Buffer/spring combo for Magpul UBR Gen 2

AR/M4 AR Technical Discussion
1

I’ve done some searching but most are for carbine or midlength upper combos

I plan on installing a Magpul UBR Gen 2 stock on the following

Stripped M&P lower with Daniel Defense internals except the trigger was replaced with a Geissele SSE flat bow.

The Upper runs a Faxon 18 gunners barrel rifle length gas tube primarily suppressed Silencer co SpecWar K

Current Stock runs a LaRue Supplied Carbine Spring with and H3 buffer, No issues runs my reloads 69 SMK over 25 grains CFE suppressed or not

Should I Run the the same Combo with the included Magpul supplied spacer

Or would I be better off to run a Tubbs rifle length spring with What Buffer to Start?

The UBR can use either.

2

I go with what I got, before going out and spending more money personally. Your combo and spacer should work as you had before…

3

If you have a buffer/spring combination that works, why change it?

4

I guess my question should be rephrased,

Is there anything a rifle length spring with the appropriate buffer, offers to this set up?

such as recoil impulse(subjective) wear on parts? or any other percieved benefit?

The Magpul UBR Gen 2 is supplied its own propriety buffer tube, which can be run with either carbine(with supplied spacer) or rifle length(A5 wish).

As I need to buy a spring & buffer I’m open to various options.

5

I have a few and run both carbine and an A5 setups. You can try an A5 but that’s $50. What you have is perfectly fine. It’s not a bandaid solution to use the spacer. It’s by design.

6

In your shoes, I would run an A5H2 buffer and a Sprinco green spring. It’s what I have now and it’s really smooth, especially with a 20" upper. It’s a bit smoother with every upper than the carbine RE and H or H2 buffer.

7

I have a Larue 18" ML and the UBR2…I’m also using a A5H2 with Sprinco green spring. Runs well suppressed at unsuppressed. This is primarily longer distance precision type shooting, not “run and gun” or 3-gun comp shooting.

8

Pretty much,

Sounds like Spring green and A5H2 Buffer it is. Atleast for starters…:smiley:

9

If the current setup runs well, then it will continue to run well with the spacer.

It took me quite a few weeks to locate an A5H2 after I received my first G2, so I used the spacer and a carbine buffer. If you want to try an A5 buffer, you can, but you shouldn’t consider it a necessity. When you think about it, the longer A5 receiver extension utilizes a longer buffer. Each buffer travels approximately the same distance within the receiver extension.

10

The A5H2 buffer with a Colt rifle action spring would be a preferred starting point for most any combination. For the timing of events that combination tends to function well overall. Using the carbine type action tends to reduce some of the time for the events over a rifle like action. I would avoid the green spring with the A5H2, while it helps bolt locked timing, it hurts the time in bolt travel over the magazine timing, reducing that timing can be a reliability issue. I would tend to use the Colt rifle action spring with more reciprocating mass if the combination requires that for preferred use over more spring loadings with the A5H2. If the combination requires an A5H4, or sometimes an A5H3, then I would consider the green spring.
The way the action cycles by “feel” does not correspond directly for timing events that are required for reliability. I’m not saying that a green spring A5H2 combination can not be reliable, but that it limits time down less than what we could have by adding more mass if the system as a whole requires that.