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Posted: 3/12/2017 8:31:36 PM EDT
| So I finally got my RR SP1 out of jail and it runs just fine with a small hole upper with the adapter pin. The problem occurs when I put a Colt large hole upper on, it will only fire one shot then I get a light primer strike. Any ideas as to what the problem maybe? |
| It sounds like the timing is too far advanced with that particular upper. You may need to shave a little bit off of the bolt carrier that is being used with that particular upper. What is happening is the carrier is tripping the auto sear before the bolt is fully closed resulting in a light primer strike. |
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Or, your timing is late, resulting in the carrier bounce impeding the free fall of your hammer.
1) Always alter/change the cheapest part first 2) Carrier bounce benefits from a heavier buffer So, my advice is to try a heavier buffer, first, before trying to change timing by altering the carrier. ETA this is presuming that the big-hole upper has had a sear relief cut added - standard SP1 big hole uppers lacked the required cutout for use with an RR. |
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[b]Quoted:[/b
ETA this is presuming that the big-hole upper has had a sear relief cut added - standard SP1 big hole uppers lacked the required cutout for use with an RR. I'm betting it's this. Don't try to run it like this, or you'll damage either the auto sear if you're lucky, or the receiver if you're unlucky. |
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Along those lines does anyone produce large pin uppers these day? Daniel Defense had in the past but I don't see them listed on their site.
ETA; If your upper has the correct sear relief make sure the front hole is not elongated or enlarged from use. I had one that was worn and the upper actually moved around enough to cause function problems, DD replaced it under warranty and it solved the problem. |
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1) try different uppers
2) try different BCG 3) Heavier Buffer or heavier spring (I use the Tubb's flat wire spring with a H1 buffer and have had good luck) 4) If you have a M16 jig check the alignment/location of all the pin holes to see if anything is off 5) If that all fails sent it t a competent gunsmith (M60Joe is a favorite around here) and have him look it over to determine the problem. |
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Quoted:
It sounds like the timing is too far advanced with that particular upper. You may need to shave a little bit off of the bolt carrier that is being used with that particular upper. What is happening is the carrier is tripping the auto sear before the bolt is fully closed resulting in a light primer strike. Please do everyone a favor and never offer advice again. Fortunately the usual gaggle of knowledgeable folks chimed in, before the OP dremel-destroyed his carrier. |
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