To my knowledge the A suffix was added after an improved firing pin was introduced, early ones had a reputation for breaking. There are also rifles with an H suffix which represents another improvement though I don't know what was changed. I killed my first and biggest whitetail buck with a pre'64 M/88 .308.
Interesting, one learns something new every day. I’ve never read anywhere that the A suffix on a M88 was indicative of the improved firing pin, can you point me to a reference?
The A suffix on the M52 and M54 were indicative of improvements on these models.
