Compiled Buffer Spring Data

[Dewey Mack]

At the risk of releasing this too early, I think this might help everyone building or tuning their large frame "non-standard" rifles:

Tested Buffer Spring Data

I used this idea from Blowback9.com when I was building my PCC. He made a spring tester for testing various springs for the "gentle recoil system." He only tested the springs for M4 carbine bolt-open/bolt-closed positions because that was the only data he had to compare. So I was inspired and created my own spring tester with multiple positions marked for M4, A5, and Rifle Length compression for AR15 and LR308. So far, I have tested 24 different springs (all of which I purchased) and are new or otherwise noted. My brother-in-law has the Aero 308 carbine and rifle springs which I should be testing soon as well. Yes, I actually spent money on this because I'm SICK of the industry not helping out the average joe and tired of tacticool keyboard warriors recommending springs when there is ZERO ACTUAL DATA behind any of their recommendations--[not meaning this forum, but Reddit/AR15.com/etc]. I tried to provide links to most of the springs in the "All Springs Tested" tab. This can be very useful for not only large-frame but fine-tuning all AR platforms. Keep in mind, most are data points of ONE spring each.

I reference 7.2 lbs / 16.5 lbs as the standard for AR10/LR308 since this is what Tubbs reported on their website. I also highlighted the EA1095 which I purchased from HeavyBuffers; I'm unsure if it's an actual Armalite component or their copy of that spring.

I have also tested some of these springs in my carbine, A5, and rifle LR308 setups. Without going into detail on this post, I have these few conclusions:

The Sprinco Orange was massive overkill. Ejection pattern direction didn't change but ejection distance cut 1/3-1/2. Maybe only try if severely over-gassed; it's $20 so maybe getting an adjustable gas block is smarter if you already have a good spring, proper gas port size, and correct buffer weight.

The EA1095 is pretty much ideal for A5 and Rifle setups. There are some GOOD alternatives as well.

The Strike Industries flat wire was extremely weak; I think it's best served in the AR15.

The Griffin Armament +15% A2 spring was more like +35%! I'm not sure if that is a defect or not. I may call them.

The KM Tactical 308 Rifle spring is also very weak; also a possible defect or I was sent an AR15 rifle spring.

ALL M4-carbine tube springs were overkill (except the weak SI flat wire), and it does not seem like an efficient nor flexible setup.

I have both A5 VLTOR and BCM MkII tubes. They both measure 7.75" internal. I don't care they're not 7 5/8" and not going to argue; I just wanted to make a standard for my measurements. And honestly, I 3D print custom shims for my buffer tubes to make all my AR bolts have 0.060-0.080" bolt catch gap. Buffer-bottoming depth varies based on how far the tube is threaded into the lower receiver, and every tube is different.

Enjoy and pin if you think it will help. I'll update when I test new springs.

Cheers,

Dewey

[Dewey Mack]

Added photo of my setup. Buffer Spring Tester Mk2 - added pulleys for easier testing and a heel on the end to catch my countertop. The scale is accurate to 0.01# and I have tested it against 2 other scales and weights. I rounded pulls to the nearest 0.25#. I have also reached out to various companies about some of the strange test results. Will update when they reply.

[Dewey Mack]

I made a second tube to test my Armaspec captured spring system.

Added Armaspec AR-10 Gen3 SRS, Aero 308 Carbine, and Aero 308 Rifle.  Both Aero springs were new/unused and brown in color from my brother-in-law. The Aero website shows chrome springs, so I'm not sure if they're the same.

Many more springs enroute including all 3 standard power Griffen Armament springs, Sprinco Green, KAK flat wire, and a few others.

[Dewey Mack]

Tested Buffer Spring Data 

44 springs tested so far!! Yes, I'm nerding-out on this because I hate guessing when the industry keeps us in the dark.

I added more springs including Wilson Combat and KAK. I also added another column on the CAR-308 side, as I realized many are using shorty 2.5" buffers with a 1/4" head instead of the 1/2" head like the Kaw Valley Precision buffer I'm using. It actually makes some carbine springs now usable. The majority of the springs designed for AR10 carbine are TOO STRONG except for the really weak Strike Industries AR10 flatwire. [I haven't tested Tubb's flatwire yet, so that might be the unicorn.]

Some observations: I don't know how many builders (or buyers) needed to drill out their gas port, but if they are running a standard 7" carbine setup, I can see why. Most of the 308 carbine springs are just too strong for that setup! I highly encourage anyone starting a new build (or fixing someone else's build) to use an A5 length 7-5/8" (or 7.75") tube such as BCM Mk2, Griffin Armament Maritime, VLTOR, Heavy Buffer's, and the like. Get an H3 standard 5.4-5.6oz buffer, and EA1095 spring or something close before testing or drilling gas ports. Look, the Sprinco Orange spring in a 7" carbine tube is 39-45% stronger than the original AR-10 spring! Of course you'll need to drill your gas port for that! ***ammo/suppressor dependent, of course***

....or use a Rifle length buffer tube setup; even more buffer weight options! Both A5 and Rifle length setups offer a VARIETY of options!

