New Carbine Build, New Issues

[n517rv]

So I've been reading this forum for some time and absorbing as much knowledge as I can. Recently completed a new build that I felt would be rock solid, but so far things aren't going so well. This is my first carbine length gas system build, so I'm hoping someone can help me troubleshoot.

Here's the build (see pic below):

• McKay Enterprises Stripped Lower
• PSA LPK
• LMT 16" Carbine Upper w/ MOE
• BCM BCG
• BCM Gunfighter MOD4 CH
• Standard Carbine Buffer
• Using 20 and 30 Round Pmags

Not sure if it was necessary, but when I received the upper and BCG, I cleaned them well and lubricated the BCG with Slip 2000 EWL. The BCG originally had a rather heavy coat of grease on the firing pin, cam pin, and bolt.

After cleaning and function check I took her to the range - immediately had problems starting with the first round. The first round fired fine, but had a FTE caused by a broken case. IIRC, ammo was Winchester white box 5.56 NATO. After clearing the case out with a cleaning rod I had a failure to go into battery caused by a part from the broken case getting stuck ahead of the bolt. OK, I can deal with that... quick fix.

After that, things did get better, but I'm not convinced it's running well yet. I proceeded to shot various ammo including Wally World Federal 223, American Eagle 223, and Wolf 5.56. I did have a FTF, but for the most part it ran smooth.

Here are my questions:

1. Do I need to break this thing in? Should I shoot another 100-200 rounds before changing anything?
2. I have a standard carbine buffer in it, should I be running an H2 buffer?
3. Any other suggestions?

Thanks in advance for any and all assistance!

[n517rv]

Hmm... for some reason it won't let me post pictures. I'm not worthy...

[johnson]

Shoot it some more.

[lethal dose]

That optic is preventing the weapon from functioning properly...














...ok... just kidding. Honestly, I usually won't call a fighting weapon reliable until it can cycle 700 rounds without a malf. Just finished up a BCM/LMT build and had serious issues at first. Don't sweat it. Buy a REGULAR H buffer... not some tungsten kryptonite arctic hybrid garbage then grab another case (of ammo) and run it. Use that ewl liberally... my ARs drip with the stuff. Nice build. Let us in on a range report and how the psa lpk holds up. Also... ditch the optic then grab a good white light and a sling.

[polymorpheous]

Run a few hundred rounds of full power 5.56mm through it.
Most of the ammo you described using is underpowered.
I'm not aware of Wolf manufacturing 5.56mm ammo.

I'm also not aware of the gas port of an LMT upper.
If the upper is overgassed, the easiest, (and cheapest), thing to do would be to switch out to a heavier buffer.

[Belmont31R]

When you cycle the action by hand is it rough/gritty feeling or any areas of high resistance? Sometimes on a brand new gun things can be a little rough out of the box, and cycling by hand (as much as you can) or just shooting it will solve those types of issues.


Also if you pull the trigger on an empty chamber, and then pull the CH backwards does it feel gritty? When you do this do it slowly, and you'll feel the trigger being reset. Sometimes there can be excessive drag on the BCG from the trigger.


Just do a general look over of the gun and see if there are any parts yet that seem excessively worn for the amount of rounds you have through the gun. Make sure your your recoil spring is good and things like that.


The grease is a type of cosmoline which is a long term rust preventative so if the rifle sits on a box for a year the new owner doesn't find a rusted out POS awaiting him. Make sure all of that stuff is out of the gun including the chamber and bore. That stuff is very tacky and can really mess up an AR.

[n517rv]

That optic is preventing the weapon from functioning properly...

I'm surprised it took almost 7 hrs before someone made fun of my RDS...

I don't recall the exact origins of this buffer, but I'm guessing its a RRA I got from Brownell's. I'll look into a different one.

As for the gritty feel, it does have rougher feel that other broken in guns. I'll check out the BCG drag next.

Thanks for the suggestions on continuing to run it with 5.56 and yes, the Wolf was probably 223. Now back to the range...

[Iraqgunz]

If you are using an O-ring with your extractor assembly take it off and tell us what happens. Ditch the questionable buffer and get an H buffer.

In addition if the other ammunition worked then you should consider that you have a bad batch of ammo. It happens even with the best of them.

[n517rv]

No O-ring under the extractor. Don't know much about that o-ring on BCM BCG, but I think it's to help with extraction/ejection on SBRs? I assume it should not be installed on 16" carbine length gas system?

I went ahead and ordered a Colt H2 Buffer from Brownell's. For some reason, they don't carry a quality H Buffer... or at least I couldn't find one online.

[saddlerocker]

H2 should be ok assuming there are no other problems

Good news is you can make two H buffers from your Carbine and H2 buffer if you want.
Just remove the roll pin and set them up with 1 Tungsten and 2 steel weights

I would say you had one bad round, that caused an issue with another round/cycle.
The random FTF does seem odd.
If you can fire another 500+ rounds without issue I think your good