Anyone into AR9s - colt or glock? Out of battery fire?

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
Been reading up a bit on AR9s.. not sure I will go this route but may pickup a dedicated lower for a rainy day.

From what I'm learning, they seem to have addressed bolt lock back on empty for glock mags, but maybe the solution isn't quite as eloquent as colt mags..

Glock mags are cool, but at the same time colt pattern mags are quite available, and few of us are going to want 33 round mags for an actual Glock pistol (ie so if you own both an AR9 and a pistol, although it's possible you aren't really sharing mags)..

I learned Aero is getting into the business (and I'm a huge fan of theirs) but will be patterning on Glock mags.. stuff is just showing signs of life on upper parts, lowers no SOL yet but I bet the virus crap is slowing them down..

Then on an aside I'm reading due to the blowback design and lack of locking lugs on the bolt, AR9s have an awful tendency to allow out of battery firing. I don't quite understand this part, seems like the bolt carrier should block the hammer from contacting the firing pin until the bolt is full closed. Anyone understand this feature/problem with AR9s?

Anyway, opinions? Ideas? Kinda leaning toward putting a Spikes colt pattern lower in the safe, see what Aero offers for upper and lower parts to build out the rest.
 

citoriguy

NES Member
Rating - 100%
27   0   0
Joined
Dec 14, 2018
Messages
2,189
Likes
1,559
Location
PRM
I have a Colt AR-9 and a Sig MPX and they‘re fun range toys. I’d be interested in an Aero if they do come out with one, as I’m a fan of their products too.
 

Uzi2

NES Member
Rating - 100%
4   0   0
Joined
Sep 5, 2017
Messages
5,841
Likes
7,226
I like the looks of the Colt designed guns better, ( straight mag rather than canted Glock style). They can also use slightly modified Uzi mags that will still work in an Uzi....and are also more prevalent as pre bans for those who need that stipulation.image.jpeg
 
Last edited:

SKumar

NES Member
Rating - 100%
13   0   0
Joined
Jan 19, 2017
Messages
3,889
Likes
5,116
Location
Middlesex
Then on an aside I'm reading due to the blowback design and lack of locking lugs on the bolt, AR9s have an awful tendency to allow out of battery firing. I don't quite understand this part, seems like the bolt carrier should block the hammer from contacting the firing pin until the bolt is full closed. Anyone understand this feature/problem with AR9s?
My bet is that the firing pin is not swinging loose enough from the bolt, resulting in the pin striking the primer and setting the cartridge off.
 

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
My bet is that the firing pin is not swinging loose enough from the bolt, resulting in the pin striking the primer and setting the cartridge off.
One thing I read was regarding a spring on the firing pin to prevent such, like what you see on certain big bore rifle designs to prevent slam fire - but the AR9 issue doesn't seem to be a slam fire so a stuck pin makes sense.
 

SJan

NES Member
Rating - 100%
31   0   0
Joined
Dec 9, 2007
Messages
3,788
Likes
1,118
Location
Attleboro, MA
I know a thing or two on this subject.

It is possible for an Out Of Battery discharge, but I wouldn't call it an "awful tendency" There are so many manufacturers making thus stuff now, more every day, many slight variations in bolt designs, along with trigger / hammer designs make it possible that the hammer can hit the firing pin and strike the primer with the bolt slightly open and the cartridge slightly not fully chambered.

On the AR15, the firing pin is only long enough to protrude through the bolt face when the bolt is fully locked in battery. 9mm bolt / carrier is a solid single piece, unlike the AR15 rotating bolt, and its pin can protrude at any time, so its firing pin is spring loaded.

Glock mag vs Colt mag... there are pros and cons to each. If you are behind enemy lines it may come down to availability of pre ban full caps. Modifying readily available and dirt cheap uzi mags to fit a colt style is the most affordable route. Making these function in last round bolt hold open is a daunting task, but it is possible.

