AR help - please :)

cathouse01

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The key with the cam
cam pin was/is loose as a goose.

I tweaked as sschevy described. Closed much more nicely. I left it with a slight bit of tension, 1/16" just before closing for a 'little' snugness.
Every time I open and close the upper, the pin moves and changes the adjustment.
Even with the lock nut pegged, that pin wiggles like a pollywog.

This concerns me. Did he f-up my lower?

This explains why I couldn't even open the upper when trying to clear it at the range.

:(
I don’t think so, as I said in my previous post, I also have the old Colt A2 lower with the large forward pivot takedown pin. The biggest problem with using a new upper is that the hole is not just smaller but also offset from the center of the old larger hole. Which adapter are you using? There are at least two types out there that I tried and one worked better than the other.
 

daveyburt

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The key with the cam

I don’t think so, as I said in my previous post, I also have the old Colt A2 lower with the large forward pivot takedown pin. The biggest problem with using a new upper is that the hole is not just smaller but also offset from the center of the old larger hole. Which adapter are you using? There are at least two types out there that I tried and one worked better than the other.

I have no idea of what type he used...but, I'd advise him not to use it again.
:)
 

sschevy

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The key with the cam

I don’t think so, as I said in my previous post, I also have the old Colt A2 lower with the large forward pivot takedown pin. The biggest problem with using a new upper is that the hole is not just smaller but also offset from the center of the old larger hole. Which adapter are you using? There are at least two types out there that I tried and one worked better than the other.

one does work better , absolute fact

if the problem persists Daniel Defense makes a .315 front pin upper which makes the cam pin unnecessary
 

sschevy

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I have no idea of what type he used...but, I'd advise him not to use it again.
:)

I don’t know who it was , but in his defense decent parts are getting very hard to find these days and sometimes you don’t know you got sub par parts until it’s too late
 

fshalor

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So this is now an sbr on an a2 stock with rifle buffer? I'm assuming this is now a carbine or mid length gas system now. You need a
carbine buffer and spring

That's sort of what I was trying to check. If you mix up spring, buffer, stock tube length and gas system, you get funky dwell times, over gassing. Hangs. Locks, etc. Just measure everything and look and you will be fine.

A miss gassed system will fire a few shots, but it will quickly get ahead of itself and lock up or FTF.
 

sschevy

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That's sort of what I was trying to check. If you mix up spring, buffer, stock tube length and gas system, you get funky dwell times, over gassing. Hangs. Locks, etc. Just measure everything and look and you will be fine.

A miss gassed system will fire a few shots, but it will quickly get ahead of itself and lock up or FTF.
[/QUOTE]

A carbine buffer and spring in a A2 stock could be disastrous
 

sschevy

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OK, looks like you can’t get the pivot pin conversion from Brownells any more. You can still get them from Specialized Armament at Pivot Pin Assembly Conversion Kit . They are also the only place you can get replacement large Colt front pivot pins (for $75 a pop).

awesome!!! 👍

I’m going to clean them out right now before they’re gone forever 😂
 

cathouse01

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awesome!!! 👍

I’m going to clean them out right now before they’re gone forever 😂
And it looks like they are out of the original Colt two piece large pivot pin replacements, but they still have a .312 replacement pivot pin with a detent ball to keep it in place. I prefer the original Colt two piece screw together as a replacement, but beggars can’t be choosers;).
 
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In a perfect world you want MPI and HP stamped on both the bolt and barrel

I would add for others, I'm sure chevy knows this.

If you see MPI in the ad but there is an * or a number near it. Scroll down to the fine print. Some manufacturers advertise their products as being MPI. But when you read the fine print you'll see that they only batch test, say 1 in 100 or whatever ratio. So you actually have a very small chance of getting one that actually has been inspected.
 

daveyburt

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That's sort of what I was trying to check. If you mix up spring, buffer, stock tube length and gas system, you get funky dwell times, over gassing. Hangs. Locks, etc. Just measure everything and look and you will be fine.

A miss gassed system will fire a few shots, but it will quickly get ahead of itself and lock up or FTF.

Keeping all this in mind too...I just want to square up that pin as it's an obvious issue.

Does it go in front of your castle nut?

Front of forearm to bottom butt of the stock

awesome!!! 👍

I’m going to clean them out right now before they’re gone forever 😂


hey - hey - what about me?? I was about to go grab an extra seeing as they're unobtanium.
hahaha - i guess I'll get my spare from you then.
:)

much appreciated folks! - still trying to digest all your help but, you provided so many things to check. Thank you!!

We'll get that pivot screw squared up cuz that's nothing but a random variable at this point - then go from there.
-learned a bunch.
thanks!
 

jkelly1229

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Keeping all this in mind too...I just want to square up that pin as it's an obvious issue.



Front of forearm to bottom butt of the stock




hey - hey - what about me?? I was about to go grab an extra seeing as they're unobtanium.
hahaha - i guess I'll get my spare from you then.
:)

much appreciated folks! - still trying to digest all your help but, you provided so many things to check. Thank you!!

