.308 20" Federal GMM 168gr Velocity

[ncyotecaller]

I have a new Remington SPS Tactical that I dropped into a new LTR stock and put a Swarovski 4-12x50 with ballistic turrent. I was wanting to get acustom turrent made to shoot 168gr GMM. I have no chchronograph or access to anybody with one to test the velocity. I know with the 20" barrel it won't make printed velocity on the box. Anybody have any good average number from personal experience?

 

[wwrhodes91]

Most velocities are recorded from a 24" barrel. I would just subtract about 80-120 fps from that

 

[Archer762]

if you are getting a custom turret, you better chrono your own rifle- buy a cheap, used one. Every shooter should have one. You can't expect a turret to work at the advertised distances using someone else's data.

 

[codemancode]

I get 2535 fps from the same setup. Trued to 600 yards. That ridiculous jump to the lands really kills velocity. Rems are notorious for excessive free bore.

My suggestion would be to plug 2550 into a ballistic app and print some groups on paper at about 800 yards. Measure the group distance from your point of aim and adjust the velocity in your ballistic app until it matches. Best of luck.

 

[ORD]

The only way to know for sure what it will do from YOUR rifle is to run it over a chrono and record your results (which I understand you don't have or otherwise don't want to invest in), OR...use your dope, along with an online source like JBM and back your way into the approximate MV.

Best GUESS...you'll achieve ~2550fps (not the 2650fps listed by Federal which they obtained using a 24" or 26"...can't recall which they used).

As for what you are wanting to do...skip it!!!! The "custom" turrets are only as good as the info used to make them and even then...they are only good with the very specific set of data (MV, atmospheric/environmental conditions, etc.) they are created with. Any variations in that data, whether its a slight deviation in MV, ambient temp, altitude, etc. can wreak havoc with your numbers and make your turret a complete waste of time and money! "Guesstimating" at anything used to make the turrets (like the MV you are attempting to find) is a bad way to go and will only cause you more problems than it will solve in the long-run. Learn to use the optic the way it was designed to be used by dialing your adjustments and leave the gimmicky BS turrets well enough alone.

 

[Niles Coyote]

I get 2535 fps from the same setup. Trued to 600 yards. That ridiculous jump to the lands really kills velocity. Rems are notorious for excessive free bore.

My suggestion would be to plug 2550 into a ballistic app and print some groups on paper at about 800 yards. Measure the group distance from your point of aim and adjust the velocity in your ballistic app until it matches. Best of luck.

Good info.

I too have the same rifle, but have not used any FGGM in it.

My reload I use in this rifle and others is a little faster than FGGM... I'd bet your going to find yourself right around 2500 +/-10. Printing a data chart from JBM and testing as far out as you plan to shoot will get you the info you need.

edited to add

sorry, I was thinking 175 FGGM, 2535fps would likely be closer for the 168

 

[Robby0931]

My suggestion would be to plug 2550 into a ballistic app and print some groups on paper at about 800 yards. Measure the group distance from your point of aim and adjust the velocity in your ballistic app until it matches. Best of luck.

I just wanted to echo everyone else, I get a consisent 2550 fps out of my 20" with 175gr FGMM.

 

[ncyotecaller]

Yea I will probably buy a chronograph so that I can atleast set up the Swarovski's ballistic turrent correctly. Im sure I will have to enter it in their program as a handload because of the shorter barrel.

 

[hk dave]

I have the same rifle with barrel shortened to 18". I get 2480 with 175 SMK.

 

[coldboremiracle]

Yea I will probably buy a chronograph so that I can atleast set up the Swarovski's ballistic turrent correctly. Im sure I will have to enter it in their program as a handload because of the shorter barrel.

Again with the "turrents"?

I feel bad for you guys and your lack of altitude, I get 2550 with a 175 out of a 16".

Definitely chrono your stuff before ordering a custom turret, personally I hate 'em for that very reason. They are great for the bullet, temp, altitude, etc. they are designed for, change one of the many variables there and now it doesn't represent what you think it should, and your back to estimating like everyone else who didn't buy custom turrets.

 

[sjb269]

Chrono your round of choice, Buy a set of FDAC cards.
Or Buy a whiz wheel and make a drop chart when you get to your shooting location.

A halfway decent chrono is what... 90 bucks. Invest in one...And don't forget to post pics when you accidently shoot it someday Haven't we all done that at one time???

Ballistic turrets = not for me

 

[escopeta]

Over the years I have clocked FGGM 168 out out of several TacOps Tango and Echo 51 at 2650FPS with 20" tubes.

 

[mark5pt56]

Chrono your round of choice, Buy a set of FDAC cards.
Or Buy a whiz wheel and make a drop chart when you get to your shooting location.

A halfway decent chrono is what... 90 bucks. Invest in one...And don't forget to post pics when you accidently shoot it someday Haven't we all done that at one time???

Ballistic turrets = not for me

This, best option. Remember, every barrel will be different, need to verify velocity.

 

[burt]

Remember too that muzzle velocity really does vary as much as 1- 200 fps over normal shooting conditions. ie temp 30-90 deg f. (it really does) So getting a mv at one temp only starts the process, although you can estimate for other temps to some extent.

 

[rlh]

Magnetospeed v3 measured factory fgmm 168 grain out of my 20 inch savage hog hunter at 2640 fps (5 shot avg) at a temperature of 80 degrees.