A5 buffer setup?

A5 is just another opportunity for balancing the action in an AR. It’s effectively an H3 weight buffer, but with a bit (effectively) longer compression stroke and using a rifle buffer spring instead of carbine spring; comparatively, it ends up having a bit softer and slower recoil impulse than a carbine tube with an H3 weight buffer.

The only disadvantage to the A5 system is the scale. They’re longer and heavier than standard carbine systems. But this is a pretty small penalty.

I’ve chatted with a bunch of builders who claim to like A5 systems for lightweight carriers, which in theory, maybe I can get on board with. The idea ORIGINALLY was to add mass and compression length, but adding compression length independently, without committing fully to a rifle length system, can be a big advantage. The carrier speed will still be ridiculously high with a lightweight carrier and buffer, then we throw an AGB on a long-for-barrel-length gas system to limit our piston pressure exposure and dwell time, but then we give our carrier a “softer landing” by having more compression catching the carrier by the spring instead of so much energy dead-length stopping on the RE. It DOES push us off target less than using a shorter carbine spring. So if you’re building a go-fast gun or a long range rifle, and don’t want a rifle tube, the A5 is a wise alternative.

I have an A5 on a BCM midlength upper.

It definitely makes the gun run smoother. Feels more like a 20 inch rifle setup. For a gaming gun i think its a good upgrade.

That being said, I'm not spending the money to change out my other carbine systems.

I love the A5 type RE assembly. The A5A2 buffer is about the same weight as the rifle buffer and has little springs inside to hold the weights in place when the buffer is stationary. With a Sprinco green spring (which is rifle length) recoil is smooth and soft and gives reliable function. I use the A5 with barrel lengths from 10.5 to 20 and with and without suppressors.

My favorite A5 style RE has 10 positions and if I recall, is made by MagPul.

I have one.
16 inch mid length but with a silencer.
That's what the m4 carbine buffer should have been. A bit longer tube than what the M4 uses, a full length rifle spring, with a 4 weight buffer (a carbine buffer is 3 weights and a rifle buffer uses 5 weights).
I'm putting them on any future carbine builds.

I run A5s in two of my lowers. I like them. They smooth the operation of the action pretty noticeably. I did have to play with the weights of the buffers to get steel ammo to run 100% in the 100+ degree heat we've been having, but the standard setup with an H2 buffer runs like a champ with full power ammo.

I don't know that it would be worth it to run out and replace your setup with an A5 if you have multiple lowers, but if you only have one, it might be worthwhile, or just getting one for one of your lowers.

I would suggest buying some steel and tungsten weights so that you can tune your buffer to your AR instead of buying multiple buffers. Right now, I'm running an H0 (I guess you'd call it, no tungsten, all steel weights) in my lower than I run 14.5"+ uppers with mid length gas systems on and an H1 in my lower that I use run shorter barrels with carbine gas systems. That was just what I settled on to run steel. No matter what I tried though, I never got an ejection pattern indicative of excessive bolt velocity.

I think you should try it.

You don’t tune buffers to your AR. If running 5.56 ammo, install an H2 carbine buffer or A5H2 buffer or rifle buffer.

Lighter buffers result in an AR that’s under buffered. Heavier buffer result in an AR that’s over buffered.

If your AR is over gassed, fix the gas drive. If it’s under gassed, fix the gas drive. Buffers do not fix gassing issues.

Switching to low pressure ammo may require a lighter buffer/reduced reciprocating mass.

I run an H3 buffer in my A5 tube, midlength 16 inch barrel with a silencer will do that.
Once I find a way to cut spring dimples in tungsten I'll run an A5H4.
My preferred carbine ammo is 223 power level. A start load of H322 for M193 and for M855 a mid load of AA2460 or W748 produces exceptional accuracy.
Those loads have has trouble cycling a rifle length gun, especially the M193 load.

You can save yourself a lot of trouble (and avoid over buffering your AR) by ordering a Black River Tactical Adjustable Gas Drive Gas Tube.

On the A3 upper I need an adjustable gas block for sure, but the other one I run A2 sights, I'll just do a diy 1990s adjustable gas A2 A pillar with a set screw.

SPRINCO - The Gas, Mass, & Springs Tuning Method for the AR Platform: AR Tuning Documents.pdf (sprinco.com)

If you’d like to experience an exercise in futility, please try tuning the gas drive in your AR according to that ejection chart.

N555 said:

On the A3 upper I need an adjustable gas block for sure, but the other one I run A2 sights, I'll just do a diy 1990s adjustable gas A2 A pillar with a set screw.

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I meant to say, BRT EZTUNE gas tube. Much more reliable and simpler than any adjustable gas block.

I would need an adjustable gas block because I get a lot less back pressure without the silencer and don't want to stop and change a gas tube when I take off the silencer.

I have had extremely good results with the Aero Precision adjustable gas block, and the price is right. I have one on an 11.5", and a 14.5" Ar15 and also a 20" Ar10 in .308. Good product if you can find one in stock.

Daniel

N555 said:

I would need an adjustable gas block because I get a lot less back pressure without the silencer and don't want to stop and change a gas tube when I take off the silencer.

