AR Sponsor
Posted: 6/10/2025 11:26:42 PM EDT
|
I am having issues with hammer follow a couple of times in a mag. My setup: RRA 10" barrel in a QC10 9mm upper QC10 Colt-mag lower RRA bolt, weight replaced with a KAK Tungsten weight (i.e. clearanced for proper activation of the trip) KAK extended 10oz buffer (I also tried the 8oz version of the same buffer) Carbine buffer spring The fire control group is all "milspec" AR15 parts with a AZR15-M2. The system seems to dry function as it should, and it is really close to wanting to run 100% reliably. The KAK 10oz buffer weight does NOT rattle - I have ordered a Kaw Valley unit that JD recommends. Anybody have any other suggestions? |
|
Quoted: I am having issues with hammer follow a couple of times in a mag. My setup: RRA 10" barrel in a QC10 9mm upper QC10 Colt-mag lower RRA bolt, weight replaced with a KAK Tungsten weight (i.e. clearanced for proper activation of the trip) KAK extended 10oz buffer (I also tried the 8oz version of the same buffer) CAR buffer spring The fire control group is all "milspec" AR15 parts with a AZR15-M2. The system seems to dry function as it should, and it is really close to wanting to run 100% reliably. The KAK 10oz buffer weight does NOT rattle - I have ordered a Kaw Valley unit that JD recommends. Anybody have any other suggestions? I'm gonna guess you want the sliding weights no matter what as that helps bolt bounce the best in my experience with other systems. |
|
Quoted: I am having issues with hammer follow a couple of times in a mag. My setup: RRA 10" barrel in a QC10 9mm upper QC10 Colt-mag lower RRA bolt, weight replaced with a KAK Tungsten weight (i.e. clearanced for proper activation of the trip) KAK extended 10oz buffer (I also tried the 8oz version of the same buffer) CAR buffer spring The fire control group is all "milspec" AR15 parts with a AZR15-M2. The system seems to dry function as it should, and it is really close to wanting to run 100% reliably. The KAK 10oz buffer weight does NOT rattle - I have ordered a Kaw Valley unit that JD recommends. Anybody have any other suggestions? It’d be the weights not rattling that would cause that Here’s the one I used in videos Weights rattle in mine which give the needed dead low effect  |
|
For full auto shooting (hence, bolt bounce was eliminated) direct blowback 9mm in an M16, I've successfully used seven different hydraulic buffers and five different "conventional" buffers. For the buffers that I tested, hydraulic buffers provided the lowest ROF and smoothest, most gentle feel; and the B&T AR9 buffer provides the lowest ROF and best feel of all. For conventional buffers, tungsten powder filled buffers produced what was in my opinion, the smoothest feel. I'm not affiliated in any way with any manufacturer or supplier. MHO, YMMV, etc. |
|
Well, I tried the setup recommended by JD - Kaw Valley 10oz buffer and XP buffer spring - but I still had the same dead trigger issue. I looked at other possible differences and noted that JD used an A2 stock with rifle-length buffer tube with a spacer of undisclosed dimensions, whereas I have the shorter carbine buffer tube. Cycling the action slowly while applying rearward trigger pressure, I noted that the trigger was not FULLY resetting. While the trigger was forced forward when the bolt was pulled fully rearward, as the bolt started to move forwards again the trigger was able to move rearward and the hammer followed the bolt forwards. It appeared that the lower cam leg was not camming over center and locking the trigger forward as it should. Looking closely at my setup, I noticed that the longer 10oz buffer was not allowing the bolt to cycle back far enough to fully depress the AZR15 upper arm. As shown in the photo below, the upper arm of the AZR15 was only reaching the ramped area of the bolt (yellow) and not the flat area (green):  To investigate this hypothesis, I replaced the longer 10 oz buffer with a carbine-length H3 buffer. Manual cycling confirmed that the shorter buffer allowed the AZR15 upper arm to reach the flat section of the bolt and thus be fully actuated, causing the lower cam leg to properly lock the trigger in the forward position until the bolt was fully closed. Test firing with this new configuration was still not 100% - I had one dead trigger event in a magazine load. Replacing the Kaw Valley XP buffer spring with a regular carbine buffer spring seemed to cure this issue, though I'd like to get more ammo through the gun to confirm. While the total reciprocating mass of this setup is in the "safe range" (22.5oz) for a blowback 9mm, the rate of fire is a little faster than I'd like. I'm going to experiment with an A5-length buffer tube and the 10oz buffer to see if the gun shoots better and remains reliable. I may also revisit the KAK buffers as they offer some intermediate weight options. I will report back when I get more data, but I wanted to let folks know what I learned in case others are struggling with similar issues. |
