Canadian Airgun Forum

At least I think that's the term for what I'm seeing... (Also, please feel free to correct any terminology I use incorrectly, I am newly coming back to this addiction and actually working on AG rather than just shooting)

Recently I've decided to try modding and repairing some of my AG. I figure the 760 being the oldest is the one that would most benefit from it (or a tune up at least), and since my son uses it to practice because it is the best size for him, I figure making it smoother would be a good thing. I forget the exact year since it's not in front of me, but it's of the vintage with the bleed screw that is exposed in front of the breech for its detune. It's probably approximately 1987 (and when I checked the serial number that was about right I think), but looking at the parts diagram, the sights are like the 1980-1983 model, which I find a bit confusing...

Anyhow, enough context. From reading up on things, I think I understood that you want to have the valve empty completely on a pumper and I don't think I'm seeing that, and I think that has always been the case. After a shot, if I cock again without pumping it will shoot again, not very powerful, but you can do it a couple of times. So I suppose the first question is whether this is what's meant by "not dumping all of the air", and the follow-on question is what can I do to address this?

Next week I am going to be signing my son up for his Apprentice Hunter and Minor's Firearms License course, so even though it's not entirely related to the above, is there a PAL-rated AG that comes in a "junior" form factor that I might consider putting under the tree for him?

Cheers,

Droopy

Hi,

I don't know that particular gun and how it's detuned, but in general yes, it's normal to have a single or multi-stroke pumper empty the valve on each shot, and "retained air" is exactly as you've described with some pressure still left after the shot. I have a 1377 set up this way on purpose, but the downside is that unless you deliberately empty the gun after each shot you get a lot of shot to shot variation in speed. Getting the gun to use all the air on each shot is usually a question of a stronger hammer spring, unless the transfer port has been deliberately under-sized, in which case you might need a larger diameter TP as well.

Jim

how many pumps you pumping it to ?
if I remember correctly anything over 10 or 12 is a waist.

_________________
"A candle loses nothing by lighting another candle"

3-5 is typically what we pump it.

Droopy

A weak hammer spring will cause this as well. If you have or know someone with a chrony, low #s would indicate this.

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Jonathan

Moderator

that's all.
definitely not getting a good proper hammer strike.
where about are located ?

_________________
"A candle loses nothing by lighting another candle"

Located in Ottawa (Kanata).

I was going to chrony the gun at the cottage last weekend but my fingers were numb from the cold even before I was set up. Once my indoor range is set up I'll run it through, with an eye on getting a better hammer strike and see how the numbers change.

Droopy