I purchased my 5.45x39 upper from Huldra Arms. I first want to say that customer service at Huldra and Adams Arms is superb. The only issue is that if you fire the rifle in the single shot gas mode, the spent case will stick in the chamber and you will have to pry or drive it out. It will not eject when you pull the charging handle. It might work if brass cased ammo existed in the caliber. You may never want to use this function but it should be noted by Huldra and Adams so the customer is aware of this before purchase. The rifle is perfect in every other way. It has been sent to Huldra and Adams with the same result. They both gave it an excellent try but the fact is it just won't work.