AR-15/9 kit questions

[m.ammer69]

I've been looking at getting an AR 15/9, I've seen a few of these U-build kits like on GunBroker. I was curious if anyone had any experience with these kits and if anyone had any feedback on them, more specifically what to stay away from. I've found two kits that I'm interested in, both are complete minus a lower receiver. One is from barrier defense, the other kit is I guess like a third party put together kit because it's got a white label armory barrel, bcg, charging handle, and reciever and an Anderson lower parts kit. So first I'm curious if anyone has had any experience with these types of kits and have any feedback on them. Are these companies I should stay away from? As far as lower receivers are they fairly universal as long as everything is mil-spec? Do you need a special reciever fir the side charging AR's versus the rear charging AR's? Looking to put together a little bit of a budget (not cheap just not expensive) AR-15/9mm rifle with A2 furniture and sights.
Also look at building a 45acp SBR with a 12-14in heavy barrel if anyone has any advice on that.

 

[outrider58]

Do you have an example of what you are talking about?

Why a heavy barrel on the .45 acp? It's not required.

 

[calicojack]

I have built one each AR9 and an AR45. I am in the process of building a Radial Delayed Blowback 45APC as well. That being said, there are others on this forum that have built multiple AR9's. I have not seen too many AR45's. If you search, you'll find a lot of threads on this forum. Let me try to answer your questions in line below:

Question:
"I've found two kits that I'm interested in ... barrier defense ... white label armory"
Answer: Never heard of them. I am familiar with Foxtrot Mike, Quarter Circle 10, Aero Precision, Angstadt Arms, New Frontier Armory, and CMMG. CMMG has it's own Radial Delayed Blowback technology, as well as "conversion" kits that convert a MILSPEC lower. Stern Defense also has conversion kits. I think these are all good companies.

Question:
"As far as lower receivers are they fairly universal as long as everything is mil-spec? "
Answer:
Yes and no. You can get a conversion kit for a standard MILSPEC lower or you can get a dedicated lower.

Question:
"Do you need a special receiver for the side charging AR's versus the rear charging AR's? "
Answer:
A side charger on the receiver itself I believe will require a custom upper receiver. A side charger on the upper receiver like what Foxtrot Mike offers, hmm, that might use a standard upper, not sure off the top of my head.

Quetsion:
"Budget?"
Answer:
NOPE! IMHO If you want budget rifle, build a standard AR.

I think you need to answer these questions before you start:

1. Do you want a rifle/carbine, braced pistol, or a registered short barrel rifle? The latter might be in a later phase.

2. What magazine format do you want? Glock, Colt, HK MP5 for 9mm. For 45 APC it could be Glock, S&W M&P, HK USC. Everybody loves Glock. IMHO, I think the Glock format is less than perfect in this application, and I would say go with a single stack mag option, esp. for 45 APC. Keep in mind a 45 APC double stack Glock mag is too wide for a MILSPEC AR 15 lower, so in that case you have to go dedicated lower.

3. Do you want a traditional straight blowback design (far simpler) or the newer (but more expensive and difficult to find) Radial-delayed Blowback or there is even a Roller-delayed blowback option. There are also "short reset" bolts, but I have zero experience with these.

4. Think about barrel length. Most guys like barrels around 4 to 8" for balance. If you live in Maryland and want to eventually make this into an SBR this, though, because of the 29" minimum overall length you will need an 11" or longer barrel.

My Advice for a Pistol Caliber Carbine (PCC) AR:
1. Start off with a braced pistol.

2. I would say go with a standard MILSPEC lower and use a conversion kit. I would also say prefer a single stack mag format over Glock unless you have shit tons of Glock mags. If you want to go dedicated 9mm lower, I had good luck with Foxtrot Mike. For dedicated, I would say get both the lower and upper from the same manufacturer. Both dedicated and conversion will give you a choice of magazine formats.

3. Go with 9mm. There are more options and advice out there. 45APC (and 10mm/40SW) seems to be the red headed step child.

