Mine is outfitted with a free float quadrail I really like it for 3 gun and other similar matches most people run 18 or 16 inche but I like the extra lethality of the longer barrel increases the distance of fragmentation of 55 grain fmj's to 250 meters
Okay... What are you saying here? Punctuation is your friend.
I shoot an 18" barrel for 3-gun, but at our matches there are plenty of 16" barrels as well, and an occasional 20" barrel. None of these guns have problems hitting the 650 yard target, some using 55 gr FMJ rounds.
If you think that it takes a 20" barrel to make a 55 gr projectile accurate at 250 yards then I question the experience that you have with the platform.
And I still have not figured out where "fragmentation" comes into this discussion from...
To the OP:
A Magpul UBR or PRS will help balance the rifle.
This was going to be my recommendation. The PRS is not as adjustable as the UBR or other carbine stocks, but it is about perfect to balance out a 20" barrel.