I haven’t fired it yet but I have a kak buffet tube, spikes 9mm buffet and a standard Carbine spring. I also ordered the spikes buffer spring spacer that goes in the rear of the spring but it wouldn’t allow the bolt to come back far enough to let the bolt hold open catch it so without it I have about 3/8 of a inch that the bolt travels past the catch so I think that will work if I feel it’s too much then I will shave down the spacer and put it back in and the bolt is a no name bolt from delta point tactical I believe
This is the exact combo i have and it works great in my 9mm pistol. You dont' need spacer b/c the spikes buffer is longer than standard already. I'd just sell the spacer off to someone who is tired of using quarters stacked in their buffer tube.