4. The traditional blowback designs are far easier to build than the bleeding edge designs. In a 45APC, I will say the blowback has more noticeable recoil. But for 9mm, meh, just go with a straight blowback. IMHO, the newer stuff is a big pain in the ass, unless you have a long time horizon (to wait for parts availability) and are prepared to spend more money.

5. If you want to use a drop-in trigger (like an enclosed cartridge), make sure you get one designed for a 9mm PCC. The PCC's are hard on triggers. If you use a MILSPEC trigger then this is not an issue, although some makers (well, one of them) will void the warranty if you run them in a PCC. However, no one on this forum has ever had a problem with a MILPEC trigger in a PCC that I am aware of.

 

[m.ammer69]

Do you have an example of what you are talking about?

Why a heavy barrel on the .45 acp? It's not required.

Like examples of the kits? Here are the two on GunBroker I've been looking at.
https://www.gunbroker.com/item/923014749
https://www.gunbroker.com/Item/923594785

The heavy barrel on the 45acp I thought would be a nice feature on a SBR and would help keep some weight in it to tame any recoil.

 

[outrider58]

Like examples of the kits? Here are the two on GunBroker I've been looking at.
https://www.gunbroker.com/item/923014749
https://www.gunbroker.com/Item/923594785

The heavy barrel on the 45acp I thought would be a nice feature on a SBR and would help keep some weight in it to tame any recoil.

Well, At least one of them comes with the proper(ish) PCC buffer. The second one shows a standard AR 15 buffer(weight unknown) and although they don't show a bolt carrier group, they say one is included. I'm not seeing a charging handle either.

Either way, you are buying a pig in a poke and if, once you get the thing all put together, you have problems, who's going to fix it?

Of the two you show, the first one at least looks like a complete kit(minus the lower). $500 is a roll of the dice and you could probably do better buying known quality parts and going that route. Who knows what kind of quality exists in these kits? I would pass, if that's what you are asking.

 

[teratos]

I wouldn't put together or buy a PCC without some kind of delayed blowback. You will be disappointed with it as soon as you shoot someone's delayed blowback gun. The felt recoil on a direct blowback pistol caliber AR is far worse than 5.56. Yes, what you are looking at is much cheaper. Buy once, cry once.

 

[m.ammer69]

I have built one each AR9 and an AR45. I am in the process of building a Radial Delayed Blowback 45APC as well. That being said, there are others on this forum that have built multiple AR9's. I have not seen too many AR45's. If you search, you'll find a lot of threads on this forum. Let me try to answer your questions in line below:

Question:
"I've found two kits that I'm interested in ... barrier defense ... white label armory"
Answer: Never heard of them. I am familiar with Foxtrot Mike, Quarter Circle 10, Aero Precision, Angstadt Arms, New Frontier Armory, and CMMG. CMMG has it's own Radial Delayed Blowback technology, as well as "conversion" kits that convert a MILSPEC lower. Stern Defense also has conversion kits. I think these are all good companies.

Question:
"As far as lower receivers are they fairly universal as long as everything is mil-spec? "
Answer:
Yes and no. You can get a conversion kit for a standard MILSPEC lower or you can get a dedicated lower.

Question:
"Do you need a special receiver for the side charging AR's versus the rear charging AR's? "
Answer:
A side charger on the receiver itself I believe will require a custom upper receiver. A side charger on the upper receiver like what Foxtrot Mike offers, hmm, that might use a standard upper, not sure off the top of my head.

Quetsion:
"Budget?"
Answer:
NOPE! IMHO If you want budget rifle, build a standard AR.

I think you need to answer these questions before you start:

1. Do you want a rifle/carbine, braced pistol, or a registered short barrel rifle? The latter might be in a later phase.

2. What magazine format do you want? Glock, Colt, HK MP5 for 9mm. For 45 APC it could be Glock, S&W M&P, HK USC. Everybody loves Glock. IMHO, I think the Glock format is less than perfect in this application, and I would say go with a single stack mag option, esp. for 45 APC. Keep in mind a 45 APC double stack Glock mag is too wide for a MILSPEC AR 15 lower, so in that case you have to go dedicated lower.

