Ah, Internet fuddlore. Smells like ……. Aqua Velva and fear.
As you guys know, I no longer like to shoot unsuppressed rifles, and I shoot a bunch of Ars, so between mine and my friends, I’ve probably put on 30 suppressor mounts, from A2 Birdcages (yep that can be a suppressor mount) to pinned and welded SF War Comps. This is not some black magic, and there’s no call to pull hair.
TL:DR: A Rearden R2S doesn’t need to be timed. Clean the muzzle threads, use blue locktite, thread the Rearden on by hand till it bottoms out on the barrel shoulder, torque to 25 ft-lbs. You can probably hold the upper in between your thighs for that torque. Then go shoot (quietly).
Long answer with a bunch of extra info just in case:
Holding and fixturing: The internet is correct that you don’t really want to hold the upper receiver and torque on the barrel assembly. You can tweak the receiver or, more commonly, damage the index pin on the barrel or the slot it rides in and allow the barrel to clock. This is almost ALWAYS something that happens when taking things
off, because someone hulked them on and then they sat there for years. Putting something on is a lot lower torque. Still it’s a good practice to hold the upper correctly. I use a Reaction Rod from Geiselle, but I build a lot of uppers and swap barrels and handguards around. For one muzzle device that’s an expensive tool. A set of barrel clamp vise blocks like these:
https://www.amazon.com/Fenyee-Universal-Gunsmithing-Constructed-Non-Marring/dp/B0C2PBQNW8/ work just fine, although depending on barrel length after the gas block you may need to pull the gas tube, or cut the blocks down a bit. Depends on your build. If this is really a one time deal, you can fab vise blocks by drilling a hole slightly smaller than your barrel OD in a hunk of word or something, then cutting it in half. Pretty easy and cheap. If possible clamp it right behind the muzzle threads.
Thread Locker: You don’t NEED it. But if your can carbon locks (and isn’t left hand threaded to the device) you risk screwing the muzzle device off with the can one day. Still not the end of the world but a PITA. I experimented early on with Rockset, which works great but now I have a specific pot to boil my barrels in if I need to get a muzzle device off. Most of the time I just use blue locktite for GPs. But I also don’t take cans off that much. Dealers choice on how you will use the gun and how much Qding you will actually do.
Alignment: You are aligning the machined back of the muzzle device on the machined barrel shoulder using trued shims. There is nothing you can do really to F this up, and if it is F’d up nothing you can do to fix it. You can skip the alignment rod. I eyeball the bore from both ends for alignment after mounting the can, you’ll be able to see if it’s out far enough for a baffle strike.
Alignment part 2: DO NOT USE A CRUSH WASHER. Buy a shim kit if your muzzle device doesn’t come with them. Quality barrel+Quality Muzzle Device+Quality Shims=No alignment issues.
Alignment Part 3: That said (and it’s good general knowledge) I just googled a Rearden R2S and it’s a symmetrical birdcage style suppressor mount. So timing is not needed. Assuming that your barrel has a thread relief machined in (if it doesn’t get a better barrel, that maker is dumb) just thread the R2S on the barrel until it bottoms out on the barrel shoulder and move on with your life.
Torque: Non-crush washer 5.56 Muzzle device torque is 20-30 ft-lbs. You aren’t timing this one so set your torque wrench at 25 ft-lbs and stop when it clicks. (To the internet comment section: don’t com at me about the conversion for a crow’s foot adapter, look at the torque range) For future proofing, if you are using one that needs to be timed, you adjust with shims until it get’s hand tight about 20 degrees before “correct” then set your torque wrench to the max allowable torque and tighten it up. As long as it times before the torque wrench clicks you are good. If you hit max torque before it’s timed, take it off and tweak the shim stack.
Let me know if you have any other questions.
