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Posted: 7/24/2020 10:56:26 AM EDT
[#1]
I've not seen any problems using a standard carbine spring but some folks just like to chase ghosts.
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Posted: 7/24/2020 5:43:49 PM EDT
[#2]
Standard carbine spring user here as well.
I tried several enhanced carbine and one 308 spring, none of them seemed to improve ANYTHING. when I was talked into trying the 308 spring I had went too my LGS to pick up a 7.5oz extended buffer replacing the colt type 9mm buffer and spacer I had(using a carbine spring). The counter guy really talked up the 308 spring so I figured what the hell I'll try it. IMHO, it SUCKED! all the smoother recoil impulse, reduced recoil BS he touted was just that IMHO, BS. The flipping bolt slammed home so hard the muzzle dipped and recoil impulse and felt recoil was the same to me... I have yet to try a buffer/spring combo that feels or works better than an extended 7.5oz buffer using a standard, plain old carbine spring. YMMV. |
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Posted: 7/24/2020 8:20:54 PM EDT
[#3]
No experience with 308 springs but I went between a std. carbine spring & a Wolff xtra power carbine spring in a 16” 9mm upper and an 8.5 oz. dedicated buffer. The stronger spring made the really hot +p loads smoother but would choke on some cheaper 115gr . I went back to the std. spring, I built a 9mm AR to run any old 9mm I have lying around.
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Posted: 7/25/2020 5:53:27 PM EDT
[#4]
@Droppoint
And right there with you on the "no pissing match"... so many people think what works for one person.. should work everytime.. typically forgetting there are many more variables involved. here is my experience with 308 springs in my 9MM PCC 308 Tubbs Flatwire recoil spring in my 16" and 11.5" Colt Pattern PCC AR's The OEM spring and buffer weight felt like the blowback action was beating the crap out of the firearm. Both barrel lengths. After changing to a 7.5oz buffer and the Tubbs 308, the difference was considerably better. Far less Linda Blair ( the Exorcist ) recoil impulse and much, much more Winnie the Pooh. ( Oh bother.. and silly comment, but you get what I mean. ) I like it so much I did the same thing to my 11.5" pistol setup, with EndoMags. JP Enterprises recommends their 308 recoil spring as well.... I haven't tried those though. To directly respond to some of your questions... And what barrel length are you using ? That might be a factor in the use of a 308 recoil spring. "- Reduce the time available for reliable ejection".... the only ejection issue I have ever had was with a brass catcher, believe it or not , the catcher was bouncing the case back into the action... a slight adjustment , fixed it. "- Reportedly cause more dot/muzzle movement (unconfirmed)" I tired a LOT of recoil setups ( various buffer weights and recoil springs )... clear up to a 10oz buffer weight and a Sprinco AR-10 Orange Extra Power... that specific setup would cause very, very obvious muzzle dip. And I instantly thought about how I had just moved the Linda Blair perceived recoil to the other end of the firearm. Needless to say, great learning experience.. waste of money. "- Make it slightly more difficult to charge the firearm"... With the Tubbs 308 spring, I don't notice it at all. FWIW, the Tubbs has slightly increased bolt closed ft/lb, and normalish function ft/lbs. I will see if I can find the "chart" showing the ft/lb differences in the various 308 and 5.56 recoil springs.... Found it. A2 (old) - 7.6lb closed, 14.5lb open A2 (new) - 9.1lb closed, 16.7lb open Tubb Flatwire - 10.5lb closed, 16.3lb open Tubb .308 Flatwire - 13lb closed, 16.7lb open SpringCo White ? (standard) - 8.3lb closed, 16.3lb open SpringCo Red (extra) - 10.5lb closed, 18.4lb open SpringCo Orange (increased) - 13.9lb closed, 24.8lb open And a comment concerning the Tubbs 308 spring... "If those are accurate then the .308 flatwire only has a higher spring rate when the bolt is closed which is where you would want it for the a blockback 9mm. With the spring rate being about the same for open I would think the bolt velocity would be about the same." Given those various different 308 spring weights, I would think everyone could have completely different experiences with their chosen buffer weight, and believe it or not, their actual physical size. ( Weight ) "- Reportedly reduce perceived recoil by decelerating the bolt rearward travel quicker (unconfirmed)" .....See Linda Blair v. Winnie the Pooh comment above. "- Are sometimes used by individuals to reduce bolt overtravel with coil bind (!!!) instead of using an extended buffer" .... can't happen with the Tubbs Flatwire, flatwire recoil spring take up far less space.  "- Reportedly cause additional wear/battering of parts (unconfirmed)"..... can't say I have seen any additional wear. FWIW... here is a ton of Chrono data from the 308 Tubbs Recoil spring 16" setup... ( I can't say I would have pursued this if I had used the OEM 5.56 standard recoil spring and typical 9MM buffer weight. I KNOW, I would have wondered if I was beating my 9MM PCC to death through all the testing. https://www.ar15.com/forums/ar-15/-/16-712312/?page=1&anc=7429025#i7429025 |
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Posted: 7/25/2020 7:17:06 PM EDT
[#5]
Curious about this as well. Was getting some pretty bad setback and FTF with the FM9 with their 308 spring. Sent it back and no setback issues, no FTF problems. Recoil is pleasant. I randomly pulled chambered round during test firing and found no bullet deformity or setback after they did whatever it was they did to fix it.
