TX200 .17 New Out of the Box question?

Happy to say I received my .177 TX200 last Friday and shared it with my buds at out monthly Air Gun get together on Saturday. One friend said I could use some of his Tung oil to finish the beautiful walnut stock. I agreed and after the meet we went to his place and prepped the stock with 00 steel wool followed with a nice coat of tung oil. Wow!...
Now back to my original question
I cleaned the barrel with a few patches and that was it, clean. ran a few FX 8.4 pellets through her to make sure things were as they should be, all seemed well and good.
Took the action out and worked in another coat of tung on Monday. Buffed and worked the stock today and back together she went. Now it's time to see what she will do over the chrony. I mount my FX chrony just under the front of the barrel end and load an FX 8.4 gr for the start off a 5 shot group. What I was expecting was readings around the upper 800's like Steve on AEAC got with his .17 back 3 years ago. Not even close is mine. His 10.3gr are shooting at 810 and mine is 680???
Do I need to shoot a tin through her to break her in? Or ?
Any advice is most welcome.
Here is my 8.4 shot string.

Patrick
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