I just purchased a DDM4V5 300 blackout 16" rifle and I’m considering installing vltor’s a5 buffer system on the rifle because of the success I’ve seen with my 5.56 16" rifle, which also has the a5 installed. I’m mainly concerned about its ability to.shoot suppressed especially after higher round counts. Any thought on the performance of the rifle with the a5 and if the a5 is a good solution for this setup? Thanks in advance guys
All I can say is that I fired my .300 BLK upper for the first time last week (10" Noveske barrel) on an A5 lower with the H3 buffer and green Springco spring. I was shooting the Remington 125gr. supersonic and it was smooth like a baby’s ass.
I think you will be fine. I would encourage you to look at a Springco spring as they truly seem to last longer than standard springs.
I run an A5 system with a 9" 300 BLK barrel and it seems to be working just fine. It’s ran with with factory Remington 115gr and 125gr loads, factory 220gr subs, and all of my handloads (including some weak subsonic loads). All rounds were shot unsuppressed as MN is not suppressor-friendly. All rounds cycled and the bolt locked open on the last shot.
I’m currently using the stock A5 buffer and VLTOR spring but will be experimenting with other buffer weights and springs, as IG suggested, to see how felt recoil changes. Since this lower shares time with a short 5.56 upper, I’m also making sure that it runs well with that setup.
As has been stated in numerous threads, the A5 system is probably the most consistent and forgiving buffer system available.
The other day I ran IMI 5.56 and MFS steel case through a 16" BCM middy upper all with perfect function and 3-4 O’Clock ejection.
Then I switched the upper out for an ARP 6.8 16" middy upper and ran 110gr and 120gr loads, again with perfect function.
Since you already have an A5 lower, your “cost to try” is zero.
I’d say try it out with the 300 and it will most likely work fine.
Thanks guys. I failed to mention that I also plan to install the green Springco spring as well. Sounds like it will be just fine. Thanks again for the info guys
As a general rule I’ve found gas ports designed to function with an H2 buffer and carbine spring do well with a rifle (or A5) buffer and rifle spring.
Your carbine gas 300 BLK is probably designed for a carbine or H buffer with subsonic. The A5 will probably do well with supersonic and may with subs suppressed, but is probably not optimal for subs unsuppressed.
The shorter 300 BLK barrels (like ours) are often designed for H2 buffers, they run well with an A5.
I don’t know how that works. I have to use a car weight buffer and colt usgi spring to get my 10" noveske barrel to work with 220gr remington.
Unsuppressed?
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The gun will run 100% flawless with a 3.0 oz Colt CAR buffer, Colt carbine spring, with 220gr Remington factory loads either suppressed or unsuppressed. It doesn’t matter if the silencer is attached. I have been using an AAC N6 with a 3 prong. This is with a standard Colt full auto bolt carrier group.
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With an H buffer and the same setup, it will not lock back about 10% of the time either suppressed or unsuppressed.
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With an H2 buffer the failure rate is more.
The barrel is the first run of Noveske .300 blk 10" barrels with 1/8 twist. I have been extensively testing this setup to find out where it will be 100% reliable and it is the configuration in #1.
Is the green spring a “standard strength” rifle spring or “extra power”?
The A5 tube being slightly shorter than the rifle tube, already has ~10% higher force using the same spring.
I don’t think too much more spring power would be desirable with the A5.
No idea to be honest. But that set up has been run with several set ups and barrel lengths to include 5.56 with 100% reliability.
I only run the A5 system on 5.56 guns (for now), but here’s my take on the A5 springs:
Vltor spring and Brownells CS spring are the “lightest” in perceived spring strength (working the charging handle manually).
Followed by the slightly-stronger Colt Rifle Spring.
Then you have the Springco Green A5/rifle spring…which is noticeably stronger than the Colt Rifle and has the same relationship with the std Vltor/Brownells springs as a Springco Blue does to a Springco White with regard to perceived spring strength. None are absurdly stiff.
I own all of the above listed A5/rifle springs currently. I did own ALL springco springs (White, Blue, Red, and Green) until I divested myself of all non-A5 recoil systems. 
The only spring I would not bother with is a Wolff XP Rifle spring…those damn things are reserved purely for .450 Bushy, .50 Beowolf, etc. I have seen some local hog hunters who repeatedly broke their PRI big-latch gasbuster CH’s just from manually working their hog guns’ charging handles (using wolff XP rifle springs in a rifle stock) just by hand. I’m a big guy, and the wolff spring is just a bitch to use…to say nothing of what it does to functional reliability or optic longevity due to extreme counter-recoil.
This is almost identical to the issues I have with my 8" Noveske tube…but more so.
I replaced the gas tube as a last resort with modest improvement in function (mirroring Scottryans’ findings).
To date, Remington 220gr Subs are the only ammo that has malfunctioned in this upper. I have close to 1800rds in this upper.
Im running an 11.3" 300blk upper on a lower equipped with the Vltor A5 system and it functions 100% with subs and supers.
The gas tube alignment is much more critical with the shorter gas system. Make sure the carrier (without bolt) will close over the gas tube by tilting the upper just enough to get the carrier to slide forward.
Try a know good carrier if you can. Give us a call if you still have problems.
I took my 300blk upper out today for the first time…It’s got a Noveske 14.5" barrel w/ a pistol length gas system. I was shooting 115gr Remington ammo.
But here’s my issue with the A5 system + 300blk. When I went to pick up the brass I noticed that all the brass had an identical indent. I matched it up on the brass deflector and it is obvious that it is hitting the deflector on the open end causing a dent.
Is this normal? I was looking to reload and I didn’t think I’d have to fix every casing. I am almost 100% sure that the a5 buffer has caused this, but I am just looking for other’s thoughts.
Pics:
This is making me a bit nervous. I am currently waiting for my permission slip to come back on an 8" Noveske LoPro in 300 BLK. I also upgraded to the A5 buffer system. I hope I don’t have any issues with it functioning. 
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Are you referring to the slightly dented case mouths?
If so, that will iron out fine when you resize the cases. I’ve had 7.62x51 cases that were more dented than that and I’ve reloaded them several times (each firing dented the case mouth) without incident.
If not, then never mind. 
Yes, that’s what I was referring to. Thanks for the heads up…I am just starting to get interested in reloading so I was concerned that it may cause issues.
I haven’t noticed this from any of my other semi-auto rifles, so yeah.
That dent is completely normal. The Blackout case is short enough that as it is kicked out of the ejection port, it spins and hits the case deflector right on the edge of the mouth. I’ve seen this confirmed with high-speed video of a Blackout gun fired on full auto, as well.