Note: This is not a clone. The goal is a functional rifle that very closely resembles the original.

As indicated, I want to build a reliable rifle that is an image of the actual. I can't actually have a KAC, so I have been forced to build a Mock 11 instead. I am a newbie at this, and I realize now that this was not the rifle to start with... buuuut I'm committed now so screw it. Currently the build list is as follows:

Genesis CNC upper receiver (In hand)
LMT MWS 308 Lower
KAC FF RAS (In hand)
KAC BCG Match grade (In hand)
KAC double rail gas block (In hand)
KAC Ambi charging handle
Rifle length gas tube
Rainier Ultramatch 20" Mk 11 replica
Harris Bipod
KAC front and rear sights
A2 stock
A2 ergo grip
KAC Scope rings
Leupold Mk 4 or Vortex Viper PST II

I may not have gotten everything on the list here, but I have a couple of questions for the experts. I have done a lot of reading, but some questions have not been answered in my endeavors. Thank you in advance.

Cont.

1. BCG in Upper Receiver.
Now I have read this before, but the KAC BCG fits very loosely in this receiver. Granted, this receiver is still raw aluminum, no barrel is seated, and I am not running the BCG in with a charging handle. When the BCG is floating where it should at the end of the road, the tail end has a lot of slop left and right. On both sides I have about 1/8" of clearance, with about 1/16" of play in either direction. On the forward section of the BCG it seems to fit very nicely, with just enough play for me to feel confident that it will stay lubricated. The back end is where I worry. I don't want to strike the lower receiver.

2. Buffer and Spring.
In order for this to work, I need to use a CA compliant lower receiver. LMT is an option, and from what I have read it is a damn good one. Their complete MWS lower is a great option for me, because I have decided I am not ready to tinker with a lower on something that I have such high expectations for. What I will need to do however is swap the current stock for the A2 stock in order to get the look I want. Is there any reason that the buffer and spring currently in the MWS would not be suitable for their A2 stock? (i.e. length, weight, grade, etc.)

Again, thanks in advance guys and gals.

At least in the case of an AR15 (and I would assume even more exagerated in AR10) there will be some play or tilt of the bcg whithin the upper and it can and will affect accuracy (precision) as confirmed by Mr. Joe Carlos (via testing with top of the line mechanical rest) and can be measured with feeler gauges. Why? Simple..consistency; carrier tilt/play allows the bolt to approach at an angle not inline with the bore, allowing bullets to become nicked and deformed which will affect accuracy. See video linked below and I suggest watching all of Mr. Carlos's excellent videos.
https://m.youtube.com/watch?v=P2-BIENNPOg

There are a few things that can be done to mitigate tilt in a DI AR.

- drill, countersink and tap tail of carrier for button head screws to level carrier within receiver.

- run a "anti tilt" buffer tube with extended lip (like those offered by PWS).

- run a National Match type carrier that is built up at the forward position. Mr. Carlos has recorded up to an 8.8% reduction in group size as a result of switching to a Match type carrier alone.

- use a combination of the above or all three.

Can the same solution rectify a tilt to the left or right? It seems that vertically the BCG will be great as long as the head space turns out right. The issue I worry about is that BCG bouncing around willy nilly during cycles.

@Talon22  You may try posting this in the Knights Armament Industry thread.  There is a wealth of knowledge there.  You may also have someone who helped develop the Mk 11 answer your questions.

- The anti tilt pads or screws are installed at angles approximately 0430 and 0830 which will provide lift (up and down) as well as centering (left to right). Pics of bcg worked by Mr. Carlos can be seen in this old EE ad
https://www.ar15.com/forums/Equipment-Exchange/Complete-High-Power-National-Match-Service-Rifle-Bartlein-Gain-Twist-Geissele-Trigger-Etc-/165-1812077/

- A anti tilt buffer tube will provide lift (up and down) only.

- A match type carrier will help (within reason) with both lift (up and down) as well as centering (left to right).

Are these things required for a rifle to function? Absolutely not.

You can find out more about carrier tilt (talking strictly DI) and its affect on accuracy (precision) by watching Mr. Carlos's video I linked in my initial post.

Thank you. That answers my question. I am going to be running a KAC match carrier, and after some searching today I was able to find a thread here that was perfect regarding this topic. Link here.

For the most part, with the interchangeable parts between KAC & LMT, most configurations seem to be pretty forgiving. Some work better than others, but it looks like it mostly comes down to preference. LMT MWS w/ A2 Lower and Buffer look like they will do the job just fine!

I am building a m110 as close as I can I have the kac gas block, rail, and centurion upper /lower and lmt lower depending on looks when i get the rest I’m going for the rainier arms m11 m110 barrel they say built Specifically for the kac has block as I think it’s the same barrel you are using now if you know or when you do know I’m curious if the rail comes to the gas block or is there a gap between the two? I really hope your gun comes out good and would like to know how it goes. I almost bought the kac bcg but people saying they are proprietary scared me away they aren’t cheap. If you can find them! but the barrel and gas block have me worried the measurements are off I plan on putting the m110 suppressor on it and I would think this part is important to do so but I would appreciate it if when you mock it up let me know how the fitting is and good luck!

@Talon22

MK11 Mod 0 clone parts list