I don't have anything new to add but I feel like after referring to this thread for years and finally having a 1301 in my possession I should make a post.
Thoughts:
1. The gun doesn't really need any upgrades other than a way to mount a light. I am going to copy this method,
https://www.reddit.com/r/beretta1301...mod_sga_spacer
I hate tape switches so this should do the trick.
I did switch to a Blitzkrieg non-tritium front sight, but would have been fine with the stock front sight post. I'll add a magazine extension and a QD socket in the rear, but again I would be fine without them. I have no plans to switch furniture. I have a SGA on my pump so I know what they are like, but the stock that comes on the 1301 is great. I've looked at the Aridus and Briley handguards and both have aspects I don't like. I also have a sling for the gun if needed.
Note about adding QD cups: My plan was to JB Weld one in the void left from removing the stock sling stud and then add one higher up on the side for primary use. I did not take my time to think things out and ran into a self-made issue.
A QD can be added to the side with ease. No problem there.
I am not an engineer, but it looks like the sling stud also acts as an anchor for the stock insert and should not be permanently removed. I am an oaf and managed to damage my insert by being careless. I'll end up with the two QDs as I originally envisioned, but if I was going to do it over I would only add the QD to the side of the stock.
2. For how light the gun is it doesn't recoil much. I went through about 130 shells of full power buck and 25 slugs in a short amount of time without issue. No hiccups from the gun either.
3. I had a tough time choosing between the tactical and 21" comp guns (this goes back to the early posts from DocGKR). I did not have a chance to hold either one before purchasing, so I had to go by what others recommended. If a 18" comp model existed I would have gone with that. In the end I went with the 18" gun.
4. I know this is not surprising, but compared to my pump the 1301 patterns better. The groups seemed more consistent and a little tighter. This was with case with 3 different loads and one other load was about the same.