Suggestions for cheap PCC build?

[DerMerchant]

Came into a new frontier armory lw-15 complete lower (almost everything is polymer, save for the buffer tube, buffer detent, bolt catch, and FCG pins) for free, and decided to put together a PCC for as cheap as I could. The lower came with a carbine spring and buffer which i changed to an H buffer and extra power spring (the same ones that came with my Palmetto State Armory AR-10) and I figure these along with a heavy BCG would provide enough weight for the blowback system. The gas block is for mounting irons. I was considering a palmetto BCG also, but the shipping and handling increased the price to that of the KAK.

Parts to buy

1. KAK Enhanced Bolt Carrier Group AR-15 9mm
2. AR-STONER Sporter Upper Receiver Stripped
3. BCA 9MM, 16" Parkerized M4 Barrel
4. Pro Mag AR-15 / M16 9MM Magazine Adapter Block
5. XTS Gas Block ($10)
6. New Frontier Armory Blow Back Hammer
7. ProMag Magazine AR-15 9mm

Parts I have

1. Lower assembly
2. Troy iron sights
3. Rifle length plastic hand guard w/ delta ring and front plate
4. muzzle nut for the threads

I just wanted to get a second opinion before taking the plunge, as far as I can tell this would be all I need, and it comes out to about $340 including shipping and one magazine. I know that PSA has comparable prices, but I don't see any in stock at the moment, and FFL+shipping would elevate it to around $400 anyways.

 

[LiveLife]

Suggestions for cheap PCC build?

I just wanted to get a second opinion before taking the plunge

You want combined bolt and buffer weight to be 20-22 oz with carbine length recoil spring for less harsh cycling impact that will be kinder to the polymer lower.

KAK bolt is advertised as .98 lb so about 15.7 oz. H3 buffer weight is 5.4 oz so combined weight is over 21 oz, perfect. But why not consider just buying a complete kit for about the same amount of money and know everything will assemble and work reliably?

BTW, I have used ProMag mag well adapter and the polymer sides will flex which affected feeding - It's junk and CANNOT recommend its use. If you must use mag well adapter, go with a metal unit. As many will agree, I also CANNOT endorse any ProMag magazines - Just do a THR search and read member experience. My experience with ProMag magazines have been Fair-OK but I want magazines to function reliably.​

And most 9mm bolts will work with regular AR hammers. I run PSA 9mm uppers and use regular .223/5.56 lowers with EndoMag along with New Frontier/Joe Bob Outfitters dedicated Glock lowers without issues with regular AR hammers.

​

Instead of using mag well block, I suggest you consider using EndoMag 9mm kit inside MagPul PMag bodies. This allows you to quickly change back to .223/5.56 simply by swapping the upper and using .223/5.56 magazines - https://www.22mods4all.com/ar-9-9mm/magazines/

Complete 16" 9mm KeyMod kit for $344 - https://npfreedom.com/ar15-9mm-16-float-complete-rifle-build-kit-unassembled/

Here's complete 16" 9mm MLok kit (without bolt) for $289 (9mm bolt for $89) - https://www.22mods4all.com/9mm-stinger-series-16-nitride-builder-kit-1-10-twist-10-mlok-handguard/

Here's 16" 9mm MLok upper kit for $189 (Add $109 for bolt + charging handle) - https://www.22mods4all.com/9mm-stinger-series-16-parkerized-upper-kit-1-10-twist-10-mlok-handguard/

 

[DerMerchant]

You want combined bolt and buffer weight to be 20-22 oz with carbine length recoil spring for less harsh cycling impact that will be kinder to the polymer lower.

KAK bolt is advertised as .98 lb so about 15.7 oz. H3 buffer weight is 5.4 oz so combined weight is over 21 oz, perfect.

I have used Pro Mag mag well adapter and the polymer sides will flex - It's junk and CANNOT recommend its use. If you must use mag well adapter, go with a metal unit. And as many will agree, I also CANNOT endorse any Pro Mag magazines.