LRBHO in any magazine pattern can be unreliable and sometimes prone to parts like the bolt catch breaking. (The bolt + buffer combo should be 18-22 oz, with a ar10 equivalent spring sending it all into the catch) Some manufacturers have the mag follower activation built into their lower receiver, others are in the upper, the most reliable system involves all parts from the same manufacturer.
 

allen-1

NES Member
Rating - 100%
4   0   0
Joined
Feb 23, 2014
Messages
7,729
Likes
10,482
Location
GA; (CT escapee)
I've got friends in CT who've modified AR's to run 9mm. I've heard lots of discussion from them about bolt and buffer selection, lots of tweaking being done to make them run right.

I took the easier route. In GA I have a PSA 9mm AR. It's factory built for the components to match and runs fine, (it was one of the guns I took to the range yesterday). For me, that's a no-brainer. I have LOTS of Glock mags, including 33 rounders which are compatible with my G17/G34s.

In CT, I went with the Ruger PCC. It's legal up there, and I swapped it over with the provided kit to use Glock Mags, (yeah - I've got a bunch of Glock mags up north too).

If you're not committed to the AR9 platform, take a look at the Ruger PCC; I like it a lot - and there are different configurations of it available now. Including the dreaded/awesome .40 caliber...
 

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
This is what happens when I get bored, I get ideas then they turn into guns.. but basically here's how I got here.

Never really liked the idea of PC carbines all that much, kinda an AR nut and am pretty well invested in the platform, though never liked the idea of AR pistols much either (biggest reason I think is I like pistols in pistol calibers, rifles in rifle calibers, and to me 300 blk is still a rifle caliber, plus w/ actual pistols holding 20 rounds I always question the purpose of big awkward pistols)..

Then I stumbled on the jazz about the Ruger PC Charger pistol. More I thought about it the more I decided I had room for a small hip fired 9mm in this form. Thought I managed to put one on layaway at buds then they cancelled the order on me (sign of the times)..

Then I got the thought - damn the ideal blaster like this would be (well in the absence of full auto) run via a binary trigger. Videos, forum posts, research followed...

Turns out (AR9 reputation for out of battery firing aside) Spikes BCG is one of the few cut right to allow use w/ a Fostech (and the videos w/ tiny AR9 pistols spewing rounds are freakin awesome of course :) )..

And I consider the next 6 months to be a potential last time buy on a lot of this stuff, so am trying to cover my bases too. Of course within 3 months there will probably be a completely built out "pistol" in my safe with 12 mags to go with it, but I am thinking for now will grab a lower and a half dozen mags.
 
Rating - 100%
9   0   0
Joined
Jun 25, 2010
Messages
7,921
Likes
1,712
Location
WNW of MHT
If you already have compatible Glock magazines, that would be a good reason to go that route. If you already have other guns which take Colt or Uzi magazines, go with those.

For MA residents, 32-round Uzi magazines (Pre-1994) are inexpensive, plentiful, and easy to adapt.
 

allen-1

NES Member
Rating - 100%
4   0   0
Joined
Feb 23, 2014
Messages
7,729
Likes
10,482
Location
GA; (CT escapee)
Fostech was at the BigDaddy Epic show at my local club last year. I helped RO it, and as it turned out, he was one of the guys at the range I was on. I shot one of his AR's with binary trigger. Took a little getting used to, but was a lot of fun.

Dunno if this will be visible, haven't done this before - but this is one of the owners of Fostech, (I forget his name), running an AR Pistol with a binary trigger.

 

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
If you already have compatible Glock magazines, that would be a good reason to go that route. If you already have other guns which take Colt or Uzi magazines, go with those.

For MA residents, 32-round Uzi magazines (Pre-1994) are inexpensive, plentiful, and easy to adapt.
I don't own either and am in NH. Both seem to be in the buck a round ballpark.
 

Uzi2

NES Member
Rating - 100%
4   0   0
Joined
Sep 5, 2017
Messages
5,841
Likes
7,226
I don't own either and am in NH. Both seem to be in the buck a round ballpark.
For Usi mags check out RTG Parts or U.S. Barrel Shrouds in their sale items tab. About half what you're thinking.
 

