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

[SJan]

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

I have 3 complete 9mm ARs, the 3rd was mostly assembled from spare parts after tinkering with everything. Two of those are SBR, 8.5", the last is a 16"
I have a box full of buffers from empty carbine buffers to sold 8oz extended length buffers and everything in-between. Some even have fancy spring loaded sliding weights on them . I settled on the Blitzkrieg / Kyntec / Kynshot hydraulic buffers for everything, they are 6oz.
For bolts, I have Taccom, CMMG, and Iron City Rifleworks, they are all 14-15oz.
All use a AR10 carbine spring, and are set with spacers to limit bolt travel to just barely not quite reach the bolt catch. No LRBHO
I have tested with lighter bolts (and combinations of bolts+buffers) but 20-21oz total is just right. This is also the optimal weight for most reliability. Going heavier and the gun may short cycle, more so if "limp wristed". Going lighter and OOB detonation becomes more of a chance. The spring is in fact holding the bolt closed in the moment of firing, but the weight of the reciprocating assembly is what keeps the bolt closed until pressure drops to a safe level... because Newton wrote a law saying the closed bolt must remain at rest until something acts against it. Too light and the bolt will open while there is still extreme chamber pressure, and cases rupture, get stuck or other bad things. I found, and others across the interwebs will mostly agree, 18-22 oz is safe.

My PCCs were assembled for competing in USPSA, where delivering accurate shots very quickly is needed to win. And not to brag, but I did some winning.

The following is all about perceived recoil, actually more about visual dot bounce, when looking through a red dot sight on a target. (how the dot returns to original placement and how it tracks up-down, or any sideways or figure 8 appearance) Making small changes within that 18-22 oz can be hard to notice. Ammo choice and the blowback parts need to work as a system. I found that using different ammo has more of a noticeable effect than changing parts in the gun. Light bullets going fast run very smooth in a 16" barrel ( I tried as light as 95gr, but 115g are close) and respond better to a lighter weight reciprocating assembly and/or a lighter spring. Overall I prefer the way heavy bullets shoot, and thats what I stuck with: 147g with a light charge of fast buring powder. Barrel length is also a considering factor. Barrel length and burn rate of powder work together here. A 147g bullet with a fast powder will be done burning and done accelerating in a 10" barrel. That load will show gains in velocity from a 4" pistol to a 5" pistol, all the way up to 10"... but no more comparing 10" up through 16".

Great info in this Full text of "Submachine gun designer's handbook" click on the title for images

 

[milktree]

Wow, you took this analysis to a whole new level!

I hate answers like, "just get the red one", or "this company makes a product..."

I much prefer knowing what the hell I'm buying. e.g. does "the red one" only work with the buffer from the same company? I don't like being locked in to stuff like that.

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.

Yikes! I'm sure it works, but that's kinda spendy, and how long will the hydraulics function properly?

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.

How much does the additional buffer weight weigh?

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

I don't understand why carbine or rifle length would make any difference.

 

[SJan]

Yikes! I'm sure it works, but that's kinda spendy, and how long will the hydraulics function properly?

Where the plunger is attached to the face of the buffer can break, there are several reported issues there in very high round count guns. I have not had a failure. I don't know of any leaking or other type of hydraulic failure in these.

I don't understand why carbine or rifle length would make any difference.

The length of travel needed in a 9mm is much less, so often the bolt travel is limited to change how the recoil functions and feels. This can be done several ways: with a longer buffer, with a spacer behind the bolt but infront of the buffer, or a spacer behind the spring. Using a longer than normal buffer, like the Spikes ST9x (7.7oz) gets you the weight you need in the buffer, and allows you to experiment with different lengths of travel when used in an A5 receiver extension (a buffer tube that is in between carbine length and rifle length) The same can be done in a more readily available rifle extension, but you will need to be sure you don't have so much travel as to allow the bolt to contact the back of the lower receiver. Using a stack of quarters in the tube is a quick and easy way to play with different travel lengths. Some guys have left the quarters in, others later made a spacer of the appropriate size out of something solid.

 

[22lr]

10 year, 1 million round warranty.
I also have a hard time just taking somebody’s word for it, but based on the feedback that I have seen from users, it is a really soft, simple setup.

