View Full Version : Taste test challenge again, same results.
Three guys on my range this morning. One instructor, two students. Both familiar with ARs, not super experienced, but good enough to be getting qualified to carry one on duty.
Instructor has a uber tier-1 BCM 16” mid with Springco Green + A5-3, no muzzle brake.
I shoot it a bit. It feels clunky and slow. I walk to the office and come back with a built up 6920, all stock on the inside.
Fast pairs and triples, all three shooters shot tighter and felt like they didn’t work as hard with the 6920 as the BCM.
Chinese proverb of the day:
Overgassed, heavy sprung, heavy buffer guns shoot like sh@t.
First thing you need to do is get that bullshit Springco crap out, and the buffer is too heavy.... I mean Fukk! That's not comparing apples to apples at all... in addition to the totally different gas systems.
But BCMs middies (unless something has changed) are gassed the best in the industry. I mean, almost too lean when it comes to the 14.5s. There's something wrong if a carbine gas is running smoother than a middy... and it's probably in the goat rope buffer/spring set up.
Five_Point_Five_Six
03-10-22, 11:40
I don't disagree about overgassed guns with heavy springs and buffers shooting like dog turds, but the Sprinco and A5H3 combo is retarded. I would bet that a standard rifle spring and A5H2 would run a lot smoother.
I don't disagree about overgassed guns with heavy springs and buffers shooting like dog turds, but the Sprinco and A5H3 combo is retarded. I would bet that a standard rifle spring and A5H2 would run a lot smoother.
Agree. Some booger eater effed up that middy. A BCM will make that dog shit combo work, because middies are pretty forgiving. But damn... you really have to work hard to make a BCM middy less smooth than even a Colt Carbine. Who does that shit?? It's not even noon, and I'm already pissed off at stupidity.
First thing you need to do is get that bullshit Springco crap out, and the buffer is too heavy.... I mean Fukk! That's not comparing apples to apples at all... in addition to the totally different gas systems.
But BCMs middies (unless something has changed) are gassed the best in the industry. I mean, almost too lean when it comes to the 14.5s. There's something wrong if a carbine gas is running smoother than a middy... and it's probably in the goat rope buffer/spring set up.
I’ve found the BCM 16” mids are some of the harshest shooting barrels IME. They’re ported at .076” which isn’t huge, but it’s way past lean, but whatever they do with the chamber or bore makes em kick. I’ve ran em side by side with 6920s and you’d be surprised.
Are we supposed to be surprised that a heavily sprung, heavily buffered AR ran slower than a factory Colt?
An AR15 custom tuned for one shooter may not impress everyone else in the room.
Are we supposed to be surprised that a heavily sprung, heavily buffered AR ran slower than a factory Colt?
It’s not only that it’s slower, it’s more difficult to control, and in my long term experience, it’s not even as reliable.
A lot of people on this forum think the A5 with a stiffer spring and the heaviest possible buffer is the end-all. I’ve disagreed for a long time and when they get put side by side, there’s no advantage.
An AR15 custom tuned for one shooter may not impress everyone else in the room.
It could have at least worked better for the guy that owned it :laugh:
I learned that lesson trying to tame my Mk18 10.3, I kept putting heavier buffers and it kept delivering more felt recoil. Heaviest buffer that will run is not the best approach.
The biggest consistency in barrel makers of all size and shape is inconsistency.
PB
Most of the issues I've seen with the A5 have to do with the weak Vltor spring supplied with the kit. I've not seen the issues with BCM rifle, Springco Green, etc. Over buffering will only make it worse.
I've tried switching the same uppers between A5 and carbine RE equipped lowers and found the system to function smoother with the A5, resulting in an easier time getting the dot back in target during strings of fire. I guess I could time them head to head some time.
Edited to add that I don't doubt the authenticity of your observations. I just feel that there's an additional X factor that's unrecognized at this point.
titsonritz
03-10-22, 13:44
I’ve found the BCM 16” mids are some of the harshest shooting barrels IME. They’re ported at .076” which isn’t huge, but it’s way past lean, but whatever they do with the chamber or bore makes em kick. I’ve ran em side by side with 6920s and you’d be surprised.