We'll get that pivot screw squared up cuz that's nothing but a random variable at this point - then go from there.
-learned a bunch.
thanks!
Then nah mine wasn't your issue
 

cathouse01

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If you guys order from Specialized Armament pay attention to the email confirmation they send you. You have to reply with your credit card’s CCV number cause they don’t ask you for it when you place the order (extra security they say).
 

LKE21

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Had this issue before - it’s most likely the charging handle itself. The front part that rides on the gas key needs to be an exact 90 degree angle. Slight variation will cause the type of binding you describe. Swap out the charging handle with something reputable and you’ll be good. Had this issue with more than one Anderson charging handle.
 

mac1911

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New upper installed by local reputable gunsmith.
First time to the range with it today.
Sighting it in. Put a couple on paper, and went to make safe to go check target.
Charging handle super hard to pull back....hmmm, maybe it'll break in.
Came back put two more on target. Charging handle even harder to pull back.
Hmmmm
Put one more on paper and cannot pull charging handle - totally locked.
Also wasn't able to pivot the upper open.

Let it cool down (not that it was that hot with 5 round thru it) while I sighted in something else. Was finally, barely, able to get the handle to pull back and remove the live round.

Packed it up and called it a (crap) range trip.

Now that I'm home I took a peek and see nothing of issue and the handle cycles normally.

A2 Sporter with new upper. Has cam pin for front pivot.
Any guesses?

thx!
maybe I,missed it but each time you racked the CH was there a live round in the chamber?
sounds more like your chamber has issues.
Now me personally if I gave a local smith the green light to build me a upper it better come with a detailed parts list.
hope you get it squared away today.
 

daveyburt

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^ - yes, chambered round

Yea, I was surprised he didn't detail the build. Things were a bit rushed (on both sides) when I picked it up but, will be asking him to do that when I chat with him.

@Sweeney - wanted to also thank you for the troubleshooting info you posted earlier - thx!
 

92G

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My head hurts after reading this thread. I have zero emotional Interest in your rifle but feel obligated to offer some thoughts in light of what bizarre ideas have been provided.

if the BCG is binding during hand cycling, there is clearly a major problem that will not resolve with lubrication nor live fire to “break it in”. minor details like chamfering on the bolt lugs is also irrelevant. issues at the bolt/barrel-extension do occur although binding should only be noted early in travel during unlocking, not once the bolt is completely free of the barrel extension and moving rearward. Occasionally a lug may shear and wreak havoc although I doubt is the case here. Similarly if there is an issue with gas tube alignment, the binding will be noted near the bolt closed position but the BCG will move freely rearward the rest of the travel.

It is extremely easy to examine your BCG and upper fit. Once you’ve confirmed that is functional, which I can essentially guarantee it is, then one can focus on your lower where the problem is likely to be found. if the BCG is binding during rearward movement, test the same movement by pushing the bolt rearward with an empty shell casing via ejection port. This will remove the charging handle from the analysis. As noted above, can also reassemble the rifle without a charging handle and move the bolt via ejection port. Any remaining binding here is due to BCG interacting with your receiver extension. Inspect the lower and receiver extension closely. It is likely something was incorrectly installed, out of spec, material in the extension tube or the extension is damaged. It is also possible if one is using two non-7075 lowers, usually billet Uppers/lowers that do not play nicely together.

this is a good opportunity to learn how to build your own uppers and not rely on a gunsmith, although I am not convinced any of these issues are related to the gunsmith’s work.
 
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mac1911

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^ - yes, chambered round

Yea, I was surprised he didn't detail the build. Things were a bit rushed (on both sides) when I picked it up but, will be asking him to do that when I chat with him.

@Sweeney - wanted to also thank you for the troubleshooting info you posted earlier - thx!
Ok so does the upper function check ok with out any ammo involved?
1. Upper split or tilted is there any felt binding?
2. Upper installed o to lower, does upper function check ok.
3. Install magazine does rifle function check ok
Now a safe place to live round function check
4 . One round in magazine , seat magazine and load round. Try to extract live round , function check ok?
Progressive checks and once you reach a fail or no to function check you can Isolate the problem.

you can also remove the bolt and insert a live round into the chamber with your finger, tip the upper muzzle high and the round should fall out if only a tiny little jiggle if not by its own weight.
 

daveyburt

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Thx folks for the continued responses - I'll keep it all in mind.

But, came to say that SSchevy spent some of his time on the rifle today. Very grateful! He's a great guy!

We found a couple things that may have been the cause.
#1 - cam pin
#2 - bolt lug wasn't playing nice

He worked on both of those things (and played with some others), and gave it a full check.

I'm hoping to get to the range soon to give it a test run.
-will report back.

Thanks @sschevy! ...and everyone else who spent time helping here.
-d
 
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