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Posted: 7/19/2015 1:01:37 AM EDT
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Is anyone out there running the Geissele Rapid Fire Trigger? I picked one up from Brownell's after a Geissele rep told me they would work with Glock cut bolts but when I got it out to the range to test today it wouldn't reset without manually charging after each round.
This is my first 9mm AR and I have read that the Heavy buffer made for the LWRC UCIW stock, the combo I'm currently running, may actually be too heavy. Could that cause this issue or is there anything I can do to resolve it? Or do I just need to go out and start looking for another trigger? If so, any recommendations? |
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The fact that the trigger will reset when you use the charging handle would lead me to think your buffer is too heavy. The bolt is traveling far enough to the rear to eject the spent round but not far enough to reset the hammer. As far as the glock cut is concerned it has nothing to do with resetting the hammer. All the modifications are towards the front of the bolt.
In the 9mm shop guns we run buffers around 6 to 7oz. Yesterday I did a 300 round torture test full auto mag dump on our new suppressor and used the Vltor A5 buffer tube and spring in a colt 9mm and did not have a problem. I was using the 6.5oz buffer. IM sent if you would like to discuss this further. |
| I was just coming here to ask why my 9mm AR pistol was not resetting the hammer. I have a Quarter Circle 10 Glock lower pistol. I am using an RRA heavy 9mm buffer. I put 50 rounds of Sellier and Bellot 115gr target ammo through it this afternoon and it would fail to reset the hammer about 25% of the time. When I changed to 124gr nato spec ammo it was about 10%. So I guess I will steal one of the 3oz buffers out of another AR to make sure that is the problem before I order another. |
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rounded hammer or notched hammer...?
OK I didn't read the whole post first..... 
Have had the problem with notched vs rounded hammers.....thought it was buffer weight as well......as it would manually reset 100% of the time when cycling manually with the charging handle.....tried several buffers...same issue.....changed hammer problem solved.....sounds like the hammer is just too short.....can you measure the height of the hammer above the deck of the lower in the fired position? |
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Quoted:
rounded hammer or notched hammer...? OK I didn't read the whole post first.....
Have had the problem with notched vs rounded hammers.....thought it was buffer weight as well......as it would manually reset 100% of the time when cycling manually with the charging handle.....tried several buffers...same issue.....changed hammer problem solved.....sounds like the hammer is just too short.....can you measure the height of the hammer above the deck of the lower in the fired position? I think it's a notched hammer. I'm not too familiar with the different hammers because I've honestly never really payed attention to them until you mentioned it so I might not have put it in the correct category. Hopefully I can sneak off to the range tonight to test the different buffer weight and get some measurements as well. |
Here's a picture of three different hammers to show the differences.
The hammer on the left is anM16 hammer. Semiauto hammers are available with essentially the same shape except with the hook at the back removed - these are called "rounded" or "DPMS" hammers. The middle hammer is "notched." Note the substantial notch at the top of the face. The hammer on the right is a "9mm hammer." It combines a light weight profile from a speed hammer with a shorter face. Supposedly this hammer is needed with 9mm AR bolts that are not ramped the way the standard AR carrier is ramped. Notice that the rounded part of the hammer face is "rounder" than the M16 hammer's face. As MadMachinist notes, notched hammers can cause issues. Since the area that is contacted by the carrier is smaller and shorter, the speed and energy of the carrier are more critical with these hammers. 9mm hammers also have these issues, but not as badly. To me, as long as your bolt is ramped, why not just use a standard, rounded hammer and not worry about all the compatibility issues? |
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Actually I'd say it falls into the notched carrier....if you have a caliper can you get a measurement form the centerline of the pin hole to the top of the hammer......the difference between a notched and rounded hammer doesn't look like much when side by side....but when it is in the position to catch the sear or disconnecter....the difference is huge
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Quoted:
Actually I'd say it falls into the notched carrier....if you have a caliper can you get a measurement form the centerline of the pin hole to the top of the hammer......the difference between a notched and rounded hammer doesn't look like much when side by side....but when it is in the position to catch the sear or disconnecter....the difference is huge Ah, I get it know. A little slow on the take but I can now see that it is notched. I didn't have the picture oriented the right way in my head but now that I do it's clearly notched. The measurement is roughly .81 inches. I used the plunger on the calipers to measure 
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After talking with Russ at QC10 we determined that it probably was a buffer weight issue not letting the bolt come far enough back to reset the trigger.
I finally got a chance to sneak off to the range yesterday and test it out with a lighter buffer... 
That's all I can say. Started off with 147gr pills out of the suppressed 4.5" QC10 barrel and it was nothing but smiles. I let the RO test it out and after that I got his blessing to do a 4 mag/122 round rapid fire dump to put it through its paces. The Geissele rapid fire trigger from Brownell's is absolutely amazing! It felt like I was running a bumpfire stock. I think I spent more time changing mags than I did dumping them. All I can say is that I now know why these PCC's are so addicting. I didn't get the LRBHO to function and the brass was ejecting pretty violently, shooting indoors and getting brass bouncing off the divider and smacking me in the face constantly, but the gun is functional. Now I need to work with buffer weight and spring tension to try and get it tuned properly. Thanks again for all the help and info from you all during the build and testing process. |
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Congratulations!
What buffer did you go with? It sounds like you went a little lighter than you might have needed. Yeah, they are sometimes that sensitive. It's really about matching the buffer to the rounds you're running - with 115gr Winchester White Box, you might need a lighter buffer than with 147gr rounds. It's quite doable, but your trigger just makes it a little more complicated. |
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I went with the stock buffer from the lwrc uciw stock kit. the heavy buffer from slash was too heavy, he makes a buffer that is inbetween the two so I will probably have to order that one to test out. Well that's a bummer. I was about to order the heavy buffer for my build this morning. I guess I should try the stock UCIW buffer before I spend the money. While doing a "functions check" I was not able to get the SD3G to pass in my build wih a QC10 Glock cut. It would reset fine though. The POF drop in trigger works great though. |
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Quoted:
Well that's a bummer. I was about to order the heavy buffer for my build this morning. I guess I should try the stock UCIW buffer before I spend the money. While doing a "functions check" I was not able to get the SD3G to pass in my build wih a QC10 Glock cut. It would reset fine though. The POF drop in trigger works great though. Quoted:
Quoted:
I went with the stock buffer from the lwrc uciw stock kit. the heavy buffer from slash was too heavy, he makes a buffer that is inbetween the two so I will probably have to order that one to test out. Well that's a bummer. I was about to order the heavy buffer for my build this morning. I guess I should try the stock UCIW buffer before I spend the money. While doing a "functions check" I was not able to get the SD3G to pass in my build wih a QC10 Glock cut. It would reset fine though. The POF drop in trigger works great though. I wouldn't rule out the heavy buffer completely, but from my experience and talk with Russ the middle weight buffer would probably be a better option than the extra heavy one that I got. |
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