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Cycling issues -- 20" Ballistic Advantage 308 barrel, rifle length gas (high frame rate video included)


renaissanceman

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11 hours ago, renaissanceman said:

All cycling issues have resolved -- it now cycles any ammo you feed it with bolt lockback every time.  The recoil is quite mild and the empty cases land at the 4'oclock position about 5 feet from the rifle in a neat little pile.  

How's that for a happy ending? 

GREAT news, man!   I love it!

I'm the gas-port-diameter whisperer...   :laffs:

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1 hour ago, Armed Eye Doc said:

You definitely know your hole sizes. 

The science behind it was all figured out in everything that Eugene Morrison Stoner devised in the mid 1950's.  He did the science. 

These days, it's all about the math.  Nothing more. 

Know your math...  ..and apply your math to the problems...  :thumbup:

Edited by 98Z5V
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13 hours ago, 98Z5V said:

The science behind it was all figured out in everything that Eugene Morrison Stoner devised in the mid 1950's.  He did the science. 

These days, it's all about the math.  Nothing more. 

Know your math...  ..and apply your math to the problems...  :thumbup:

Care to share the math if there's a clean derived equation?  I'd love to be able to set up a spreadsheet that predicts what is needed based on a QuickLoad predicted port pressure, but I think it'd be decently messy to derive.  

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7 hours ago, renaissanceman said:

Care to share the math if there's a clean derived equation?  I'd love to be able to set up a spreadsheet that predicts what is needed based on a QuickLoad predicted port pressure, but I think it'd be decently messy to derive.  

It's decently messy to learn that stuff from what goes wrong, what goes right, and what it takes to make it work.  First, you have to know what works, then you apply basic engine math to the gas port - calculating a bore cylinder size, for bore and stroke.  You need the same cylinder volume to make the gun work right - as one that works, in another example.  The big thing is the different gas journal sizes, and figuring it out for those. 

6 hours ago, shooterrex said:

Is she still hiding in the cabinet???

She's out all the time when nobody is here.  She's just a scared freak when people come over...   :lmao:

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3 minutes ago, 98Z5V said:

It's decently messy to learn that stuff from what goes wrong, what goes right, and what it takes to make it work.  First, you have to know what works, then you apply basic engine math to the gas port - calculating a bore cylinder size, for bore and stroke.  You need the same cylinder volume to make the gun work right - as one that works, in another example.  The big thing is the different gas journal sizes, and figuring it out for those.

I'll give more info.  Gas system length is number one, because that determines the cycling pressure that you'll be able to build.  Dwell Time is second, because that determines how long that cycling pressure will affect the BCG.  THEN, it's determining gas port diameter, and barrel construction is the big thing that you need to pay attention to, in order to figure out a workable gas port diameter.

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On 2/3/2021 at 8:09 PM, 98Z5V said:

I'll give more info.  Gas system length is number one, because that determines the cycling pressure that you'll be able to build.  Dwell Time is second, because that determines how long that cycling pressure will affect the BCG.  THEN, it's determining gas port diameter, and barrel construction is the big thing that you need to pay attention to, in order to figure out a workable gas port diameter.

Can you post links to your calculations, ? I'm still looking for the sweet spot.. I'm trying to get that to sink in I'd say 98% of our gas port posts have your fingerprints all over them...

Edited by billymagg
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On 1/25/2021 at 10:15 PM, renaissanceman said:

I'll take a drill bit to it soon -- I've done one in the past with a hand drill and a 3d printed guide to keep it straight and a 3d printed insert to keep the bit from going all the way through and into the opposite side.  Sort of shady, but lacking a drill press...whatcha gonna do?  Kinda strange that a rather large and reputable company (Aero) would under-drill a port -- I'm thinking a lot of AR10s are undergassed, despite everyone online seeming to think overgassing is the issue that causes chronic cycling headaches.  Of all my buddies who have built one, I've still never seen one just run without issues.

Yep, how's she doing now, break in proceeding as per plans?

 

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13 hours ago, billymagg said:

Can you post links to your calculations, ? I'm still looking for the sweet spot.. I'm trying to get that to sink in I'd say 98% of our gas port posts have your fingerprints all over them...

