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Posted: 7/29/2015 8:07:09 PM EDT
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I recently received a complete 16" upper from a reputable company. Well I just got around to pairing it with a lower and immediatly noticed a problem that doesn't occure with any of my other ARs. When manipulating the bolt and locking it back with the bolt catch, with or without a magazine, I can give the weapon a soft bump and it releases the bolt home.
At first I thought it was either an out of spec bolt catch on the lower or an out of spec lower (this one is an Anderson). Then I mounted the new upper on three different lowers ( Spikes, Yankee Hill and a PSA) and they all had the same problem. Lock the bolt back, give it a bump and the bolt slams home. What's the deal? Is my bolt out of spec or am I missing something simple here? I have yet to contact the dealer about this problem. So what's the hive say???? EDIT: read my next reply for a better explanation of the problem. |
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Quoted:
what kind of bump? Like bumping the stock on the ground? yeah, that's normal. I know that bumbing stock to the ground will release the bolt. But that's not the case. I guess I should of explained it better in the first post. But I can bump the upper or lower on either the left or right side with my hand and it will release the bolt. And it doesn't take a whole lot of force to do so. On all three lowers. None of my other uppers do that. Yes, I'm making sure I'm not accidentally hitting the release. Also, the bolt doesn't always catch on the bolt catch on any of my lowers. Maybe 6-7 times out of 10 I can feel it beginning to catch then it slips off and slams home. Think my upper is out of spec causing everything to sit a few thousandths of an inch too high on the lower? |
| As far as I'm aware, the bolt is in right. Unless there is something I don't know about inserting a bcg into the upper or inserting the bolt into the bcg with ejector facing the ejection port. No sarcasm intended. I ask these things because I am far from a gunsmith and knowledge is power. |
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Is the bolt carrier assembly going back rearward enough so that the bolt lugs lock behind the bolt catch, or is the bolt catch trying to lock behind the bolt lugs on the bolt carrier face?
CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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Ditto with Sully,
Is the bolt catch in front of the face of the bolt to hold the bolt back, or is the catch only catching the bottom of carrier alone to hold the bolt back. If the bolt catch is only grabbing the bottom of the carrier, and not rising up to catch the entire B/C in front of the bolt, then time to send the upper back for a possable gas leak/blockage problem. Also to point out, you have scrubbed the chamber with a chamber brush and CLP before firing the upper to get all the storage grease and debries out of the chamber, Correct? And, not trying to run a brand new upper with steel case ammo? |
| Just woke up for work. I will check later to see where exactly the catch is trying to hold the bolt. And yes, I scrubbed the entire firearm to get shipping gunk off. Have not shot it yet as I havent had a day off for a while. No steel cases ammo will be shot from any of my firearms. |
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Quoted:
The "bottom" side of the bolt's cam pin hole is swaged at manufacture, and the cam pin cannot be installed if the bolt is turned 180 in the carrier.  Quoted:
Quoted:
is the bolt in the right way? might be 180 out. The "bottom" side of the bolt's cam pin hole is swaged at manufacture, and the cam pin cannot be installed if the bolt is turned 180 in the carrier. I learned something new! Well that's not the case as I cleaned the bolt and it was properly put back together. Going to check to see where the bolt catch attempts to hold the bolt when I get off work. I seem to think it's trying to catch on the carrier itself, which is causing it to slip off the catch. If so, I will attempt the test with different bolts and different buffer/spring combos. If all fails, I will contact the dealer about this. |
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pretty normal to bump drop without the magazine it should hang tighter with a magazine how does it hold after a magazine has been fired and it locks back on empty? can you drop the empty, reload and have it hold? Read my second reply in this thread. I can get the bolt to slam home with or without a magazine just by bumping either the upper or the lower with my hand. I can even bump the rail and it releases the bolt. I haven't shot this rifle yet due to a lack of free time. The bolt also doesnt always get held back with manual manipulation of the bolt catch. Hence why I'm going to check to see where the bolt catch is trying to hold the bolt, on the lugs or the carrier itself. I havent checked that yet. |
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Quoted: The "bottom" side of the bolt's cam pin hole is swaged at manufacture, and the cam pin cannot be installed if the bolt is turned 180 in the carrier. Quoted: Quoted: is the bolt in the right way? might be 180 out. The "bottom" side of the bolt's cam pin hole is swaged at manufacture, and the cam pin cannot be installed if the bolt is turned 180 in the carrier. |
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Quoted:
Ditto with Sully, Is the bolt catch in front of the face of the bolt to hold the bolt back, or is the catch only catching the bottom of carrier alone to hold the bolt back. If the bolt catch is only grabbing the bottom of the carrier, and not rising up to catch the entire B/C in front of the bolt, then time to send the upper back for a possable gas leak/blockage problem. Also to point out, you have scrubbed the chamber with a chamber brush and CLP before firing the upper to get all the storage grease and debries out of the chamber, Correct? And, not trying to run a brand new upper with steel case ammo? Just tested. The bolt travels back enough to catch on the lugs. Problem is with three different lowers and even three different bolts, the bolt catch is on the tip of the lugs. It then begins to slip off the bolt catch as soon as I let go of the charge handle. So do I have an out of spec upper? |
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Post a photo of the amount of bolt catch engagement but when it self locks back, and when you pull the charging handle back by hand with a empty mag.
You should have about this amount of engagement. 
Also, with the charging handle pulled all the way back, where does the bolt face stop in regards to the back of the ejection window edge/ how far back behind the catch as well (photo of the charging handle pulled all the way back, and a empty mag installed in the well). Also, since it sounds like you have extra B/C's, use another B/C in the question upper to weed out a problem with it just a leaking gas key or bad bolt on that uppers B/C the problem alone. |
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