Buffer spring preload

[BeeKay]

I first started shooting my AR 10 build a few yrs ago and I haven't met any guys locally whose weapons I've handled.

I started thinking that I may have an issue when I watched some videos and it looks like some other .308 AR guys have buffer springs that are lighter than the one I have,          just judging by how they're able to cycle the charging handle... or else they've been doing charging handle specific weight training.

I can't remember for certain where I got my buffer tube / stock system, but I think it may have been PSA.                                                                                                                        It's a full size fixed stock like the Vietnam era M-16s.

But if I can get by with a lighter buffer spring, it would make the ergonomics of this a lot better.

Any ideas ? 

Thank You In Advance

Edited December 9, 2022 by BeeKay

[BeeKay]

Poor quality pic enclosed - for legitimacy

[shooterrex]

That spring and buffer has to counter the mass and speed of the bolt carrier group. If your gun is running ok leave it alone. Change the charging handle to a bigger latch if needed. Changing the spring and buffer to a lighter set up will only cause you problems.

[BeeKay]

Thanks - I was hoping that AR 10s would be like 1911s with a wide variety of recoil springs, but apparently not.

[308USK]

28 minutes ago, BeeKay said:

Thanks - I was hoping that AR 10s would be like 1911s with a wide variety of recoil springs, but apparently not.

There are tons of "options" when it comes to springs, but as @shooterrex stated, it's really a matter of mass (buffer & spring) vs. gas.  For example, my build (using Aero Precision upper/lower/BCG/18" barrel with rifle-length gas tube, Superlative Arms Adjustable Gas Block and carbine length buffer tube) required me to do some tuning because the gas port on the barrel was NOT drilled to proper specifications.  After asking for help/guidance here (thank God for the knowledge-base on this forum), I ended up having to purchase a stock Armalite Spring and 5.3oz heavy buffer to verify my rifle cycled properly.  It did not.  Gas port was too small.  Had to drill out gas port.  blah blah blah and eventually I got the rifle running like a dream!

Long story short, every large frame AR has its' own character and once you identify the proper mass vs. gas proportions, where your rifle will cycle correctly and eject casings at 3:00 -> 4:15'ish, you will love the large frame AR platform (in my opinion).  One other thing to note: the large frame AR's prefer to be shot WET (meaning well lubricated), whereas the AR15/M4 platform isn't as persnickety!  

I'm sure the heavy-hitters with WAY more knowledge than I have will respond.  Good luck!

[98Z5V]

@BeeKay, if you're looking for the proper spring that will work, tell me what the details are on your gun.  I can give you the information that you need.  I just need to know the setup on the gun. 

P.S.  Don't worry about what other guys are doing when they're charging their gun.  It's either setup right, or it's not.  It'll last forever, not beat up parts, eat any ammo - or not.

I can tell (obviously) it's a fixed stock, so the extension is a rifle extension.  The rifle buffer needs to be 5.200" long and weigh 5.4oz.  If the spring was PSA, throw it away, and buy the Armalite EA-1095 spring or the Sprinco Red spring. 

That will fix the recoil system, forever.  The gas system is another story.  That might need attention.  That's where the details come in.

Edited December 10, 2022 by 98Z5V

[BeeKay]

On 12/9/2022 at 8:30 PM, 98Z5V said:

@BeeKay, if you're looking for the proper spring that will work, tell me what the details are on your gun.  I can give you the information that you need.  I just need to know the setup on the gun. 

P.S.  Don't worry about what other guys are doing when they're charging their gun.  It's either setup right, or it's not.  It'll last forever, not beat up parts, eat any ammo - or not.

I can tell (obviously) it's a fixed stock, so the extension is a rifle extension.  The rifle buffer needs to be 5.200" long and weigh 5.4oz.  If the spring was PSA, throw it away, and buy the Armalite EA-1095 spring or the Sprinco Red spring. 

That will fix the recoil system, forever.  The gas system is another story.  That might need attention.  That's where the details come in.

Thanks for offering - I have a few uppers 

I'll focus on my Aero Upper that has a 16" barrel made by KAK and a KAK BCG  and a heavy buffer and Adjustable Gas Block.   The gas system is mid length (about 13.5"-14" from the back of the barrel extension to the gas port)     I just followed the instructions that came in the package and I don't really have any issues with the way it runs . But it seems like the spring is heavy.   Recently I got an Aero Ambi Charging Handle, with hopes that operating the charge handle with my right hand would simplify the ergonomics, but it's impossible to charge it with the butt of the stock shouldered.  I need to lower the rifle and hold it away from myself to pull it.  So that's the only issue.  Maybe that's normal ?   The ambi charging handle didn't really solve any problems, because the forward assist hits my fingers and prevents me from getting a really positive grip.

I have a .358 Winchester upper also and that runs okay too and with the AGB and Heavy Buffer recoil is not at all harsh.

I could give some numbers for the gas port, but I'd have to disassemble it... Possibly I could find the size in the specs from the company if that's important.

I appreciate your help - Sorry it took a while to reply,  I'm disorganized because I have to move this month.

[98Z5V]

16" midlength gas on a .308 with a 0.750" gas block journal will need a gas port diameter really close to 0.090".  KAK usually gets the gas ports right, so I wouldn't worry about taking the gun apart to check it, if it's running.  They're good for this stuff, that other companies ignore.  

