Adjustable Power Spring/Hammer - Why?

[DaveB50]

After reading many posts on adj hammer spring devices, I want to try one out.  I would use it to  reduce fps for  good target shooting/plinking, while increasing # of shots per cart. When the opportunity arose to do some varmint reduction, I can increase fps for knock down power. Sighting for the lower fps, then seeing what hold was needed on high fps. Has anyone done this, and how does it work for you?

[cheewee]

i have one PA that i use to finetune my guns.  when i am happy with the fps, accuracy and shot count, it is all a juggling act compromising one to acheive the other. i then remove the PA and install a new cap with a spring guide machined to the same size(spring preload)as the PA. works just fine.

[arkmaker †]

i have one PA that i use to finetune my guns.  when i am happy with the fps, accuracy and shot count, it is all a juggling act compromising one to acheive the other. i then remove the PA and install a new cap with a spring guide machined to the same size(spring preload)as the PA. works just fine.

Good idea! 

[brz-ryder †]

Well all i know is with the PA out i get 20 to 25 full power shots with it screwed in i get 12 to 15 wheres the CO2 going if not pushing the pellet faster. Most of what rsterne talks about is pcp guns i don`t know if that applys to CO2 guns i`m new to the sport


Jim

[breakfastchef]

Well all i know is with the PA out i get 20 to 25 full power shots with it screwed in i get 12 to 15 wheres the CO2 going if not pushing the pellet faster. Most of what rsterne talks about is pcp guns i don`t know if that applys to CO2 guns i`m new to the sport

Hammer bounce is likely the short answer to your question.

The hammer hits the valve stem and releases CO2, which in turn propels the pellet. When the CO2 rushing into the valve from the powerlet creates enough pressure, the valve spring closes the exhaust port sending the valve stem back into the hammer. The hammer is pushed backwards and bounces off the hammer spring and rebounds to hit the valve stem again, but with much less force. This rebounding causes CO2 to be lost out the exhaust port after the pellet has long left the barrel. This whole rebounding process takes place very quickly. Hammer debounce devices (HDDs) are made to reduce or eliminate hammer rebound in order to increase shot count by not wasting CO2.

[cheewee]

x2 wasted co2
there is a point at which at a fixed pressure (950psi) adding extra volume will not give an increase in fps but only waste co2.

[blake.l]

I was reading some about those HDD's anyone using them? can you actually tell any difference?

[DaveB50]

Depending on the barrel length, releasing more co2 per shot does not necessarily mean it all goes to higher fps. If the pellet leaves the barrel before the volume of co2 has propelled it to it's highest fps , some is wasted. Longer barrels benefit most from higher volumes of co2 expulsion. I have read that somewhere around 18" is optimal barrel length for these modded pistols.

[quickster47 †]

I was reading some about those HDD's anyone using them? can you actually tell any difference?

I have used HDDs off and on.  Several of my target shooting guns have them and they appear to work.  How well is quite subjective.  In theory there application makes a lot of good sense but the problem is making one that works reliably and good.  Steve in CT, his handle on the Green and Yellow forums, probably makes the best one but they are expensive for what you are getting.  arkmaker tried his hand at making some and his did okay too.  There was another design that used o-rings and sort of looked like a backward pellet.  And basically what they are doing is applying friction to the hammer after the initial shot to slow the bouncing of the hammer against the valve stem.

Carl

[quickster47 †]

Here are a couple of pictures of the two different HDDs I've been using as of late.

The all white one is from Airguns of Arizona, designed by Steve, and the other is by a fellow that I cannot remember his name.

Carl

[breakfastchef]

and the other is by a fellow that I cannot remember his name.

Steve McCann. His HDD seemed like a good idea but was far from 'prime time'.

[quickster47 †]

Steve McCann. His HDD seemed like a good idea but was far from 'prime time'.

Thanks Chef. 

I also thought he made a second version but never have heard from him again.  Guess I should send him an eMail and check it out.

But you are correct, the results of using his was very lacking.

Carl

[arkmaker †]

Steve McCann. His HDD seemed like a good idea but was far from 'prime time'.

I made a bunch of these with all different angles and tried a half dozen materials for both pieces. Never could get it to work consistently. I believe the part is just to short to allow for the proper angle. My take anyways. When I was approached to make them, my first thought was that we may have a winner. Alas, it was not to be.
I wonder if one like used on the qb rifles could be fashioned to work?

[quickster47 †]

I wonder if one like used on the qb rifles could be fashioned to work?

Now there is a good though Rich.  May have to try something like that.  But alas, like you, it is way down there on my priority list.

Carl