Tuning Goals

[KF5MLT]

Some time previously, I found this ejection angle chart. When building a rifle, one of the obvious goals is to get that ejection angle into the 3:00 to 4:30 range.

Knowing you can still achieve that with too much gas compensated by too much mass, what are some of the less obvious goals when tuning a rifle or carbine? What are some of the things we should look for in addition to the ejection angle to know we have everything right or not as it pertains to the cyclic operation of the weapon?

[tom12.7]

How about looking how far it spits brass.
Making sure the bolt locks back on an empty mag when the rifle is cold and fouled.
Checking for harsh extraction signs on spent brass.
Looking around the ejection port for signs of brass swiping it.
Using multiple types of ammo, and checking for consistent function.

[3 AE]

My 6920 ejects @ 1455, my BCM ejects @ 1637. Shit, I knew I should have bought a left handed Stag. Live and learn! :suicide:

[Dead Man]

If a weapon is choking, and you notice extreme fore or aft ejection, it can be used as a diagnostic tool. I.E., if your weapon is occasionally closing on an empty chamber and brass is limply spitting toward the rear, try a lighter buffer and see if your ejection pops a little stronger. But if your weapon otherwise runs fine, you should not modify it because you notice your brass drops forward of the firing line. That could very well just be where it spits when it's running optimally.

Edit.. coffee break between reading and posting. Forgot the whole point.

To the point - firing with a wide variety of ammunition and running the weapon dirty are going to be the two best indicators of how well the weapon is cycling. Use good parts, start with an H buffer for standard configurations (not SBR or carbine stock on a 20" upper, etc), and check for shorting, extraction, and ejection issues with all the ammunition you'll be using. These guns are very reliable, overall, when put together right... if it fires and cycles, all is probably well.

[AKDoug]

From 3 thousand miles away I can hear IG beating his head on a table.

[VIP3R 237]

Op you are way over thinking this. Just go out and shoot your rifle, if it runs well with your ammo why try to fix it? A rule of thumb is run the heaviest buffer that will cycle reliably.


From 3 thousand miles away I can hear IG beating his head on a table.

My thoughts as well.

[Iraqgunz]

Actually I was beating my trigger finger with a full auto SCAR16 suppressed and some other stuff.

At no time was I thinking what o'clock is my brass ejecting nor do I care. That ejection chart is part of of the program, nothing more.

People are overthinking this whole buffer shit waaaaaaay too much.


From 3 thousand miles away I can hear IG beating his head on a table.

[JSantoro]

What are some of the things we should look for

As noted....the first thing you shold look for is a malfunctioning AR. Until you have one, don't even peek at that bloody pie-chart.

Once you've found a gun with consistent stoppages, that thing stops being stupid, and becomes a useful guide that can allow you to narrow your troubleshooting steps, and save you some time. As a stand-alone item...it's a giant Venus Flytrap; the pretty colors draw folks in, they get ensnared and start "fixing" things on an otherwise-well-functioning AR that was never broken or "untuned" in the first place.

Until your gun starts choking, your time is better spent fretting over where your rounds end up.

Until your gun starts choking, where your brass ends up is pretty universally DOWN.....because gravity....

IF your gun starts choking, and you've been able to eliminate boilerplate items like 1) bad mags, 2) bad ammo 3) lack of lubrication.....what's obvious is that whichever well-meaning fool it was who ginned up that chart either neglected to include the prerequisite (malfunctioning gun), or deliberately left it out. No way to know which.

If you stumbled across that thing, no drama, it's all over the danged place and it's not being correctly defined is certainly not your doing.

If somebody SENT that to you...punch them in their brain-face with a knowledge-fist, before they mislead somebody else.