Check the recoil spring in that thing.  Details in wire diameter, coil count, relaxed length...   If it's not very, very close to the specs on the Armalite EA-1095 spring, then just get rid of it.  Use the EA-1095 or the Sprinco Red, and you'll be happier.  It might charge easier, too.  Look at that recoil spring first, in this situation.

[BeeKay]

14 minutes ago, 98Z5V said:

16" midlength gas on a .308 with a 0.750" gas block journal will need a gas port diameter really close to 0.090".  KAK usually gets the gas ports right, so I wouldn't worry about taking the gun apart to check it, if it's running.  They're good for this stuff, that other companies ignore.  

Check the recoil spring in that thing.  Details in wire diameter, coil count, relaxed length...   If it's not very, very close to the specs on the Armalite EA-1095 spring, then just get rid of it.  Use the EA-1095 or the Sprinco Red, and you'll be happier.  It might charge easier, too.  Look at that recoil spring first, in this situation.

Great  !    Thanks for your help  !

I'll check out that spring

As long as we're on the topic of gas ports :  I also have a 20" long .308  barrel thats from Bear Creek,  and that barrel has a rifle length gas tube.   Should the gas port be .090" on that barrel as well?

Have a Great Holiday

 

[98Z5V]

21 hours ago, BeeKay said:

Great  !    Thanks for your help  !

I'll check out that spring

As long as we're on the topic of gas ports :  I also have a 20" long .308  barrel thats from Bear Creek,  and that barrel has a rifle length gas tube.   Should the gas port be .090" on that barrel as well?

Have a Great Holiday

 

Yep, 0.090" is exactly where you want to be, provided that gas block journal diameter is 0.750".  Standard gas block size.  You can get by with 0.085" if that recoil system is right on the money, and the ammo is either great handloads, or Federal Gold Medal Match purchased ammo.  

[BeeKay]

16 hours ago, 98Z5V said:

Yep, 0.090" is exactly where you want to be, provided that gas block journal diameter is 0.750".  Standard gas block size.  You can get by with 0.085" if that recoil system is right on the money, and the ammo is either great handloads, or Federal Gold Medal Match purchased ammo.  

That's very interesting 

I measured the ports on a couple of barrels that aren't assembled and they are a couple 1/1000" over .080"

I ought to enlarge them then.  But that may be the reason why I'm getting dents in brass on ejection. Because the KAK bolts feature double ejectors, which could possibly compensate for being undergassed ?   I handload, so little details like consistent patterns of dented brass catch my attention.

Next question : Can a guy with a regular drill press open up the ports or does it take an EDM machine or some other expensive equipment ?

[308USK]

1 hour ago, BeeKay said:

That's very interesting 

I measured the ports on a couple of barrels that aren't assembled and they are a couple 1/1000" over .080"

I ought to enlarge them then.  But that may be the reason why I'm getting dents in brass on ejection. Because the KAK bolts feature double ejectors, which could possibly compensate for being undergassed ?   I handload, so little details like consistent patterns of dented brass catch my attention.

Next question : Can a guy with a regular drill press open up the ports or does it take an EDM machine or some other expensive equipment ?

FWIW, I had to open up my gas port, so I got a couple of #'d drill bits (#41 and #42) and started small.  Taped the drill bit at a point where it would go into the barrel a little ways, but NOT all the way and nick the bottom of the inside of the barrel.   (note: I used a corded drill, lubed the hole with 3-in-1 oil and drilled slowly but methodically holding the drill as perpendicular to the barrel as humanly possible!)

I had used my digital micrometer to measured the opening size, so I knew where I was starting (0.0835").  When I finished, I was at 0.0945"...

I took the rifle to the range, opened up my adjustable gas block to WIDE OPEN and shot a couple rounds.  The rifle cycled...YAY!  Closed the AGB down to the factory spec (Superlative Arms AGB. 18 turns from closed).  Shot the rifle again.  Rifle cycled pretty much perfect, but really close to the 3:00 position, so I opened up 1 click...shot again.  3:15'ish. 1 more click (20 turns total now).  Shot again...3:20'ish.  Good enough for me!

Edited December 13, 2022 by 308USK
clarification.

[Armed Eye Doc]

1 hour ago, BeeKay said:

Next question : Can a guy with a regular drill press open up the ports or does it take an EDM machine or some other expensive equipment ?

It can be done with a drill press or even a hand drill.  The pilot hole is there.  Just lube it and go slow.  Don't push the drill. Let the bit do the work.

[BeeKay]

Excellent - Thank You Much - That information is very helpful 

[jtallen83]

17 hours ago, BeeKay said:

Because the KAK bolts feature double ejectors, which could possibly compensate for being undergassed ?

Sig made that change in their 716 to help ejection, It was light in the buffer end. Most large frames will leave some sort of dent on the brass, tuning with an adjustable gas block helps but running the gas on the light end risks malfunctions, I put a thick chunk of rubber grip tape on the shell deflector to help with the dents.

[BeeKay]

Thanks - I got it done 

My greatest worry was that I'd break the drill bit - But Success

I'm looking forward to seeing how it runs.

[Albroswift]

2 hours ago, BeeKay said:

My greatest worry was that I'd break the drill bit - But Success

It's happened. And been saved. Probably more then once.