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Ah

I installed a couple of adjustable gas blocks with the same intention. But in actual practice, for a variety of reasons, I don’t remove the suppressor to shoot or to install on another AR. It’s been on the same upper for the last three years.

MistWolf said:

I meant to say, BRT EZTUNE gas tube. Much more reliable and simpler than any adjustable gas block.

Click to expand...

I used a BRT EZTUNE gas tube on an overgassed 16" mid-length upper and it works great. I got it from Forward Controls Design (FCD) instead of BRT because BRT offers so many different ones that I got overwhelmed trying to figure out which one to get. FCD did all the selection work for me by offering just a select few EZTUNE gas tubes.

My only concern is erosion of the smaller gas port on the gas tube.

MistWolf said:

If you’d like to experience an exercise in futility, please try tuning the gas drive in your AR according to that ejection chart.

Click to expand...

It looks like Sprinco changed the paper since I last read it in detail. It used to recommend changing to a heavier buffer spring first, before changing to a heavier buffer, as a heavier spring does the same thing as a heavier buffer but doesn't add reciprocating mass, which increases recoil.

As for ejection pattern tuning, I've changed ejection pattern from 1 o'clock to 4 o'clock just by replacing a Spike's Tactical NiB coated BCG with a SOLGW phosphate BCG.

Shawn Dodson said:

…I've changed ejection pattern from 1 o'clock to 4 o'clock just by replacing a Spike's Tactical NiB coated BCG with a SOLGW phosphate BCG.

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That’s because SOLGW uses a Sprinco extractor spring. Not a generic spring with a weak spring rate.

A weak extractor spring doesn’t hold the case completely against the bolt face. When the case is not held completely against the bolt face, the ejector is not completely compressed and does not forcefully eject the case. When the case hits the case deflector, it bounces forward. This can lead the the case bouncing back into the ejection port and interfere with the feeding of the next round. This will manifest as the new round being only partially stripped from the magazine and the bolt overriding the base.

That ejection chart is pushed as an indicator of gas drive. This is a misinterpretation. The reason the angle of ejection sometimes changes with carrier speed is because the faster the carrier, the more stress placed on the extractor. The more stress placed on a weak or failing extractor, the less hold the extractor has on the case. The less the extractor holds the case against the ejector, the more forward the ejection.

Pro Tip- If you notice your ejection pattern moving towards 1 o’clock, replace your extractor spring with a Colt Sprinco M4 spring and save yourself trouble and confusion.

MistWolf said:

That’s because SOLGW uses a Sprinco extractor spring. Not a generic spring with a weak spring rate.

A weak extractor spring doesn’t hold the case completely against the bolt face. When the case is not held completely against the bolt face, the ejector is not completely compressed and does not forcefully eject the case. When the case hits the case deflector, it bounces forward. This can lead the the case bouncing back into the ejection port and interfere with the feeding of the next round. This will manifest as the new round being only partially stripped from the magazine and the bolt overriding the base.

That ejection chart is pushed as an indicator of gas drive. This is a misinterpretation. The reason the angle of ejection sometimes changes with carrier speed is because the faster the carrier, the more stress placed on the extractor. The more stress placed on a weak or failing extractor, the less hold the extractor has on the case. The less the extractor holds the case against the ejector, the more forward the ejection.

Pro Tip- If you notice your ejection pattern moving towards 1 o’clock, replace your extractor spring with a Colt Sprinco M4 spring and save yourself trouble and confusion.

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The extractor spring in the Spikes Tactical bolt had been replaced with a Sprinco spring. No bueno.

Shawn Dodson said:

The extractor spring in the Spikes Tactical bolt had been replaced with a Sprinco spring. No bueno.

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That’s interesting.

I wonder if the spring pocket was too deep….

MistWolf said:

That’s interesting.

I wonder if the spring pocket was too deep….

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It was two Spikes Tactical NiB BCGs. Just for troubleshooting purposes all the guts from an SOLGW bolt were swapped with the two Spikes with no change in results.

The slick NiB coating on the boltface may have had an effect, as opposed to the phosphate finish.

Shawn Dodson said:

It was two Spikes Tactical NiB BCGs. Just for troubleshooting purposes all the guts from an SOLGW bolt were swapped with the two Spikes with no change in results.

Click to expand...

That's why I suspect the spring pocket is too deep (reducing spring pressure)- or some other dimension is off.

The slick NiB coating on the boltface may have had an effect, as opposed to the phosphate finish.

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The coating shouldn't affect ejection.

MistWolf said:

That's why I suspect the spring pocket is too deep (reducing spring pressure)- or some other dimension is off.

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Without gauges to measure, who knows? The BCGs in recreational ARs right now. They previously had Viton O-rings, before the Sprinco ejector springs, but the O-rings didn't change things either.

I'm not a fan of Spike's Tactical parts. These BCGs were purchased years ago, before SOTAR began alerting folks to the abundance of out-of-spec parts.

The coating shouldn't affect ejection.

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Yeah, that's just conjecture on my part.