scoped SBR?

[zignal_zero]

does it make sense? i mean part of me is saying that it goes against everything - make something shorter it's for CQB and long range precision, BUT part of me is saying it would kick glutes to have a scoped rifle short enough to put a can on.

here are my choices:

(1)
have my existing AR15 (5.56x45) barrel cut down. all that would extend past my four rail gas block would be the portion of barrel that is threaded. my can would butt right up against (or look like it did) my gas block.

OR
(2) buy the Spike's 300 BLK upper, the one where the HG's are longer than the barrel and attach that to my lower.

either way, i'm not looking for 'across town' shots. i just wanna hit paper plates past 100yd and poster board slightly past 200yd.

i was worried about the 5.56 because in order to get in super quiet, i'd have to go subsonic and 55gr (or even 70) and sub sonic speeds is not a very threatening though. whereas the 220gr subsonic 300BLK seems like a hefty thunker, but i worry that it won't be very flat shooting or carry the same POI at different distances. keep in mind, i know next to nothing about 300BLK, but have been issued, carried, and relaoded for the 5.56

what do you guys have to say about his idea?

oh also - how much velocity is lost with barrel length with each cal? i mean like does 5.56 have some formula? some kind of 50fps for every inch of barrel? as a reloader, i realize burn rate plays a big part, but is there some kind of rule of thumb? and is either caliber more or less prone to lose power when chopped down?

thank you

 

[wally]

There is an article in this week's Shotgun News about an 11.5" LWRC factory SBR and the good groups he got with a scope -- 0.9 moa with Hornady 75gr loads.

As a general rule the heavier bullets lose less velocity proportionally than the lighter ones, but individual barrels vary too much for any rule to be very accurate.

Google "ballistics by the inch" for a web site with a lot of tests, mostly handgun rounds though.

I think for sub-sonic .223 you might as well get a CMMG .22lr conversion kit and use the Aguila 60gr .22lr ammo -- be a whole lot cheaper.

For subsonic AR I like a 9mm shooting 147 grain loads, or if you want to handload the .300 Blackout, but it'll cost a lot more per shot.

The subsonic .300 Blackout will shoot flatter than the subsonic .223 because it retains velocity better due to having 4X the mass, but both are rainbows compared to normal near mach3 .223 loads.

 

[lead slinger]

I have a trijicon ta24 on my sbr on low power it's just like a red dot but when u need it you can turn it up

 

[KingTiger]

I've got a Hi-Lux/Leatherwood CMR 1-4 on my 9.5" 300 BLK that has worked well for me. It has an illuminated dot/horse shoe reticle for close range & a BDC lower cross hair for longer ranges. You can zero it at any distance & then lock in that setting as the "0" on the turret. I zeroed it at 50 yards with the 115 gr. & just crank it up the the "8" setting to achieve the same with the 220 gr. subs.

 

[zignal_zero]

Cool, you guys have cleared up most of what I was wondering.