I am not a tinkerer, or fixer. In my opinion any air rifle that costs close to $2000, and does not shoot perfect, upon recepit, should immediately be returned to the seller for a full refund. The only problem I would have is waiting for the refund to be credited to my account.
I suppose we all have different definitions of "perfect" or "acceptable."
If you say you would return a rifle if it wasn't "perfect" out of the box that would mean I would have returned every single air rifle I've ever had pass through my hands, as I've never had any rifle be perfect out of the box... I've found little issues I wasn't happy with in all of them. That goes for Edgun, Daystate, Benjamin, Kalibr, FX.
Were they all acceptable out of the box-- i.e. functioned properly, didn't leak, and exhibited reasonable accuracy? Nearly 100% yes, with the exception of my first production batch .25 R3M which had the wrong .22 magazine indexing lever installed that would not fully rotate the .25 magazines. The .25 R3M was the only brand new air rifle I've ever dealt with that had a legitimate functionality issue right out of the box.
A far as being "perfect" out of the box... NONE of them were. While all but the .25 R3M functioned out of the box they all had something that could benefit from a little tuning or adjustment-- some more than others. What I mean by that is accuracy tuning for a specific pellet, tuning for a bit higher shot count, making a slightly rough action a bit smoother, trigger adjustment, etc. Could you have taken any of them out of the box and gone and made acceptable size groups on paper or hunted with them and never touch them until they needed some kind of maintenance? Certainly. Could accuracy or some aspect of function be improved by some amount tuning and adjustment? Absolutely.
I will say the most trouble free air rifles that myself and several of my friends have owned have been my old .25 R3 single shot Edgun and a friend's 40 ft-lb Daystate Air Ranger. Both have provided many years of trouble free service and have been passed around through
several owners now but are still in the same circle of friends.
Back to the OP's situation, here's what I would do:
1. Magazine indexing: Remove the bolt block housing from the back of the rifle. With an empty magazine inserted into the bolt block, manually work the bolt all the way forward and all the way back smoothly and slowly by pulling on the protruding pin that cocks the hammer. If the magazine does not fully rotate and index when the bolt is pulled all the way to the rear of the breech block, there's a problem. Possibly an incorrect indexing lever from a .22 was installed, or possibly the screw and o-ring that supports the indexing plate and serves as the pivot is loose.
2. Accuracy: First I'd thoroughly clean the barrel while the breech block is off for step #1. Next, remove the front shroud cap and pull the baffle stack out of the moderator and check the tightness of the front barrel nut, I believe you need a 10mm hex bit. Too loose can hurt accuracy, as well as too tight, and my experience has been they can be way, way too tight from the factory.
Before reinstalling the baffle stack, shoot the rifle with the baffle stack removed from the moderator. If the o-ring at the front of the baffle stack under the retaining nut isn't lubricated and/or the baffle stack retaining nut is overtightened, when the baffle stack retaining cap is tightened it can distort/twist the baffle stack and possibly lead to pellet clipping. If the accuracy substantially improves at this point it may have been the pellets clipping the baffles.
After both of those steps I would try JSB 25.4's and see what the velocity is. With the exception of the limited run "superlong" rifles which have larger plenums, Ed really built the .25 R5's up around the 25.4gr JSB pellet and not the 34gr JSB pellet. Around 850-880fps for the 25.4gr pellets (and make sure the hammer spring is set at least 10 fps below the velocity peak for the regulator pressure) should be where that rifle is set up to shoot out of the box, and it should be reasonably accurate at those settings.
As I mentioned earlier my experience with the .25 R5M is that the stock plenum volume isn't ideal for the 34gr JSBs, you have to run the regulator pressure and hammer spring tension far too high because there really isn't enough plenum volume for the 34gr pellets. The R5M is much happier shooting 25.4gr pellets out of the box, and really benefits from the larger huma power plenum when shooting the 34gr pellets.
Finally, it could very well be the OP's rifle isn't happy with the 34gr Mk2 pellets which is why accuracy is poor... many rifles don't like the JSB Mk2 34gr pellets, and it seems JSB isn't making the Mk1 34 gr pellet anymore since they are shipping Mk2 pellets in Mk1 tins. If the rifle isn't shooting the 25.4gr pellets with reasonable accuracy between 850-880fps with the stock regulator and plenum at this point after trying all of the above steps, I would then suspect a possible barrel or crown issue.
Finally, I will say my .25 R5M barrel needed some time to settle in and is more sensitive to cleaning than my other Edguns.