Instead, I suggest you consider using EndoMag 9mm kit inside MagPul PMag bodies. This allows you to quickly change back to .223/5.56 simply by swapping the upper and using .223/5.56 magazines. Simple.

And most 9mm bolts will work with regular AR hammers.

Thanks for the feedback, I had heard of the endomags, but preferred the look of the skinnier colt style mags. I was also looking at the torkmag adapter.
This would allow me to use modified glock magazines. This definitely gives me some stuff to think about, especially since all these bolts look exactly the same, but with pretty big price differences, best to go with the lowest price.

 

[LiveLife]

best to go with the lowest price.

No, if you want reliability, you should go with what's been proven to work reliably.

After going through these builds:

• ProMag plastic magwell block
• PSA metal magwell block
• Just Right carbine with Glock magwell
• New Frontier/Joe Bob Outfitter dedicated Glock lower
• AR/EndoMag/PMag

I can say dedicated Glock lowers produced the most reliable feeding followed by EndoMag/PMag and would recommend them.

I had about 95-98% reliability with PSA metal magwell block and would recommend dedicated Glock lowers/EndoMag for greater reliability.

Once ProMag plastic magwell block thin walls flexed, reliability went out the window.

 

[12Bravo20]

Decide which magazine you want to use. The two main choices are Colt style or Glock. I went with the Colt style for a few reasons. The main reason was I wanted a Colt SMG clone. I prefer the look of the straight magazine vs angled plus the last round hold open just works every time. I used a CMMG dedicate lower and bolt along with a Rock River barrel and Fulton Armory 604 upper. I use Metalform magazines which are the gold standard of Colt style magazines (OEM for Colt). The Glock style lowers are popular too and nothing wrong with them.

I also suggest staying away from the ProMag block and magazines. I have not had any luck with any magazine from ProMag for any firearm. If you want to go with Colt style magazines, I suggest the Kak Industries mag adapter.

https://www.kakindustry.com/ar15-9mm-mag-adaptor

 

[LiveLife]

I suggest the Kak Industries mag adapter.

$100 and out of stock.

 

[DerMerchant]

No, if you want reliability, you should go with what's been proven to work reliably.

After going through these builds:

• ProMag plastic magwell block
• PSA metal magwell block
• Just Right carbine with Glock magwell
• New Frontier/Joe Bob Outfitter dedicated Glock lower
• AR/EndoMag/PMag

I can say dedicated Glock lowers produced the most reliable feeding followed by EndoMag/PMag and would recommend them.

I had about 95-98% reliability with PSA metal magwell block and would recommend dedicated Glock lowers/EndoMag for greater reliability.

Once ProMag magwell block thin walls flexed, reliability went out the window.

I was talking about the bolts, not the magazine adapters. You're right, I will avoid the promag adapter.

Decide which magazine you want to use. The two main choices are Colt style or Glock. I went with the Colt style for a few reasons. The main reason was I wanted a Colt SMG clone. I prefer the look of the straight magazine vs angled plus the last round hold open just works every time. I used a CMMG dedicate lower and bolt along with a Rock River barrel and Fulton Armory 604 upper. I use Metalform magazines which are the gold standard of Colt style magazines (OEM for Colt). The Glock style lowers are popular too and nothing wrong with them.

I also suggest staying away from the ProMag block and magazines. I have not had any luck with any magazine from ProMag for any firearm. If you want to go with Colt style magazines, I suggest the Kak Industries mag adapter.

https://www.kakindustry.com/ar15-9mm-mag-adaptor

Thanks for the suggestion, I do prefer the look of the colt magazines, unfortunately this adapter is out of stock, i'll be on the lookout.

 

[LiveLife]

I do prefer the look of the colt magazines, unfortunately this adapter is out of stock, i'll be on the lookout.

Dayton Tactical "metal" magwell block $69 and in stock - https://daytonatactical.com/products/9mm-drop-in-magazine-conversion-block

If you are interested, I can "Pay It Forward" my PSA metal and ProMag plastic magwell block and AR Stoner magazines for your build.

PM me if interested.

