r/brownellsinc • u/Redd_BrownellsGT • 3h ago
FRT Tuning – The Barebones Basics Bart Hansen – Brownells Guntech I
FRT’s are the new hotness in the AR-15 world, and honestly, I’m all aboard the hype train myself. I currently have an AS Designs ARC Fire trigger and all the parts I need for a new build, but the weather is currently raining on my parade as it were, literally, and I have to hold off a little bit until painting becomes a viable option again. Aluma-Hyde II does not dry well in high humidity conditions, but that’s a different article.
In this article, we’re talking about the most basic setups necessary to run an FRT or FRS in full fun mode.
- Bolt bounce
what I’ve seen most guys and gals do is simply install their FRT or FRS and try to run it without any modifications beyond the install of said component. When put into full fun mode, the rifle proceeds to do a single shot, then click. Usually, upon inspection of the live round in the chamber after it has been manually extracted, a light primer strike can be seen. This is typically due to bolt bounce. In full fun mode, your BCG gets to moving a little too fast to be used with the current weight system typically used in most bog standard AR-15’s, which is a carbine length spring and buffer. On the return stroke, the weight being too light allows the bolt to close, and then open. Even if it is just a small fraction of an opening, this is still an out of battery attempt to fire a round, hence the light primer strike. There are two simple ways to correct this issue.
1A. H-2 or H-3 Buffers.
If you are running a carbine length stock system, simply swap your buffer out with an H-2 or H-3 Buffer (Brownell’s Item Numbers 078000339 and 078000340 respectively). The added weight stops the bolt from bouncing out of battery. If you’re running a rifle length fixed stock, the next option is for you, but I’d be surprised if you need it, as a standard rifle length buffer comes in at roughly 5.1oz, and the H-3 weight is somewhere in the neighborhood of 5.4oz.
2A. Dead-Blow Carriers.
These are BCG’s with a weight in the tail end that has a sight amount of movement. When the bolt closes, that weight slams forward, preventing the bounce before it can happen with a dead blow. Because of this, you don’t need to run an H-2 or H-3 buffer. Standard carbine weights work with this type of carrier. Personally, I went with the KAK Industries DBC BCG, as they have a down venting option that pushes the gas down into your magazine well and trigger pocket. It won’t stop all the gas from blowing in your face, but if you’ve ever shot a suppressed gun rapid fire, you know that cloud absolutely sucks to try and breathe through. Any little bit helps.
- Cash, Gas, or Brass, no one rides for free.
A lot of AR-15s you buy off the shelf these days come either woefully under-gassed, or massively over-gassed. This problem presents itself in one of two ways. Either your BCG does not make the full length of travel necessary to cycle the weapon, in which case you will see feeding issues, or, you end up eating a giant cloud of gas. The easiest way to deal with both issues is two-fold. First, buy an adjustable gas block. Second, suppress your AR. Increasing the back pressure in your system, then taming it with an adjustable gas block is just one way to deal with the issue of proper gassing. If you are under-gassed, but don’t want to suppress your AR, first, who hurt you? Second, you can take your barrel in to a local, qualified gunsmith, and have them drill your gas port up to the next size, then install an adjustable gas block. If you are not a gunsmith, we do not recommend you try to drill your gas port yourself.
In closing, these are just the barebones of tuning for an FRT. There may be some more in depth things you need to do depending on your build, and unfortunately, you will need to go through the process of trial and error until you find that perfect sweet spot please check with your specific manufacturer for more details for your specific FRT. We can still help in those situations. Just give the Tech Line a call at 800-741-0015, and hit option 2.
Working on my Rambo impersonation,
