5.56 sbr barrel lengths and velocity help

Farmboy20

Regular Member
I am looking at buying a short barrel upper to use under nods for coyote hunting where I’m at the longest shot i will take is 250-300yrds max. Im looking at 11.5-13.5 inch barrel and I just want to know what barrel length will give me enough velocity and range to drop coyotes at said distance with horndy vmax 55 grain and similar rounds. Also it will more likely than not have a can on it.
 

ggammell

Does not pass up an opportunity to criticize P&S.
I have 11.5” inch data on about a dozen rounds. Not that particular one though. Gold dot in 3 flavors, TBBC in 55/62, TSX 50/62, 70 GMX, 62gr Fusion. If you want specific numbers let me know.

From what I’ve read the, the Fusion 62 round will prob be your best bet to have good terminal effect at those ranges. Gold dots probably a close second.
 

Jameskac

Newbie
Cursory googling suggests that from an 11.5 barrel, 55gr V-MAXwill have a muzzle velocity of around 2550 fps.

Hornady claims that their 55gr V-MAX expands down to 1600 fps, for reference.

For those of us who like math, this combined with a stated .255 G1 BC gives us the following.

1800 fps to 240yds with 10 inches of drop.
1700 fps to 275yds with 16.5 inches of drop.
1600 fps to 315yds with 23 inches of drop.

An existing post regarding 11.5 with a SOCOM RC lists 2930 for the BH 50gr TSX load with a SOCOM RC can. With a stated .197 G1 BC, that's

1800 fps to 265yds with 10.5 inches of drop.
1700 fps to 295yds with 15.5 inches of drop.
1600 fps to 325yds with 22.5 inches of drop.

I would suggest running the 50gr TSX, as the higher velocity (likely due to faster burning powder) means a flatter trajectory. You could also benefit from tweaking your zero to maximize the point blank range.

Here is 55gr V-MAX vs 50gr TSX with 200yd zeroes.

To answer your question with this rough math, an 11.5 with a fast bullet is certainly sufficient with regards to lethality. How much drop matters is up to you to decide. The 55gr TSX loading is a bit sub-optimal, but I have three numbers so it's a decent example.

200yd Zero 55gr TSX comparison. Going off of the fact that 50gr TSX is substantially faster at the muzzle, you'd probably be just fine with an 11.5 or 12.5 weapon.

The above is all citing other people's numbers and is somewhat limited by the dearth of data for 50gr TSX, which I suspect is your winner. Thus, I'm going to go ahead and construct a sloppy data fit to estimate 12.5 and 13.7 velocities for you, using the found 10.5, 11.5, and 20" velocities. I must emphasize that these are estimates.

Using the following data as reference -
0 0
10.5 2750
11.5 2930
14.5 3250
20 3419

Produces the following trendline.

From this, we derive our 12.5 and 13.7 velocities of

3046 fps
and
3179 fps

respectively, leading to the following set of trajectories with 200yd zeroes. I must reiterate - this is an approximation on my part, but one I am fairly comfortable making.

Tl;dr - 50gr TSX or 55gr V-MAX will expand in a coyote out to 300yds with whatever you choose. Go longer if you need to to get better drop and more margin for error. Buy 50gr TSX.
 

Farmboy20

Regular Member
All this knowledge hurts and i love it thanks so much I really appreciate it this helps a lot any more knowledge be awesome thxs
 

tacweapon

Newbie
I am using a 12.5 midlength Triarc Track 2.0 barrel.

With 75gr gold dot my average muzzle velocity is 2430fps at approximately 4000 feet above sea level at 60 degrees with a 20 shot string.
Triarc claims their rifling creates a better gas seal which leads to improved velocity, I dont have enough data on that yet to compare the results.

With a previous 12.5 carbine barrel with traditional rifling I have the following numbers
64gr gold dot 2560fps at approximately 4000 feet above sea level at 60 degrees with a 15 shot string.
 
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