AA HFT 500 pellet will not load

Posting for a friend guys can anyone help.

I have a pretty new AA HFT 500. I was planning on shooting in my first FT event next weekend in Northeast Ohio. During a practice session today. I was loading a pellet and it would not go in the breech. I did not force it and was able to pull it back out. The next pellet did the same thing. I spoke with my fellow airgunners and we think the breech o ring is out of place. I looked in the owners manual and it appears that I need a 4.5 x 1.5 NRB70 to replace the damaged o-ring. I need some help with the order of disassemble. Is the HFT 500 more similar to S500/400 series or the FTP 900? I plan to order the new O ring today from McMaster Carr.

I really appreciate any information you can provide in helping me repair this rifle.
 
Posting for a friend guys can anyone help.

I have a pretty new AA HFT 500. I was planning on shooting in my first FT event next weekend in Northeast Ohio. During a practice session today. I was loading a pellet and it would not go in the breech. I did not force it and was able to pull it back out. The next pellet did the same thing. I spoke with my fellow airgunners and we think the breech o ring is out of place. I looked in the owners manual and it appears that I need a 4.5 x 1.5 NRB70 to replace the damaged o-ring. I need some help with the order of disassemble. Is the HFT 500 more similar to S500/400 series or the FTP 900? I plan to order the new O ring today from McMaster Carr.

I really appreciate any information you can provide in helping me repair this rifle.