Variable power hw99

[averageplinker]

I reckon it is either the spring and/or barrel. If you can be bothered try swapping barrels over and see what happens. If that makes no difference try swapping the springs over.
Rich.

[Damned 69]

Have swapped springs and also tried a titan 10. Never thought about barrel but assume different batches and possible minute differences? - older one has registration number stamped on lhs whilst new one has it stamped on bottom.

[harvey_s]

Kind of unclear what you mean really...
It's common for guns to give different power outputs with different pellets.
As long as the same make/model of pellets gives the same power it's not a problem.

[Damned 69]

My query was that with one 99 the power spread between 3pellet types was relatively close, whilst the spread with my other 99 using same 3 pellets was what I would consider rather large at 1.6ft/lbs.

[averageplinker]

I guess another possibility could be a different transfer port size. Have either been adjusted?
Rich.

[Damned 69]

Both have Tbt top hat / guides /slip washer, original HW weights removed, spring ends polished. Seals are good. Older spring approx 5mm shorter than newer one - assumed such 'settled' . Purchased second one to use as self challenge with just open sights. So I guess it's just one of the curious quirks of air rifles.

[harvey_s]

My query was that with one 99 the power spread between 3pellet types was relatively close, whilst the spread with my other 99 using same 3 pellets was what I would consider rather large at 1.6ft/lbs.

Ah, understand now...if it helps my own .22 certainly shows that kind of difference between say RWS Superdomes & JSB Exact.

[Damned 69]

BDTB - thank you for very informative reply. I guess that I may have not been as carefull on my reassembly of my misbehaving gun and that maybe some lube has managed to get in front of piston causing a degree of dieselling/detonating to a degree (never been sure of the real difference as both are degree of combustion) and unlike my old meteor which would give obvious tell tale puffs till settled down I didn't detect such. Shooting at range tomorrow and will check power on return in hope that surplus lube 'burned' off - if not then strip down. Once again thank you.

[Damned 69]

Appologies for the 3 degrees

[BTDT]

BDTB - thank you for very informative reply. I guess that I may have not been as carefull on my reassembly of my misbehaving gun and that maybe some lube has managed to get in front of piston causing a degree of dieselling/detonating to a degree (never been sure of the real difference as both are degree of combustion) and unlike my old meteor which would give obvious tell tale puffs till settled down I didn't detect such. Shooting at range tomorrow and will check power on return in hope that surplus lube 'burned' off - if not then strip down. Once again thank you.

Just to clarify, I'm not saying the issue is necessarily connected with autoignition, just that the symptoms can be caused by it, and it's a strong possibility.

[PCPShooter]

My query was that with one 99 the power spread between 3pellet types was relatively close, whilst the spread with my other 99 using same 3 pellets was what I would consider rather large at 1.6ft/lbs.

Those Hw star nut barrels in 22 ...emm........

As others have said - Combo of spring / seal set up / TP size, barrel choke (if any - or on hw if any intentional or barrels pinched for open sights) / lead in on throat of barrel

If I have a springer that handles most pellets within .5 ftlb - result - never sell that one then !