For CQB gaming I had run my Tanaka K98 on 134a gas (with restrictor fitted) very succesfully, it shot fairly consistently around the 320 -330 FPS mark. I believe 134a gas has now been withdrawn from sale due to its damaging CFC contents, and most airsoft outlets now market 144a gas as its replacement / direct equivalent.
Ok great so far. 
My last can of Abbey 134a is getting low so I purchased a can of Abbey 144a. Problem is, when tested through my K98 it was spitting out 0.2s through my chrono at upwards of 440 FPS! 
Which is only fractionally lower than Abbey's Sniper brut gas! 
I loaded another mag with 134a, 310 FPS no problem. 
Soooooooo, have I got a rogue can? Or does this match any one elses experience? I only have the one restrictor for the gun so can anyone recommend a lower powered/different supplier's gas before my 134a finally runs out? 
The first casualty of war is innocence.
The first casualty of airsoft is your wallet!
I used 144a at Eagle over the Rhine, with a restrictor fitted in my Tanaka and got consistent readings below 350fps.
When I want your opinion - I'll tell you what it is!
iirc the 144a is propain mix with lubracent. it suposadly has a higher pressure 'vaper point' at room tempreature.. or it expands into more space than the old stuff did. ..something like that. i'll have to dig the forum post that explained it on zero in it may take some time as it was over a year ago they posted that convo.
Thanks for the info gents, must have missed that convo first time round. The restrictor I have (the smallest one I think) originally gave sub 200FPS with 134a and sub 300 with green gas; it has been opened out to give sub 350FPS on 134a and sub 500FPS on green/sniper gas which is why I was surprised to find 144a coming out at 440FPS (tested indoors at room temperature). I did have another restrictor a while back but thus far have not been able to find it, time to start rooting I guess! 
The first casualty of war is innocence.
The first casualty of airsoft is your wallet!
Problem solved - new restrictor made (for my spare bolt head) from slightly oversized Plastruct plastic tube which was eased into place with a little plasticweld solvent. this was tested and gradually opened out to 3.2mm which now gives 350FPS at room temp with 144a gas. Although semi permanent it could be removed later by drilling out, and I still have the other bolt head for use with Brut Sniper gas for woodland games (470FPS). Sorted! 
The first casualty of war is innocence.
The first casualty of airsoft is your wallet!