ReluctantDecoy

NES Member
Rating - 0%
0   0   0
Joined
Oct 17, 2017
Messages
1,983
Likes
1,689
Location
Cambridge, MA
I went Glock mag because I have preban Glock mags, but if I were given a choice for a do-over, I'd go Colt mag. I just think it is easier/cheaper to find preban Colt/Uzi mags, and I have a feeling the whole system from LRBHO to insert/drop free would work better on Colt pattern because of the metal mags.

I was sold on the idea of being able to swap mags between my pistol and PCC, but honestly, I don't know how often that perk would present itself in actual use. In fact, I kind of made things impossible, as I put +5 extensions on my prebans and now don't use them on my G19 carry because I just can't conceal them anymore. "Does it take Glock mags" is overrated.
 

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
I went Glock mag because I have preban Glock mags, but if I were given a choice for a do-over, I'd go Colt mag. I just think it is easier/cheaper to find preban Colt/Uzi mags, and I have a feeling the whole system from LRBHO to insert/drop free would work better on Colt pattern because of the metal mags.

I was sold on the idea of being able to swap mags between my pistol and PCC, but honestly, I don't know how often that perk would present itself in actual use. In fact, I kind of made things impossible, as I put +5 extensions on my prebans and now don't use them on my G19 carry because I just can't conceal them anymore. "Does it take Glock mags" is overrated.
Ya that's kinda what I think - not to mention even if say I owned another PC that wanted 30 round mags, I would feel the need to own 2x the mags anyway so doesn't save me much $$... like if I had 10 mags for 2 guns I would probably end up buying 10 more eventually..
 

ScottS

NES Member
Rating - 100%
41   0   0
Joined
Jul 19, 2006
Messages
4,797
Likes
2,765
Location
Live Free or Die
I don't own either and am in NH. Both seem to be in the buck a round ballpark.
I'm in NH, too. I have both (Glock-compatible lower and Colt-compatible lower). I've run dedicated 9mm ARs, drop-in conversions (both Colt and Glock), etc. Here's my take:

Colt: standard AR BHO. Operates just like a normal AR, manual of arms-wise. Looks better to me because of the straight mag. I bought a shitload of Metalform mags when PSA was blowing them out at $12.99 ea. Mags are a bit harder to find now, but still out there.

Glock: no BHO; I didn't want to screw with some of the Rube Goldberg setups I saw. Good enough for the MP5, good enough for me. You can find mags cheaply if you look. I have a mix of OEM and SGM Tactical mags. They run great. Big advantage of the Glock: I have a .40S&W upper, and I can switch calibers at the push of two buttons. In .40S&W 180gr FMJ, it's a real thumper.

Both run great. Both are fitted out exactly the same; same rail, same optic, same furniture. I was running Spike's ST-9X buffers in both, but I've recently switched to a captured Armaspec buffer in the Colt. Softens the "bounce" of a blow-back gun.

Gun to my head, I pick the Colt. It just looks better to my eye.

I don't know where you are in NH, but if you're anywhere in the South, you're welcome to drop by and shoot either one, or both. We'll just stay 6' apart.
 

ReluctantDecoy

NES Member
Rating - 0%
0   0   0
Joined
Oct 17, 2017
Messages
1,983
Likes
1,689
Location
Cambridge, MA
I'm in NH, too. I have both (Glock-compatible lower and Colt-compatible lower). I've run dedicated 9mm ARs, drop-in conversions (both Colt and Glock), etc. Here's my take:

Colt: standard AR BHO. Operates just like a normal AR, manual of arms-wise. Looks better to me because of the straight mag. I bought a shitload of Metalform mags when PSA was blowing them out at $12.99 ea. Mags are a bit harder to find now, but still out there.

Glock: no BHO; I didn't want to screw with some of the Rube Goldberg setups I saw. Good enough for the MP5, good enough for me. You can find mags cheaply if you look. I have a mix of OEM and SGM Tactical mags. They run great. Big advantage of the Glock: I have a .40S&W upper, and I can switch calibers at the push of two buttons. In .40S&W 180gr FMJ, it's a real thumper.