|
Quoted: Well, I tried the setup recommended by JD - Kaw Valley 10oz buffer and XP buffer spring - but I still had the same dead trigger issue. I looked at other possible differences and noted that JD used an A2 stock with rifle-length buffer tube with a spacer of undisclosed dimensions, whereas I have the shorter CAR buffer tube. Cycling the action slowly while applying rearward trigger pressure, I noted that the trigger was not FULLY resetting. While the trigger was forced forward when the bolt was pulled fully rearward, as the bolt started to move forwards again the trigger was able to move rearward and the hammer followed the bolt forwards. It appeared that the lower cam leg was not camming over center and locking the trigger forward as it should. Looking closely at my setup, I noticed that the longer 10oz buffer was not allowing the bolt to cycle back far enough to fully depress the AZR15 upper arm. As shown in the photo below, the upper arm of the AZR15 was only reaching the ramped area of the bolt (yellow) and not the flat area (green): https://i.imgur.com/SfhXhBQ.jpeg To investigate this hypothesis, I replaced the longer 10 oz buffer with a CAR-length H3 buffer. Manual cycling confirmed that the shorter buffer allowed the AZR15 upper arm to reach the flat section of the bolt and thus be fully actuated, causing the lower cam leg to properly lock the trigger in the forward position until the bolt was fully closed. Test firing with this new configuration was still not 100% - I had one dead trigger event in a magazine load. Replacing the Kaw Valley XP buffer spring with a regular CAR buffer spring seemed to cure this issue, though I'd like to get more ammo through the gun to confirm. While the total reciprocating mass of this setup is in the "safe range" (22.5oz) for a blowback 9mm, the rate of fire is a little faster than I'd like. I'm going to experiment with an A5-length buffer tube and the 10oz buffer to see if the gun shoots better and remains reliable. I may also revisit the KAK buffers as they offer some intermediate weight options. I will report back when I get more data, but I wanted to let folks know what I learned in case others are struggling with similar issues. yep thats what made me list the short barrel 9mm info in the TM Man had a short pistol upper and had to swap to standard carbine spring the light strike, when was that round second round middle of mag random in mag last round also check out the 9mm section of the TM talks about short barrel 9mm pistols AZR-15 9mm Tech: For General Tech details see 5.56 Tech AZR-15 9mm Configuration specifics are covered below. This is how we did it with what we had on hand. Every 9mm blow back setup is different. Upper brand should not make any difference as long as its machined to Colt Mil-Spec upper specs which the majority of AR uppers are to Colt specs. Another brand bolt or buffer/spring should not matter as long as the bolt has the same or very similar bottom profile as a normal 5.56 FA BCG and the buffer is heavy enough to eliminate bolt bounce. How we made the ARIZONA REGULATOR AZR-15 run with 9mm: We used the same standard 5.56 A2 rifle lower that we had been using for the 5.56 development. Pulled the 5.56 Colt upper, buffer, and buffer spring. Pinned on a 16" Colt 9mm upper with a Foxtrot Mike Colt style mag BCG part # FMC-9BCG. Dropped in a Kaw Valley Precision 10 oz tungsten carbine buffer part # KVP-10oz and Kaw Valley Precision XP carbine buffer spring part # KVP-PCC-XP- Spring. Installed the proper length spacer configuration to take up the extra space in the rifle buffer tube to accommodate the shorter carbine buffer and get the bolt catch to work properly without having excess rearward travel when the bolt locks to the rear when the mag is empty. Ran a Mean Arms Endomag 9mm mag conversion kit with built in ejector in a PMAG 30 marked AR/M4 GEN M3 part # MAG557-MCT. Shot Federal 115g brass case bulk ammo. AZR-15 Short barrel 9mm Pistol Upper Note: When running a short barrel 7.5 inches with a suppressor we had to go to a standard weight carbine buffer spring. 