can hammer bounce affect acuracy ?

In a match grade PCP where any cyclic vibrations "May" create a slight shift in POA before pellets exit ... yes it could.

For most if not all sporting guns / pcp's you'll never notice it.



IMO tho ...

Scott S

There are 1000s of different ways to tune a gun and potentially any of those can affect accuracy. In the uk we have strict power levels so velocity is reduced, A typical .22 cal airgun here will be spitting 16grn pellets at 570fps and a 8.4grn pellet at 800fps and accuracy rarely suffers, in fact accuracy can be extremely good

here is 26 shots at 25 yards with my .22







and this 17 shots with my .177 at 45yards





Depending on your gun, I would start with 900psi for .22 and 1250psi for .177, you will also need to test several different types of pellets as some work better at slower speeds others faster. 

Jsb 16grn .22 and jsb 8.4grn in .177 are a good starting point, also h&n, forget heavier pellets or bullet shapes, these generally perform badly .

Good luck

Bb

ideally, with the hammer screwed in a little slowly adjust the reg until the speed is 30-50fps faster than you would like, then back the hammer off until the speed drops to where you want. This way you are wasting the minimal amount of air. With a short strong hammer spring, load adjuster will be very sensitive, a slightly longer weaker spring is less sensitive.



bb





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ideally, with the hammer screwed in a little slowly adjust the reg until the speed is 30-50fps faster than you would like, then back the hammer off until the speed drops to where you want. This way you are wasting the minimal amount of air. With a short strong hammer spring, load adjuster will be very sensitive, a slightly longer weaker spring is less sensitive.



bb





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Click to expand...

I'm in absolute agreement! This is how I have been tuning my EdGuns and FX rifles. Most will recommend 10-20fps higher, but I find that a nice, quick, strong tap on the valve holding higher pressure creates a nice and quick burst that is less violent (and ultimately more accurate). 

The hammer weight is too heavy for the speed your after. And too little spring can cause bigger es because of inconsistent valve strike. If it were mine, I'd go the opposite way. Turn the reg pressures up and back the factory spring out. velocity will go down. Its almost like valve lock so to speak. You'll get a more consistent hammer strike, and no hammer bounc and tighter extreme spreads.

If you keep going down on reg pressures, you'll reintroduce hammer bounce. By bumping the reg, you can speed up the shot cycled and reduce dwell

The upping to valve lock may well have merit. I'am also thinking a light striker is in order for what you want, naturally lees mass moving wont make the rifle move/jump anymore and should make finginga spring balance that works easier.



John

The hammer weight is too heavy for the speed your after. And too little spring can cause bigger es because of inconsistent valve strike. If it were mine, I'd go the opposite way. Turn the reg pressures up and back the factory spring out. velocity will go down. Its almost like valve lock so to speak. You'll get a more consistent hammer strike, and no hammer bounc and tighter extreme spreads.

If you keep going down on reg pressures, you'll reintroduce hammer bounce. By bumping the reg, you can speed up the shot cycled and reduce dwell

Click to expand...

You are absolutely correct, however once the gun comes off reg then there will almost certainly be a power hike as it becomes increasingly easy for the hammer to open the valve against the reducing pressure. While this it not a problem in countries that have no power limits other that altering the poi, in other countries that do have restrictions this can and does cause legal problems.

There are some guns, the fx impact for example, where it is possible to restrict the travel of the valve, this effectively stops the power hike but the normal state of tune here (I live in the uk) is to balance the reg pressure with the hammer load, done correctly ES can be in the low single figures throughout the whole fill, this method also eeks out the most amount of shots per charge.



this is a couple of screen shot of the results of a gun I recently tuned.









Bb

I had a gun that had a definite preference for heavy pellets, I altered the hammer spring and reg setting to achieve exactly the same speed but it’s preference changed to lighter pellets.



Bb

Clipping more likely

If you're happy with the group's at your intended range, i wouldn't worry about it. The farther you stretch the distance the more your ES will show up.