TM 5.1 Hi-Capa - cannot engage safety

[Styrak]

Originally Posted by Mister Donut

Yep, I think you're right. I've slid the o-ring back down the blow-back unit. Is it in the right place now?

Yup that was the problem. You'll want to put it in the groove at the end. You'll want to lube it so that doesn't happen, it was probably completely dry or something. Or you have to get a smaller/tighter oring.

Should work fine now.

[RacingManiac]

Personally I've never had this happen to me before, but I've heard its a common issue....

but then I never had mine BBU interface stock for long...

[Mister Donut]

Originally Posted by Styrak

Yup that was the problem. You'll want to put it in the groove at the end. You'll want to lube it so that doesn't happen, it was probably completely dry or something. Or you have to get a smaller/tighter oring.

Should work fine now.

Cool, thanks! Here's a pic of where the o-ring should be, and I hope this thread can help anyone else who may run into this problem.

The green gas I used when I first got the gun was self-lubing, but then lately I started using propane and it probably got a bit dry. Is it ok to use this silicone lube on the gun?

[ILLusion]

You have an old Hi-Capa with the older piston head design. These were prone to having o-ring blow outs like you are experiencing. Newer TM Hi-Capas have a piston "cup" design which eliminates the problem. It was switched when the 4.3 hit the market.

Switch to an aftermarket piston head setup to eliminate the chance of it happening again. Once it happens, it will happen more and more frequently until you swap the part out.

I have some cheaper ones ($8) that use a high quality German o-ring in stock if you don't want to spring for a fancy schmancy one. Can ship anywhere in Canada for $10 via lettermail.

[Mister Donut]

Originally Posted by ILLusion

You have an old Hi-Capa with the older piston head design. These were prone to having o-ring blow outs like you are experiencing. Newer TM Hi-Capas have a piston "cup" design which eliminates the problem. It was switched when the 4.3 hit the market.

Switch to an aftermarket piston head setup to eliminate the chance of it happening again. Once it happens, it will happen more and more frequently until you swap the part out.

I have some cheaper ones ($8) that use a high quality German o-ring in stock if you don't want to spring for a fancy schmancy one. Can ship anywhere in Canada for $10 via lettermail.

I'm still new to airsoft. I'll read up a bit about piston heads in the upgrade section and see what I should do. Fancy or plain....not sure yet.

[ILLusion]

Basically, the "fancy" ones are ventilated and made of metal. Other than that, they can't get much more fancy. The cheap ones I'm selling are made of some synthetic material - I'm guessing nylon/Delrin. The o-rings used are stronger than the Japanese ones, so they're not as likely to blow out of the groove.

[Mister Donut]

Originally Posted by ILLusion

Basically, the "fancy" ones are ventilated and made of metal. Other than that, they can't get much more fancy. The cheap ones I'm selling are made of some synthetic material - I'm guessing nylon/Delrin. The o-rings used are stronger than the Japanese ones, so they're not as likely to blow out of the groove.

I'm a sucker for fancy. But it seems I need to change a bunch of other stuff before I can reap the benefits of just changing to a ventilated metal piston head right?

[ILLusion]

Originally Posted by Mister Donut

I'm a sucker for fancy. But it seems I need to change a bunch of other stuff before I can reap the benefits of just changing to a ventilated metal piston head right?

wrong. You can just go directly with the head alone.