7.5" Yankee Hill Machine 9mm Upper Foxtrot Mike Colt Mags 9mm BCG Kaw Valley Precision 10 oz tungsten carbine buffer Standard carbine buffer tube Standard carbine buffer spring Bowers CAC9 Suppressor AZR-15 9mm BCG Note: Ensure whichever std FA compatible BCG you use does not have an additional pinned in weight in the tail of it that extends forward past the trip release surface. Notably the Colt pinned in weight does exceed forward of the trip surface. When the pinned in weight exceeds forward it interferes with the upper cam and the receiver will not close. You can either mark the weight, unpin it, and relive a bit of material so it clears the upper cam. Or use the Foxtrot Mike BCG that has a pinned weight that does not exceed forward of the trip surface. BCG buffer info BCG / Buffer: Buffer weight does factor in during rapid fire. We use a 5+ oz buffer with 5.56. We have found that in 20” A1 / A2 guns with a regular rifle buffer there are zero issues. Everything runs perfect. Once we went to another AR in true carbine config with carbine buffer tube, shortened up the barrel length, and or threw on a suppressor we had to go to an H3 buffer that weighed in at 5+ oz to eliminate bolt bounce. It has nothing to do with slowing the bolt down and everything to do with mitigating bolt bounce. How do we know this. Simple. With a lighter H2 carbine buffer in the suppressed 12.5 SBR Carbine we ran into a last round light strike situation. Did not matter if we ran 5rds 10rds 20rds 30rds. The mag would run perfectly then last round would light strike. This was due to there being no drag on the bottom of the BCG from the empty mag after it chambered the last round. That slight bit of drag from a round in the mag pressing up against the bottom of the BCG was enough upward force and drag to counteract the last bit of bolt bounce while using a lighter H2 carbine buffer. Ran perfect thru the mag then light strike last round every time with the lighter H2 carbine buffer. Swapped to an H3 carbine buffer that weighed in at 5+ oz and never had any problems after that regardless of barrel length or adding a suppressor on that AR Carbine. Thus for the reasons above is why we require a 5+ oz buffer. Bottom line is if you are getting light strikes it is due to bolt bounce. Increase the buffer weight till the bolt bounce goes away. |
|
Quoted: ... the light strike, when was that round second round middle of mag random in mag last round ... Dead trigger with the 10 oz buffer was the second round (i.e. the first chambered round fired, then I had a dead trigger on the second round). As I expected this due to the aforementioned timing issue, I didn't waste any more ammo testing that configuration further. Dead trigger with the 5.4 oz H3 buffer and XP spring was random - maybe 20 rounds into the mag? Once was enough. The same 5.4 oz H3 buffer with carbine spring fired a full magazine without issues. There are just some things I don't love about this configuration - RoF seems fast and bolt travel is full-length (thus risking a broken BHO). I hope to get a couple of other configurations tested tomorrow... watch this space 
|
|
Quoted: Dead trigger with the 10 oz buffer was the second round (i.e. the first chambered round fired, then I had a dead trigger on the second round). As I expected this due to the aforementioned timing issue, I didn't waste any more ammo testing that configuration further. Dead trigger with the 5.4 oz H3 buffer and XP spring was random - maybe 20 rounds into the mag? Once was enough. The same 5.4 oz H3 buffer with CAR spring fired a full magazine without issues. There are just some things I don't love about this configuration - RoF seems fast and bolt travel is full-length (thus risking a broken BHO). I hope to get a couple of other configurations tested tomorrow... watch this space Re-read above We do not have a timing issue You have a configuration issue man You are going to have to get the buffer tube issue corrected We run the 10oz with weights that rattle Dawned on me looks like your buffer tube is short which is why the carrier doesnt come back to spec location allowing the 10oz buffer to do its job and everything to work as normal We dont mess with normal H3 buffers in 9mm as there is a safety risk due to some 9mm carriers are only 13.4 ish oz which 13.4 plus 5.4 equals 18.8 oz which is under weight for 9mm reciprocating mass |
|