That is the same port size used by SOLGW and SIONICS as well as BCM. I've never shot a 16" BCM middy, mine are both 14.5" and also have .076" GP, but I'm using a carbine RE w/ an H2 buffer.
I have A5’s with VLTOR springs and 7 position RE’s in all of my builds.
All but the two 10.3” MK18’s contain A5H2 buffers. The MK18’s each have an A5H3.
The scratch builds have barrels from various and popular suppliers everyone would recognize as producing quality barrels.
All shoot wonderfully smooth and compare very favorably to my two stock 6920’s, which “may” shoot a tad more harshly given the carbine gas system.
Realize, this is 556 we are talking about so recoil and harshness is pretty minimal regardless.
I’d toss an A5 spring and an H2 into that BCM and I bet it fixes any perceived issues.
That is the same port size used by SOLGW and SIONICS as well as BCM. I've never shot a 16" BCM middy, mine are both 14.5" and also have .076" GP, but I'm using a carbine RE w/ an H2 buffer.
For whatever reason, the BCM middie I've shot recoiled a bit harsher than the Sionics middie I shot next to it. Could just be confirmation bias, but the other shooter felt the same. May just be the result of such a lightweight barrel (BCM ELW-F, iirc).
grizzlyblake
03-10-22, 15:17
For whatever reason, the BCM middie I've shot recoiled a bit harsher than the Sionics middie I shot next to it. Could just be confirmation bias, but the other shooter felt the same. May just be the result of such a lightweight barrel (BCM ELW-F, iirc).
Overall weight obviously plays a big part with the minimal recoil energy of 5.56 as well.
Anecdotal - My 16" BCM ELW mid was set up with an Aimpoint H2 and the factory BCM muzzle device. I switched to a Trijicon Credo in an ADM mount and an A2 birdcage muzzle device. When zeroing the new setup I was surprised how much less perceived recoil I experienced.
I would have probably been educational had you pinned his BCM upper onto your Colt lower so he could quickly tell the difference himself.
As was stated earlier, rifle weight can't be ignored, and neither can muzzle devices. How was each carbine set up? You stated that the BCM didn't have a comp but didn't say what it does have. What muzzle device did the built up Colt have?
I would have probably been educational had you pinned his BCM upper onto your Colt lower so he could quickly tell the difference himself.
As was stated earlier, rifle weight can't be ignored, and neither can muzzle devices. How was each carbine set up? You stated that the BCM didn't have a comp but didn't say what it does have. What muzzle device did the built up Colt have?
Surefire 3-prong on the BCM, Smith Vortex on the Colt.
I’ve ran that test with 6920 uppers on carbine/H&H2 lowers and A5 lowers and 5/5 shooters had better results with the H. The H2 and A5 were closer.
Surefire 3-prong on the BCM, Smith Vortex on the Colt.
I’ve ran that test with 6920 uppers on carbine/H&H2 lowers and A5 lowers and 5/5 shooters had better results with the H. The H2 and A5 were closer.
Now I'm going to have to go do science and stuff. What drills did you guys do?
fedupflyer
03-10-22, 21:46
Mike Pannone recommends a blue spring paired with an H2 buffer.
titsonritz
03-10-22, 21:57
Mike Pannone recommends a blue spring paired with an H2 buffer.
That's what I'm running.
Now I'm going to have to go do science and stuff. What drills did you guys do?
They had paper 7 yards and 25 yards. Present from low ready, 3 rounds at 7, 2 at 25.
When I did the 6920s I had a B8 at 50, 5-5-5 standing kneeling, prone, and triples and doubles at 10 and 25 standing.
That set up is just wrong. No wonder it shot like shit. Maybe if it was a carbine length set up but not for a middy. I use the A5H2 Sprinco green set up in my 13.7 mid length and it shoots fine. I am still not convinced its the be all to end all over a standard set up but I haven't had the chance to run it hard yet either.