3. Do you want a traditional straight blowback design (far simpler) or the newer (but more expensive and difficult to find) Radial-delayed Blowback or there is even a Roller-delayed blowback option. There are also "short reset" bolts, but I have zero experience with these.

4. Think about barrel length. Most guys like barrels around 4 to 8" for balance. If you live in Maryland and want to eventually make this into an SBR this, though, because of the 29" minimum overall length you will need an 11" or longer barrel.

My Advice for a Pistol Caliber Carbine (PCC) AR:
1. Start off with a braced pistol.

2. I would say go with a standard MILSPEC lower and use a conversion kit. I would also say prefer a single stack mag format over Glock unless you have shit tons of Glock mags. If you want to go dedicated 9mm lower, I had good luck with Foxtrot Mike. For dedicated, I would say get both the lower and upper from the same manufacturer. Both dedicated and conversion will give you a choice of magazine formats.

3. Go with 9mm. There are more options and advice out there. 45APC (and 10mm/40SW) seems to be the red headed step child.

4. The traditional blowback designs are far easier to build than the bleeding edge designs. In a 45APC, I will say the blowback has more noticeable recoil. But for 9mm, meh, just go with a straight blowback. IMHO, the newer stuff is a big pain in the ass, unless you have a long time horizon (to wait for parts availability) and are prepared to spend more money.

5. If you want to use a drop-in trigger (like an enclosed cartridge), make sure you get one designed for a 9mm PCC. The PCC's are hard on triggers. If you use a MILSPEC trigger then this is not an issue, although some makers (well, one of them) will void the warranty if you run them in a PCC. However, no one on this forum has ever had a problem with a MILPEC trigger in a PCC that I am aware of.

Eventually I plan to build both a 9mm and 45acp, but to simplify things I'm just going to focus on the 9mm build for now. For the 9mm I definitely want a pistol caliber carbine, with a traditional blow back system. As you pointed out, traditional blow back systems are fairly simple, and consider I'm just starting to get into building them, the simpler the better. Plus I figured if 9mm runs fine in the thousands of different pistol designs out there that use traditional blow back, why would I really need something more then that? I would like to keep everything caliber specific, so 9mm lower and upper receiver, as far as mags, I was thinking Glock because they're easier to get ahold of and are cheaper.
Now these kits don't have a lower receiver, so I have thought about getting a pistol build kit and matching it with a rifle reciever and stock but I'm not sure of how legal that is. I mean until it's actually put together with a lower these kits are just boxes of parts, it's the receiver that designates if it's supposed to be a pistol or rifle. Correct? Then if you put a pistol brace and short barrel on it could get you in trouble

 

[outrider58]

Eventually I plan to build both a 9mm and 45acp, but to simplify things I'm just going to focus on the 9mm build for now. For the 9mm I definitely want a pistol caliber carbine, with a traditional blow back system. As you pointed out, traditional blow back systems are fairly simple, and consider I'm just starting to get into building them, the simpler the better. Plus I figured if 9mm runs fine in the thousands of different pistol designs out there that use traditional blow back, why would I really need something more then that? I would like to keep everything caliber specific, so 9mm lower and upper receiver, as far as mags, I was thinking Glock because they're easier to get ahold of and are cheaper.
Now these kits don't have a lower receiver, so I have thought about getting a pistol build kit and matching it with a rifle reciever and stock but I'm not sure of how legal that is. I mean until it's actually put together with a lower these kits are just boxes of parts, it's the receiver that designates if it's supposed to be a pistol or rifle. Correct? Then if you put a pistol brace and short barrel on it could get you in trouble

Incorrect.

