Here's a target I shot yesterday, indoors, 25 yards, single loaded the pellets. Numbers are the pellet weight and the pellet head diameter as I measured a sample of 50 and averaged them on the spot. Indeed, the barrel isn't installed backwards, all other features are where they're supposed to be. The choke at the muzzle is of the appropriate length etc. It just opens up for a good 5-6" before tightening up to what I can only assume is the correct bore diameter. In my opinion it shoots poorly compared to what I expect. But maybe I'm just expecting too much from this brand/pricepoint of an air rifle. Frankly it should be shooting sub MOA at a minimum and pushing 1/2 MOA at 50 yards with perfect conditions. My centerfire bolt guns all hold 1/2 MOA at 200 yards no problem and I'm capable of doing that off of a bipod and rear bag. And I do understand that shooting air rifles requires a completely different touch than firearms- I've been shooting airguns for 35+ years.
Like I said before this is really weird and unexpected so I reached out to this forum community which quite frankly has been absolutely awesome with their openness and willingness to help. Extremely friendly, which is a pleasant surprise.
Badlighting:
We will need to know average velocities for the groups you shot in order to be able to understand better the issues...
You seem to be measuring the heads of your pellets with calipers....DON'T!...Calipers do not provide you a good reliable number but most important is the fact that the flat sides of the calipers tend to flatten the sides on the heads and this fact destroys any possible precision. Get a PELLET GAUGE, those are cheap and a very good investment if you intend to head size your pellets for most accuracy.
Your gun shot 2 groups that are acceptable with JSB 13.6 gr...It seems to be that those 2 groups are around 1/4" c.t.c. or less and that means you are at 1 MOA at 100 Yards (Theoretically). Keep in mind that that 1 MOA is the precision that FX and other companies target on their guns, so you are not so way off and anyone telling you that .500" at 50 yards is not good enough ask them to shoot 2 consecutive 10 shot groups to prove their point!...Don't believe Internet marksmen, see what competitors and champions shoot at competitions.
In general, those 13.6 gr. pellets like to be pushed harder that 10.3's and 8.4's...In my experience the general sweet spot lies from around 760 to 840 fps...Of course, your gun/barrel will have the last word and these numbers I am disclosing are merely a ball park for the sweet spot...As an example: I currently have a RAW TM-1000 that loves to shoot them at 820-840 fps. and by comparison a Steyr LG-110 likes 760 to 780 -785 fps Max...If you lower the velocity on the RAW or increase it in the Steyr the guns will not shoot them satisfactorily for a BR match. Bottom line: use a chrony and get your velocities so we all know where you are.
Seeing those groups at 25 Yards I wouldn't be so much concerned about the barrel, I would try tuning for velocity and efficiency of the gun...Note: The "Harmonics Tuning" is not the right wording for what they do on those videos claiming harmonics tuning...Harmonics tuning is much more complex procedure that matching a pellet to a gun but this is a good start. When you harmonically tune a gun, you will never reach a 100% tuning stage, but when you approach a good level of tuning at around 85% or upwards, your gun will shoot ANY pellet at any velocity without having to mess with your regulator, valve spring (dwell) ports...Then head sizes become transparent and your gun will shoot 4.49's as good as 4.53's and 4.54's...This tuning procedure (harmonics) requires very high tech equipment that is extremely costly and the technician needs to know how to interpret the data and know what to do.... In any case, keep in mind watching some of those abundant harmonics tuning videos from the "experts" as you may need to follow a similar procedure to refining the tune on your gun.
I (we in this thread) could help you better if we knew what kind of barrel you are using: Is it a proprietary Brocock barrel or is it a LW either in their 12 groove or Polygon configurations?...If it is proprietary of the brand, Brocock is owned by Beretta and if that is the case then the barrel was manufactured most likely in Valtrompia or Brescia; Gardone no longer manufactures barrels for any Beretta guns. Beretta originally used CZ barrels that were hammer forged in Czechoslovakia, EXCELLENT barrels if you ask me...Given the fact that Brocock is an English gun ,they may very well be using a BSA barrel that is also manufactured with very good tight specs. All of the barrels mentioned are very good but all have very different tastes for pellets and velocities. The different bore choke configurations combined with the profiles of rifling (lands and grooves) and the deepness of the rifling are critical. So if you can, call your vendor and ask him about the barrel...In the meantime count the grooves/lands at the crown and provide us that number.
At what power do you want to shoot your gun? What is the barrel length? Are you suing a moderator or muzzle brake? Do you know what is the BAR pressure on your regulator?
Best regards,
AZ
