Crosman 160 tuning

[jirushi]

A few years ago I bought a 2nd type Crosman 160 via this forum.
I wanted to improve its efficiency, as it is a "gas guzzler"/"gas hog" in standard form.
I got about 20 consistent shots per two powerlets. For a Dutchman, that's a nightmare!

After many unsuccesful attempts at improving efficiency by using stiffer valve return springs and preload washers in the valve, I concluded that the massive hammer was the culprit. Plus the hammer spring hole in the hammer was too small for my other hammer springs (QB78).

So, frakor was kind enough to slim my spare 160 hammer down. Ped did this with my QB78 hammer previously, and that worked well.
The 160 hammer now weights 56 instead of 76 grams. That's a 25% reduction. It also has a bigger hammer spring hole so that I can now test with various other springs.

Original hammer on the left; diet type hammer in the middle; diet type QB78 hammer on the right


I tinkered using this Sheridan type seal in the tube cap. This way I can use the gun with one powerlet, in an efficient way:
an empty powerlet pushes against the seal. This way the pressure in the cylinder remains high for longer.



End result:
50 consistent shots, at 15.5 degrees Celcius, with 15.89 gr JSB
Between 525 and 545 ft/s. That's about 10 ft/lbs.

It's easier to cock (shorter hammer spring), quieter, and the shot count is much better.

The S331 comes from a friend in the USA.

Cheers, Louis

[Josie & John]

These are lovely rifles Louis.

20 shots is way below what the shot count should be. I was getting over 30 from 1 Powerlet when I recently took my 2nd type for a range outing.

Kind regards,

John

[jirushi]

Hi John,
Wowsers, 30 shots on 1 powerlet!
At what power is that? Did you determine shot count by pellet drop, or did you do a shot string, if I may ask?
I think that 50 shots at 10 ft/lbs is quite good. 160-166 m/s; 6 m/s spread, so that's about 20 ft/s.
I think on a hot day, velocity would be 10 m/s higher, but that's a rough guess.
A shot count of 20 wasn't good, for sure. I think the valve spring was way too weak.
But I often read that their normal shot count is 30 with two capsules. That will be around 11-12 ft/lbs.

[Josie & John]

Hi John,
Wowsers, 30 shots on 1 powerlet!
At what power is that? Did you determine shot count by pellet drop, or did you do a shot string, if I may ask?
I think that 50 shots at 10 ft/lbs is quite good. 160-166 m/s; 6 m/s spread, so that's about 20 ft/s.
I think on a hot day, velocity would be 10 m/s higher, but that's a rough guess.
A shot count of 20 wasn't good, for sure. I think the valve spring was way too weak.
But I often read that their normal shot count is 30 with two capsules. That will be around 11-12 ft/lbs.

Hi Louis,

The rifle fired more than 30 shots - probably nearer 40 but the last 10 or so were audibly lower powered and landed under the tin I had placed out as a target at 25 yards. I didn't have a chrono with me as it was a 'fun' session!

Kind regards,

John

[jirushi]

Thank you John.
I understand.
I'm a bit of a shot string geek; I stop counting shots when I think velocity drops too much.
If I would count whilst plinking, the number would be higher. A few cm's drop on an empty beer can "don't matter"!
Can't wait to do try the S331 peep sight outdoors. A bit chilly for CO2, but a sunny October weekend would be just right.

[--ped--]

that's a good result Louis

[ratbuster2240]

I can picture you with your white tunic and shot string graphs and equations like a mad scientist. 50 consistent shots is very good for any co2 rifle, I've never thought to play around with hammer weights for adjusting power and economy.

[MrGreengrass]

Nice job on a very nice gun.

[Geezer]

20 shots is crazy low. I get more than that on a 180, unmodified.

[cinedux]

Crosman 'must haves', the 160/600/150!!!!

[Jerry Cornelius]

Crosman 'must haves', the 160/600/150!!!!

Was Rudy Merz the greatest airgun designer ever? I think there’s a strong argument for yes.

(Jerry runs for cover before the Frank Clarke fan club gets him)

[Josie & John]

Crosman 'must haves', the 160/600/150!!!!

Agreed sir!

[GreenwayJ]

Crosman 'must haves', the 160/600/150!!!!

You missed out the best of the bunch the 180

[jirushi]

20 shots is crazy low. I get more than that on a 180, unmodified.

The question is, what are your criteria for shot count?
I stop counting when velocity drops more than 10 m/s (roughly 30 ft/s).
The shot count was too low, for sure. But it's not that the gun was empty after 20 shots. For plinking, I could probably have kept shooting longer.
The Crosman 180 is more efficient out of the box. Except the early ones with a massive, single power hammer.
Power is lower compared with the 160. Mine do about 430 ft/s with 15.89 gr JSB. I should use lighter pellets in them, but I always test with one type to make comparing easier.

[Shed tuner]

an SSG (google) will improve even further...