The extra weight adds about 2 oz I think.

Spendy it is, but I have seen videos of people with a pile of buffers and springs that they used to try and dial in their 9mm so hopefully this will avoid all of that cost and time and hassle. Could be totally wrong!

I hate answers like, "just get the red one", or "this company makes a product..."

I much prefer knowing what the hell I'm buying. e.g. does "the red one" only work with the buffer from the same company? I don't like being locked in to stuff like that.




Yikes! I'm sure it works, but that's kinda spendy, and how long will the hydraulics function properly?



How much does the additional buffer weight weigh?



I don't understand why carbine or rifle length would make any difference.

 

[DW357]

I have 3 complete 9mm ARs, the 3rd was mostly assembled from spare parts after tinkering with everything. Two of those are SBR, 8.5", the last is a 16"
I have a box full of buffers from empty carbine buffers to sold 8oz extended length buffers and everything in-between. Some even have fancy spring loaded sliding weights on them . I settled on the Blitzkrieg / Kyntec / Kynshot hydraulic buffers for everything, they are 6oz.
For bolts, I have Taccom, CMMG, and Iron City Rifleworks, they are all 14-15oz.
All use a AR10 carbine spring, and are set with spacers to limit bolt travel to just barely not quite reach the bolt catch. No LRBHO
I have tested with lighter bolts (and combinations of bolts+buffers) but 20-21oz total is just right. This is also the optimal weight for most reliability. Going heavier and the gun may short cycle, more so if "limp wristed". Going lighter and OOB detonation becomes more of a chance. The spring is in fact holding the bolt closed in the moment of firing, but the weight of the reciprocating assembly is what keeps the bolt closed until pressure drops to a safe level... because Newton wrote a law saying the closed bolt must remain at rest until something acts against it. Too light and the bolt will open while there is still extreme chamber pressure, and cases rupture, get stuck or other bad things. I found, and others across the interwebs will mostly agree, 18-22 oz is safe.

My PCCs were assembled for competing in USPSA, where delivering accurate shots very quickly is needed to win. And not to brag, but I did some winning.

The following is all about perceived recoil, actually more about visual dot bounce, when looking through a red dot sight on a target. (how the dot returns to original placement and how it tracks up-down, or any sideways or figure 8 appearance) Making small changes within that 18-22 oz can be hard to notice. Ammo choice and the blowback parts need to work as a system. I found that using different ammo has more of a noticeable effect than changing parts in the gun. Light bullets going fast run very smooth in a 16" barrel ( I tried as light as 95gr, but 115g are close) and respond better to a lighter weight reciprocating assembly and/or a lighter spring. Overall I prefer the way heavy bullets shoot, and thats what I stuck with: 147g with a light charge of fast buring powder. Barrel length is also a considering factor. Barrel length and burn rate of powder work together here. A 147g bullet with a fast powder will be done burning and done accelerating in a 10" barrel. That load will show gains in velocity from a 4" pistol to a 5" pistol, all the way up to 10"... but no more comparing 10" up through 16".

Great info in this Full text of "Submachine gun designer's handbook" click on the title for images

I just bought one of the Blitzkrieg buffers for my Foxtrot Mike 7" SBR upper and a JP Carbine length AR10 spring as that’s what Blitzkrieg recommended for 7-16" barrels using their buffers. I was getting an occasional failure to eject, usually towards the end of the mag with just a few rounds left. I figured it was my bunny fart 150 gr reloads not having the power so I swapped in a JP AR15 spring I had laying around and that seemed to have solved the FTE’s. It also seems like it’s even softer shooting compared to the AR10 spring.

I’m using a stern defense glock mag adaptor FWIW.
Ejection isn’t all that consistent. Getting some brass ejecting at 2-3 o clock and some at 4-5 o clock. As long as they eject I guess I don’t really care.

I played around with quarters and could only put in 3 to allow the LRBHO to work.