There aren't links, brother.  I can't link different articles on the web about it - because I've never found any.  This stuff is experience, and it's all in my brainpan.  I don't know how to put up a link to that stuff - if you followed a bad link there, you'd be scarred for life...   :laffs:

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On 2/8/2021 at 10:40 PM, 98Z5V said:

There aren't links, brother.  I can't link different articles on the web about it - because I've never found any.  This stuff is experience, and it's all in my brainpan.  I don't know how to put up a link to that stuff - if you followed a bad link there, you'd be scarred for life...   :laffs:

Yeah, you're right but I love you man, if NOT for YOU, I would have never bought a 308AR, if NOT for you I would certainly not have built my small frame Bill et 300 Ham'r, (I know that wasn't your first choice of caliber for my rifle),, if not for YOU! I never would have had the patience to get that Ham'r running like a freight train... I realized after I started getting the Ham'r to run, that my 308 AR was a lazy ejector, I put off what I thought was a simple gas block adjustment until I had the Ham'r purring like a kitten... I then took the 308 out and opened that gas block all the way! guess what, NOTHING! so here we go... Thanks Bub, and there are lots of other guys on here that I owe...

but the body of research you have published here is really priceless, I kinda, sorta actually am starting to understand my rifles, and that is awesome... all because of your experience, and your research, and your writing about it in a legible coherent, consistent manner,,, you should get a pulitzer on the 308AR, and all the other AR's as well! well done my friend, but my mind is scary enough...

now this may sound like azz kissing and bullshiet, but its all true bullshiet!

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On 2/2/2021 at 10:58 PM, 98Z5V said:

The science behind it was all figured out in everything that Eugene Morrison Stoner devised in the mid 1950's.  He did the science. 

These days, it's all about the math.  Nothing more. 

Know your math...  ..and apply your math to the problems...  :thumbup:

OK, one more request,,, where is you history of the AR-10 and most particulary the AR-10 carbine as designed and built by Mr. Stoner!! I know I've read some of it here, but I can't remember where, but I'll try search first!

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On 2/8/2021 at 7:03 AM, billymagg said:

Yep, how's she doing now, break in proceeding as per plans?

 

Seems to be fine, I'm working on load development now.  It'll cycle min loads with 147gr FMJ bullets, so I think it's got the right size port.  Not too gassy, either.  Once I've got my pet load, I may tune the gas block down a bit if there's a bit more gas than I like.  

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7 hours ago, billymagg said:

OK, one more request,,, where is you history of the AR-10 and most particulary the AR-10 carbine as designed and built by Mr. Stoner!! I know I've read some of it here, but I can't remember where, but I'll try search first!

You'd have to dig for that stuff - best way to track it all down is by searching out the complete history of Eugene Stoner - and there's not just one resource out there.  Here's a good start:

https://ammo.com/articles/eugene-stoner-creator-ar-15-americas-rifle-forgotten-history

All of the Carbine variants - ALL of them, were "developed by Colt," after Armalite sold the rights and specs to Colt.  Stoner left Armalite in 1961, to go work for Colt.  So...   you know who designed all the Carbine variants...   More of his work came out starting in 1990, until his death in 1997, when he worked with Knight's Armament. 

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7 hours ago, billymagg said:

but the body of research you have published here is really priceless, I kinda, sorta actually am starting to understand my rifles, and that is awesome... all because of your experience, and your research, and your writing about it in a legible coherent, consistent manner,,, you should get a pulitzer on the 308AR, and all the other AR's as well! well done my friend, but my mind is scary enough...

That's my whole goal here, man - ALL of us here...   If you learn how the rifle works, then you know how to fix it when it does "x" or "y".  Or, if a part breaks, you can figure out why it broke, and fix that part or situation that lead to the breakage, so it doesn't happen again.  Or, if you know the different systems, and how they interact, you can change one, and know what you need to change for the other(s).  Writing legibly, and concisely - ever train an Army Private?...  :lmao:  Some of those guys can be just like a rock with lips, and you have to get them to understand.  I spent more than 20 years training some pretty crazy shiit - and it payed off for me.  I can't take the credit for that - that has to go to the US Army, and all those that "trained me to train" in my past.  I had some very badass mentors.

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