I'm sticking with the A5 setup because I have the PRS Lite stock which I really like. I'm also hoping to experiment by making a hybrid/heavier 3.25" buffer on the cheap.

If you get a kit such as the Kaw Valley Precision 5.6oz shorty with spring (JoeBobOutfitters), you may want to cut the spring down (while measuring the strength) as a cheaper alternative. Or buy an extra spring and cut that one, they're cheap. I just noticed Slash's Heavy Buffer offers a custom 308 carbine spring that I may also try. I need to re-test the Aero 308 carbine spring as well.

Also, holy cow is the KAK AR10 Rifle spring a chonker! So far the thickest and strongest spring in the rifle tube. I honestly can't see any reason for it, and I may start cutting it down to see if I can make a 308 Carbine spring from this beast.

When I'm done testing, or think I'm done, I'll start a new post with specific recommendations that hopefully gets pinned. I'm honestly thinking about building another just for a test rig. At least that's what I'd tell my wife. 😆

Cheers,

Dewey

[Dewey Mack]

https://tinyurl.com/DeweySpringData

I ordered 4x brand new Aero Precision springs in December, and they arrived this month.  Their new 308 buffer springs are stiffer than the older ones I tested that came with the buffer tube kits.

I still recommend the A5 or Rifle length gas setup over carbine to give the most options in springs and buffer weights.

I'm building a lower for my 6.5 Creedmoor, and I will use this lower to test a spring to see how it changes over the increments of 100 rounds.

Happy upcoming 4 years of freedom,

Dewey

[Dewey Mack]

https://tinyurl.com/DeweySpringData

I finally tested the infamous Tubbs flatwire spring.....and what a disappointment. I also added the AR-Stoner springs.

So the only flatwire spring that would be close to the original "bolt open" pressure is the Wilson Combat AR-10 Flatwire spring, but only in the A5 or Rifle length buffer tubes; it's still too strong for the 7" carbine tube.  All other flatwire springs are weak-sauce (that I've tested).

Tubbs was a complete waste of money, and I can count on one hand the number of springs that provide the correct force in the 7" tube. I'm not planning on buying any other springs to test right now. I may pickup more later this year if I'm asked for another rifle build by family.

BTW, I purchased both of AR-Stoner's "heavy" buffers. The SS AR-10 Carbine Heavy buffer weighed 5.08oz (5.3oz advertised), and the AR-10 Rifle Heavy buffer weighed 9.23oz (9.3oz advertised).

[98Z5V]

6 hours ago, Dewey Mack said:

So the only flatwire spring that would be close to the original "bolt open" pressure is the Wilson Combat AR-10 Flatwire spring, but only in the A5 or Rifle length buffer tubes; it's still too strong for the 7" carbine tube.  All other flatwire springs are weak-sauce (that I've tested).

There's a brand new flat-wire spring on the market, but it's for a specific buffer.  KAK is making a flat-wire, and it's use is mandatory, according to KAK, for their new buffer.  I'm testing this right now in a 16" rifle gas BA SPR profile 22 ARC barrel (full gun), and I'm running one of their heavier A5 buffers.  This is an A5 system, in mine - KAK makes this combo for the traditional carbine recoil system for AR15s, running their new 3.250" long buffer.

Here's the buffer - I'm running the A5H3, at 6.5oz, with their flat-wire spring:

Here's the link to it:

https://kakindustry.com/k-spec-enhanced-ar15-buffer-a5h2-6-5-oz/

So, they sprung the head of the buffer with an internal spring, strong as hell.  It acts as a dead-blow, when the BCG bottoms out.  I've seen a difference, it works, but I don't have enough time on that gun yet to see how much of a difference it makes.  The reason you have to run their flat-wire, is because a round wire spring will hit coil-bind before the BCG can get full travel - just because the head of that BCG is that much longer - just because of that additional spring in the head of the BCG, doing it's work.

Hope all that makes sense...  

 

[98Z5V]

FWIW, all AR-10 springs are going to be too strong, and be too long, to run inside a 7.000" internal depth AR15 Carbine Receiver Extension, in a .308 AR or other Large Frame caliber, and they will all coil-bind before the BCG can get full travel.  The compressed length of all AR-10 springs is greater than the 2.500" buffer will allow.

The exception is the Sprinco Orange Spring.  Specifically designed for 7.000" internal depth, 2.500" buffer length, running in Large Frames.  It also works in some blow-back pistol-caliber builds, but not many.  Sprinco Red is the solution for almost all PCCs, and that's an identical replacement spring for the Armalite EA-1095 spring.

