Originally Posted by Alex
I have a problem with my HW97 and I'm running out of ideas what might be the reason.
My setup: HW97K left hand factory sporter stock, .177, 12ft/lbs, V-Glide bought 07/2012, Steve Pope trigger, softer spring in the cocking lever latch, aluminium handle on the cocking lever.
Machined aluminium 11mm to weaver rail with 0.3° drop comparable to the Steyr rail, low B-Square mounts, Bushnell Elite 8-32x40 with Bushnell custom shop Mil-Dot reticle.
The V-Glide has some dampening material in the front of the piston, acc. to S.P. this was newly introduced around the time I bought my kit.
After fitting the V-Glide in 08/2012 and a short run-in the HW performed flawlessly and with constant velocity and superb accuracy with my testet lot of JSB 8,44gr 4,53. The rifle is capable of 20mm groups at 47m at ideal conditions, probably better, but I'm the limiting factor. I use dots and I didn't remove the caps on the turrets of my bushnell for about 3 months, perfect. The HW shot time after time spot on. End of october with temperatures dropping below 10° I began to realize shifts in the POI. First from one training to the next, then during one training from one shot to the next. The shift is vertically and to compensate I have to make about 20 clicks up or down. Its always this shift, not more or less, not a process of several shots and small shifts. Always one shift, about 35mm off at 40m. The V0 is still constant and OK. The ballistic curve is not effected. After clicking and zeroing in again all my holding points work as usual. Until the next shift...
I've tried the following to find the cause, I've disassembled the rifle and inspected everything, at this time I had about 8000 shots on the V-Glide and everything looked like the day I first put it in the HW. Absolutly no visible wear. I've stored the HW cold so there's no temperature difference from storing to the range. I replaced the Bushnell with a brand new one. I loosend and tightened the bolts on mounts and rail on the range before shooting. I moved the rail forward on the prism so that the rear clamping of the rail reaches over both trigger block and main system tube. I've moved the mounts on the weaver rail from furthest apart to closest. I bought a new one piece Diana mount with 1mm drop. Today finally we had a nice spring day with temperatures up at about 18°, same problem, after it happened, I tapped the back of the system using a piece of wood and a hammer. No change, tried the same from the muzzle side. No change. My last idea was that there might be a shift between system and stock which might affect the tension on the trigger housing. After tapping today without anything happening I guess this is not the problem either.
Please help! A bit desperate here, I find myself thinking about a TX200...
Picking up from your last line. I have a TX 200 that does exactly the same thing. Its taken me over a year and four scopes before I've gotten around to considering the gun as being at fault. As an addition to other things that have been touched on in the thread; I have also swapped the spring guide from (relatively) loose fitting metal to tight fitting delrin and back again and also a looser fit delrin, changed the spring and piston seal and for good measure the breach seal. I've ruled out the bad lock up/seal issue and loose barrel too. I have also swapped the piston out of my Prosport for the one in the TX both being short stroke alloy jobs: made no difference. My TX is in a Ginb and that is now the main suspect.
Low temperature seems to be involved in my case too and although I also get a power increase, its nothing like enough to give the POI shift involved. Mine also moves fairly precisely between two zeros. I have recently witnessed the shift occurring, once with my Burris on, once with my Nikko on. In both cases it made the shift to the other zero in something around 20 shots, then stabalised. It usually moves back within a few days. I have always associated this with low temperature but I now have a thermometer on the gun and it has shifted when temperatures have been fairly stable at around 9 - 11C. This was one of the ones that occurred while I was on the zero range. I have only one incidence of this though and although it shifted after I'd been shooting for 20 minutes or so, the gun had been in the car boot overnight so temperature could still be playing a part. Whatever the cause is, in my case it has started happening a lot more often recently.
I recently spoke to Nick Murphy about this and he is familiar with the problem but doesn't know what the cause is but barrel or stock are what he puts in the frame. I was also relieved to know it wasn't me going off me trolley
. Though if NM doesn't know the answer, I doubt if I'm ever going to find it.
Amusingly, I'm now desperately trying to get my V-glided HW77 in an FT stock and ready for the first GP
The TX is now with a mate who also has TX's including an ally piston modded one. I'm hoping that maybe a fresh pair of eyes will see something I have overlooked.
Springers eh? I love em but they don't always love me back!
Sorry this is of no actual help Alex and worse, I seem to have put your TX escape route in doubt.