convex face.  The buffer that came out of the gun and all the buffers I see on re-sealing videos are flat on the face.

The seal and buffer I ordered are for a FWB 150/300.  Is there a difference between the 300 and 300S piston buffer and I got the wrong one or is this just another suitable version?

ChrisK

All the 150 & 300s I've resealed were flat. I use maccari's. Where did you get yours?

I got mine from Pyramid Air.  I called them about this but they are closed today.

Left to right, ARH red flat faced, FWB OEM green replacement, FWB buffer removed,

Left to right, FWB original removed, ARH dark green flat faced, green Air Venturi seals, FWB OEM replacement light green,

If they come from PA, most likely Air Venturi seals and source un-known.  They were darker green and slightly rounded, very similar to OEM, but not as hard.  ARH seals are flat front, red and very dark green in pics.  We had some discussion some time ago on the yard about possible increase in 'cc air colume, but couldn't tell much really.  I have used all the different styles available and prefer the Air Venturi and ARH over the FWB OEM green ones.  They feel like injection molded hard plastic.  Most durable I imagine will be ARH due to his choice of machined materials.

?

Jason Garvin

Matter of fact, here are some results of different setups from rebuilds I have done in the past.

Feinwerkbau 300s, ARH Seals and one piece Artic mainspring,

Feinwerkbau 300S - OEM dual spring set up, FWB seals (green)

30 yd 5 shot group slight cross wind,

My brothers Feinwerkbau 300s mini,

First rebuilt with FWB OEM green seals, OEM dual spring setup,

Chrony before tear down,

Notice the fracture starting on the hard green seals,

Air Venturi seals from P Air,

Seals installed,

Artic spring from ARH installed, one piece main,

New chrony numbers,

And accurate,

Jason Garvin

Great reply, THANKS!  My buffer looks like the Air Venturi in your pics.  Another source also confirmed that I am good to go with what I have.

BTW, what lube do you use?  The only lube I have on hand is that gooey black tar that came with a PG2 kit for another gun.  Seems too heavy for this application, even if used very sparingly.  I thought I once read that these guns aren't even supposed to be lubed.

Kind Regards,

ChrisK

Well, I guess everyone has there own secret recipe.  What I have been doing is, 

Using synthetic moly oil on the piston ring and behind, fanned very lightly with a small brush (maybe 1-2 drops total for the piston O.D. including ring).

The cocking arm gets moly grease as seen here,

I treat all metal (All) with TSI 301 from the start, and use the TSI 321 on the recoil pins,

Extreme weapons grease, which I use on my Volquartsen speed pistols, on the O.D. of the comp tube, I use this in all my sliding comp tube tunes,

https://www.slip2000.com/slip2000_ewg.php

Seen in the receiver, it fans real thin, doesn't move around, and is slick slick slick,

Volquartsen recommends it in their custom pistols, and I have been using it on the sliding bolts with great results, such as these,

https://volquartsen.com/inventory_configurations/897

And last but not least, ARH Euro tar on the mainspring, guide, small amount of his moly on the spring ends, which I polish and clean,

http://www.airrifleheadquarters.com/catalog/item/251484/4810952.htm

You can run them dry, and they tend to sound dry.  My brothers mini on the first tune was all but dry (synthetic oil and moly mix), I used my recipe above and still achieved higher numbers well lubed.  I see very little deviation on numbers also with lube.

Jason Garvin