Edited March 11 by 98Z5V

[98Z5V]

This is all great, great info, Dewey @Dewey Mack- don't let up, man.  You're doing something here that's never, ever been compiled before, into one resource. 

[Dewey Mack]

On 3/10/2025 at 8:16 PM, 98Z5V said:

This is all great, great info, Dewey @Dewey Mack- don't let up, man.  You're doing something here that's never, ever been compiled before, into one resource. 

Sorry I've been busy and missed your message. I actually have 3 or 4 new AR-Stoner springs from Midway USA to test now, but I think I've actually tested 2 of those KAK springs, because I bought 2 of those kits (K-SPEC Enhanced AR-15 H2 Buffer & Flatwire Spring - 4.7 oz $30 & K-SPEC Enhanced AR-15 H4 Buffer & Flatwire Spring - 7.3 oz $40) from Primary Arms in October during a super sale. I associated them with spring part# 510-2101-001. Is this the same spring you have you think? The KAK spring tests are logged in the spreadsheet, added test on 11/2/24.

My Sprinco Red was slightly weaker than my EA1095, but both were a sample size of 1 each. The EA1095 was very close to what Tubbs said was the original spring rate so who knows? Regardless, I do have a tab in the spreadsheet breaking out the springs relevant to 308 so hopefully it's easier to digest. And yes, I now have a metric ton of springs waiting for homes HA!

Also, I just tried my new Athlon Rangecraft yesterday at Ben Avery. I compared it to my Magnetospeed v3 and it was extremely close. The Athlon read 0-10fps slower than the Magnetospeed, but I had the Magnetospeed sensitivity turned up slightly as it had trouble picking up some shots. Rangecraft used 50% battery after 3 1/2 hours, left on the entire time. Overall, I'm very impressed with the Athlon and I can finally chrono my hunting rifles with tapered barrels!

I'd would've liked the Garmin, but I'd rather put the savings toward an FX-120i scale for my 3D printed OpenTrickler...

[Dewey Mack]

I tested 4 more rifle springs, 2x AR15 and 2x AR10. AR-Stoner variety. Definitely not bad for the price, but there are differences between their chrome silicone and stainless steel springs. I'd really like to test their new flatwire springs, although I suspect they're re-branded.

https://tinyurl.com/DeweySpringData

On 3/10/2025 at 8:12 PM, 98Z5V said:

FWIW, all AR-10 springs are going to be too strong, and be too long, to run inside a 7.000" internal depth AR15 Carbine Receiver Extension, in a .308 AR or other Large Frame caliber, and they will all coil-bind before the BCG can get full travel.  The compressed length of all AR-10 springs is greater than the 2.500" buffer will allow.

The exception is the Sprinco Orange Spring.  Specifically designed for 7.000" internal depth, 2.500" buffer length, running in Large Frames.  It also works in some blow-back pistol-caliber builds, but not many.  Sprinco Red is the solution for almost all PCCs, and that's an identical replacement spring for the Armalite EA-1095 spring.

I disagree that ALL AR-10 springs are too long, because "AR-10" labeled springs are labeled such by the manufacturer regardless of "mil-spec", unless you are specifically tying AR-10 to = A5 length buffer tube. If you look closely at my first tab in the spreadsheet, I've calculated the compression distance carefully, and I actually went back and re-tested the springs when I realized there are 1/4" and 1/2" variations on 2.5" buffer head depth. Yes, many springs will bind, but some will not since they are specifically designed with the 7" tube in mind. I have ran multiple springs in the 7" tube without binding, but obviously it isn't my tube-length of choice. Where springs are binding or fully collapsed during tests, I noted that in their respective rows. Do you see something displayed in my spreadsheet that is inaccurate with regards to binding and my testing, or that I should re-assess?

My goal is to have tangible evidence of functional AR-10/LR308 buffer spring data since all firearm marketing is nebulous.

[shooterrex]

The original AR10 carbine tube's are 7 5/8" inside. So Armalite springs are designed for that length and also work in rifle length tubes.

[98Z5V]

4 hours ago, Dewey Mack said:

I disagree that ALL AR-10 springs are too long, because "AR-10" labeled springs are labeled such by the manufacturer

False labeling by a manufacturer does not make a spring a true spring to run in an AR-10.

You cannot get a true AR-10 spring - and there are only TWO that I know of - to compress enough for a buffer, in a 7.000" internal depth AR-15 Carbine Receiver Extension.   The EA-1095 won't do it, and the Sprinco Red won't do it. They'll both hit coil-bind before they'll cycle a BCG, in a Large Frame AR.

