BudsGunShop.com - Compatible ammo.

you may get one that works great with a 55 gr. bullet and the next one off the line may hate them I suggest trying a box or 2 before you go to the 62 grain bullets if it has a issue with the 55s I would shoot the 62 gran bullets for 800-1000 rounds then try the 55s again

Tim - I have a 7.5" pistol I built myself, and have well over 1000 rounds of 55 grain ammo through it with no malfunction - including some steel cased Russian ammo. One could use the 5.56 62 grain but I've certainly not found a reason to do so. Every firearm has its own quirks, and if you have problems with 55 grain then try the 62 grain .. but I don;t anticipate you will have a problem.

Timothy, the best weight range for this barrel length is the 62gr bullet weight or SBR calibrated ammunition (I have a 7.5" barrel version and 62gr is the ticket) : budsgunshop.com/catalog/product_info.php/products_id/411557886/hornady+556+nato+75gr+sbr%e2%84%a2+training+50ct