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My friends SI Defense build.


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SI Defense .308 matched set.

SI Defense BCG Nickel Boron (will ship in 4-6 weeks)

Criterion SS 18" from Fulton

JP EZ trigger

JP adj. gas block

JP comp

Magul MIAD, PRS (going to have to loan him one of my LR-20's)

I don't remember the FF hand guard name now.....



Edited by NoFail
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Yup..... I'd post the titties too but that would be pushing it on this forum.

But so anyway I've been texting with my bud and he said the upper and lower don't fit well with the take down pins inserted. I told him must be wrong kind of pins. He said there is 1/8" gap between halves with pins inserted. He said the pins feel sloppy in the upper holes.

???? Robo?

Edit: please don't misconstrue that last paragraph as having anything to do with said avatar..... I realize it could be misinterpreted, maybe. :)

Edited by NoFail
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1/8" is a hell of a lot. Is there wobble between the upper and lower, or just a solid gap?

Sounds to me like the pivot pin hole is out of spec on either the upper or the lower.

If your buddy can send pictures, they always speak louder than words.

Did he get the new gen4? Or is this an older model?

I forget who makes it, I think JP or KNS, but there's a tensioning type pin that can be used to tighten that part up.

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Is this the guy that bought the CMMG LPK? If so, I take back everything I said before... I hate pointing out the obvious to those who say they built a gun with CMMG parts and now they are having issues. They get all pissed off when I point out the problem was THEY USED CMMG PARTS!!!

Don't get me wrong. CMMG can be a decent product if purchased by 98Z5V, SurvivalShop, Jgun, MikeH, PlaneFlyer.... Or any of the other guys here who can actually build (not assemble) a gun. Not all parts get the 'Lego Certification' seal of approval, and they may require some modification to work properly. In my short experience i have come to believe that CMMG has the QC of a Pakistani sweat shop. I think all their products should say "some fitting my be required".

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Thanks for all of your responses guys!! It is SI Defense, not CMMG. In any case I'll be able to have a good look at it tonight. I'll take measurements and pictures to post here at that time, but with iPhone 4.

Hard to believe SI made a mistake. This particular set was made a few during si's most recent run of their .308/multi-cal receivers within last few months. Jason has also ordered the SI Nickel Boron BCG which i guess will be ready in a month or two. But I hope it is just somehow the wrong pins, still I think Jason would have gotten the correct ones.

I had inspected this set maybe 3 or so weeks ago when it was dropped off here and I did not notice anything wierd about them, didn't notice any alignment issue with the coupling holes, or whatever we call them.

Oh well we will see tonight...... Thanks again you guys!!!!

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Yeah, I know, he said he got pins from some whatever source. I'll do the pics tonight so stay tuned.

He said the pins feel sloppy in the upper's holes. The 1/8" gap he said is estimate, it could be less than that, idk. I still can't see SI screwing up though. That would be a huge screw up, I think. If it was SID issue then would they have not run off a poop load of them at the same time with this problem? I don't know the processes, but I'd think the whole lot would be controlled and come out the same for each unit, and the problem would be caught at some point in the process. Idk...

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Ain't no nuttin wrong whit it!!! Pretty normal how it is me thinks.

He did have one of those shim thingy's in the rear of the lower behind rear pin placement.

I didn't like the job it was doing so I did what I did for mine. Some dense foam rubber with adhesive bottom. I trimmed it up until it made a snug fit between the halves. No real movement now of upper sliding backward on lower. There is wobble laterally. I think it's called lateral? But it's not too bad anymore.

I think maybe my JD Machine .308 set is just a little little bit better but this SI is good too.

He has the VLTOR BCM Gunfighter charge handle with mod 3 latch just like mine but its different.

Seems they have improved the design at least in the looks department. Damn it looks way better now, I'm jealous and want it...

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I have a matched set coming for a friend soon. I'll see how it comes out...

... And I'll at least remember to post pictures!!

Yeah Yeah Yeah.. I didnt forget, just had to wait for wife to get off of this thing... :mellow:


But here they are now. I'm sorry, Robo, I knew you would be waiting!!


Well, I don't like that there is such a gap between them. I compared with mine, a JD Machine and there is a tighter looking fit with it, but the side to side wobble is about the same. Upper moving along the front to back axis on lower is the same, which is nill with the foam rubber wedges I have in the both of them.






Edited by NoFail
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