[Samuel_Gray]

On 10/23/2024 at 3:57 PM, Dewey Mack said:

At the risk of releasing this too early, I think this might help everyone building or tuning their large frame "non-standard" rifles:

Tested Buffer Spring Data

I used this idea from Blowback9.com when I was building my PCC. He made a spring tester for testing various springs for the "gentle recoil system." He only tested the springs for M4 carbine bolt-open/bolt-closed positions because that was the only data he had to compare. So I was inspired and created my own spring tester with multiple positions marked for M4, A5, and Rifle Length compression for AR15 and LR308. So far, I have tested 24 different springs (all of which I purchased) and are new or otherwise noted. My brother-in-law has the Aero 308 carbine and rifle springs which I should be testing soon as well. Yes, I actually spent money on this because I'm SICK of the industry not helping out the average joe and tired of tacticool keyboard warriors recommending springs when there is ZERO ACTUAL DATA behind any of their recommendations--[not meaning this forum, but Reddit/AR15.com/etc]. I tried to provide links to most of the springs in the "All Springs Tested" tab. This can be very useful for not only large-frame but fine-tuning all AR platforms. Keep in mind, most are data points of ONE spring each.

I reference 7.2 lbs / 16.5 lbs as the standard for AR10/LR308 since this is what Tubbs reported on their website. I also highlighted the EA1095 which I purchased from HeavyBuffers; I'm unsure if it's an actual Armalite component or their copy of that spring.

I have also tested some of these springs in my carbine, A5, and rifle LR308 setups. Without going into detail on this post, I have these few conclusions:

The Sprinco Orange was massive overkill. Ejection pattern direction didn't change but ejection distance cut 1/3-1/2. Maybe only try if severely over-gassed; it's $20 so maybe getting an adjustable gas block is smarter if you already have a good spring, proper gas port size, and correct buffer weight.

The EA1095 is pretty much ideal for A5 and Rifle setups. There are some GOOD alternatives as well.

The Strike Industries flat wire was extremely weak; I think it's best served in the AR15.

The Griffin Armament +15% A2 spring was more like +35%! I'm not sure if that is a defect or not. I may call them.

The KM Tactical 308 Rifle spring is also very weak; also a possible defect or I was sent an AR15 rifle spring.

ALL M4-carbine tube springs were overkill (except the weak SI flat wire), and it does not seem like an efficient nor flexible setup.

I have both A5 VLTOR and BCM MkII tubes. They both measure 7.75" internal. I don't care they're not 7 5/8" and not going to argue; I just wanted to make a standard for my measurements. And honestly, I 3D print custom shims for my buffer tubes to make all my AR bolts have 0.060-0.080" bolt catch gap. Buffer-bottoming depth varies based on how far the tube is threaded into the lower receiver, and every tube is different.

Enjoy and pin if you think it will help. I'll update when I test new springs.

Cheers,

Dewey

On a side note, when working on your setups or building new systems, it’s always good to check your vehicle’s condition if you’re planning a trip to the range or out for testing. I use https://www.faxvin.com/vin-check/accident to check my vehicle’s history and make sure everything is in working order. It’s helped me avoid any surprises before long drives. Keep up the great work, looking forward to more updates!

This is fantastic data, Dewey! You’ve clearly put a lot of time and effort into testing these springs, and it’s awesome to see someone providing real-world, hands-on results. As you mentioned, the lack of solid data in the industry is frustrating, and your approach is a great way to fill that gap. The conclusions about the Sprinco Orange and EA1095 are particularly interesting—especially with how the Sprinco overkill affected ejection distance. I’m sure others will find this info valuable when fine-tuning their setups.

[98Z5V]

20 hours ago, Samuel_Gray said:

The conclusions about the Sprinco Orange and EA1095 are particularly interesting—especially with how the Sprinco overkill affected ejection distance.

Just so you know, those are two completely different springs, designed for two completely different purposes, and two completely different (radically different) recoil systems.  If Dewey, above, made a direct comparison to those two springs, that was a mistake on his part, and a gross misunderstanding of those two springs.

Welcome aboard - go hit the Intro Section - it's right here:

https://forum.308ar.com/forum/22-introductions/

Edited yesterday at 04:49 AM by 98Z5V

[Armed Eye Doc]

8 hours ago, 98Z5V said:

Just so you know, those are two completely different springs, designed for two completely different purposes, and two completely different (radically different) recoil systems.  If Dewey, above, made a direct comparison to those two springs, that was a mistake on his part, and a gross misunderstanding of those two springs.

Welcome aboard - go hit the Intro Section - it's right here:

https://forum.308ar.com/forum/22-introductions/

The previous response sounds like an AI generated summary.  If @Samuel_Gray can prove me wrong, then I apologize.  However, that is their only post since joining in 2023.

[98Z5V]

14 hours ago, Armed Eye Doc said:

The previous response sounds like an AI generated summary. 

I'll fight some AI Bots on the intricacies of all this shiit, all day long...