TX200SR Recoil System Puzzle

[billsnibby]

'Evening all,

I’m puzzled by some unexpected results from my 0.177 TX200SR Mk2, and wonder if someone more knowledgeable or ‘SR experienced’ could replicate and/or explain them.

I set the slide bolts evenly such that the action just moved when the gun was held vertical as per the instructions in the AirArms TX200SR manual, then chrono’ed it without a ‘scope fitted giving an average of 770 fps.

Then I thought “should I have set the slide tension and chrono’ed with a scope on?” as the recoiling mass would increase by the mass of the scope and thus increase the muzzle velocity (‘scope is an old Mamba Lite). Searching the internet counter-intuitively left me with the impression (against my intuition) that any difference would be negligible. Chrono’ed again and an average of 800fps. Too high for me.

Before taking the SR apart I re-chrono’ed but with the SR’s action held in the forward position so it couldn’t slide backwards. An average of 775 fps.

The action started at the same forward position and didn’t recoil to the end of its travel for any shot. Slide bolt tension was unchanged throughout. Chrono was checked against a combo on each occasion. Gun operates smoothly, is consistant and accurate.

So, what to do now? I’d appreciate it if anyone with a TX200SR could do a similar test to see if they get a similar effect, or educate me if “it’s all been done before”!

Best Regards,
Bill.

[Shed tuner]

yes.. if the gun's action slides backwards at say 20fps, then you will get a reading 20 fps lower. One could argue that is the real reading - ie that's the velocity the rifle discharges a shot at.

but you seem to have got a 5 fps variance with the action locked forwwards - which makes sense - but a much bigger one with the scope fitted - which doesn't.

[jonnyone]

Just stumbled on this thread and read with interest.
I own three Diana Airkings and I've often wondered if the action sliding backwards as it spits pellet out robs the pellet of negligible velocity. Gut instinct rather than an in depth knowledge of physics has always told me it would affect velocity.
Now this thread has confirmed that via another prestige semi recoiling springer. Another school day get again
Dave

[TopDog]

yes.. if the gun's action slides backwards at say 20fps, then you will get a reading 20 fps lower. One could argue that is the real reading - ie that's the velocity the rifle discharges a shot at.

but you seem to have got a 5 fps variance with the action locked forwwards - which makes sense - but a much bigger one with the scope fitted - which doesn't.

Hi Jon

When I did accelerometer based tests on my TX200SR Mk1; I found that the action was travelling forwards (lunge or surge phase) at pellet exit was 1.5 fps so the pellet velocity measured in free space beyond the muzzle would be 1.5fps high - well within the usual pellet too pellet spread methinks!

That was one helluva nice shooting rifle though! Was a casualty of one of my clearouts!

atvb
David

[Turnup]

I have some questions regarding the methodology:

Are you using a barrel mounted chrono such as a combro or a free standing fixed chrono?

How many shots were in the average strings?

What was the spread of each string?

Were pellets weight matched?

Are the breech seals sound?

Is the compression tube end cap properly sealed?

I have found on my MkII (non SR alas) that iffy breech seals and end cap seal can lead to inconsistent Mv.

[Shed tuner]

Hi Jon

When I did accelerometer based tests on my TX200SR Mk1; I found that the action was travelling forwards (lunge or surge phase) at pellet exit was 1.5 fps so the pellet velocity measured in free space beyond the muzzle would be 1.5fps high - well within the usual pellet too pellet spread methinks!

That was one helluva nice shooting rifle though! Was a casualty of one of my clearouts!

atvb
David

Hi david.. very interesting..

Whilst the gun would defo be in the "piston going the wrong way" phase, I'm surprised it would have had chance to cancel out the action's recoil to the extent it was actually moving forwards at pellet exit.. then again, if it has the std piston weight and factory short stroke, it's a pretty fast action cycle time...

ATB - JB

[billsnibby]

'Evening Jon,
I agree: something doesn't seem right with the 'scoped numbers; a change of 30fps isn't insignificant!
I intend to test again to recheck and determine repeatability of results (action locked / 'scope on / scope off / scope on / action locked / scope off).

'Evening Turnup,
Thanks for your interest. In response to your questions...

Are you using a barrel mounted chrono such as a combro or a free standing fixed chrono?
A free-standing chrono.

How many shots were in the average strings?
5.

What was the spread of each string?
Extreme spreads between 9 and 16 fps.

Were pellets weight matched?
No.

Are the breech seals sound?
I think so; I can't detect any fore and aft movement of the cylinder when it battery (ready to fire), and there isn't an indication of leaking from either a tissue or talc test.

Is the compression tube end cap properly sealed?
I'm only assuming so from the tissue / talc tests.

Best Regards,
Bill.

[TopDog]

Hi david.. very interesting..

Whilst the gun would defo be in the "piston going the wrong way" phase, I'm surprised it would have had chance to cancel out the action's recoil to the extent it was actually moving forwards at pellet exit.. then again, if it has the std piston weight and factory short stroke, it's a pretty fast action cycle time...

ATB - JB

Hi Jon

It was the action dynamic I was looking at then and things are quite different (as designed to be) for stock dynamics.

Trouble is that I don't have any SRs left now so can't pick this up again! Was all superceded in my programme by the SS LWP 97k investigations. All a bit difficult to get testing teams now with clubs and ranges being closed and I never want the subjective view to be predominantly my own! The only sled-based recoil-less rifle I now have is my AS380 which is in a different league!

atvb
David

PS. Sorry for the short hijack!