How much hammer throw..?

[Jensen]

Does anyone with experience of many modern PCP's know, roughly, on average, how far the hammer actually travels on modern pcp's..?

When you cock it, how far are you actually pulling the hammer away from the valve stem, given it's usually just the last little bit of lever throw that cocks it..?


Thanks

J.

 

[Triggertime]

Does anyone with experience of many modern PCP's know, roughly, on average, how far the hammer actually travels on modern pcp's..?

When you cock it, how far are you actually pulling the hammer away from the valve stem, given it's usually just the last little bit of lever throw that cocks it..?


Thanks

J.

Its the last little bit that cocks the trigger sear/hammer,thats the click you hear,but the hammer moves(is pulled back) much further (in some cases) its quite possible on some rifles its the entire pull of the lever that is the stoke length you ask about,most a little less.
It will vary quite a lot from rifle to rifle,some maybe 10mm some may be 25mm +

 

[Jensen]

Its the last little bit that cocks the trigger sear/hammer,thats the click you hear,but the hammer moves(is pulled back) much further (in some cases) its quite possible on some rifles its the entire pull of the lever that is the stoke length you ask about,most a little less.
It will vary quite a lot from rifle to rifle,some maybe 10mm some may be 25mm +

I'm working on a cheap bolt action rifle that started out with at least 40mm of hammer travel..!! With lock time measured in minutes not milliseconds
I've managed to get this down to around 10mm with various alterations whilst balancing the power output, and i'm wondering if many modern PCP's are any lower than that.. Given what i can feel from my AGT Vixen, i suspect that's probably similar. I'm boing to keep experimenting but wondered if anyone has any definitive numbers for modern sub12 rifles...

 

[John79]

think my isp had 2-3 mm travel

 

[Jensen]

think my isp had 2-3 mm travel

No harm in trying 5mm then

I've lightened and substantially lengthened the hammer, as well as used a much shorter, and much stiffer hammer spring, i want get get the hammer moving very very quickly. Improvement in lock time has been drastic, going to try for more

 

[Triggertime]

You may find as you balance stroke/hammer to valve the fill pressure will end up lower, less stroke=less umff=less inertia to open valve against hp air
Changing the curve

 

[1260engineer]

It all depends on the weight of the hammer . i heavy hammer will accelerate slower and need a longer run up . where a lighter hammer can have a longer run up but still get to the EV in half the time producing less recoil from the hammer launch .
thing of a spring rifle piston . basically the hammer in a pcp is a miniature version . it has the same effects.

 

[32:1]

Regulated or not as the unregged will need testing over the whole fill pressure as what one gains one loses elsewhere
I’ve found regged guns much easier to setup

 

[Jensen]

You may find as you balance stroke/hammer to valve the fill pressure will end up lower, less stroke=less umff=less inertia to open valve against hp air
Changing the curve

The rifle is regulated which adds another million dimensions of complications lol. I've set the reg pressure at a ridiculous 75 bar, seems to be very consistent still but i do wonder about valve return spring pressure now not being optimal.. I have LOTS of 'balancing' to do

For now i'm just trying to get it firing nicely.

 

[Jensen]

It all depends on the weight of the hammer . i heavy hammer will accelerate slower and need a longer run up . where a lighter hammer can have a longer run up but still get to the EV in half the time producing less recoil from the hammer launch .
thing of a spring rifle piston . basically the hammer in a pcp is a miniature version . it has the same effects.

The hammer, even though i have lightened it, is still and will always be a heavy beast, hence i have a strong hammer spring behind it now but with a fraction of the travel. It was even heavier, with a lighter spring, but travel was massively long as stated above at 40mm+.

Being a cheap rifle clearly meant for 40 - 50 ftlb in the fun countries, it is simply strangled by a 1.2mm transfer port restrictor, but reg pressure was set at 140 bar..!

So you can see this rifle all but has its underwear on the outside and it's clothes all back to front, nothing is quite where it should be..!

There's a good gun in there somewhere once i get all it's ducks in a row, no matter what i do to it, it remains very accurate, and consistent over the chrony

 

[1260engineer]

The hammer, even though i have lightened it, is still and will always be a heavy beast, hence i have a strong hammer spring behind it now but with a fraction of the travel. It was even heavier, with a lighter spring, but travel was massively long as stated above at 40mm+.

