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Discussion Starter · #1 ·

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Re: Gap between upper & lower, normal?

All I get is a white square with a red X in it.

I don't have a red X anywhere on any of my XCRs.
 

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Discussion Starter · #3 ·
Re: Gap between upper & lower, normal?

Funny Bravo! I just changed the pics to links.

Also, just found a "in lb" torque wrench at work! Guess I'll borrow it overnight to confirm bolt is correct.
 

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Re: Gap between upper & lower, normal?

Gap looks normal to me.

Slight movement bewteen the upper and lower (just like the AR) is normal. Has absolutely NO affect on accuracy.

Barrel retaining bolt is supposed to be that way. It stops against the barrel extension - if it stopped against the bottom of the lower, it wouldn't be pushing against the barrel extension all the way.

FWIW, I get rid of the barrel retaining bolt, and put a socket head screw in there instead. Fits flush with the bottom of the upper, so that there's nothing to abraid your left trigger finger (if you use the front-of-magwell hold).

And I'm BIG on using a torque wrench ;D
 

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Re: Gap between upper & lower, normal?

your rifle looks fine to me trio, some xcr's have a bit more gap than others but function shouldn't be affected.

bravo I wish you had your own digicam, some of your mods are interesting to everyone and I haven't seen what your setup is for quite a long time :)
 

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Discussion Starter · #6 ·
Re: Gap between upper & lower, normal?

Thanks for the replies. Good info about the bolt. A set screw would definitely look much better there; a trip to the hardware store is in order! ;D
 

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Re: Gap between upper & lower, normal?

Yeah, if I had a cam, it'd be easy for me to take a pic now -

One of 'em is disassembled for cleaning ;D
 

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Re: Gap between upper & lower, normal?

Completely normal on both counts. Hold down the receiver lock lever and you will notice that the upper/lower will fit together flush, and when you release the lock it will push the halves apart very slightly.
 

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Discussion Starter · #9 ·
Re: Gap between upper & lower, normal?

qyv, thanks for the response. Another related question...
If the observed "gap and looseness" is somewhat normal, how much gap or looseness would be considered abnormal?
 

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Re: Gap between upper & lower, normal?

I asked the question about the gap between the upper and lower a while back in this forum. My XCR has a little over a half a mm. The largest gap observed with the AR15's I own is half that of the XCR about .25mm. My XCR shoots fine and the gap seems to be a non-issue. You think though, with the cost of this weapon system the tolerances would be a little tighter. I also think that the offset angle the upper is in relation to the lower to allow clearance for the charging handle is a little "Mikey Mouse". Despite these observations I do like my rifle overall.
 

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Discussion Starter · #11 ·
Re: Gap between upper & lower, normal?

At the end of this video link, the person describes how the "take down button" needs to be flush with parting line. As in fully engaged to the lower receiver. So I presume that as long as this engages correctly, the rifle is safe to operate.

http://www.robarm.com/videos/Bolt_Carrier_&_Oprod_Install.wmv

This video was very helpful tonight since the items "fell out" when I opened the upper from the lower.
 

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Discussion Starter · #12 ·
Re: Gap between upper & lower, normal?

Took the XCR out to the range to align the Aimpoint Comp M4s at 25 yds. I wanted to align at 25yds first to get closer to POA/POI before going to the 50 & 100 yds.

Granted that it only has 15 shots through it; functioned perfectly, even on setting #2, using Remington 6.8 ammo.
 

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Discussion Starter · #13 ·
Re: Gap between upper & lower, normal?

FWIW, I get rid of the barrel retaining bolt, and put a socket head screw in there instead. Fits flush with the bottom of the upper, so that there's nothing to abraid your left trigger finger (if you use the front-of-magwell hold).
Bravo, Thanks for the suggestion. The gun looks better and there is room for gripping the magwell area now.

