Advise on which piston to get for G&P Sentry ?

[Chewybacka]

I took my first V2 gearbox apart last night and I saw that my piston is quite shot. The threads are very well worn, everything else showed no sign of breakage. I am wondering do I need to replace with same version or can I use a full metal piston, would this indeed be better ?. Also do I need to use a similar piston head ?.

[Sir Stephen]

Re: Advise on which piston to get for G&P Sentry ?

unless you know exactly what you are doing, stay away form metal toothed pistons. if they aren't set up correctly, you you will break a lot more then just the piston.

stick to plastic pistons, for the £10 they cost, they can be your deliberate weak link if anything goes wrong, saving the rest of your gearbox.

if the piston head is in good condition, just use it on the new piston, no need to fix what isnt broke

[Chewybacka]

Re: Advise on which piston to get for G&P Sentry ?

Cheers mate, the rubber ring on the piston head is very loose. I saw on ebay the same piston, but they were saying for barrel lengths, does this matter too much ?.

[Sir Stephen]

Re: Advise on which piston to get for G&P Sentry ?

the hole (or lack of) in the cylinder wall is what matters for barrel length, but don't worry about that if you haven't changed the barrel length from stock.

the o-ring should fit snugly from side to side, but not across (if that makes sense). e.g, if its 15mm across, but 2mm thick, then the gap for it should also be 2mm think so its snug, but it doesn't matter if its loose/moves freely on the 15mm plain. you want this because it need to be able to expand and contract as the piston moves backwards and forwards.

[Chewybacka]

Re: Advise on which piston to get for G&P Sentry ?

Ok cheers mate, very muchly appreciated, I kind of get your meaning. Will order same piston on ebay.

[jonny lovegrove]

ASG ultimate ones are a good start, as they are made without the first teeth.

[dave38x]

Re: Advise on which piston to get for G&P Sentry ?

ASG ultimate are very good pistons

[Caldymoose]

Re: Advise on which piston to get for G&P Sentry ?

Dont use a full metal tooth piston. Just dont! The piston acts like a mechanical fuse in your gearbox. If something is going to break, its more than likely going to be the piston. A £12 piston is easier to replace than a £30 gear set, or worse. Having a few metal teeth on them is fine, but full metal toothed racks arent the best.

Personally, I'd go for a Lonex Blue, or Red if you want a little extra strength. £12 from a laboratory of air in the UK. (Cant name the exact retailer...good old zero in)

Remove the 2nd to last tooth, maybe a bit of the next one as well to correct the AOE and your good to go.