Need Help, AR Timing is Off

[Scorpio64 5,190]

I finally got the M4gery I built last fall out to the range last weekend.  It shoots fantastic but the timing seems to be off.  I dunno if it really matters but the brass is ejecting at between 1 o'clock and 2 o'clock, but mostly closer to 1.  First lemme give y'all some specs.  Radical Firearms 5.56 16" 1:9 M4 profile carbine length gas system.  I dunno what the gas port size is.  Tried to look it up but no luck. Also, I was shooting AE M855

 

Anyway, from what I've read elsewhere it seems it is "over gassed" but I can adjust the timing with a heavier buffer.  The one that's in there now came with a PSA LPK and weighs in at 2.85 Oz.  I think the difference is negligible  from the 3.0 it's supposed to be but I thought I should mention it just in case.

 

So the question of the day is: how much heavier a buffer do I need to go with to get the ejection closer  to 3 o'clock?

[OfcrFek 21]

Can always pick up an H3 buffer for cheap and give it a shot. Or just buy the weight and put it in your current buffer. Only other advice I have, and I don't really advise it, is to get a longer buffer spring and start cutting links out little by little until you get the desired ejection pattern. Quite frankly, I'd get a heavier buffer (H3) and call it a day.

[Lalo 13]

So you're saying that the AR is functioning just fine, but the direction in which the brass is ejected is not what others consider "normal" so you want to make changes so that the brass piles up over here instead of over there?

 

If it bothers you that much, get a Spikes T2 buffer.

 

Personally, I would fix something that ain't broken.

[T Bill 649]

[Vlad G 345]

Most ARs are over gassed, hell the entire thing is designed to be overgassed by a lot.  You can "fix" the ejection pattern with heavier buffers, but that doesn't actually do anything about reducing the wear on the parts that handle the gas and adds more mass that moves back and forth. Personally I don't view that a solution that is worth doing, all you are fixing is where the brass piles up.

 

I think being overgassed is probably not good but it is better then undergassed so if you are going to error in one direction that is the one to use.  I would suggest a few alternatives:

 

1) shoot something other then high pressure m855. An AR that tries to run on vanilla .223 is probably always going to be a bit overgassed with 5.56

2) get an adjustable gas block
3) get a different barrel with a longer gas system and perhaps a smaller gas hole.

[Scorpio64 5,190]

Most ARs are over gassed, hell the entire thing is designed to be overgassed by a lot.  You can "fix" the ejection pattern with heavier buffers, but that doesn't actually do anything about reducing the wear on the parts that handle the gas and adds more mass that moves back and forth. Personally I don't view that a solution that is worth doing, all you are fixing is where the brass piles up.

 

I think being overgassed is probably not good but it is better then undergassed so if you are going to error in one direction that is the one to use.  I would suggest a few alternatives:

 

1) shoot something other then high pressure m855. An AR that tries to run on vanilla .223 is probably always going to be a bit overgassed with 5.56

2) get an adjustable gas block

3) get a different barrel with a longer gas system and perhaps a smaller gas hole.

 

Based on what you, and others, are telling me, I'm wondering if the problem may resolve itself over time with some build up in the gas system.  I've only put about 120 rounds through it so far.  I will get some tamer 55gr 223 and give that a try, though I'm already invested in a lot of M855.  The idea behind going with a 1:9 twist on the M4gery was so I could share the M855 with my 1:8 SPR but also shoot the lighter less expensive stuff in the M4 too. 

 

Another idea comes to mind now, I dunno how good an idea it is but I may try it anyway just for kicks. I really like the sight profile on the flip up front sight gas block so that would be the last thing I'll change,  I agree 100% that an adjustable block would resolve this but they add moving parts.  My inner engineer is telling me to keep it as simple as possible with the least amount of moving parts.  What I will do is look for gas tubes with a smaller ID, or maybe just get another plain vanilla tube and experiment by crimping it to restrict the flow until the gas pressure is correct.

 

Thanks to everyone for you help.  I am OCD about some things, like ejection patterns, because they are a symptom of an underlying problem.  After reading your suggestions, it's apparent that going with a heavier buffer would only remedy the symptom and not fix the problem.  Your input has helped me realize this and put me on the right track.

[MidwestPX 172]

If anything, the problem will get worse as the gas port erodes and opens up.  Your best solution to this is an adjustable gas block.  They're relatively cheap ($20-30ish for a low-profile one) and allow you to do more than what a heavier weight buffer will.  An adjustable gas block has two "moving" parts with the first being the screw that adjusts gas flow and the second being a set screw that immobilizes the first.  I wouldn't sweat these parts inducing new failures.  I probably run ARs harder than anyone on this board as most of mine have the therapeutic third position and I've tried to get those very screws to fail but haven't (yet?).

