Career 707 carbine hammer lightening and spring shortening!

[Lord Geordie]

anyone got any experience they can share reguarding the lightening of the hammer and shortening of the hammer spring?

 

I have recently had to tune the rifle DOWN and would now like to improve consistency and shot count by doing the above mod!

 

I assume the main spring is a simple case of cutting away a few coils and refinish the end, but how does one lighten the hammer?

 

It would be nice to get it to a point where I can re use the power adjuster wheel instead of having it locked as I do at the moment!

 

Any info from someone who has carried out this mod would be greatly appreciated!

 

Martin.

Edited September 24, 2015 by Lord Geordie

[kenj]

There is no need to cut down hammer springs etc. The power for the Career 707 comes from the transfer port. Check the diameter of the hole in the port. For a 12 ftlb rifle it should not be bigger than 1 mm. My carbine is FAC rated. When I bought the rifle, the transfer port had been opened out to 4.5 mm and probably gave five shots at around 80 ftlbs. I put in a new standard 1mm port, which I had opened up to 2.5 mm, giving 28 ftlb.

 

This is my review of the Career 707. http://www.urbanfieldsportsman.com/index.php/shin-sung-career-707-22-carbine-pcp/

 

T.E.Robb of Benfleet, Essex carried spares for the Career. If he has no transfer ports left, he could easily make you one. http://www.trrobb.com/

[Lord Geordie]

I can check it out! This is the second I have had that's been way over when purchased! First was a tanker version pushing out 40+ this one was 25

 

Reading between the lines! Shortening the spring and lightening the hammer offers more shots per fill due to less wastage of air! This was worth investigating on this merit alone! The transfer port seemed to be pretty much standard on inspection in the stripped stage! But I will dump the air and check again!

[drut]

" The power for the Career 707 comes from the transfer port"

 

This is true but altering the hammer spring for 12ft/lb as well gives a sweeter action and more consistency/greater shot count.With a lighter or shorter hammer spring you will have to play with fill pressure to find "sweet spot".Also check you have the correct rubber hammer buffer(fits in recessed end of power adjuster),UK/12ft/lb versions had shortened exhaust valve stems & many were modified by removing buffer or replacing with thinner alternative.

[Lord Geordie]

" The power for the Career 707 comes from the transfer port"

 

This is true but altering the hammer spring for 12ft/lb as well gives a sweeter action and more consistency/greater shot count.With a lighter or shorter hammer spring you will have to play with fill pressure to find "sweet spot".Also check you have the correct rubber hammer buffer(fits in recessed end of power adjuster),UK/12ft/lb versions had shortened exhaust valve stems & many were modified by removing buffer or replacing with thinner alternative.

The tap washer I used as a bump stop is the same depth as the original bump stop, I managed to source a bump stop from a kind chap on BBS.

 

The question is "how do I lighten the hammer"

 

I know how to shorten the spring, and when I had a lathe I would have just turned an alloy hammer! But I am assuming they just remove material from the existing steel hammer! I wanted to know how to do this? And how much to remove?

 

Tinkering to find that perfect setup is half the fun! I just need the info on how to reduce hammer weight! I was thinking of drilling in specific areas much like they do lightening a crank shaft!

Edited October 7, 2015 by Lord Geordie

[drut]

"Tinkering to find that perfect setup is half the fun! I just need the info on how to reduce hammer weight! I was thinking of drilling in specific areas much like they do lightening a crank shaft!"

 

Hammer is hardened,tinker(difficult!)all you like but in my experience,granted from some years ago,you have enough adjustability in hammer spring/port size..707's were basically designed to run at FAC power(.22 : 50 accurate shots@47ft/lb using power wheel),best answer to lower power use was a joe korick or "A-team" regulator http://www.network54.com/Forum/79537/thread/1341614488/Can+a+regulator+be+installed+in+a+Career+707-but some years since I looked into this(IIRC 2003).Joe Young who was the approved gunsmith for the then importer:Rangeright,,did some tuning/mods but frankly I was unimpressed.I believe there was some good info especially from "john budd" & "Baz" on the BBs but it was many years ago.

[kenj]

This is an interesting topic. I have just checked my 707 spares and found that I have two exhaust valves with a shaft length of 52 mm and one with a length of 58 mm. One of the shorter valves looks like a genuine part, all hardened steel, the other two "homemade", one with a brass outer enclosing a nylon insert holding the shaft, the other all nylon with the shaft inserted. I put a new exhaust valve in, when I rebuilt the carbine 707 10? years ago, with parts from T.E.Robb, trouble is I can't remember, (senior moment) what length I put back in.

 

At 28 ftlb, I get about a dozen shots with .22 Bisley Magnums dead on at a 40 yard zero with a 180 psi fill, before the shots start to drop. This can be adjusted on the power wheel, or with hold over, usually the latter, although on a rabbit hunt, I rarely take more than 10 shots. One shot equals a dead rabbit with this accurate rifle.

 

Is it possible that I have the wrong length of exhaust valve?

[K-B-T]

I would like to re open this post to see if any one else has an opinion on increasing shot count on 12ft / pound 707