There was a big discussion on another forum about it. It is permanent in the sense it can't readily be taken off without heating the thing red hot. There is no pinning. Actually pinning and welding is not really permanent as it can be reversed but with more work involved. I would Google and see...
If this is going to be a truck gun then why not just take a torch to it and solder what you want on it, then later heat it back up and trade it out to something else. Soldering makes it perfectly legal though it may discolor your barrel ...or it may not.
I know it wouldn't fly over well at my house but my wife does not get in to the shooting sport nor self defense. Your situation may be different in that she goes to the range frequently and wants to CC a gun. If not, well, I have a basement I rent cheap.
I encourage you to read this . It is first hand experience.
High round count AR/M4's (over 100,000 rounds) and how they have handled on our range - AR15.COM
I'm sure that has alot to do with it but if I were to drop my AR with a direct hit to the rail I'd be wishing it was a drop-in rather a free float of the best brand.
A lot can be learned from reading a thread on Arfcom from Henderson Defense. They tell what works and what doesn't in their classes. I always thought I wanted a free float rail for my shtf / go-to rifle but they tell how so many have failed during their classes and that they can't take the abuse...
I'll chime in to say that they are good to go. I bought my VP9 from them when they were still in their electronics store around the corner. I was going to order online but they price matched for one they had in stock.
If you were going with a powered scope for long shots then a non chrome lined barrel with a low profile gas block that you can install a free float handguard later and start squeezing the most accuracy out of is what you will want. Of course you will also want to install a better trigger also...
Would depend on whether the dad or the lad wanted to go with chrome lined barrels or not. I know a lot of companies are choosing Melonite/Nitriding to bring the cost down. I myself bought a pistol upper from PSA that was nitrided just to have a a cheap truck gun. There is just not enough info...
BCM M4 16" Upper Receiver Group Just configure it without the charging handle and get a cheaper one at PSA or somewhere, then add the cheap M4 handguard and update the price.
Anderson AM-15 AR-15 Complete Lower Receiver with 6-Position Collapsing Carbine Stock