I used a 5/16-18 UNC X 5/8" long Cup Point Socket Set Screw. (Holo-Krome, MSC# 75561068) I ground the "lead thread" to be flush with the tip of the screw. I didn't want to chance rolling the thread once engaged to the barrel. I was worried of possibly dragging on the heli-coil insert when I would remove the screw later. You can see the "shine" on the tip of the screw. The grinding might not be needed, but I wanted the peace of mind. This would not be an issue if I were to purchase the proper "Flat Point Socket Set Screw (MCS# 67849166) at 3x the price.

The original bolt uses a 1/4" hex vs. 5/32" hex for the set screw. A word of warning... look at the "ball hex tip" pictured, the force of 200 in/lb was enough to round off the edges. I had to use a normal hex driver to tighten correctly. One might be tempted to use blue loctite. It is not needed if tightened correctly.

http://pasig.myphotoalbum.com/view_photo.php?set_albumName=album13&id=img_2603_001
 

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Re: Gap between upper & lower, normal?

Looks good.

I bought a bag of 100 that look extremely close to what you've got. That was the minimum order......

Sent a BUNCH of 'em out too. Seems I'm not the only guy that likes that mod (GRIN)
 

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Discussion Starter · #15 ·
Re: Gap between upper & lower, normal?

Yeah Bravo, look at what you started! A very practical mod. :thanks:
 

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Re: Gap between upper & lower, normal?

FWIW, I get rid of the barrel retaining bolt, and put a socket head screw in there instead. Fits flush with the bottom of the upper, so that there's nothing to abraid your left trigger finger (if you use the front-of-magwell hold).
Bravo, Thanks for the suggestion. The gun looks better and there is room for gripping the magwell area now.

I used a 5/16-18 UNC X 5/8" long Cup Point Socket Set Screw. (Holo-Krome, MSC# 75561068) I ground the "lead thread" to be flush with the tip of the screw. I didn't want to chance rolling the thread once engaged to the barrel. I was worried of possibly dragging on the heli-coil insert when I would remove the screw later. You can see the "shine" on the tip of the screw. The grinding might not be needed, but I wanted the peace of mind. This would not be an issue if I were to purchase the proper "Flat Point Socket Set Screw (MCS# 67849166) at 3x the price.

The original bolt uses a 1/4" hex vs. 5/32" hex for the set screw. A word of warning... look at the "ball hex tip" pictured, the force of 200 in/lb was enough to round off the edges. I had to use a normal hex driver to tighten correctly. One might be tempted to use blue loctite. It is not needed if tightened correctly.

http://pasig.myphotoalbum.com/view_photo.php?set_albumName=album13&id=img_2603_001
Hey TRIO,
Would you happen to have a few of those Headless barrel bolts your not using?
If you have any extra I'll love to buy them from ya.
thanks
 

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Re: Gap between upper & lower, normal?

where do you get those flush barrel bolts at? Do they use the same alan wrench? That is a GREAT idea whoever thought of it. Also, where do you get locktite at? I looked at walmart and couldn't find any.
 

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Re: Gap between upper & lower, normal?

where do you get those flush barrel bolts at? Do they use the same alan wrench? That is a GREAT idea whoever thought of it. Also, where do you get locktite at? I looked at walmart and couldn't find any.
You may be able to get them at a Lowe's or a Home Depot,or possibly even your local hardware store.Just use the thread pitch mentioned and take your barrel screw with you to make sure the tip is the same,as mentioned by others,you may have to take a file and just knock the tip off of the new screw.You can get loc-tite at any hardware store and Wal-mart sometimes has it,but whatever you do,get the blue kind which means it's removable,and don't use it on the barrel screw! It's meant to be removable for a reason,and it can mess up the threads on the helicoil the barrel screw goes in.The proper torque setting for the barrel is 200 inch pounds,please do not confuse that with foot pounds or you WILL STRIP IT! A T-handle Allen wrench is good to use if you don't have the proper inch pounds screw driver.200 inch pounds sounds like alot,but it's really not gutwrenching tight,just get it snug then maybe another half turn.
 

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Re: Gap between upper & lower, normal?

thanks, get the blue kind, and you said DON'T use it on the barrel bolt? I could have sworn it had the red kind on there when I first got it. I will take your word for it though
 
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