Both run great. Both are fitted out exactly the same; same rail, same optic, same furniture. I was running Spike's ST-9X buffers in both, but I've recently switched to a captured Armaspec buffer in the Colt. Softens the "bounce" of a blow-back gun.

Gun to my head, I pick the Colt. It just looks better to my eye.

I don't know where you are in NH, but if you're anywhere in the South, you're welcome to drop by and shoot either one, or both. We'll just stay 6' apart.
BHO is a continuing problem with my Glock mag set up, so 100% agree there. It has it in the lower, but because Glock mag, uses this extended bar connected to the BHO that reaches over to the mag follower. It just doesn't get enough leverage to lift it consistently after last round. That's even with a reduced power BHO spring and bending the follower tab on the BHO bar. Rune Goldberg indeed. What's worse is that I opted for a side charger. It is currently on the left like an MP5, but can't be locked open manually by itself like an MP5. I have to do this crazy reach under with my grip hand to hold the BHO button while charging it to lock it open. Not ideal.

So, yeah, another reason to go Colt mag.
 

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
I'm in NH, too. I have both (Glock-compatible lower and Colt-compatible lower). I've run dedicated 9mm ARs, drop-in conversions (both Colt and Glock), etc. Here's my take:

Colt: standard AR BHO. Operates just like a normal AR, manual of arms-wise. Looks better to me because of the straight mag. I bought a shitload of Metalform mags when PSA was blowing them out at $12.99 ea. Mags are a bit harder to find now, but still out there.

Glock: no BHO; I didn't want to screw with some of the Rube Goldberg setups I saw. Good enough for the MP5, good enough for me. You can find mags cheaply if you look. I have a mix of OEM and SGM Tactical mags. They run great. Big advantage of the Glock: I have a .40S&W upper, and I can switch calibers at the push of two buttons. In .40S&W 180gr FMJ, it's a real thumper.

Both run great. Both are fitted out exactly the same; same rail, same optic, same furniture. I was running Spike's ST-9X buffers in both, but I've recently switched to a captured Armaspec buffer in the Colt. Softens the "bounce" of a blow-back gun.

Gun to my head, I pick the Colt. It just looks better to my eye.

I don't know where you are in NH, but if you're anywhere in the South, you're welcome to drop by and shoot either one, or both. We'll just stay 6' apart.
Cool thanks! I'd definitely take you up on that, am in Plaistow.
 

milktree

NES Member
Rating - 100%
27   0   0
Joined
Aug 31, 2008
Messages
4,671
Likes
2,106
LRBHO in any magazine pattern can be unreliable and sometimes prone to parts like the bolt catch breaking. (The bolt + buffer combo should be 18-22 oz, with a ar10 equivalent spring sending it all into the catch)
Any idea what the spring rate is of an AR10 buffer spring?
 

milktree

NES Member
Rating - 100%
27   0   0
Joined
Aug 31, 2008
Messages
4,671
Likes
2,106
No I don't know. The AR10 carbine springs I use in my AR9s are noticably stronger than AR15 carbine springs.

OK, good to know. Thanks.

Could you take some measurements of your AR10 spring? You'll need a good caliper or micrometer.
- diameter of the spring wire
- free length of the spring
- number of coils (technically it's "active coils", but in this context with a large number of coils, the distinction doesn't matter)
- overall OD of the spring

With that I can calculate the spring rate.

I'm building (very, very slowly building) an AR9, and more data is better, right?
 

gxx9sdb

NES Member
Rating - 100%
81   0   0
Joined
Oct 1, 2010
Messages
2,737
Likes
1,650
Another thing to be aware of is that most people on YouTube / forums etc are building pistols with short barrels and less pressure. Blitzkrieg, for example, recommends a different buffer of you have a barrel in the 8-16” range due to the higher pressure, vs building a pistol. And the pistols have a different receiver extension tube also I guess.

