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Short of talking to manufactures and convincing them to release their tech info, there is no way to say. Or, I guess, you can buy a bunch of barrels and measure ports, then run bunch of tests...
There is a lot of tangential guessing that goes here that has little relevance. You say BCM has it figured. A couple of years ago somebody posted that BCM's gas ports are the same for 14.5 and 16", quoting BCM as a source. I have a 16" BCM middy that was cut down to 14.5". Nothing was done to gas port. I've actually sourced the weakest ammo I could to test it with. The rifle has ran nonstop in temps from 28 to 115 F, any ammo, any volumes if fire including famous MD carbine 2 class. If you thought these two bits of info through carefully, you'd come to a conclusion that BCM 16" theoretically should be overgassed. Does it matter a whole lot to a ton of people who run BCM's middies in all bbl lengths?
I've got a 14.5 BCM middy with about 5000 rnds through it with everything from lake city M855 to cheap PMC crap. I've tried to make it fail and it has yet to, the thing runs like a clock!!
Last edited by .300; 09-30-12 at 18:32.
BCM 14.5 w/ BCE 1.5
Thanks Grant!!!
SCAR 17
Rem 870 Tactical {going to Wilson's soon)
S/A 1911A1
Yea it's been to Novaks!
Glock 22
Unfortunatly, the above is bullshit.
Being able to diagnose an overgassed gun is pretty damn simple.
The only problem is that the "best" way to do it is looked down on by most people here. Those same people also say stupid shit like "If it isn't malfunctioning, don't worry about it and keep shooting it until it breaks.".
So, knowing that, I really don't feel like explaining the diagnosis process only to get dogpiled by people who "think" they understand machines, when they really don't.
And making judgment calls like you did without considering other possibilities puts you in the same league as the rest.
If your going to go with a mid length bcm does it the best. All i own are middies and one noveske intermediate, and the bcm is head and shoulders ahead in the middies.
It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori
Alright, i'll give you the benifit of the doubt. Once.
All things being equal, i.e. known milspec parts with very low round count, meaning that springs are not excessivly worn, parts are expected to be in spec from the factory, etc., and using M193 milspec ammunition, brass throw (yea, I use brass throw) is extreme forward to the 1:00 to 1:30.
Most people I explain this to have a knee-jerk negative reaction to using brass throw as an indicator simply because some folks on here poo-poo it.
The fact of the matter is that every machine has optimal operating perameters, and when the machine starts operating outside of those perameters, it becomes more prone to failure.
Lots of folks try to view a rifle simply as its only expected operating indicator is whether it's throwing lead out the front end, and to not worry about the gun until it stops doing that. If the people who subscribe to that ideal were to do that with their cars, they would literally drive their cars until the wheels fell off.
So, with that being said, a "properly working" AR with mil-spec parts, shooting Mil-spec ammunition, will exhibit certian behaviors, not just in the rounds coming out of the barrel, but also in cycle speed, empty cartridge ejection, etc.
Understanding that things like ejection pattern is a bahavior indicator for an entire sections of possible issues, we then use the process of elimination to narrow down the cause of an "out of spec" ejection.
First starting with simple fixes such as out of spec springs, normally caused by excessive cycles, then moving on to components.
In this case, the gun was exhibiting traits of an over gassed gun. First thing to look at would be worn action springs, removing an "O" ring if one were present, verifying proper buffer weight for the system, measuring action spring length to ensure it's within Mil-spec, etc.
A quick check through of those issues coupled with the fact that over the first 500 rounds from brand new, the issue became slightly worse, It's a fact that the gun was in fact "over-gassed" and was showing signs of excessive bolt speed. A swap out to a known, in spec performing BCG from another gun that resulted in the same behavior, followed by swapping lowers to obtain the same behavior, and finished off with swapping to a lower that used the Vltor A5 with the XP spring, pretty much cinched it.
So, if you're one of those folks who misunderstands the brass throw chart, you won't give a crap as to how I diagnosed excessive bolt speed as caused by being over-gassed.
The fact of the matter is that when used PROPERLY, brass throw is a great indicator of where to start looking for issues, and perhaps even more importantly, returning the gun to expected operating behaviors using only proper, milspec parts instead of stupid aftermarket bullshit.
Regarding the "shoot it until it breaks" crowd, I wouldn't drive my car until the wheels fall of, so why in the blue **** am I going to ignore the signs of issues that mu gun displays and have it shit the bed on me when I *may* need it. I prefer to have the brass throw between4:00 and2:30. Anything outside of that makes me start diagnosing the gun. Anything past 4:00 indicates undergassed with a possibility of FTE's, etc. Anything under 2:30, while still generally pretty reliable, starts causing unecessary wear on the gun due to the excessive bolt speeds, increases dot-bounce and makes the gun more difficult to control, and means that springs are more prone to catestrophic failure as they are starting to reach the end of their fatigue life.
