6.8 sbr

[Tmm]

how short can you go before you start to loose velocity, and ultimately all the benefits that come with? Have searched around and can’t seem to find an answer. Hope this question makes sense . Thanks

 

[FrankT]

You lose velocity at the first inch. I have an 8.5" but still kills pigs easily at 125yds and it loses over 400fps, the 12.5 is recommended. I am not going to be restricted in travel and pay a $200 stamp so mine is in pistol configuration.

 

[pruhdlr]

The loss of velocity can be slightly mitigated by the powders used for loading. Although I am not really sure all this trouble is worth the true FPS saved.
I would suggest that you keep the bbl at least 10.5 inches. You could also switch to a slightly lighter weight bullet if velocity is a great concern.
I shoot a 85gr Barnes TSX at a greater speed than most longer bbl'ed guns can shoot a 100gr.
I will NEVER own a SBR. It's "pistol" for me. ---- pruhdlr

 

[hdfireman]

You will lose around 30-35 FPS per inch. A 12.5" is as short as I would go because it allows you to run mid-length gas. I've killed coyotes out to 240 yards with my 12.5"

 

[Tmm]

Not overly concerned with velocity. But am concerned about physics. Shoot 120ish grain projectiles at 2750 = less energy -120ish @ 2400 ect ect. At 30-35 FPS, where do terminal effects fall off and now you might as well be shooting 556. Hope this wusrion makes sense.

 

[theblakester]

With a 12.5" AR15 performance barrel, I'm about 1.5" high at 100 yd, and 1.5" low at 200 yds with a zero of about 175 yd shooting a 120 grain factory Hornady SST. This gives me about 1500 ft/lbs at the muzzle, 1250 ft/lbs at 100 yds and over 1025 ft/lbs at 200 yd and just under 900 ft/lbs at 275 yd... (according to Hornady ballistic calculator with a MV of 2375 fps, BC of .400).

 

[Tmm]

That’s exactly what I was looking for. Thanks.