So many variables; no wonder there are so many different opinions out there on what works

- barrel length
- Ammo
- bolt weight
- buffer weight
- buffer spring length
- buffer spring strength
- receiver extension length
... even saw some people touting heavy hammer springs ?!
 

teamRR

NES Member
Rating - 0%
0   0   0
Joined
Apr 24, 2019
Messages
535
Likes
361
I've got a couple examples of AR10 springs around (at least an Aero M5 and Sprinco orange). My mic isn't here, but will grab it after work and take a look tonight.
 

SJan

NES Member
Rating - 100%
31   0   0
Joined
Dec 9, 2007
Messages
3,788
Likes
1,118
Location
Attleboro, MA
Could you take some measurements of your AR10 spring? You'll need a good caliper or micrometer.
- diameter of the spring wire
- free length of the spring
- number of coils (technically it's "active coils", but in this context with a large number of coils, the distinction doesn't matter)
- overall OD of the spring
With that I can calculate the spring rate.
I have 3 AR10/ 308AR/9mm AR carbine length springs on hand. They all measure .069", two of them have 27 coils, the lengths are 11.5, 11.25 and the other has 25 coils and is 9.5". The various lengths could either be due to differing manufactures, or because of wear from use, probably due for a replacement on that short one.

I also checked out my AR15 carbine length springs, all are .067", have 35 coils, and are 10.5-11" long
 

milktree

NES Member
Rating - 100%
27   0   0
Joined
Aug 31, 2008
Messages
4,671
Likes
2,106
I have 3 AR10/ 308AR/9mm AR carbine length springs on hand. They all measure .069", two of them have 27 coils, the lengths are 11.5, 11.25 and the other has 25 coils and is 9.5". The various lengths could either be due to differing manufactures, or because of wear from use, probably due for a replacement on that short one.

I also checked out my AR15 carbine length springs, all are .067", have 35 coils, and are 10.5-11" long
OK, I measured some rifle and carbine springs and used your numbers and a spring rate calculator:

Spring namewire diameter (in)coil diameter (O.D.)No. of coils (total)spring rate (lb/in)free lengthpreloadbuffer strokeinitial forcefinal force
AR-10 carbine 1 SJan
0.069 "​
0.922 "​
27.0​
2.20 lb/in​
11.25 "​
4.50 "​
3.74 "​
9.89 lb​
18.10 lb​
AR-10 carbine 2 SJan
0.069 "​
0.922 "​
25.0​
2.39 lb/in​
9.50 "​
2.75 "​
3.74 "​
6.57 lb​
15.49 lb​
AR-15 carbine SJan
0.067 "​
0.922 "​
35.0​
1.48 lb/in​
11.75 "​
5.00 "​
3.74 "​
7.40 lb​
12.93 lb​
AR-15 carbine 1 mine
0.071 "​
0.922 "​
38.0​
1.71 lb/in​
10.00 "​
3.25 "​
3.76 "​
5.56 lb​
11.99 lb​
AR-15 carbine 2 mine
0.070 "​
0.925 "​
37.0​
1.65 lb/in​
11.00 "​
4.25 "​
3.76 "​
6.99 lb​
13.18 lb​
AR-15 carbine 3 mine
0.071 "​
0.942 "​
38.0​
1.60 lb/in​
11.13 "​
4.36 "​
3.76 "​
6.96 lb​
12.96 lb​
AR-15 rifle 1 mine
0.070 "​
0.952 "​
39.5​
1.40 lb/in​
12.50 "​
4.36 "​
3.70 "​
6.10 lb​
11.27 lb​
AR-15 rifle 2, Bushmaster
0.071 "​
0.934 "​
43.3​
1.43 lb/in​
12.75 "​
4.61 "​
3.70 "​
6.59 lb​
11.88 lb​

"preload" is how much the spring is compressed when the upper is assembled.
"initial force" is how much it takes to assemble the buffer/spring into the tube.
"buffer stroke" is the *maximum* the buffer can travel before hitting the back of the buffer tube
"final force" is how much it takes to push the buffer to the back of the buffer tube.

This does not take into account the mass of the buffer, or any spacers used to prevent the AR9 bolt from overtravel.

It's clear the AR10 springs are about 50% stiffer than AR15 springs.