Yea, i've been accused of being a perfectionist, but I don't have a lot of failures in my guns because I address possible issues BEFORE they become issues. Just like I keep my car in good running order BEFORE things break on me.
Ok, I apologize. Normally when someone asks something like "how did you determine X, Y, or Z, and follows it with "did it malfunction?", it ususally accompanied by some snarky comment like "shoot it until it breaks".Edit: maybe I should have posed this question another way. What is your definition of "normal" function? Since you had zero malfunctions, but still deemed your N4 to be overgassed, I assume you're using some other method to quantify what you refer to as "normal" function.
I apologize if that's not where you were going with that.
Like I said above, every machine has obvious performance expectations regarding its primary function (in this case throwing lead downrange), but it also has secondary functions which are indicators of the "health" of the machine and express how well it is performing its primary function (throwing lead down range). Actual failure of the primary indicators is not the only way to diagnose the health of the machine, nor is it the optimal way.
Many people want to ignore the secondary indicators and rely soley on the primary indicators, and that's how components of their guns reach full failure as well as experience more overall wear then a well taken care of gun. I like machines, so I take care of my machines. I pay attention to them and I ensure that they are kept within acceptable operating perameters so that I don't ever have to worry about failure barring unforseen issues with the components themselves.
A properly built gun with Milspec parts using milspec ammunition, *should* throw brass at approx the 3:00. Like I said above, I personally accept a range between 2:30 and 4:00 before I start looking at spring replacement, etc. This usually allows a wider range of ammunition to be used without fear of undergassing with weak ammunnition, and be gassed enough to overcome fouling buildup over time. Makes it less picky so-to-speak.
Last edited by GrumpyM4; 09-30-12 at 18:34.
It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori
I don't blame you for not running something till it breaks that is plain stupid. Also judging a malfunction by using that stupid ejection chart is just as stupid. You used the example of a mil spec rifle performing a certain way. I was not aware that a noveske mid length was a mil spec rifle. If someone like IG came in here and said the chart is how they check for overgassing i would believe it to be relavant. As far as i know nobody reputable uses the chart and for good reason. I still say it is odd for a gun so obviously ovegassed, and not malfunctioning is very odd.
****in' really?
This is the exact bullshit I was expecting earlier that made me not want to explain the diagnosis. People who don't understand machines and accept everything their spoonfed.
Let's set our baseline of understanding......firstly, given the milspec standard, that means that there is an "optimal" bolt speed to ensure reliability, useability (recoil control, etc.), and miminal wear on the weapon.
Let's go back to cars as an example. An engine will run with a variety of fuel/air mixtures. But there is an optimal mix that allows the car to run without damaging the engine, using more fuel then it needs to, and gives it the power it needs without either flooding or starving when pushed. By your ****ing logic, we ignore that and run the **** out of the car because, ****-it, it's working, who cares? How can you say it's running "over-gassed"(fuel rich) when it seems to be working fine? Paying attention to the exhaust to notice that the engine is exhausting a lot of unburnt fuel, or paying attention to the other secondary performance issues of the engine is ****ing retarded because it still runs, right?
That optimal bolt speed is the same, regardless of which length gas system is actually on the gun.
For you slow people, that means that the milspec operating perameters are the BASELINE from which everything else is judged.
Just because a gun has a different length gas system doesn't mean it's supposed to work right with a slower or faster bolt speed. The factors involved such as dwell time, pressure at the gas port based on distance from the chamber, etc. all have an effect on this, hence why the gas port diameter is changed for each lenght gas system to accomdate for those variables in trying to reach the EXACT SAME PERFORMANCE EXPECTATIONS.
Just because a mid length isn't "milspec" doesn't mean we throw the expecations of the milspec baseline out with the bathwater. If you cannot understand this and keep ignoring the brass throw chart without having any concept or idea of how the system works, keep your mouth shut.
Same goes unless you have something worthwhile to say other then "IG would disagree with you.".
And I don't give a shit who else does, or doesn't use the ejection chart. Strangly enough, my ideal ejection pattern doesn't match the chart either.
But, ****it, people like you don't want to hear it. Ejection pattern as a trouble-shooting starting point is pretty ****ing good. I use it very successfully and havn't destroyed my guns (or anybody elses for that matter) and I don't have problems with my guns other then stupid shit that cannot be accounted for or just good old fashioned honest mistakes (nitriding fireing pins for example).
It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori
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