Looking at getting either a 13.7inch or 14.5 inch with a short can max overall length under 17 inches. Rifle is going to used for ranges between 0-400 yards. Im in the UK so the having to adhere to the min 16inch barrel length does not apply. After some research the 13.7 inch barrel has 66fps (62gr ss109) less then a 14.5inch barrel. At 500 yards the difference is 48fps. Will the 66fps more velocity from the 14.5inch barrel going to make much difference for range and accuracy ?
I wholly understand what you're looking for. I am of shorter stature and prefer an AR that is easier to manipulate.
I do a good bit of shooting out to 400 yards. There was a time when I had one each of an 11.5, 12.5, 13.9, 14.5 and 16" barrels. I also shoot a lot of m855 and various 77gr loadings.
I haven't done any formal testing, but something I have noticed is that differences in performance among the differing barrel lengths did not become meaningful until the differences in velocity approached 300 feet per second. Put more plainly, when starting with an 11.5" barrel and increased barrel length and took note of performance increases, I did not see a meaningful increase in performance until I got to a 16" barrel where the velocity increase amounted to about 300 fps. I now run two setups. An 11.5 and a 16".
I run the 11.5" barrel with a YHM Fat Cat suppressor. The Fat Cat is one of the shortest suppressors you can get for a 5.56 and my setup measures just over 15".
If your decision is one of choosing between a 13.7 and 14.5, go 13.7. The difference in velocity is negligible. I just don't think you're going to meet your length goal with a 13.7.
If you decide to go shorter, consider the 12.5 rather than the 11.5. From a performance perspective, the 11.5 is fine, but even I feel a bit cramped by the limited space on the handguard. The extra space you get with a 12.5 is very noticeable..
You can also do a bit of velocity loss mitigation by going with a "fast" barrel. Some barrels typically get more velocity than others. For me, I've had good luck with Criterion barrels. Proof barrels run pretty fast as well.
I don't know what your budget is, but check out the Cobalt kinetics direct thread suppressor. It is very light, fairly short and performs very well. It is also pretty expensive. I like my Fat Cat. It's very short and performs very well. In terms of sound mitigation, it is one of the best I've heard. The downside is that it is gassy. A method of gas regulation was necessary.