For whatever reason, the BCM middie I've shot recoiled a bit harsher than the Sionics middie I shot next to it. Could just be confirmation bias, but the other shooter felt the same. May just be the result of such a lightweight barrel (BCM ELW-F, iirc).
One thing to remember is that gas drive increases as gas block journal diameter decreases, for a given port size. IOW, a .625 gas block journal barrel (as on the ELW) will produce harsher recoil than a .750 journal barrel, everything else being equal. According to Clint at BRT, you need to go down one gas port size from a .750 to a .625.
One thing to remember is that gas drive increases as gas block journal diameter decreases, for a given port size. IOW, a .625 gas block journal barrel (as on the ELW) will produce harsher recoil than a .750 journal barrel, everything else being equal. According to Clint at BRT, you need to go down one gas port size from a .750 to a .625.
I do not doubt that they did the testing to make that determination but curious if you have a link to where I can learn / read more about that or him explaining the 'why' behind it.
Appreciate you pointing me in the direction to learn more if you can sir.
I do not doubt that they did the testing to make that determination but curious if you have a link to where I can learn / read more about that or him explaining the 'why' behind it.
Appreciate you pointing me in the direction to learn more if you can sir.
Ouch! Wish I could remember where I read it. It was almost certainly here, but it's been a few years. I also had a correspondence with Clint about it a few years back when he was helping me decide on a gas block insert, before he started selling the gas restricted gas tubes.
As to the thinking behind it, IIRC, it has to do with the length of the gas port, not just its diameter (maybe its overall volume?). Hopefully someone who knows more about the flow dynamics can jump in, but it may have something to do with a longer gas port restricts peak gas flow more than a shorter one.
I know that in cars, longer venturi velocity stacks of a given diameter on an intake manifold do increase torque at lower RPM, at the expense of inhibiting peak power, ie shorter stacks increase peak power at the expense of lower end torque. Peak power is all about maximum airflow as that is when the motor is hungriest for air.
Find a finger diameter tube like a foot long. And a clothespin. Do 20 burpees and start breathing through the tube with the clothespin on your nose. After you regain consciousness, cut the tube in half. Repeat.
You can do this with ET tubes if you have them… thats how I learned about this. Its obvious how much slower your visual field narrows with a shorter tube.
Alternatively, just realize that a longer tube passes less air for a given effort (pressure). And a hole in a barrel is a tube defined by the difference in bore radius and total radius. I think its called tunnel drag, but I’m not sure.
Find a finger diameter tube like a foot long. And a clothespin. Do 20 burpees and start breathing through the tube with the clothespin on your nose. After you regain consciousness, cut the tube in half. Repeat.
You can do this with ET tubes if you have them… thats how I learned about this. Its obvious how much slower your visual field narrows with a shorter tube.
Alternatively, just realize that a longer tube passes less air for a given effort (pressure). And a hole in a barrel is a tube defined by the difference in bore radius and total radius. I think its called tunnel drag, but I’m not sure.
:sarcastic:
Alternatively, just realize that a longer tube passes less air for a given effort (pressure). And a hole in a barrel is a tube defined by the difference in bore radius and total radius. I think its called tunnel drag, but I’m not sure.
Pretty good way of explaining it. Appreciate you making it stupid simple to understand sir...
Find a finger diameter tube like a foot long. And a clothespin. Do 20 burpees and start breathing through the tube with the clothespin on your nose. After you regain consciousness, cut the tube in half. Repeat.
You can do this with ET tubes if you have them… thats how I learned about this. Its obvious how much slower your visual field narrows with a shorter tube.
Alternatively, just realize that a longer tube passes less air for a given effort (pressure). And a hole in a barrel is a tube defined by the difference in bore radius and total radius. I think its called tunnel drag, but I’m not sure.
Poiseuille's law:
velocity of a liquid flowing through a capillary is directly proportional to the pressure of the liquid and the fourth power of the radius of the capillary and is inversely proportional to the viscosity of the liquid and the length of the capillary.
Oh, finding those synapses really hurt….
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