Being a cheap rifle clearly meant for 40 - 50 ftlb in the fun countries, it is simply strangled by a 1.2mm transfer port restrictor, but reg pressure was set at 140 bar..!

So you can see this rifle all but has its underwear on the outside and it's clothes all back to front, nothing is quite where it should be..!

There's a good gun in there somewhere once i get all it's ducks in a row, no matter what i do to it, it remains very accurate, and consistent over the chrony

The main thing you have to watch out for is the hammer spring over powering the EV at lower cylinders . or smacking the EV that hard it bottoms out on its travel either damaging its spring /seal face /seat or bending the valve stem . be very careful chap .
mine are 4.5g with the spring guide and made of titanium.

They are very fast i use speed over weight .
they also have a restrictor in the end which lets me stop over travel.

 

[Triggertime]

The rifle is regulated which adds another million dimensions of complications lol. I've set the reg pressure at a ridiculous 75 bar, seems to be very consistent still but i do wonder about valve return spring pressure now not being optimal.. I have LOTS of 'balancing' to do

For now i'm just trying to get it firing nicely.

I had assumed unregged for some reason
Good luck it will be a nice time filler over the holidays

 

[32:1]

Regulated or not as the unregged will need testing over the whole fill pressure as what one gains one loses elsewhere
I’ve found regged guns much easier to setup

Exhaust valve size and it’s dwell, reg pressure and plenum size, TP size, barrel length, calibre will/can have an effect

I tinker with Krals and like yours these are designed for more power so hammers and travel are huge, I invested some time with hammer and force to find the standard spec hammer at near 50g and 27mm of travel had way to much energy as I went right down to 20g and just 5mm and still made legal power.
I now run 25g and 15mm travel with an SSG in all my regged Krals as I can run slightly nicer cocking effect with the softer spring

If your quest is to help save air too as hammerbounce bleeds air away, I found Lanes instructions an excellent read
I

 

[Jensen]

The main thing you have to watch out for is the hammer spring over powering the EV at lower cylinders . or smacking the EV that hard it bottoms out on its travel either damaging its spring /seal face /seat or bending the valve stem . be very careful chap .
mine are 4.5g with the spring guide and made of titanium.
View attachment 869580
They are very fast i use speed over weight .
they also have a restrictor in the end which lets me stop over travel.

I'm going to try shortening the stroke a tiny bit more, then i'm going to up the reg pressure and just see what happens to the power curve. I have a suspicion that incrementally upping the reg from 75 bar to 90 bar will be interesting, as pressure behind the EV may counteract the power increase from the reg pressure... Who knows without trying, like i said i just want to get lock time as short as practically possible with this ridiculous hammer first..

 

[1260engineer]

I'm going to try shortening the stroke a tiny bit more, then i'm going to up the reg pressure and just see what happens to the power curve. I have a suspicion that incrementally upping the reg from 75 bar to 90 bar will be interesting, as pressure behind the EV may counteract the power increase from the reg pressure... Who knows without trying, like i said i just want to get lock time as short as practically possible with this ridiculous hammer first..

There should be no power curve thats the whole idea of a reg compared to a none regged rifle . what you do have to watch is the drop off when the cylinder pressure is lower than the reg . often you will get a power spike.
have a look at Rob Lanes 5 step process.

 

[Jensen]

There should be no power curve thats the whole idea of a reg compared to a none regged rifle . what you do have to watch is the drop off when the cylinder pressure is lower than the reg . often you will get a power spike.
have a look at Rob Lanes 5 step process.

By 'curve' i was kinda referring to the possibility of a non linear power change/increase with increasing reg pressure..

 

[1260engineer]

By 'curve' i was kinda referring to the possibility of a non linear power change/increase with increasing reg pressure..

You will get fluctuations due to pellet weights
but they should all fall in a 10 to 12 fps window for standard rifle . and single figures for a target rifle .
im talking with a good reg with no creep . and hammer /valve /pressure balance.
you need a flat line with a steady fall off as the rifle comes off the reg .