Quoted: Re-read above We do not have a timing issue You have a configuration issue man You are going to have to get the buffer tube issue corrected We run the 10oz with weights that rattle Dawned on me looks like your buffer tube is short which is why the carrier doesnt come back to spec location allowing the 10oz buffer to do its job and everything to work as normal We dont mess with normal H3 buffers in 9mm as there is a safety risk due to some 9mm carriers are only 13.4 ish oz which 13.4 plus 5.4 equals 18.8 oz which is under weight for 9mm reciprocating mass Just confirmed buffer tube statement above Pulled out my factory built DD MK18 pistol Pulled the factory DD 5.56 upper and buffer Left same factory buffer spring in gun Pinned on Colt A1 upper with 9mm Colt carrier and 10" bbl ( cool side note its a grey Colt A1 upper ) Put Kaw Valley 10oz buffer in Pulled charging handle to rear and locked carrier Carrier locks to rear just behind the bolt stop as it should, no excess travel Function checks no prob Buffer tube man Buffer tube |
OK, I got out to the range yesterday with a bunch of parts and think I have my blowback 9mm PCC figured out. The configuration that seems to be working best is as follows:
Overall weight of the bolt + buffer is 22.6oz which is firmly in the "safe" range, and brass comes out undamaged. I went with the weaker buffer spring to hopefully slow down the rate of fire and reduce bolt bounce - once I have established reliability with this configuration, I will try a brand new spring and confirm that it still works. It looks like I will have to live with the longer bolt travel. I managed to fire 4 magazines full of Maxx Tech 124gr FMJ factory ammo yesterday, both bursts and mag dumps. Rate of fire was measured at 721rpm, which is workable for my application (submachine gun competition). I will continue to test this configuration with different ammo and see how it holds up. In the meantime, I hope this information is helpful to others. |
|
When I tried my AZR in a Colt pattern gun, it wouldn't fit in the upper receiver oval pocket. It's a bummer to have an out of spec upper. I'm going to try installing a 3 position FRT 15 L3 and get it to run. If that doesn't work, I'll go back to trying to set up a 9mm upper that's in spec. |
|
Quoted: Got 1 upper that it won't sit down in the pocket and my 458 I forgot was a Billet upper and it will not sit in it either  Fortunately, forged MilSpec upper receivers have never been cheaper. Bonus: The now-unwanted upper receivers can be the start of your next build 
|
|
Originally was not going to use my AZR in my 9mm AR but Iv'e decided to give it a go. Current setup... My bolt carrier weighs 12.3 oz. bare 13.8 oz. with the weight pinned in. I have a 7.5 oz. solid buffer for 21.3 oz. total. If leave out the pinned weight(I'll have to notch it to clear for the trip leg if I use it anyway) and get the KVP 10 oz. buffer JD shows above I'll be at 22.3 oz. Should be GTG? I'll be using this suppressed as well would I be better off going with Slash's 12 oz. buffer for more mass? |
|
Quoted: Originally was not going to use my AZR in my 9mm AR but Iv'e decided to give it a go. Current setup... My bolt carrier weighs 12.3 oz. bare 13.8 oz. with the weight pinned in. I have a 7.5 oz. solid buffer for 21.3 oz. total. If leave out the pinned weight(I'll have to notch it to clear for the trip leg if I use it anyway) and get the KVP 10 oz. buffer JD shows above I'll be at 22.3 oz. Should be GTG? I'll be using this suppressed as well would I be better off going with Slash's 12 oz. buffer for more mass? Should work with A5 or Rifle buffer tube + spacer. In my experience it won’t work with a carbine buffer tube as the bolt stroke will be too short to properly reset the trigger. |
|
Quoted: OK, I got out to the range yesterday with a bunch of parts and think I have my blowback 9mm PCC figured out. The configuration that seems to be working best is as follows:
Overall weight of the bolt + buffer is 22.6oz which is firmly in the "safe" range, and brass comes out undamaged. I went with the weaker buffer spring to hopefully slow down the rate of fire and reduce bolt bounce - once I have established reliability with this configuration, I will try a brand new spring and confirm that it still works. It looks like I will have to live with the longer bolt travel. I managed to fire 4 magazines full of Maxx Tech 124gr FMJ factory ammo yesterday, both bursts and mag dumps. Rate of fire was measured at 721rpm, which is workable for my application (submachine gun competition). I will continue to test this configuration with different ammo and see how it holds up. In the meantime, I hope this information is helpful to others. nice 9mm rof man |
| Got my 10oz. KAK buffer yesterday and took my 9mm 5.5" AR out today and the AZR worked like a charm. Only issue I have is the 10oz. Buffer is .02 longer than the old solid 7.5oz I was using. Just enough that the bolt can't move far enough back so BHO doesn't engage. I'm using a Stern Defense magwell adapter. |
AR Sponsor