 

[SJan]

I just bought one of the Blitzkrieg buffers for my Foxtrot Mike 7" SBR upper and a JP Carbine length AR10 spring as that’s what Blitzkrieg recommended for 7-16" barrels using their buffers. I was getting an occasional failure to eject, usually towards the end of the mag with just a few rounds left. I figured it was my bunny fart 150 gr reloads not having the power so I swapped in a JP AR15 spring I had laying around and that seemed to have solved the FTE’s. It also seems like it’s even softer shooting compared to the AR10 spring.

I’m using a stern defense glock mag adaptor FWIW.
Ejection isn’t all that consistent. Getting some brass ejecting at 2-3 o clock and some at 4-5 o clock. As long as they eject I guess I don’t really care.

I played around with quarters and could only put in 3 to allow the LRBHO to work.
View attachment 368920View attachment 368921

My PCC load is 130pf in the 8.5" barrel, it's below 120pf in a 5" pistol... And my pcc will run with the same spring/buffer with 100pf steel challenge ammo.

If your FTE is only near the end of a mag you may have weak extractor tension and it is relying on the magazine spring pressure tohelp the empty case get out the ejection port.

 

[DW357]

My PCC load is 130pf in the 8.5" barrel, it's below 120pf in a 5" pistol... And my pcc will run with the same spring/buffer with 100pf steel challenge ammo.

If your FTE is only near the end of a mag you may have weak extractor tension and it is relying on the magazine spring pressure tohelp the empty case get out the ejection port.

Interesting your bunny fart reloads run with a AR10 spring. My reloads are 132ish PF in my CZ pistols and 1911's. Haven't chronod them in the AR9 yet. But I really think it was the buffer spring as I shot almost 100 rounds after changing the spring and didn't have any FTE's. I took the FM bolt out and it holds a loaded run fairly snug even when I shake the bolt.

Was just reading this on the Blitzkrieg website:
In 9mm AR-15s these are recommended for 4-6" barrels if using our 9mm Hydraulic Buffer or 4-10" barrels if using our 9mm AKTIVE Buffer.
If you plan on shooting mostly lighter or softer running loads in these barrel lengths then you may need to go with the Sprinco Blue spring or the JP AR-15 Carbine spring.

But what your saying makes perfect sense regarding the mag spring etc. I just don't think that's what is happening here.

Do you get inconsistent ejection with your AR9? Does all your brass eject in the same direction?
Maybe the ejector on my stern defense adaptor needs some tweaking.

 

[ReluctantDecoy]

I just bought one of the Blitzkrieg buffers for my Foxtrot Mike 7" SBR upper and a JP Carbine length AR10 spring as that’s what Blitzkrieg recommended for 7-16" barrels using their buffers. I was getting an occasional failure to eject, usually towards the end of the mag with just a few rounds left. I figured it was my bunny fart 150 gr reloads not having the power so I swapped in a JP AR15 spring I had laying around and that seemed to have solved the FTE’s. It also seems like it’s even softer shooting compared to the AR10 spring.

I’m using a stern defense glock mag adaptor FWIW.
Ejection isn’t all that consistent. Getting some brass ejecting at 2-3 o clock and some at 4-5 o clock. As long as they eject I guess I don’t really care.

I played around with quarters and could only put in 3 to allow the LRBHO to work.

Just spitballing, but AR10 spring, which is often suggested in AR9's because of how violent and heavy straight blowback can be, may actually be too strong if you're running lighter loads. This is particularly true if you also have an active/2 stage buffer. It is completely possible that the lighter loads with the heavy spring aren't even compressing the buffer set up all the way to achieve the full benefits of the 2 stage buffer, then returning the BCG into battery before the case gets ejected.

That being said, a lot also depends on the weight of your BCG (if weighted or not).

 

[DW357]

Just spitballing, but AR10 spring, which is often suggested in AR9's because of how violent and heavy straight blowback can be, may actually be too strong if you're running lighter loads. This is particularly true if you also have an active/2 stage buffer. It is completely possible that the lighter loads with the heavy spring aren't even compressing the buffer set up all the way to achieve the full benefits of the 2 stage buffer, then returning the BCG into battery before the case gets ejected.

That being said, a lot also depends on the weight of your BCG (if weighted or not).

Yup I think you're right.

The Foxtrot Mike bolt is weighted. I believe the total weight of the bolt is 15 oz if I recall correctly.