This kit includes:

  • A2 / Carbine Length Flat Spring ~$24.95
  • KTactical H3 Buffer ~$39.95
  • Fortis K2 Locking Castle Nut System ~$54.95
  • 7075 Mil-Spec Carbine Receiver Extension ~$27.95
  • SB Tactical SBA3 Pistol Brace ~$129.95


OUR PRICE: $249.95

Problems with “Micro” ARs being Unreliable

If you’re running a small AR pistol 5″ – 7″ barrel length, cambered in 223 / 556, there are many variables and factors that could upset the balance of the system and cause malfunctions to occur.

Most of the malfunctions can easily be resolved by putting in a heavy buffer, but sometimes users have to mix and match different buggers + spring combinations to get the right balance with their AR pistol.

Most AR Pistol manufacturers don’t even try to build 5″ – 7″ builds and instead opt for a more stable 10.5″ barrel length. However, if you really want to experience the thrill of shooting a true micro AR, then you’ll need to figure out a solution for all the potential problems you will have!

We have battle tested this combination of Buffer + Spring combo in many “micro” 5 inch 556 builds, and have found great success and reliability with this combination.

The flat spring really helps keep the build running smoothly and reliably, and the “flatness” of the spring contributes to more reliable recoil of the bolt carrier group, which we believe adds to the reliability of the gun locking back on the last shot.

Note: If you are running an adjustable gas block, you may still need to tweak the gas a bit to get the perfect cycle going.

Designed for KTactical Complete Micro Upper Builds

This is not a drop-in solution for all micro ARs, however if you are running one of the KTactical complete 5″ upper builds, this kit was specifically designed to work with it!

Common Problems with Micro ARs and How to Fix Them

Problem: The bolt does not lock back on the last shot!
Potential Fix: Try using a heavy buffer + LOW POWER spring combination (like ours!) If this still does not fix the problem, your system might be under gassed. Try adjusting the gas block to increase gas!

Problem: The bolt gets stuck in the closed position after every shot (and it’s very hard to get it unstuck).
Potential Fix: Most likely your system is over gassed and under weight! The bolt is moving back too fast before the bullet shell finishes expanding / contracting, causing it to get stuck mid-expansion.

You can try options to reduce the initial speed of your bolt going back such as: reducing the gas in the system, using a heavier buffer, using a stronger spring, using a heavier BCG (if you’re using a skeletonized one).

Problem: Stovepipes, spent casings jammed, and other jamming / feeding issues.
Potential Fix: Your AR may be either under gassed or over gassed, you can check this chart to determine what it is and address the issue accordingly.

  • Over Gassed: Try to reduce the speed at which your BCG is reciprocating back: reducing the gas in the system, using a heavier buffer, using a stronger spring, using a heavier BCG (if you’re using a skeletonized one).
  • Under Gassed: Try to increase the speed at which your BCG is reciprocating back: try a lighter buffer, a lighter spring (or cutting some loops of your current spring if you’re daring enough), adjusting your gas block, or using a lighter / skeletonized BCG.

Problem: My gun shoots extremely dirty, there’s flakes / powder / black stuff inside my gun and everywhere.
Potential Fix: Assuming your gun runs perfectly fine otherwise, this is a normal byproduct of running a 556 micro AR build. There might not exactly be a fix for this issue, and as long as it doesn’t cause your gun to malfunction, it might not be a real issue to address. However, if it bothers you, you can try running a nice Polished TiN coated BCG in your build, as well as running cleaner / higher quality ammo.

OR If You’re Feeling Lazy…

Keep in mind, these are just generalizations and may not exactly fix your issue. Micro ARs are very delicate systems that require fine tuning and experimentation to get it functioning perfectly. With a little patience and a hand full of ammo, you can probably figure it out within 1 or 2 range trips.

However if you aren’t so patient, you can try buying one of our pre-build fully completed custom uppers and dropping it onto this spring + buffer combo!

Buffer Weights Explained

H1, H2, H3, what does it mean? These are different weight ratings for buffers.

The exact weights differ from one manufacturer to the next, but generally fall in a similar weight range.

H1 – 3.0oz : Mostly used for full length 16″ 556 Rifle builds

H2 – 4.3oz : Mostly used in shorter barrel builds, such as 10.5″ 556 builds, or whenever a heaver buffer is called for.

H3 – 5.4oz : Ideal for micro 556 AR builds (5″ – 7″ barrels) and can greatly help with fixing reliability.

However, depending on the ammo used, your BCG may lose momentum and not fully cycle. So we recommend for 5″ 556 barrels, that you use our low power spring option for greater reliability!

Weight 16 oz
Dimensions 9 × 7 × 1 in

H1 (For 16" Barrels), H2 (for 10.5" – 16" Barrels), H3 (For 7.5" – 10.5" Barrels), H3 Low Power Spring (For 5" Barrels)