Servicing a 70s Mercury - Spring Choice

[james_stan]

Thanks. I can at confirm hat the BS212 (21.82 ID 28.88 OD is too tight at least in combination with Chamber's alloy piston as you push it through the threaded section it bucks up at the slotso I cut it in the end to get it off. My digital verniers are out of commission at present but the old verniers measure an ID of 22.2 ish on the piston ring slot and about 27.4mm on the outside of the piston. With this in mind I guess we should be aiming for a BS 211 (20.22 ID 27.28 OD) or metric might be better at (21 ID 28 OD). @ CapitalB ee do you know what your size is? These things are easy and cheap to source on - once you know what works!

[look no hands]

Thanks. I can at confirm hat the BS212 (21.82 ID 28.88 OD is too tight at least in combination with Chamber's alloy piston as you push it through the threaded section it bucks up at the slotso I cut it in the end to get it off. My digital verniers are out of commission at present but the old verniers measure an ID of 22.2 ish on the piston ring slot and about 27.4mm on the outside of the piston. With this in mind I guess we should be aiming for a BS 211 (20.22 ID 27.28 OD) or metric might be better at (21 ID 28 OD). @ CapitalB ee do you know what your size is? These things are easy and cheap to source on - once you know what works!

You have to make sure you have the right shaw with the O ring, otherwise it will destroy itself after a short time in the cylinder.

Pete

[james_stan]

Hi Pete

'Shaw' ?

Cheers

james

[Shed tuner]

Hi Pete

'Shaw' ?

Cheers

james

"Sure" rating, e.g. 90 instead of 70. i.e. something a bit tough, but I've never found it that critical. I'd go with Pete's advive though, he's rebuilt more than most of us

[look no hands]

"Sure" rating, e.g. 90 instead of 70. i.e. something a bit tough, but I've never found it that critical. I'd go with Pete's advive though, he's rebuilt more than most of us

I just realised I said shaw and it should be shore, I couldn't remember how to spell it when I replied this morning, just woken up and was a bit dopey, as I said (and others) I just use the Meteor size O ring now as they don't seem as tight in the bore, the cylinder threads can be a bit of a pain sometimes when getting the piston back in, when I did the parachute seal conversion (for the life of me I can't remember which rifle in my collection has it in now) I had to get some very thin delrin sheet and wrap it round the greased up piston head and push it in that way to avoid the threads.

Pete

[Mr. Gen]

I got fed up with messing with airsporters and mercuries ages ago and had some steel piston heads made up, they take a single o ring and are half the size of the original nylon head so add a little more swept volume as well as the weight - gets the power up easily. you have to extend the cocking slot by a few mm as the piston rests a little further forward but they are an excellent mod, I prefer them to alloy heads.

[Shed tuner]

I just realised I said shaw

Yeah, I just woke up too when I said "sure"

[junglie]

i tried softer shore rated ones in mine the correct size & slightly smaller same as the meteor, lasted a few shots before failing.Maybe I was unlucky with cheap o-rings but I always use the correct ones now & no more problems. Only saying as the're my least favorite rifles to strip because of that curved end block & fine thread to engage on re-assembly.