Scored some +6's for my M&P and my son's G34, both 9mm.  Can get only 22 in the 34 and M&P except for one M&P mag which will take 23 and still seat.  Do I just need to load them to 22 and let them sit for a few days to relax the springs a bit for that 23rd round, or have I overlooked something else?

Mine only hold 22, my Arrendondo extensions also only hold 22 for my G34.

Mine only hold 22 until they've been used for a while then they hold 23 with no issues

Some base pads need to be tuned. I had to file a little off of the back of one of mine.

It helped with mine to leave them loaded for a week.  After that I was able to get the last round in.

Are you talking about filing the follower a bit shorter?



 

I had older style followers in mine since they are old mags. I did have to file a little off of the back edge as it would catch on the back of the extension and not allow me to fully load it. It was just a tiny ammount I needed to take off. 2 swipes with a file on the front and back and it was good.

Taylor Freelance has a video about tuning the followers that I used. I had the #5 followers that they mention starting at about 1:50 in the video. 1st the back edge of the follower caught on the extension, so I did a couple swipes with a file on the legs. Then it was catching on the spring itself, so I did a couple of swipes on the inside area of the legs. Worked fine after that. My 170mm mags with the Taylor Freelance +8/10's didn't like the older style followers. Would feed fine, but didn't always lock the slide back on the last round. Used a newer style #9 follower with it and beveled the front top edge of the follower like they show in the video and it worked after that.

Taylor Freelance follower tuning video