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Posted: 8/5/2017 1:52:18 PM EDT
[#1]
If everything is made to the correct specifications, a spacer is not required. Your receiver extension could be inlstalled incorrectly. Your receiver extension internal depth could be too long. Your buffer miggt be too short. The tip of the buffer could be way too soft.
I do think the extra mass of the extended pistol caliber buffers is better for blowback operation. |
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Posted: 8/5/2017 2:37:35 PM EDT
[#2]
Give us a parts List of what you are using, This will help diagnosing your problem.
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Posted: 8/5/2017 3:23:49 PM EDT
[#3]
Ok well here's the critical parts list
BA 5.5" barrel NFA standard 9mm bolt Hahn top drop in adapter BCM H2 buffer Standard spring BCM buffer tube CMT billet upper receiver BCM CH And I was shooting with a bowers vers9s suppressor. |
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Posted: 8/5/2017 3:27:57 PM EDT
[#4]
Take a look at the Vltor A5 buffer. 9mm weight option with a buffer body length that's equal to the carbine buffer body+spacer.
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Posted: 8/5/2017 4:16:19 PM EDT
[#5]
I should add that I prefer to not use a spacer or extended buffer because I am planning to use this setup on a transferable colt m16, and want to keep the ROF down. I'm extremely happy that this test run was only on a spikes sbr'd lower receiver and not the colt
I was planning to get a colt x buffer(7.9 oz, standard length) |
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Posted: 8/5/2017 5:02:08 PM EDT
[#6]
I think your Buffer is to light
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Posted: 8/5/2017 5:13:45 PM EDT
[#7]
^yea i was just looking into it some more.
When I push the bolt back into the buffer tube with the buffer and spring it stops a quarter inch before the receiver. I don't know how it made up that 1/4" when I was shooting, unless the lower weight allowed the bolt to travel backwards so hard that it was able to compress the rubber bumper on the buffer and gain that extra 1/4". The rubber bumper is pretty damn solid though. Could this be the issue? Would a heavier buffer be the answer, and I'd be fine with no spacer? |
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Posted: 8/5/2017 5:40:31 PM EDT
[#8]
I use a KAK 5.6oz Carbine length buffer and Carbine Spring, I have not noticed or seen any evidence that the bolt is traveling far enough into the buffer tube to make contact with the lower receiver, look at your buffer to see if there is any deforming of the buffer bumper. With a Blowback 9mm system, your bolt is moving pretty fast to the rear and may be squashing your buffer bumper enough to let the bolt make contact.
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Posted: 8/5/2017 6:00:45 PM EDT
[#9]
^That's what I'm thinking...
So I took a few pictures, I also noticed some new markings on my hammer....kind of odd, after only 150 rounds of 9mm.... 
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Posted: 8/5/2017 6:31:03 PM EDT
[#10]
I'll Post my personal opinion here, I use an NFA Buffer spacer even without LRBHO, mainly to limit bolt rearward travel and to keep crud and other stuff out of my Fire control group. The Spacer only takes less than a minute to install and the same to remove, they cost about $8 and solve a lot of problems before they start, your current set up runs the risk of damaging the lower and possibly shearing your gas key off.
My personal recommendation would be, get a 5.6oz Buffer and spacer with carbine spring, both of my 9mm Pistols, one a Colt mag lower and the other a Glock mag lower have over 500rds through them and not one problem has been encountered with the same set up. If you decide to switch lowers among other calibers, it only takes a few moments to remove the buffer system. I bought my KAK 5.6oz Buffer and New Frontier Armory Spacer from Joe Bob's for less than $35 shipped, a lot less than a Lower or Bolt. |
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Posted: 8/5/2017 6:46:33 PM EDT
[#11]
Is your receiver extension fully screwed into place? It is hard to tell from your pics., but it looks like it is a turn or two out from normal position. The bottom edge of the receiver extension should be almost touching the skinny part of the buffer retaining pin. Is the buffer retaining pin under the receiver extension at all?
