AR9 Upper Questions

Suleiman · Feb 19, 2019

I know the AR9 questions come up all the time, but in my search I didn't really find what I was looking for. Rather than revive an old thread, I'll just start another.
I'm hoping to finish up my first AR9 pistol build. I've got a spikes lower with an SB PDW Brace, and 3 EndoMags that I can't wait to try out.
I have a suppressor in jail and I'd like to use a 3 lug mount on the pistol for quick attach of the suppressor. When attaching a muzzle device, should I use Loctite?

Because I intend to use it with a suppressor, I'm planning to get a heavy buffer and spring. Should I expect to need two different buffers, one for suppressed, one for unsuppressed?
Is buffer weight sort of a test it out and see what works? Is there damage that can be done by running too heavy a buffer, or is it primarily just cycle issues?
I think I've read that too light a buffer can lead to shearing the catch, so would erring on the side of heavier is better be a safer option?

I've got around $600 budgeted for the complete upper.
My budget is preventing me from going with a QC10 or Angstadt Arms. I didn't get the CMMG specific EndoMags, so that upper isn't an option for me. What am I missing out on if I go with a KVP or PSA upper?
Typically I'm a buy once cry once kinda guy, but I would like to be able to understand what i'm paying for? $300 for PSA, $500 for KVP, or $800 for the higher end ones?

Would I be better off building it myself? I've never built an upper, but it seems like a 9mm blowback system is pretty straightforward.

Irresponsibily, this money is burning a hole in my pocket, so I can't get the upper off my mind, but I am also super indecisive. Figured I would bring my thoughts here and ask for some feedback and advice.

-Suleiman

j_h_smith · Feb 19, 2019

If you have full confidence in yourself then build it.

engineerbrian · Feb 19, 2019

I recently had Chad work over my CMMG 9mm AR that is run both suppressed and unsuppressed. We went with a Heavy Buffers 12.5oz buffer and a Tubbs 308 flatwire spring. It cycles everytime with supersonic and sub sonic ammo, suppressed and unsuppressed.

Those two parts broke my budget but they were well worth it.

https://www.instagram.com/p/Bpfd8z9HUsI/?utm_source=ig_share_sheet&igshid=13zj1oi4ibdc7

https://www.instagram.com/p/BtPHBLpHs70/?utm_source=ig_share_sheet&igshid=1k2cqjrb213v2

Suleiman · Feb 19, 2019

Confidence I have in spades, knowledge is where I'm deficient. Haha!

Brian, besides the Buffer and Spring, what else was touched up to get your CMMG running so smooth?

engineerbrian · Feb 19, 2019

Suleiman said:
Confidence I have in spades, knowledge is where I'm deficient. Haha!

Brian, besides the Buffer and Spring, what else was touched up to get your CMMG running so smooth?

My CMMG was a big piece of shit from the factory. It was sent to me with a faulty magazine and a charging handle that CMMG had to replace. There was a pin that backed out of the bolt and grooved the upper receiver and CMMG replaced the bolt and upper. After that the trigger pin (i think thats what it was) snapped in half so thats when i brought it to Chad.

Chad checked over the entire rifle, he had to hone (probably the wrong word) the trigger pin hole to prevent the pin from binding and breaking again since it didnt pass the Go gauge, and he straightened out the extractor so it would reliably extract spent rounds.

The gun hasnt missed a beat since then and i have yet to clean it. I just keep putting Mobil 1 on the bolt.

rouchna · Feb 19, 2019

I used an Adco barrel, Vltor upper and an SLR handguard. Came in under your budget for the upper. I also have a heavybuffers Buffer. Works like a dream.

4guyz1stool · Feb 19, 2019

Rocksett for the mount. It will operate at higher temps than Loctite.

I used a CMMG 9mm buffer and a wolf Extra power spring for my build and it works great. Since the AR9 is straight blowback, you really want to slow down that bolt.

mike j · Feb 19, 2019

I used kvp barrel,bolt,heavy spring and 7.5 oz buffer in a spikes receiver for my build. Runs subs and supers suppressed and unsuppresses I had to do some fine tune trimming on the buffer end for the LRBHO to work. I’m sure chad or outrider will chime in with more help.

Suleiman · Feb 20, 2019

Everything I've read online says that the EndoMags I picked up should make the LRBHO work without any modification. I'm hoping that's the case.
I'll order the 12.5oz buffer and .308 spring today.

Still a little lost as to what makes PSA so affordable compared to the others. It seems too good to be true. Is it?

DutchV · Feb 20, 2019

Suleiman said:
Everything I've read online says that the EndoMags I picked up should make the LRBHO work without any modification. I'm hoping that's the case.
I'll order the 12.5oz buffer and .308 spring today.

Still a little lost as to what makes PSA so affordable compared to the others. It seems too good to be true. Is it?

PSA quality control is nearly non-existent. Sure, they'll make it right, but you'll do the testing for them.

outrider58 · Feb 20, 2019

Suleiman said:
I know the AR9 questions come up all the time, but in my search I didn't really find what I was looking for. Rather than revive an old thread, I'll just start another.
I'm hoping to finish up my first AR9 pistol build. I've got a spikes lower with an SB PDW Brace, and 3 EndoMags that I can't wait to try out.
I have a suppressor in jail and I'd like to use a 3 lug mount on the pistol for quick attach of the suppressor. When attaching a muzzle device, should I use Loctite?

