Hey all!

Purchased a barrel for my first build, and it came with dimples for set screws.
The purpose of my build will be my home defense rifle and plinker until i can SBR it and put a 12.5" barrel on it.

I've been told that using set screws with loctite is better because the pinning process stresses the barrel and affects accuracy.
I can't imagine the method of attaching FSBs that has been used for 30+ years affects accuracy ALL that much.

What are your opinions?

They both work fine as long as they are done correctly, I don't pin anymore, I use clamp on's or set screws for the most part, if you have the ability to pin, then have at it, it has been an acceptable way to do it as long as this platform has been around.

I think i'll take the gunsmiths advice and have him use set screws then.
Thank you!

I am not convinced that taper pins have any real affect on barrel accuracy.

Setscrews that are properly tightened almost certainly won't benefit from thread locker.  NO threadlocker holds above about 450ºF, and it only takes a few shots to get a gas block up to that neighborhood.  Instead, if I worried about setscrews loosening, I'd stake them.

I think it still keeps fasteners from just rattling off even at high temps. I have wondered though my self. Harley Davidson calls for red loctite on internal engine parts, that's gotta get mighty hot! I use red loctite on my FSBs, no problem yet. I also tighten them so tight I twist the Allen wrench and use a new one for each screw. Make sure it is centered first, because it's permanent.

You have to drill holes thru the barrel for pins, and there isn't much room for that. Barrels can and have been distorted from it with the rifling pushed out of shape. It's a gunsmith level operation at best. The milspec on the design was to prevent soldiers from monkeying around with the parts, or having screws back out over a 20 year service life. It's considered a "fleet" maintenance issue with 7 million rifles in the system.

YOUR rifle, not so much. Set screws allow disassembly in the future and fewer issues.

There is also the new ITAR interpretation that may require smiths to pay a $2000 yearly fee to alter any part. Set screws are a simple adjustment, pinning is a drill operation and materially changes the as-shipped nature of the barrel.

I expect that barrels won't get pinned FSB's casually removed or installed in the future because of this. The traditional gun owner, however, is likely to discover a major source of heartburn over it as most proprietary designs aren't lego and I suspect things are going to get ugly. Filing, buffing, stoning, fitting locking lugs, etc can and likely will all fall under it.

It's the STATE department who changed this. Not the ATF. Think who used to have that job as Secretary of State.

Loctite 2620...650 degrees F

Like I said, if I worried about it, I'd stake the screws.  I do not trust a thread locker to hold AND to be removable when I want to remove it.  Staking is easy, essentially free, and it lasts until you work at getting the setscrews out.

Not a lot to add to the excellent comments except that some people think it might possibly make a difference on precision rifles.  The thinking is that both set screws and cross drilling affect the pressure on the barrel, and that clamping does not.
I honestly have never thought about staking set screws until reading Cruffler's (Porter's) post.

I have no opinion on the barrel pressure issue personally.  Just something to keep in mind when building a high end precision rifle.  I would not worry about that if I were you.  I would spend those resources on ammo and training instead.