A dedicated pistol lower(only takes pistol caliber magazines) are cash and carry. No 7 day wait. They can be built into a rifle or pistol. Pick it up from your FFL after NICS and filling out 4473 and walk out that day.

Standard AR 15 lowers have a 7 day wait along with NICS, 4473, and 77r(on line now). You will need to buy a magazine block that fits inside the mag well appropriate to the caliber and type of magazine you will be using(Glock or Colt...). Can also be built into a pistol or rifle.

HQL is not require in either of these cases.

 

[Gcs7th]

I wouldn't put together or buy a PCC without some kind of delayed blowback. You will be disappointed with it as soon as you shoot someone's delayed blowback gun. The felt recoil on a direct blowback pistol caliber AR is far worse than 5.56. Yes, what you are looking at is much cheaper. Buy once, cry once.

^ This exactly, if you don’t want to build your own too there’s a couple 9mm PCCs/Pistols you can buy obviously cmmg guard/radial delay, stribkg spa3, sig mpx, and a mp5 clone like a zenith or ptr.

 

[Melnic]

I wouldn't put together or buy a PCC without some kind of delayed blowback. You will be disappointed with it as soon as you shoot someone's delayed blowback gun. The felt recoil on a direct blowback pistol caliber AR is far worse than 5.56. Yes, what you are looking at is much cheaper. Buy once, cry once.

What built and purchased in MD 9mm PCC is available thru an IP that you might recommend and approx what kind of $ are we talking about?

Incorrect.

A dedicated pistol lower(only takes pistol caliber magazines) are cash and carry. No 7 day wait. They can be built into a rifle or pistol. Pick it up from your FFL after NICS and filling out 4473 and walk out that day.

Standard AR 15 lowers have a 7 day wait along with NICS, 4473, and 77r(on line now). You will need to buy a magazine block that fits inside the mag well appropriate to the caliber and type of magazine you will be using(Glock or Colt...). Can also be built into a pistol or rifle.

I have several lowers that are sitting on the shelf and was thinking if a magwell adapter at their price is not already more than half way to a dedicated 9mm lower. Like the question above, which IPs have dedicated 9mm lowers typically available?

Myself, I"m looking braced pistol. I have lots of Glock mags including larger capacity but I won't discount buying all new mags if reliability is a factor.

 

[smdub]

Remember that many (most?) AR9 blowback kits use a ramped carrier and can fire out of battery. The orig Colt 635 used a non-ramped carrier. The RDB setups don't have this problem as the rotation of the bolt works the same as an AR15 and blocks the firing pin until its in battery. I'm not sure if any of the new roller delayed setups have some similar protection as I haven't seen any in person yet.

The main advantage to using a magwell insert over a dedicated lower is if you already have a SBR stamped lower. If you don't, the dedicated pistol lower is probably the better bet.

 

[outrider58]

I have several lowers that are sitting on the shelf and was thinking if a magwell adapter at their price is not already more than half way to a dedicated 9mm lower. Like the question above, which IPs have dedicated 9mm lowers typically available?

Myself, I"m looking braced pistol. I have lots of Glock mags including larger capacity but I won't discount buying all new mags if reliability is a factor.

Quarter Circle 10 and New Frontier are the first that come to mind. I have had had good results with both of these companies. I also have an Engage 9mm lower, but that was a limited run.

 

[alucard0822]

There are a couple things that will make or break a blowback AR9, some things you can save money on, and some that frequently cause problems. There are some alternative designs like the CMMG RDB, Scheel roller delay buffer and most companies are working on delayed blowback systems, but simple blowback is easy to build and troubleshoot. You can use assembled uppers, but you have fewer choices for individual components. Furniture generally doesn't matter as long as it fits and is comfortable, I like to use the LPK for pins springs and things from the same company as the lower, otherwise CMMG or Aero are nice. Aero's enhanced buffer tubes are nice for PCCs, a little added protection from carrier tilt. Will need punches, armorer's wrenches, hand tools, a torque wrench, a mag block to install the buffer tube, and a fixture for the upper being there aren't bolt lugs for a reaction rod to engage. Built properly a blowback AR is a lot of fun and useable, they can be reliable with recoil that is similar to a 5.56 gun, but feels just a little different. Their popularity is less in how they shoot, being recoil is similar or can be worse than 5.56, but more to do with where you can shoot, indoor and pistol ranges, steel at close range or a lot of competition classes for PCC.