The 25 coil AR10 spring is stiffer (because of the fewer coils) but actually exerts less force on the buffer because of its shorter free length.

@SJan How heavy is your buffer? Did you change the weights to tungsten or anything like that? How heavy is your bolt?

My current plan (based on reading and forgetting and re-reading way too much so I'm all mixed up now) is:
- Rifle length stock
- Rifle buffer with all three steel weights replaced with tungsten
- Rifle AR-15 spring
- 0.75" spacer to prevent buffer overtravel (which will also add about 0.5" preload to the spring)
 

gxx9sdb

NES Member
Rating - 100%
81   0   0
Joined
Oct 1, 2010
Messages
2,737
Likes
1,650
Wow, you took this analysis to a whole new level!
just to throw another variable into the equation, check out the Blitzkrieg hydraulic buffer. It is expensive, but if it lives up to the hype, it should be soft shooting and work across different ammo types. Also, no bolt bounce.

My plan, per their recommendation, is to try their HD buffer (for 16” barrels) + the additional buffer weight in an A5 extension with the orange Springco 308 carbine spring.

I may also try it in a carbine length extension to see what this short stroking is all about.

Corona has give me way too much time to research this! Too bad the range is closed



OK, I measured some rifle and carbine springs and used your numbers and a spring rate calculator:

Spring namewire diameter (in)coil diameter (O.D.)No. of coils (total)spring rate (lb/in)free lengthpreloadbuffer strokeinitial forcefinal force
AR-10 carbine 1 SJan
0.069 "​
0.922 "​
27.0​
2.20 lb/in​
11.25 "​
4.50 "​
3.74 "​
9.89 lb​
18.10 lb​
AR-10 carbine 2 SJan
0.069 "​
0.922 "​
25.0​
2.39 lb/in​
9.50 "​
2.75 "​
3.74 "​
6.57 lb​
15.49 lb​
AR-15 carbine SJan
0.067 "​
0.922 "​
35.0​
1.48 lb/in​
11.75 "​
5.00 "​
3.74 "​
7.40 lb​
12.93 lb​
AR-15 carbine 1 mine
0.071 "​
0.922 "​
38.0​
1.71 lb/in​
10.00 "​
3.25 "​
3.76 "​
5.56 lb​
11.99 lb​
AR-15 carbine 2 mine
0.070 "​
0.925 "​
37.0​
1.65 lb/in​
11.00 "​
4.25 "​
3.76 "​
6.99 lb​
13.18 lb​
AR-15 carbine 3 mine
0.071 "​
0.942 "​
38.0​
1.60 lb/in​
11.13 "​
4.36 "​
3.76 "​
6.96 lb​
12.96 lb​
AR-15 rifle 1 mine
0.070 "​
0.952 "​
39.5​
1.40 lb/in​
12.50 "​
4.36 "​
3.70 "​
6.10 lb​
11.27 lb​
AR-15 rifle 2, Bushmaster
0.071 "​
0.934 "​
43.3​
1.43 lb/in​
12.75 "​
4.61 "​
3.70 "​
6.59 lb​
11.88 lb​

"preload" is how much the spring is compressed when the upper is assembled.
"initial force" is how much it takes to assemble the buffer/spring into the tube.
"buffer stroke" is the *maximum* the buffer can travel before hitting the back of the buffer tube
"final force" is how much it takes to push the buffer to the back of the buffer tube.

This does not take into account the mass of the buffer, or any spacers used to prevent the AR9 bolt from overtravel.

It's clear the AR10 springs are about 50% stiffer than AR15 springs.

The 25 coil AR10 spring is stiffer (because of the fewer coils) but actually exerts less force on the buffer because of its shorter free length.

@SJan How heavy is your buffer? Did you change the weights to tungsten or anything like that? How heavy is your bolt?

My current plan (based on reading and forgetting and re-reading way too much so I'm all mixed up now) is:
- Rifle length stock
- Rifle buffer with all three steel weights replaced with tungsten
- Rifle AR-15 spring
- 0.75" spacer to prevent buffer overtravel (which will also add about 0.5" preload to the spring)
 
Top Bottom