"jaybo"Thanks for the detailed information. It really helps me and, I'm sure, other serious airgunners. I will probably leave my 850 stock for now, but may have it tuned at a later date. As an interesting side note, I live at 7000 ft. and often hunt at a higher altitude, so air density at altitude might also factor into the equation.
Warm wishes to you too.
I own a factory original Hammerli 850 which was my first, then I got an Archer QB79 that was factory tuned to the ragged edge, then I bought another Hammerli 850 for the express purpose of Roald of the 850 store tuning it. I am very happy with all three.
If you want a really powerful CO2 rifle the Archer QB79 will shoot 14.3 grain pellets at 770fps for an honest 19 FPE approaching break barrel power and you can order one today arriving on your doorstep in less than a week. Just ask for all the power related options and the extra power tune, it's almost like you can get the Dinan tunes on a BMW from the dealer directly while still enjoying the factory warranty. The Archer has an amazing trigger but the downside is the rifle's balance is not as nice, it's not as refined as the Hammerli 850 and it's somewhat less accurate. The bolt is smoother on the Archer but it does use Marauder magazines that are spring fed so you don't want to leave them loaded a long time. For the Hammerli I have a ton of magazines I just keep loaded and then unleash a storm of lead when I feel like it.
The tuned Hammerli requires you to contact Roald at the 850 store who is a joy to talk to and will walk you through the whole process but it takes a month or two for turn around because Roald is busy. Mr. Steven Archer is more commercial and sells his QB's as a day job while Roald does it more for hobby purposes because Roald has another day job. Steven wants to make you happy to make the sale and does so in an honest, straightforward, no frills but excellent customer service kind of way. Roald wants to spend an hour talking to you on the phone and emails you tons of updates if you're up for it because he knows everything there is to know about the 850, loves the gun and is receptive if you enjoy it just as much. The tuned Hammerli has a stiffer cocking and will net about 690fps with 15.9 grain pellets (which is what it ends to shoot best, better than the 14ish grain) and 730fps with 14ish grain pellets. It is more accurate though thanks to its Walther barrel so you give up a little power for some more accuracy.
They are fun in different ways, I cannot say which I like better but for a novice I would recommend the stock Hammerli and keeping it as such maybe for a year as you get a feel for the gun, the next step being the QB 79 and as your skills progress buy a second 850 to tune, it's nice to have both configurations. MAybe the money might be better spent on PCP's but they are much more expensive and in my situation PCP level air is not easy to find as paintball level air or CO2. As far as the Archer and tuned Hammerli when (not if) you will get the higher power versions do buy a scope with mil dots as it will really help you get the most out of the gun. Also download Chairgunpro to calculate the ballistic trajectory so you know exactly how much to hold over or under at what distance. This is even more important if you plan to hunt with these guns which are definitely powerful enough for the job.
For now I suggest you keep shooting and enjoying the Hammerli 850 in its factory original form. There is a learning curve; it's fun to shoot at things with the stock Hammerli 850 and make close to 1 hole groups at 10-20 yards. You can successfully hit objects from further out or group but shot drop becomes a factor. I've been at airguns for nearly 2 years now and I am able to hit small duplo blocks or empty shotgun shell husks from 40+ yards. When you're ready to start reaching out is when you'll be ready for the tuned versions which eventually IMHO are very worth it as your skills grow but let yourself enjoy every step of the way so you know what the upgrades involve so as to appreciate and enjoy them better.