YankeeBluejeans from United States, MN Public Profile

The others may look nicer but this one fits tighter overall and doesn't feel cheap like the SBA5.

Bought this based off of the good professional reviews. IME the 11.5" is the perfect combination of compact and smooth shooting.

Fit and finish is first class, inside and out. Using a bore scope, the chamber and bore was smooth and uniform. Checks out with what I had been hearing. The gas port was drilled right into the center of the rifling groove which is ideal. The single dimple lined up the gas block and tube perfectly. This aided in perfect carrier key alignment (I used a BCM block and SOLGW tube; both are excellent). Crown and chamber was perfect.

Physically, the balance of this Core SBR contour is distinct and I'm sure it will help with handling. I used a BCM4 thermal fit upper receiver and the Criterion barrel extension allowed for a very tight install (using a torch and heat gun). The feed ramps lined up perfectly with the upper's M4 cuts. Dry fitting a BCG was butter. Lock up was super smooth. Muzzle device went on with very little wiggle on the threads. Nice. No issues encountered.

Everything related to the barrel for inspection and install was perfect. I was particularly impressed with the gas system alignment. Often the carrier key will rub a little on the tube so to get it perfect requires a little bending. Not with this barrel. IMO, that's what a $300 should give you but I've had $450 barrels having slight issues so maybe this was a lucky build. Overall, I'm very happy with the value so far. Now, off to the range to verify that legendary Criterion accuracy!

I own three MI Combat rails (the originals) and I can safely say that this HD version seems more combat grade than any of those. Don't get me wrong. I really like the original rail and would buy it again. They are lighter, sleeker, and cost less. They've held up well to training and if added weight is a concern, these work fine.

Here's the deal. The rail walls on the HD are thick and you can feel the heft immediately along with the double long steel barrel nut and steel QD cups. This thing is a beast.

To my eye, the inner area is the same diameter but the outside is girthier (hence thicker walls). I have big hands so this is fine. The new machining just after the barrel nut is interesting. Taking out Mlok slots wasn't on my wish list but the way I configure my rail, it's actually okay.

Overall happy with the purchase!

Nice tight fit in all in-spec uppers and barrel extensions. This tool ensures gas port and front sight alignment. It also acts like a gauge in assembled guns.

I've been wrenching on ARs for over 30 years. This adds to what the Geissele Reaction Rod does by adding a sail that engages the upper receiver, keeping alignment during torque. The sail is removable but there is no reason to.

If you have a really tight barrel nut, use this and a clam shell together to keep from breaking the upper and/or the index pin. Lifesaver for gorillas!

Bolt tail bore too large and caused short stroking. JP Enhanced bolt tail = 0.250" and the bore was 0.264"

Weak, uneven gas key staking, too. Looks like it was done with a square punch. Shame since they went the extra mile with OACKS.

Finish was excellent, though, but felt a bit rough in the gas ring run. Bolt run, gas ring run, and gas key bore were in spec and gas efficient.

Besides the staking and out of spec tail bore, this would have made one amazing BCG.

I've been building and shooting ARs for 30 years. I can troubleshoot almost all issues and have the tools, gauges, and drawings to predict performance and make repairs. Sometimes a tolerance stack up can work to the builder's advantage but often it will ruin a build if too large.

The design and appearance of the carrier body is top notch. The only visual issue I had was the gas key staking. It was uneven and looked like it was done with a square punch. It left sharp burrs that were not impressive. The OACKS screws are wonderful but only a proper staking can utilize their innovation. Star deduction.

With this carrier I used a brand-new JP Enterprises bolt, cam pin, firing pin, and fp retainer. All critical dimensions were well within spec. After assembly, I checked headspace and headed to the range. Note: The feel of the new carrier in relation to the new gas ring was surprisingly course but not unusual being brand new.

Upon firing I immediately ran into issues. Short stroking and misfeeds. I then used a lighter buffer (A5H0) and it helped but only with full power M193 5.56 NATO. I swapped out the Sprinco green spring with a polished rifle spring (used) and now it locked back on low power .223 Wolf ammo. The gas port on this barrel can cycle everything so upon closer examination I found that the bolt tail bore was oversized and leaking way too much gas. The JP bolt tail measured exactly .250" and showed almost no wear associated with a good seal. All other dimensions were i

Yep, quite pricey for what it is but if you have a MK2 scope mount and want to piggyback a RMR/507C red dot, this is your only choice.
Great quality part.
It does come with removable steel bosses/studs and this I don't understand. First, they sit pretty loose in the mount and the optic. Since the optic is fixed in place by the screws, perhaps this isn't a problem but I like tight fitting parts especially ones designed to index an aiming device. This is my only concern.

Buy the 407C and save some cash if you don't need more than a dot reticle. Everything else is the same.

I'm using this to cover a Holosun 407C on a LPVO piggyback rig. It fits nice and tight. Looks fantastic.
The front lens cover works great to eliminate glare. I am hoping that this cover provides added protection for bumps and dings.

This flip lever for Primary Arms GLx series scopes is functionally better than any other lever I've tried. When folded down it still allows easy zooming but in the up position it has incredible leverage. Truly effortless.

The only initial concern I had was long term durability but after a year it's been holding up well. I agree with another review that it is expensive for what it is, but given the OEM design there is no alternative as a bolt on solution. This won't slip or shift.