Knackered TM Hop?

[Machaon]

My TM AKMS, was chrono'ing at 268fps consistently a few weeks ago. Yesterday it struggled to get above 170fps. What's that about?

I bought the gun used, and I've basically done nothing to it apart from clean the outside.

Does it need a new hop rubber, and if so, what else? Alternatively, what else could it be?

[Gaffa]

Re: Knackered TM Hop?

A major airleak.

Surprisingly, the above is the most common form of FPS-loss.

However, a question:- Have you ever left the rifle in a ready state: what I mean by this is have you ever forgotten to fire a few rounds off on Semi Auto after using it, to de-compress the spring?

If the spring was left compressed for a month, say, then that could be the issue.

I'd disassemble to the gearbox (obviously) and check the air seal, fix if necessary, pop a new M100 spring in, check the hop rubber, replace if necessary and go. There's no way that can be shooting less than 300 then.

[Machaon]

Re: Knackered TM Hop?

I've always been careful to decompress the spring, and as I fire on semi-auto almost all the time, it's unlikely (although I guess it's a possibility) that I've left the spring compressed. I'll have to look into it though. It probably hasn't had much in the way of servicing for it's lifetime, so I'll get onto that.

Thank you