 

[DerMerchant]

Dayton Tactical "metal" magwell block $69 and in stock - https://daytonatactical.com/products/9mm-drop-in-magazine-conversion-block

If you are interested, I can "Pay It Forward" my PSA metal and ProMag plastic magwell block and AR Stoner magazines for your build.

PM me if interested.

Thanks for the link, not sure how you guys keep up with all these websites.

 

[LiveLife]

Thanks for the link, not sure how you guys keep up with all these websites.

Retirement and laptop full of vendor tabs and of course, Google.

Here's a growing list just for reloading components we use in the Handloading & Reloading category - https://www.thehighroad.org/index.p...ponents-on-sale.707473/page-178#post-11161685

 

[12Bravo20]

Here is a mag adapter at Midway USA. I have no idea who actually makes them or how good they are.

https://www.midwayusa.com/product/1019567735

I know that you want to use the NFA lower that you have and I won't try to talk you out of it. Just a word of warning: watch the back of the receiver where the buffer tube attaches for cracks. 9MM does recoil a bit more than 223 due to it being blow back. I know for a fact that if you buy a new lower and a mag adapter, together they can cost as much if not more than a dedicated lower.

Now for your other parts.

Buffer - get a buffer that is a minimum of 5.5 oz. I would either use a longer 9mm buffer or get the spacer if using a standard length carbine buffer. Especially true if running Colt style mags.
This is to prevent the bolt from going too far and breaking the bolt hold open.

Hammer- Yes you will need to use the NFA blow back 9mm/22lr hammer. I know I did when I used a NFA lower for a 22 build.

All other parts minus the ProMag stuff is good to go. Food for thought - you could go with a cheap free float rail and not even bother with a gas block

Magazines (Colt style) - Metalform is the best (and most expensive). C Products and ASC also make Colt style magazines. Some people have had luck and others have not with the C Products and ASC mags. Again STAY AWAY FROM PROMAG.

 

[DerMerchant]

Here is a mag adapter at Midway USA. I have no idea who actually makes them or how good they are.

https://www.midwayusa.com/product/1019567735

I know that you want to use the NFA lower that you have and I won't try to talk you out of it. Just a word of warning: watch the back of the receiver where the buffer tube attaches for cracks. 9MM does recoil a bit more than 223 due to it being blow back. I know for a fact that if you buy a new lower and a mag adapter, together they can cost as much if not more than a dedicated lower.

Now for your other parts.

Buffer - get a buffer that is a minimum of 5.5 oz. I would either use a longer 9mm buffer or get the spacer if using a standard length carbine buffer. Especially true if running Colt style mags.
This is to prevent the bolt from going too far and breaking the bolt hold open.

Hammer- Yes you will need to use the NFA blow back 9mm/22lr hammer. I know I did when I used a NFA lower for a 22 build.

All other parts minus the ProMag stuff is good to go. Food for thought - you could go with a cheap free float rail and not even bother with a gas block

Magazines (Colt style) - Metalform is the best (and most expensive). C Products and ASC also make Colt style magazines. Some people have had luck and others have not with the C Products and ASC mags. Again STAY AWAY FROM PROMAG.

Thanks, the mag adapter appears to be some mass produced item that has been rebranded (like most things), the Daytona Tactical one is about 30 bucks cheaper, they also have a bolt for $85. As for the buffer, I may get a 8 oz buffer with a carbine spring, as I have heard that more weight and a weaker spring is the way to go. I have always had reservations about polymer lowers being weak and snapping in half, so time will tell if the NFA lower holds up, I can always replace with a ATI omni hybrid reinforced lower, mill out P80 lower, or I could use an 80% /k/ lower I got a while back.

 

[DerMerchant]

I have another question, the bear creek arsenal barrel I'm looking at says that it has glock style feed ramps. I emailed BCA and asked whether their barrels were compatible with colt style magazines, and they replied that the barrels were only compatible with glock magazines. Since the feed ramps seem to be built into the magazine conversion block, I'm wondering whether the cut of the barrel even matters, and if anyone has suggestions for any other cheap barrels.