I just finished assembling an SPRish project. I went to test fire and had some issue. I used two types of crummy ammunition: old Wolf and Remington UMC. Both were .223 Remington and not 5.56.
The rifle wears a WOA 18" middy barrel with Wylde chamber and M4 feed-ramps in the ext. The upper is an M4 upper purchased stripped from Bravo. I used a MI gas block. I checked it and it appears to be completely secure and tightly clamped, so I do not believe I have a gas leak. The stock is a standard A2 with a rifle buffer and spring.
I lubed everything with my usual Mobil 1 synthetic motor oil treatment that I've been using ever since I started shooting AR type rifles.
Here is my issue:
With the Wolf ammunition, the rifle was a genuine single-shot and would not eject. at the end of the magazine, the bolt would not hold open at all using a Colt 9-round magazine, a 20-round P-Mag, and a 30-round USGI mag.
Using the Remington UMC ammunition, it would cycle about every third round. It ejected every round but wouldn't always pick up rounds from the magazine.
The mag-catch appears to be fine. There were no issues loading the first round out of the magazine. Cycling the charge handle with any of the mags empty, it would hold the bolt open.
The rifle shot very smoothly and was very accurate, but the thing just would not cycle. My assumption is that I need to move away from the rifle buffer to possibly an H1 buffer. Is that a likely solution? Do I also need to change the spring? If so, to what?
Thanks in advance for any help.

