HW/Weihrauch Reasons for variable muscle velocity?

Your mainspring probably broke off a coil, if it’s a factory spring still

Spring or seal. It's common. I've been fighting that for months on a couple new HW's.

A Vortek kit and seal is looking really good right now.

Started out at 670 +or- 15 fps. 1000 shots later a 50 fps variance and an average of 620 fps. Some shots are in the high 590's.

I'm beginning to understand this is just the nature of the beast with HW springers with factory seals/springs.

That's pretty low velocity for a factory 177 97. Something is ill. Probably a piston seal and or spring. I'd open her up.

Keep the spring lubed.
Every 1000 shots.
My first R1 spring….250,000
My first TX200 spring…62,000

Problems with "muscle velocity"? You need more protein and go heavier with less reps..lol.
Sorry I couldn't help myself.

Cmiller said:

I think this variance has been going on for a while. Sometimes the gun is great and then shots will start dropping low. I thought I had a scope problem. It was averaging 725 fps with 8.44 pellets, then dropped to 710 to 715. I think it goes up and down but regardless it's time to have a look inside.

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Could have breech sealing issues as well, some guns are hard on breech seals. Also JM ARH springs have a history of being consistent once set and settled in. Some springs sag early and loose velocity. How they're tempered has a lot to do with longevity.
I've never had a JM spring to sag on me, but I have broke one after thousands of shots.

Yeah blame it on the autosmell. B.

Cmiller said:

I opened up the gun this morning. I can't get the guide off of the spring to see if it's broken, but there is a layer of very thick sticky grease on all the sliding parts. It seems like it would really slow down the piston. Is this kind of grease normal or would you expect a thinner consistency on the piston?

If I re- grease it, what should I use? I think I'll just order a Vortek kit just to get a fresh start anyway.

Anyone recognize this kit?

View attachment 492601

View attachment 492602

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Looks like a vortek to me IDK, not sure who else uses that plastic slip on guide. I use Krytox grease, ARH spring and make my guides. I'm sure some kits come with some kind of grease, you don't want it in front of the piston seal.
Also look at the breech seal, if it's cut or chewed up, replace it.
you can also leave that trigger block thing off if you want to be able to decock the gun, some people do including myself.

Did you replace the breech seal?

My 97k had a linkage problem that created slack in the compression tube/breech fit. When the linkage was repaired it began to loose velocity. I figured it was a spring or seal. The breech seal looked OK to me.

I had a replacement breech seal and changed it. Problem solved. At least until the spring broke again...

The innards look like a vortek kit. What does the head of the seal look like? From what the photos show it looks good....

I'd clean it all up, lube it, change the breech seal and try again. I'm no expert but I sure can't see anything obviously wrong with it.

Your post is timely and I appreciate it. I'm going to dig into mine soon. I've never taken it apart. And I'm chasing the same low velocity problem constantly....

Mycapt65 said:

That's pretty low velocity for a factory 177 97. Something is ill. Probably a piston seal and or spring. I'd open her up.

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+1
- Yes, when I had a (.177) HW97, it shot 7.9 CP at 900+ with a ARG Hornet spring. I'd say your velocity is very low.

Cmiller said:

I used the grease that came with the kit. Not sure if it's changed viscosity over time but I think I'll try something lighter.

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That grease drys out over time and become caked up.

The base of the outer guide looks like it might be bulged. If it is the spring of broken. That outer guide should have pretty close to the same OD along the full length. I've got a trick to disassembling the Vortek kits. It's a pain in the ass but doable. Unfortunately its too long to type. I've done lots of the Vortek kits. Message me for my phone if you want my help.

Be well
Ron