10 shot 293fps ES!

[Buzby]

My father has a Crosman Fire nitro piston in 177. His scope mount came loose, and he asked me to resecure it.

I degreased screws in the rings, mounted it all back up with some blue loctite, and went to zero the scope. I was having a hell of a time getting the thing to group. I suspected cheap scope that came with it was an issue. I mounted that on a PCP and shot 2 good groups.

I then shot the rifle over a Garmin chrono. Wholly hell, the FPS all over the place! The higher FPS shots did group, but the lower ones were thrown all over.

Any ideas what could be causing this? Is it worthwhile to look into it? It’s a cheap rifle, with a horrendous trigger (which I slightly improved with a longer trigger screw mod).

 

[phoenix_cow]

My guesses;
The pump is going bad, leading to inconsistent air going into the gun.

Something is gunked up inside the gun, clean the insides of the gun and try again.

O-ring some where is bad. You might have a small leak.
Pump it, let it sit for a min, then shoot. Pump it, then shoot it immediately. If the fps of the shot is much lower for the first shot, then you likely have a leak somewhere. Might want to try doing this a few times just to be sure that is your problem.

My bet is on the pump going bad.

 

[Sqwirl57]

Piston or breech seal more than likely. The breach seal is easy to check, the piston seal will require a full tear down. Id start with the breech. Make sure it isn't torn and that it isn't flush with the breech.

 

[Treefrog]

What Sqwirl said. Lay a piece of tissue over the breech and see if it flies off when you shoot it. If so, it's the breech seal.

Those are some crazy numbers!

Cheers,

J~

 

[maxtrouble]

@Buzby - I suggest getting your father a new rifle. A HW95 or HW98 in .22 would be my suggestion.

Krale has some decent prices and they ship to the US in a few days.

Weihrauch HW98

Weihrauch air rifles are engineered and manufactured in Germany in accordance with the latest sporting arms technology. With decades of experience and a strive for perfection and innovation, Weihrauch is able to deliver top quality, for maximum performance and a long service life. The Weihrauch...

www.krale.shop

 

[Buzby]

@Buzby - I suggest getting your father a new rifle. A HW95 or HW98 in .22 would be my suggestion.

Krale has some decent prices and they ship to the US in a few days.

Weihrauch HW98

Weihrauch air rifles are engineered and manufactured in Germany in accordance with the latest sporting arms technology. With decades of experience and a strive for perfection and innovation, Weihrauch is able to deliver top quality, for maximum performance and a long service life. The Weihrauch...

www.krale.shop

I was going to try and steer him down this road initially. I have a HW95 that I adore. My brother found him a “good deal” though.

 

[Buzby]

I’ll try the tissue test. If it’s a breech seal that’s easy enough to fix. If it’s any more than that, I probably won’t take the time to tear it down. We’ll just have to get him an upgrade.