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Posted: 8/5/2017 6:50:17 PM EDT
[#12]
Quote HistoryQuoted:
I'll Post my personal opinion here, I use an NFA Buffer spacer even without LRBHO, mainly to limit bolt rearward travel and to keep crud and other stuff out of my Fire control group. The Spacer only takes less than a minute to install and the same to remove, they cost about $8 and solve a lot of problems before they start, your current set up runs the risk of damaging the lower and possibly shearing your gas key off. My personal recommendation would be, get a 5.6oz Buffer and spacer with carbine spring, both of my 9mm Pistols, one a Colt mag lower and the other a Glock mag lower have over 500rds through them and not one problem has been encountered with the same set up. If you decide to switch lowers among other calibers, it only takes a few moments to remove the buffer system. I bought my KAK 5.6oz Buffer and New Frontier Armory Spacer from Joe Bob's for less than $35 shipped, a lot less than a Lower or Bolt. The h2 buffer I'm using weighs 4.6oz. I was planning to pick up the colt which weighs 7.9 oz. This upper will only be fired with a suppressor. |
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Posted: 8/5/2017 6:53:14 PM EDT
[#13]
Quote HistoryQuoted:
Is your receiver extension fully screwed into place? It is hard to tell from your pics., but it looks like it is a turn or two out from normal position. The bottom edge of the receiver extension should be almost touching the skinny part of the buffer retaining pin. Is the buffer retaining pin under the receiver extension at all? This lower has been sbr'd for a few years and has a few thousand rounds of 5.56 through it, with no issues. I drop this 9mm upper on it, and 150 rounds later it looks like hell... |
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Posted: 8/5/2017 7:07:55 PM EDT
[#14]
An H2 buffer is too light for a 9mm blowback.
Colt spec'ed a 5.5 ounce buffer weight for their 9mm SMG models. The H2 buffer only weighs 4.6 oz. I use an 8.5 ounce buffer in my 9mm's If you are not running a LRBHO block, there is no need for a spacer. |
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Posted: 8/5/2017 7:36:42 PM EDT
[#15]
Agreed.
Colt used the H3 buffer on their 9mm ARs and the H3 buffer weighed about 5.5 ounces - about the same as their .223 rifle buffer. The H2 buffer only weighs 4.6 oz. The H3 is as light as you ever want to go and the buffers on the RRA and PSA pistols and carbines are in the 5.5 to 5.6 oz range. However, depending on the loads you are using you may want a heavier buffer. I load mine with powders that make the most of their 11.125" and 16" barrels and with the resulting velocities I find I need buffers in the 8.5 oz to 11 oz range to keep the bolt velocity at reasonable levels. And, since I run Colt pattern ARs with a LRBHO's I used extended buffers. |
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Posted: 8/5/2017 8:25:20 PM EDT
[#16]
Quote HistoryQuoted:
Is your receiver extension fully screwed into place? It is hard to tell from your pics., but it looks like it is a turn or two out from normal position. The bottom edge of the receiver extension should be almost touching the skinny part of the buffer retaining pin. Is the buffer retaining pin under the receiver extension at all? I would double check that. Then I would check the buffer to see if the bumper is compressed/damaged and replace if necessary. Finally, I would grind away the back of the key on the 9mm bolt to keep it from making contact since you don't want to add quarters/spacer. Personally, I'd ditch the NFA bolt and go with a Colt/RRA/Spinta, but that's just me. |
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Posted: 8/5/2017 8:46:33 PM EDT
[#17]
I can't see how the bolt is to blame in any way in this situation. And I did post above that the buffer tube is installed correctly, I'll upload a pic in a few with the buffer removed to show it.
I think I will start off with getting the colt x buffer, and hopefully that fixes the issue. The rubber bumper on the buffer shows no damage, which is odd, since it had to have compressed for the bolt to make up the 1/4" gap and hit the receiver. |
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Posted: 8/5/2017 11:57:44 PM EDT
[#18]
Is the distance from the back of the 9mm bolt key to the back of the bolt the same distance as the back of a 5.56 carrier key to the back of the carrier?
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Posted: 8/6/2017 7:58:45 AM EDT
[#19]
Quoted:
I was under the impression that a spacer or extended buffer was only necessary to prevent a case from dropping into the FCG or to prevent damage to the bolt catch/receiver if utilizing LRBHO. Because I'm not using LRBHO I went with no spacer, and a standard length carbine buffer. The gas key is slamming into the rear of my receiver, the buffer extension area..... So, did I misunderstand, is the spacer actually necessary when using a standard length carbine buffer in a standard length collapsible buffer tube? The spacer for the buffer tube is needed for another reason. The additional weight of the 9mm bolt assembly is extremely hard of the bolt stop. If a 9mm is ran without a spacer, the bolt will eventually shear the bolt stop. The spacer limits the distance the bolt travels rearward to about 3/16-1/4" aft of the bolt stop. This distance limiting allows for a normal bolt stop life. As far as your receiver the extremely light weight buffer is the source of your issues. The Colt 9mm carbine uses a 5.5oz or heavier buffer. |
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Posted: 8/6/2017 8:45:51 AM EDT
[#20]
Thanks guys, that's what I figured....I was a little premature in my range trip.