ETA: FM uses a 308 carbine spring and heavy buffer in the FM9. |
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Posted: 7/25/2020 7:24:32 PM EDT
[#6]
I agree. I lean more to heavier reciprocating mass and lighter spring.
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Posted: 7/25/2020 7:33:38 PM EDT
[#7]
Many people seem to think that a more powerful spring will slow down the opening of the bolt, or slow down the cyclic rate, or otherwise compensate for inadequate weight in a blowback system. This is incorrect. Spring tension makes a minimal amount of difference in the opening, but makes all the difference in the bolt closing velocity. The main function of excessive spring force is to cause feeding problems and batter the parts together as well as increasing bolt bounce. It takes far less force to strip a 9mm round and close the bolt on a 9mm blowback than it does to strip and feed a 5.56 as well as cam the bolt locked.
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Posted: 7/25/2020 7:39:36 PM EDT
[#8]
Quote HistoryQuoted: Many people seem to think that a more powerful spring will slow down the opening of the bolt, or slow down the cyclic rate, or otherwise compensate for inadequate weight in a blowback system. This is incorrect. Spring tension makes a minimal amount of difference in the opening, but makes all the difference in the bolt closing velocity. The main function of excessive spring force is to cause feeding problems and batter the parts together as well as increasing bolt bounce. It takes far less force to strip a 9mm round and close the bolt on a 9mm blowback than it does to strip and feed a 5.56 as well as cam the bolt locked. You mean drawback? I don't think its an intended function.. |
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Posted: 7/25/2020 7:40:46 PM EDT
[#9]
Quote HistoryQuoted: You mean drawback? I don't think its an intended function.. I doubt it's what is intended, but it's what it does. |
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Posted: 7/26/2020 9:15:39 AM EDT
[#10]
Quote HistoryQuoted: Many people seem to think that a more powerful spring will slow down the opening of the bolt, or slow down the cyclic rate, or otherwise compensate for inadequate weight in a blowback system. This is incorrect. Spring tension makes a minimal amount of difference in the opening, but makes all the difference in the bolt closing velocity. The main function of excessive spring force is to cause feeding problems and batter the parts together as well as increasing bolt bounce. It takes far less force to strip a 9mm round and close the bolt on a 9mm blowback than it does to strip and feed a 5.56 as well as cam the bolt locked. Not all 308 recoil springs are designed the same. Please See the measurements. You can see the Tubbs ( locked back ) spring weight is the same as a new A2 recoil spring. And has more weight holding the bolt closed. Chart added again for convenience A2 (old) - 7.6lb closed, 14.5lb open A2 (new) - 9.1lb closed, 16.7lb open Tubb Flatwire - 10.5lb closed, 16.3lb open Tubb .308 Flatwire - 13lb closed, 16.7lb open SpringCo White ? (standard) - 8.3lb closed, 16.3lb open SpringCo Red (extra) - 10.5lb closed, 18.4lb open SpringCo Orange (increased) - 13.9lb closed, 24.8lb open  Everything You Should Know About AR Buffer Springs So, tuning is going to be part of the equation. If you desire. The 7.5oz buffer weight and Tubbs spring works far better then the OEM setup for my 16" and 11.5".... is it going to work better in every setup ? I don't 100% know ... but again it made a big difference in mine. On a side note, I purchased a Lantac Muzzle brake for my 9MM PCC... absolutely worthless on the 16"... "seems" to help on the 11.5"... so again, YMMV. Might even be more "effective" on a shorter barrel. The 9MM in a 16" simply doesn't have the gas to make use of the Lantac... a different brake design ( single chamber ) might be more effective... again YMMV. The added mass and spring weight certainly will be easier on the hammer and hammer pin ( ALG NIB ) it is very noticeable at