Because I intend to use it with a suppressor, I'm planning to get a heavy buffer and spring. Should I expect to need two different buffers, one for suppressed, one for unsuppressed?
Is buffer weight sort of a test it out and see what works? Is there damage that can be done by running too heavy a buffer, or is it primarily just cycle issues?
I think I've read that too light a buffer can lead to shearing the catch, so would erring on the side of heavier is better be a safer option?

I've got around $600 budgeted for the complete upper.
My budget is preventing me from going with a QC10 or Angstadt Arms. I didn't get the CMMG specific EndoMags, so that upper isn't an option for me. What am I missing out on if I go with a KVP or PSA upper?
Typically I'm a buy once cry once kinda guy, but I would like to be able to understand what i'm paying for? $300 for PSA, $500 for KVP, or $800 for the higher end ones?

Would I be better off building it myself? I've never built an upper, but it seems like a 9mm blowback system is pretty straightforward.

Irresponsibily, this money is burning a hole in my pocket, so I can't get the upper off my mind, but I am also super indecisive. Figured I would bring my thoughts here and ask for some feedback and advice.

-Suleiman

You can get a QC 10 'blem' side-charging upper for $240. If you went with their standard upper, you'd still need a charging handle which would end up costing you more, in the long run.

An Adco 4.5"-7" barrel with your choice of threading(I recommend the 5" with 13.5x1 LH TP) for $155. These are great barrels!

And a UTG Pro hand guard for as little as $70(debending on length and model, as high as $160). For the money, these are very affordable, well made rails.

Top it all off with a Faxon Gen II 9mm bolt for $165

Depending on what handguard you choose, you should be in pretty decent shape.

For buffers, you could look at Heavy Buffers. I would start at 6.5 oz. You shouldn't need to jump on a 12 oz buffer right off the bat.

I'm not familiar with the Wolf springs so I can't comment as to their effectiveness nor their longevity. I use Tubb's AR 10 FW springs. By the time you wear one of those out, it might be time to shop for a new barrel. That's how long they last.

I'm running a Geissele G2S two stage trigger with a trigger break at 3.5 lbs. They run around $165 retail.

outrider58 · Feb 20, 2019

mike j said:
I used kvp barrel,bolt,heavy spring and 7.5 oz buffer in a spikes receiver for my build. Runs subs and supers suppressed and unsuppresses I had to do some fine tune trimming on the buffer end for the LRBHO to work. I’m sure chad or outrider will chime in with more help.

Haha! Chad had to do a little mill work on my Spike's 7.5 oz ST-9X buffer to allow my bolt catch to work. Though my QC 10 QC5 doesn't have an LRBHO(due to its design), my bolt catch now works, thanks to Chad's fine work.

outrider58 · Feb 20, 2019

rouchna said:
I used an Adco barrel, Vltor upper and an SLR handguard. Came in under your budget for the upper. I also have a heavybuffers Buffer. Works like a dream.

My friend rouchna builds a fine AR. Is that a KVP linear comp on there? Those things are great. I have one on my AR9 SBR.

rouchna · Feb 20, 2019

outrider58 said:
My friend rouchna builds a fine AR. Is that a KVP linear comp on there? Those things are great. I have one on my AR9 SBR.

Thanks for the kind words my friend. Yes, it's a KVP comp. It works well and most importantly...it looks good. We all know that's all that matters

Suleiman · Feb 20, 2019

rouchna said:
...most importantly...it looks good. We all know that's all that matters

It's insane how accurate this statement feels. The aesthetic of the PDW brace is why I spent so much on it when there are a dozen others that would do the job for a third of the pricetag.

outrider58 · Feb 20, 2019

Suleiman said:
It's insane how accurate this statement feels. The aesthetic of the PDW brace is why I spent so much on it when there are a dozen others that would do the job for a third of the pricetag.

Trust me. You'll like that brace.

redeye · Feb 27, 2019

DutchV said:
PSA quality control is nearly non-existent. Sure, they'll make it right, but you'll do the testing for them.

Hogwash.

I’ve assembled a LOT of PSA stuff, and I’ve never found any of it lacking.

Their business model isn’t just based on volume sales, it’s based on an ideology.

PSA wants to see 50,000,000+ AR’s out there in the hands of Citizens. And they’re all about doing their part in that effort. That’s why they’re content to make pennies on the dollar, because it’s literally a personal crusade for them.

They could certainly charge more for their stuff. And they’d make more money on fewer sales. But that wouldn’t increase the numbers of AR’s in circulation as much as blowing them out at low prices. And increasing the numbers IS the goal.

Palmetto State Armory is a National Treasure.

clandestine · Feb 27, 2019

redeye said:
Hogwash.

I’ve assembled a LOT of PSA stuff, and I’ve never found any of it lacking.

Their business model isn’t just based on volume sales, it’s based on an ideology.

PSA wants to see 50,000,000+ AR’s out there in the hands of Citizens. And they’re all about doing their part in that effort. That’s why they’re content to make pennies on the dollar, because it’s literally a personal crusade for them.

They could certainly charge more for their stuff. And they’d make more money on fewer sales. But that wouldn’t increase the numbers of AR’s in circulation as much as blowing them out at low prices. And increasing the numbers IS the goal.

Palmetto State Armory is a National Treasure.

You have assembled a lot of PSA? Can you elaborate?

I have worked on at least a thousand of their uppers/complete AR's and they are very much problem ridden. No guess work on my end. I use Gauges, Scopes, Detailed Inspection, and Rigorous Testing.

Held a class with 4 students last week and one had a PSA upper that wouldn't close on a 5.56 Go Gauge. A week before that the same story. Common theme with them.

AR9 Upper Questions

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