Does anyone know the difference between the 2 piece colt smg buffer and the x buffer? |
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Posted: 8/6/2017 9:18:02 AM EDT
[#21]
Quote HistoryQuoted:
Thanks guys, that's what I figured....I was a little premature in my range trip. Does anyone know the difference between the 2 piece colt smg buffer and the x buffer? I have a DDLES lower with a Colt upper. I used the Colt buffer at first, when I switched to the HeavyBuffer, I noticed a bit smoother action. The heavier buffer seems to slow the bolt a bit, allowing for a smoother operation of the bolt. This buffer also does away with the need of a spacer as it is a bit longer. There is a buffer that can be adjusted for the weight needed for your particular set up. The 9Q-T buffer can be ran at 12 ounces or lightened. Many use this with an auto sear lower. |
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Posted: 8/6/2017 9:39:28 AM EDT
[#22]
^Thank you for the help!
Can you explain why the sliding weight in the 2 piece is desirable? If it is? When you say the heavy buffer, are you taking about the x buffer? That "modular" buffer, isn't that an extended buffer? I'm trying to avoid that to keep the ROF down when I can take home the m16. While I'm waiting I'd like to shoot this in semi, doesn't have to run perfect, but to at least not damage my lower would be nice. I'm heavily leaning towards the x buffer. It sounds like that buffer might actually be nice shooting with a 10.5" suppressed 5.56 upper as well. ETA : looked it up, heavy buffer is the company, now I understand you |
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Posted: 8/6/2017 10:18:43 AM EDT
[#23]
Things have changed in a very short time in the buffer department for pistol caliber AR's with USPSA adding the PCC devision. We use to think heavy buffers and springs were the way to go to soften the recoil impulse and keep things running right.
Here is a very good thread on buffer setups: Buffer thread I personally started with a Heavy Buffers Q buffer, then went to a JP SCS, and now I run a Blitzkrieg buffer with a JP 308 carbine spring in one rig and a Taccom adjustable buffer with a JP .223 rifle spring in another. Both produce much softer recoil impulse and double taps on target are much faster and sight movement is greatly reduced. If you are not worried about last round hold open, I would use a spacer that limits bolt/buffer travel just enough to eject the spent cartridges. This will give you a super fast cycling rig with extreamly soft recoil impulse. Again, read through the pages in the above link. For a visual reference, here is a video of me and my friend shooting a USPSA match with almost identical rigs. Mine has the Taccom adjustable buffer setup (I am in the blue shirt) and my friend has the JP SCS. Watch the muzzle movement of each carbine. USPSA video  NCPL USPSA Indoor match using PCC |
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Posted: 8/6/2017 10:42:40 AM EDT
[#24]
^thanks for that info.
I'll read through that thread, and nice video, I could certainly see the difference between the buffers. The only thing is that this will ultimately end up on a full auto lower. So I need the cyclic rate to be lower, so spacers, and extended buffers are out for my purposes. I'm testing the setup on a sbr'd lower to get it functioning decently and try to work the kinks out before dropping it on a $25k+ lower. I would be crying right now if I had ran this setup on the m16 and did this to that lower. Although I wouldn't have shot it until I KNEW the buffer was correct lol |
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Posted: 8/6/2017 11:46:11 AM EDT
[#25]
Quote HistoryQuoted:
^Thank you for the help! Can you explain why the sliding weight in the 2 piece is desirable? If it is? When you say the heavy buffer, are you taking about the x buffer? That "modular" buffer, isn't that an extended buffer? I'm trying to avoid that to keep the ROF down when I can take home the m16. While I'm waiting I'd like to shoot this in semi, doesn't have to run perfect, but to at least not damage my lower would be nice. I'm heavily leaning towards the x buffer. It sounds like that buffer might actually be nice shooting with a 10.5" suppressed 5.56 upper as well. ETA : looked it up, heavy buffer is the company, now I understand you I have acquired the Blitzkrieg hydraulic buffer but have not gotten any range time with it yet Reviews are very promising |
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Posted: 8/7/2017 11:28:06 AM EDT
[#26]
Quote HistoryQuoted:
If everything is made to the correct specifications, a spacer is not required. Your receiver extension could be inlstalled incorrectly. Your receiver extension internal depth could be too long. Your buffer miggt be too short. The tip of the buffer could be way too soft. I do think the extra mass of the extended pistol caliber buffers is better for blowback operation. 