the shoulder. The brass ejection pattern was not flinging it forward into space anymore... so clearly it is limiting bolt firing velocity. I tired every buffer weight / recoil spring combo I could configure. Tubbs 5.56 , 308 recoil springs, Various Sprinco recoil springs, Standard AR recoil springs, buffer weights from 3.0oz clear up to 10.0oz I settled on the 7.5oz buffer and a Tubbs 308 recoil spring.... is it for sure the perfect 9MM PCC setup ? Realistically, they are many more variables involved. Bolt ramped ? Hammer spring weight ? Ammo used ? Powder used in the ammo, fast or slower powder ? Good crimp on the ammo ? Feed configuration ? Barrel length ? Who knows... if there was a perfect 9MM PCC S/A AR setup, we wouldn't be talking about it. We would all just be following that recipe. So... as with anything AR.. YMMV. |
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Posted: 7/26/2020 12:27:05 PM EDT
[#11]
I'm sorry but I'm struggling with this discussion. I understand that you will use a buffer spring of various strengths for multiple reasons such as delaying bolt opening and controlling rate of fire, but if I just want to look at slowing down the bolt in the fire stroke (not the return to battery stroke) I wanted to see if I could quantitatively see what a "stronger" spring would do versus weight of the reciprocating parts. I make a ton of assumptions here so this may be all goofed up as far as my thinking. I start with the Newtonian equation of F=ma. I'm particularly interested in the "a" or acceleration of the moving mass (bolt and buffer). A lower "a" means a slower reciprocating mass. This is for a blowback PCC (no delay mechanism like CMMG RDB or ball detent, etc)
Start with the base case. Carbine spring that has a holding force of say 9 lbs. A buffer weight of 8 oz. Call this the 1 PU (per unit) case. Next is the strong spring case. Everything is the same except the spring is 13 lbs. Finally there is the heavy buffer case. Every thing the same as the base case except a buffer weight of 12 oz (what I use in my 9mm PCC) Lets say that in the base case, the chamber pressure minus spring force, friction, hammer spring force, etc, is 3500 lbs or 1 PU (per unit). The mass of the reciprocating parts is the bolt mass plus the buffer mass (call it 15 + 8 oz) = 1 PU. So F = ma, and a = F/m = 1 PU. In the strong spring case, the difference is 4 lbs, which is minuscule compared to the force on the bolt face from the gas pressure of a fired round. Like 30,000 PSI acting on a 0.4 inch diameter bolt face. I estimate that the amount of force difference is F=0.999 PU. Since the mass is the same, a=0.999 PU or a 0.1% decrease in acceleration. In the heavy buffer case, m = 27/23 = 1.174. So a = 8.852 PU or 14.81% decrease. So a heavy buffer is much more effective at decreasing the acceleration of the reciprocating mass than a stronger spring. Now. Where has my thinking gone wrong here? In testing, I know that a extra power spring (not a Tubbs .308 flatwire spring) reduces port pop on my suppressed 9mm blowback PCC significantly. So, to me, that stronger spring does keep the bolt closed longer. A strong spring (like a Spingco Red) combined with my heavy buffer will cause some ammunition to not be able to properly cycle, but I haven't had any issues with a plain old carbine spring. In addition, I do not like the effects of the strong return to battery stroke, so I stayed with a standard carbine spring, and live with the small port pop. Perhaps, there is another factor that I call sticktion or the force necessary to break loose the reciprocating mass just to get it moving. Maybe the stronger spring provides a lot more sticktion so that even with such high force on the bolt face, it takes longer for the bolt to even start moving? Ah crap... I'm just a dork not thinking straight as usual. To me, this all tells me that a heavier buffer is more effective at slowing down the reciprocating parts, but doesn't really tell the whole story. How would you guys approach this quantitatively? |
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