[Vlad G 345]

Your inner engineer should should keep track of what Bernuolli has taught us about gas flow restrictions and speeds of gases. I wouldn't screw with the gas tube because you should probably try to not mess with different pressures at different ends of it. It might work, or it may do strange things. 

 

The Adjustable gas blocks don't add more moving parts, they just add more parts that MIGHT move if they are not incorrectly set. Broadly speaking, I agree with you and I don't have an adjustable gas block on any of my rifles, but I do chose barrels with smaller gas holes to make up for it. The other problem is that there aren't any two piece adjustable gas blocks for normal sized barrels (JP makes one for their fat barrels) so in NJ screwing around with the gas blocks is a bitch if you can't remove them easily.  

 

Your other option could be an adjustable gas key. These are a newer thing, and while I'd prefer reducing the gas at the barrel, reducing it in the key might be the next best thing. I think of my buddies is using one now and I haven't heard him bitch about it. RCA and SunDevil make such things and they are fairly cheap to try out. 

[Scorpio64 5,190]

If anything, the problem will get worse as the gas port erodes and opens up. ........

 

I thought the opposite would happen, that the gas tube would become clogged with carbon buildup over time, like my arteries from eating too much butter.

[Scorpio64 5,190]

Your inner engineer should should keep track of what Bernuolli has taught us about gas flow restrictions and speeds of gases. I wouldn't screw with the gas tube because you should probably try to not mess with different pressures at different ends of it. It might work, or it may do strange things. 

 

.............so in NJ screwing around with the gas blocks is a bitch if you can't remove them easily.  

 

Your other option could be an adjustable gas key..............

 

Good point, I was wondering where I would crimp the tube, probably as close to the gas block as possible.  In spite of the abundance of good advice, I'm going to give it a try anyway.  It is not dangerous and can easily be undone.  Like I said, inner engineer, experiments, I just have to know.

 

Originally I wanted a NJ compliant fixed sight tower but my bbl lacked the detents, so I went with a folding two piece.  Changing the block won't be difficult if I go that rout.

 

Now that is interesting, didn't know they existed.  Will look into that too.

[Vlad G 345]

Your liquefied butter doesn't operate at 52k psi inside your arteries. Gas ports wear out bigger and don't clog. 

[MidwestPX 172]

I thought the opposite would happen, that the gas tube would become clogged with carbon buildup over time, like my arteries from eating too much butter.

With tens of thousands of PSI of pressure passing through there, nope.

[MidwestPX 172]

Also, given the choice between a gas block and gas key, unless the block is really difficult to access (monolithic upper with the handguard over the block), use the adjustable gas block.  At the gas port, your adjustments don't need to be as discrete versus at the key.  For instance, when I'm adjusting gas blocks, I'm measuring in quarter or half turns of the adjustment screw.  With a gas key, I'm adjusting in increments of ten degrees or less which consumes more time and ammo.

[Vlad G 345]

Oh I agree, blocks are better then keys, but with our laws and perma-attached muzzle devices, gas blocks are more of a pain to remove and install, given a lack of two piece adjustable gas blocks. 

[Old School 611]

This is why ARs are not erector sets.

 

Do any of the cobblers actually know what size their gas port should be? No offense not directed at OP. 

 

Difference in diameter between carbine and rifle length gas systems?

 

I know one assembler, and I buy parts from them, that on their assembled uppers drills WAY oversized.

 

Now I buy good barrels but I spec the gas port size.

 

Like Vlad said, adjustable block if you want to save this barrel.  Just trash the pinned comp and lesson learned.

 

The existing condition will not add to the life of your rifle.

[Scorpio64 5,190]

I contacted Radical Firearms to get the spec for the gas port.  I was told the gas port size they use on my barrel is .089"

 

Then I found this on the interwebs.  It's from a chart listing gas system specs.

 

bbl length-bbl diameter-distance to muzzle-min gas port diameter - max gas port diameter
16 - .750 - 8.375 - .070 - .086

 

assuming the chart is correct, this probably explains the overgassing with the gas port on my bbl being .003" larger than the maximum recommended diameter..

[Scorpio64 5,190]

For the cobblers.

 

[Silence Dogood 468]

With an M-16 bolt carrier, I still eject at around 3:00 - 4:00.

[OfcrFek 21]

that's good enough, at least if that was my AR lol

[raz-0 1,261]

This is why ARs are not erector sets.

 

Do any of the cobblers actually know what size their gas port should be? No offense not directed at OP. 

 

Difference in diameter between carbine and rifle length gas systems?

 

I know one assembler, and I buy parts from them, that on their assembled uppers drills WAY oversized.

 

Now I buy good barrels but I spec the gas port size.

 

Like Vlad said, adjustable block if you want to save this barrel.  Just trash the pinned comp and lesson learned.

 

The existing condition will not add to the life of your rifle.