First is what receiver set, definitely build a blowback for your first, they are simpler, and take less tuning and experience, they require an ejector in the lower, and feed from different mags, I suggest GLOCK mags if you want one to feed from a dedicated factory pistol mag. You essentially have 3 options, Standard mil-spec AR15 receiver using Endomags, the ejector is built into the mag, and with just a buffer change can run a 9mm blowback upper, mags are expensive. A GLOCK mag lower, this is what most do, and it's the simplest for a new build, Aero, NFA or FM products are the easiest, Aero and NFA have a last round bolt hold open(LRBHO) in the upper, the FM has the linkage in the lower, other brands may or may not have one, and it might or might not work well. Third option is a stern defense adapter that installs in a standard AR15 lower, better than endomags as it allows GLOCK mags to be used, but ends up costing as much or more than a dedicated AR9 lower.

Barrel, BCG and buffer are critical, they will make it run or suck. Macon Armory and Taccom have flat out the best barrels and BCGs, they work 100% with most bullet profiles due to their feed ramps and good finish. Aero, BA, Faxon, and a lot of others have small or rough feed cones. Kinda like the feed ramp in a pistol, the barrel has a chamfered or angled cons in the chamber to help feed ammo, if it's steep and rough, it will jam on anything other than FMJ, and sometimes even some brands of FMJ, a nice smooth and wide feed cone is best, Macon armory and some gunsmiths can do feed work on other brands. There are a few BCGs that work, and a couple different designs, choose one with an M16 style extractor, 1 peice design and a weight pinned in the tail. Taccom is awesome, $150 for standard, the $200 short stroke is great, but not for a first build as it has some unique benefits and challenges. KVP, faxon or Macon's are good, avoid Aero and NFA bolts. THe whole "ramped vs non-ramped" thing was an issue before, the squared rear of a colt 9mm BCG really slammed down the hammer, and caused trigger problems, some manufacturers cut a ramp in the rear to help, and left enough of the firing pin exposed so they could fire out of battery if the hammer dropped a little early. Most designs now (FM, Taccom, KVP) use a modified ramp where the bottom lug has a shallow ramp, but extends all the way back, and the firing pin is inertial, meaning it is shorter than the distance from the hammer (after contacting the BCG) to the primer. The hammer hits it with enough force that it isn't driven into the primer directly, it leaves contact with the hammer driven forward against a spring, and hits the primer from inertia alone. This protects from out of battery, but can quickly give light strikes with weak hammer springs or some triggers. For a buffer, it's a simple answer, the 10oz KVP buffer, it has floating weights, and enough mass that it runs smooth and functions well in exerything. You can try a DPMS 308 carbine spring, and recoil will be a little softer, but it can cause bump firing with some triggers, a standard AR15 carbine spring will work too, and can cure some bump firing issues as it doesn't slam into battery quite as hard.

IMO shorter barrels are better for function, less residual gas, especially suppressed, and past 7" you don't really gain much velocity. IMO for pistols or SBRs in other states, choosing a barrel is largely a function of overall size and enough length with a muzzle device to clear the desired handguard, but from a functional standpoint a 5" barrel with 4" linear comp will run a little cleaner than a 9" barrel. to avoid the NFA/pistol brace route you need either a 16" barrel, a 16" sleeved short barrel like Taccom offers or a permanently attached muzzle device to make 16". In MD will need about an 11" barrel to make the 29" length requirement for an SBR.