Op...I run blowback FA in 9mm, 40 and 45......to slow the cyclic rate you want to get the mass up in the buffer. An 8 ounce buffer in a 9mm is too heavy for a semi gun trying to shoot fast with the semi trigger as the shooter can pull the trigger faster than the bolt cycles, but once you put the auto trip into the equation you can manage cyclic rate quite handily. Extra power spring will also speed cyclic rate as the bolt closes faster. and causes a much more violent firing cycle. I'd avoid. Feel free to give me a shout at the shop if I can help. |
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Posted: 8/7/2017 12:38:15 PM EDT
[#27]
@Mad-Machinist, exactly what part of the quoted text do I need to rethink? The first part was dealing with length of the recoil stroke. The second part specifically mentioned that the extra mass offered in the extended pistol caliber buffers was better. I did not mention spring rate at all. I usually use an ST-9X buffer, 5.5" barrel, full-auto, suppressed.
I physics, bro.
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Posted: 8/7/2017 12:43:15 PM EDT
[#28]
Quote HistoryQuoted:
@Mad-Machinist, exactly what part of the quoted text do I need to rethink? The first part was dealing with length of the recoil stroke. The second part specifically mentioned that the extra mass offered in the extended pistol caliber buffers was better. I did not mention spring rate at all. I usually use an ST-9X buffer, 5.5" barrel, full-auto, suppressed. I physics, bro. I thought you said you didn't believe in heavy buffers......My apologies.....
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Posted: 8/7/2017 2:36:55 PM EDT
[#29]
Quote HistoryQuoted:
KarlSG1................ Looks like my senile/blind ass misread..... I thought you said you didn't believe in heavy buffers......My apologies.....
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Posted: 8/7/2017 2:45:25 PM EDT
[#30]
Quote HistoryQuoted:
Things have changed in a very short time in the buffer department for pistol caliber AR's with USPSA adding the PCC devision. We use to think heavy buffers and springs were the way to go to soften the recoil impulse and keep things running right. I personally started with a Heavy Buffers Q buffer, then went to a JP SCS, and now I run a Blitzkrieg buffer with a JP 308 carbine spring in one rig and a Taccom adjustable buffer with a JP .223 rifle spring in another. Both produce much softer recoil impulse and double taps on target are much faster and sight movement is greatly reduced. Quote HistoryQuoted:
Things have changed in a very short time in the buffer department for pistol caliber AR's with USPSA adding the PCC devision. We use to think heavy buffers and springs were the way to go to soften the recoil impulse and keep things running right. I personally started with a Heavy Buffers Q buffer, then went to a JP SCS, and now I run a Blitzkrieg buffer with a JP 308 carbine spring in one rig and a Taccom adjustable buffer with a JP .223 rifle spring in another. Both produce much softer recoil impulse and double taps on target are much faster and sight movement is greatly reduced. Quoted:
The only thing is that this will ultimately end up on a full auto lower. So I need the cyclic rate to be lower, so spacers, and extended buffers are out for my purposes. |
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Posted: 8/7/2017 4:23:41 PM EDT
[#31]
^By "extended" I am referring to the longer carbine buffers, the ones with the "spacer" built in. Not weight at all.
Based on this experience and many people's opinions, I am rethinking my decision to shoot a 9mm setup on my transferable colt m16a1. I may continue to shoot limited amounts on an ar15 lower, but I'll leave 9mm to subguns. This does make things a little easier, since I'll now be shooting this only in semi auto. |
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Posted: 8/8/2017 9:22:26 PM EDT
[#32]
You can run on an A1 lower...just use the carbine extended buffer and spring......and a 2.7 inch spacer inside the tube under the spring.......Army has an NSN for it even.......to slow cyclic on an FA....go to around 8 to 8.5 ounces on the buffer.....a solid steel buffer with an OAL of 4 inches including the buffer weighs about 8.3 ounces. I don't recommend heavier than 7.5 ounces for semi because heavier it is too easy to cycle the trigger faster than the action......with an auto trip it is no longer an issue....here is one I shot this afternoon......has a 7.5 ounce extended buffer, perceived recoil is very light...........
 Test fire trilug upper 9mm |
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Posted: 8/9/2017 9:12:20 AM EDT
[#33]
Quote HistoryQuoted:
^By "extended" I am referring to the longer carbine buffers, the ones with the "spacer" built in. Not weight at all. Based on this experience and many people's opinions, I am rethinking my decision to shoot a 9mm setup on my transferable colt m16a1. I may continue to shoot limited amounts on an ar15 lower, but I'll leave 9mm to subguns. This does make things a little easier, since I'll now be shooting this only in semi auto. There's lots of people shooting 9mm SA and FA without issue. Guns are made for shooting and pretty much any damage to a lower can be repaired (see M60Joe). All you need to do is get your issue sorted and you should be good to go. |
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