 

I've never seen anyplace that lists a correct sizing for gas ports that isn't a range. You can pretend there is one right answer, but there isn't. Between various ammo attributes, weather, how tight or shot out the barrel is, rifling type, etc. you'll never narrow it down to a single number that's guaranteed to work. 

 

As to fixes.. gas port too small? You can drill it out. 

Gas port too big? You can use an adjustable gas block or gas key, or get a new barrel. 

 

ARs are pretty erector set like. I've built more than a few, and the only thing that was ever a problem with making a gun run was a part I knew I was stepping outside of the norm on. Given the number of franken guns out there vs. the rate of people with tricky problems making them run, it seems a good deal form being hard, especially if aiming for the middle of the road. 

[High Exposure 5,680]

FYI:

 

JP Clamp On Adjustable Gas Block for .750 barrels:

https://www.jprifles.com/buy.php?item=JPGS-9

 

Many companies make their gas ports bigger than the spec so they will run on the shitty cheap ammo many people buy. It creates a false sense of reliability.

[n4p226r 105]

For the cobblers.

 

 

why would the thickness of the barrel at the gas port change the gas port size?  also, wouldn't most of these numbers still be over-gassed?   the mil-spec for a 14.5" should be around .063 (what should be on all colt 14.5" and 16" barrels) and the mk18 @ 10.3" should be .07.  both of which have .750 diameter barrels.   

[n4p226r 105]

FYI:

 

JP Clamp On Adjustable Gas Block for .750 barrels:

https://www.jprifles.com/buy.php?item=JPGS-9

 

Many companies make their gas ports bigger than the spec so they will run on the shitty cheap ammo many people buy. It creates a false sense of reliability.

 

 

 

 

I've never seen anyplace that lists a correct sizing for gas ports that isn't a range. You can pretend there is one right answer, but there isn't. Between various ammo attributes, weather, how tight or shot out the barrel is, rifling type, etc. you'll never narrow it down to a single number that's guaranteed to work. 

 

As to fixes.. gas port too small? You can drill it out. 

Gas port too big? You can use an adjustable gas block or gas key, or get a new barrel. 

 

ARs are pretty erector set like. I've built more than a few, and the only thing that was ever a problem with making a gun run was a part I knew I was stepping outside of the norm on. Given the number of franken guns out there vs. the rate of people with tricky problems making them run, it seems a good deal form being hard, especially if aiming for the middle of the road. 

 

 

that's why you either buy from a respectable manufacturer or get one spec'd to your liking.   even noveske and DD are known to be a tad overgassed. 

[MidwestPX 172]

that's why you either buy from a respectable manufacturer or get one spec'd to your liking.   even noveske and DD are known to be a tad overgassed.

That's because they know people will drop $3k on a rifle and skimp on feeding it properly

[n4p226r 105]

This is true. Not much you can really do about it.

[raz-0 1,261]

that's why you either buy from a respectable manufacturer or get one spec'd to your liking. even noveske and DD are known to be a tad overgassed.

So's the m4.

[n4p226r 105]

So's the m4.

 

 

technically thats designed that way so wouldn't that be "properly" gassed?

 

i don't really see the issue with slight overgassing and a slightly heavier buffer.  it should run pretty smooth and reliably that way.  but you can definitely tell shooting a slightly overgassed gun with a H or H2 buffer vs one of the heavily overgassed carbine buffer, semi-auto carrier designs.   i think in an ideal world, where you cleaned your stuff regularly, the smoothest shooting is the 3 gun competition stuff,  adjustable gas port with lightweight carrier.   but that doesn't lend itself well to running dirty at least in theory.

[raz-0 1,261]

technically thats designed that way so wouldn't that be "properly" gassed?

 

i don't really see the issue with slight overgassing and a slightly heavier buffer.  it should run pretty smooth and reliably that way.  but you can definitely tell shooting a slightly overgassed gun with a H or H2 buffer vs one of the heavily overgassed carbine buffer, semi-auto carrier designs.   i think in an ideal world, where you cleaned your stuff regularly, the smoothest shooting is the 3 gun competition stuff,  adjustable gas port with lightweight carrier.   but that doesn't lend itself well to running dirty at least in theory.

 

 

Yes, most ARs are set up to be somewhat overgassed. It the easiest way to make it so that you can produce a lot with small variances and keep the thing running despite the tolerances, and still have it last a decent amount of time before gas port erosion kills it. 

 

Old school would insist I'm wrong, and all these ARs are built wrong though, so... 

[Old School 611]

Yes, most ARs are set up to be somewhat overgassed. It the easiest way to make it so that you can produce a lot with small variances and keep the thing running despite the tolerances, and still have it last a decent amount of time before gas port erosion kills it. 

 

Old school would insist I'm wrong, and all these ARs are built wrong though, so... 

 

Hey Raz - I agree.  It's not the way I would want MY rifle but you are correct.  Most guns I see are over gassed for mass production and reliability.

[mipafox 438]

Sell it.