Blowback operation beats up triggers, and the weight of the BCG/buffer can chamber with enough force to cause bump firing with really light triggers. There are a few PCC rated 9mm triggers that run well, CMC, Hiperfire comp or PDi Timney and a few others, be sure to choose the PCC version, and not other models. When test firing I do load 1, load 2, then several mags loading 5 rounds or less ejecting a live round in the middle to check for pin dents or damage, then a couple with mags fully loaded. Shoot holding tight, loose, and see what happens, the big things to look for are bump firing/doubles or jams, especially if the round gets slammed into the feed cone and gets shoved into the case.

 

[calicojack]

The main advantage to using a magwell insert over a dedicated lower is if you already have a SBR stamped lower. If you don't, the dedicated pistol lower is probably the better bet.

True - but at least you can change your mind and use the lower for another purpose if it's MILSPEC.

 

[calicojack]

Quarter Circle 10 and New Frontier are the first that come to mind. I have had had good results with both of these companies. I also have an Engage 9mm lower, but that was a limited run.

The Joe Bob Outfitters "Spartan" lowers are New Frontier lowers rebranded. I have not personally used the Aero Precision PCC lowers, but Aero makes excellent products and I have more than one of their AR15 lowers. Joe Bob Outfitters is an IP here as well:

https://www.joeboboutfitters.com/Pistol-Caliber-AR-Lower-Receivers-s/176650.htm

 

[calicojack]

I wouldn't put together or buy a PCC without some kind of delayed blowback. You will be disappointed with it as soon as you shoot someone's delayed blowback gun. The felt recoil on a direct blowback pistol caliber AR is far worse than 5.56. Yes, what you are looking at is much cheaper. Buy once, cry once.

I totally agree. For me though, I don't think the issue with RDB is cost as much as availability; just trying to find a lower receiver that works with the CMMG bolt (since CMMG lowers are unicorns right now). And if you are doing a 45 APC build, your options seem to be even slimmer.

 

[Slimjim]

Macon armory offers a Gas operated .45 acp upper.

 

[calicojack]

Macon armory offers a Gas operated .45 acp upper.

Interesting:
https://maconarmory.com/products/11-upper-receiver-group-direct-impingement

 

[calicojack]

Here's a lower for a 9mm Radial Delayed Blowback build: https://grabagun.com/cmmg-banshee-100-mk17-ar-pistol-platform-lower-hardcoat-anodized-receiver.html
[EDIT] Oops! This one takes Sig Sauer M17/P320 mages.

 

[smdub]

Most designs now (FM, Taccom, KVP) use a modified ramp where the bottom lug has a shallow ramp, but extends all the way back, and the firing pin is inertial, meaning it is shorter than the distance from the hammer (after contacting the BCG) to the primer. The hammer hits it with enough force that it isn't driven into the primer directly, it leaves contact with the hammer driven forward against a spring, and hits the primer from inertia alone. This protects from out of battery

I don't see how an inertial firing pin protects from OOB. If the hammer can reach and hit a regular pin hard enough when out of battery an inertial one should set it off too. Maybe it gives slightly more protection but doesn't eliminate it. There its at least one case of a FM bolt firing OOB.
A shallower ramp can help. So if they are doing that, that is probably where most of the protection comes from. Maybe a little of column A and a little of column B is enough.

IMO shorter barrels are better for function, less residual gas, especially suppressed, and past 7" you don't really gain much velocity. IMO for pistols or SBRs in other states, choosing a barrel is largely a function of overall size and enough length with a muzzle device to clear the desired handguard, but from a functional standpoint a 5" barrel with 4" linear comp will run a little cleaner than a 9" barrel.

You make a good point here. I've got an 8" RDB on backorder. I picked that length 'because MP5' and my other AR9 is similar. Gives a decent amount of handguard to hold onto. I kept waffling between that and the 5". Finally just picked one and ordered. Now wondering if suppressed the 5" would be less gas in the face than the 8". I shoot 147 subs almost exclusively. Though I'd have to run an ultra short handguard on a 5" bbl as that suppressor doesn't fit down inside one.