QB78 End Cap Problems

[iconoclast]

I just got my QB78 Deluxe air rifle a couple of days ago.
From the beginning, the end cap screwed on roughly.
It sounds and feels like metal grinding on metal.
I've cleaned the threads on both the rifle and the end cap.
I've examined the threads with a magnifying glass for any damaged threads.
And I've lubricated the threads with silicone grease.
But the grinding continues.
I've also noticed that the cap wants to go crooked and begin cross threading.
But I apply downward pressure so it can't cross thread.
It almost seems as though the threads are too loose fitting.
Is this a common problem?
Or should I return the rifle for an exchange?

[iconoclast]

I applied a thin film of Permatex Antiseize to the threads.
It screws in pretty smooth now.
However, when I closely watched the End Cap as I put in a new catridge, the End Cap went crooked when the pressure was released.
I'm afraid that the threads are so loose, that the cap may actually pop off when the pressure is released.
This is kinda scary.
Since I'm brand new to this CO2 stuff, any advise on what I should do?

[iconoclast]

Upon further examination, I noticed that I can PUSH ON the End Cap over 10 threads of the 13 thread total.
This is without screwing on the End Cap, but just pushing with my fingers.
Since the threads are this loose, I guess I'm lucky that the End Cap didn't pop off and hit me in the head.
That would definitely hurt.
I guess I'm going to need a new rifle.
Or at least a new tube and end cap.

[shadow]

Sound's kinda spooky might want to return it for another. My 78 screw's on smoothly with no problem's, I would hate to hear of one of our member's getting hurt over a faulty shooter. Another of fine member's will chime in with some more idea's. Ed

[RCnMo]

If you bought it new, I would contact the vendor and send it back. That is definitely not correct and very unsafe in my opinion. My cap threads from start to finish and 800 or so psi from a powerlet could send that cap out the front of the rifle like a bomb. I think archer air sells the cap for a very reasonable price if you choose to just replace the cap.

[Jaymo]

My TF78 Gold had a cap that was a bear to screw on. I swapped it out with my TF78 Thumbhole and now both caps work just fine. I even bulk fill my 78 Gold with my Axsor hand pump to 1,150 psi in cold weather and have had no problems.
Then again, I couldn't push mine on, past the threads, either.
I think I'd send it back, as there's really no telling, without another cap, whether it's the cap or the tube that's causing the problem.

[iconoclast]

I received a new cap today from Best Airguns.
WOW! What a difference.
I can see the difference just looking at them side by side.
The old cap looks distorted compared to the new cap.
The new cap screws on so nice and backs off easily to release the pressure.
I'm just thanking my lucky stars that I did not get hurt with that faulty end cap.
Thanks to all for the helpful input.

[shadow]

Good to hear, we want to keep our member's safe. Ed