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FGM 168 Ballistics Question

I

ingobwetrust

Private
Full Member
Minuteman
Oct 19, 2006
53
0
58
Stoddard, NH
#1
Recently picked up 10 boxes of this ammo and got to the range with it. I know that you can't rely on factory published ballistics but my results were way off what was on the Federal web site. I zeroed my 700 PSS at 100 yards and then moved to the 200 yard line where my groups were about 8" low. The federal site says the drop is 4.3" low at this range. Is this much deviation normal?

I'm new at this so please be gentle with me! Thanks in advance for the feedback.
 
#2
Re: FGM 168 Ballistics Question

This is what I had for my scout rig using FGMM. I can't remember if I've changed anything, so it might not be 100% accurate. It was out of a 22" sporter barrel.


Range Traj ComeUp Wndg 10 Wndg 10
(yds) (in) (mils) (in) (mils)
100 0 0 0.8 0.2
150 -1.2 -0.2 1.8 0.3
200 -4 -0.6 3.2 0.4
225 -6 -0.7 4.1 0.5
250 -8.5 -0.9 5.1 0.6
300 -14.9 -1.4 7.5 0.7
350 -23.4 -1.9 10.4 0.8
400 -34.1 -2.4 13.9 1
450 -47.2 -2.9 17.9 1.1
500 -62.9 -3.5 22.6 1.3
550 -81.5 -4.1 27.9 1.4
600 -103.2 -4.8 33.9 1.6
650 -128.3 -5.5 40.6 1.7
700 -157.1 -6.2 48.1 1.9
750 -189.9 -7 56.4 2.1
800 -227.2 -7.9 65.4 2.3
* MPBR is 260 yards with 225 yard zero.


If it were me, I'd double check for loose base, rings, stock, etc. And then rezero using a Caldwell sled or a solid bag setup. Then double check your come-ups. Other more experienced guys will know more than I, however.
 
#3
Re: FGM 168 Ballistics Question

Thanks for sharing that. I double checked everything and went to the range again and got the same results; At 200 yards my groups are 8" low. This is out of a 26" barrel. I even switched boxes of ammo from a different lot# and got the same results. Anyone got any clues as to why or should I switch loads? The groups are good but not as good as I get from my .308 hunting rifle with Winchester 150 grain Ballistic Silvertips.
 
#4
Re: FGM 168 Ballistics Question

I'm at the other end using factory 168gr. At 200 yards I'm only 3.7" low out of a 26 inch barrel as opposed to the advertised 4". Remington and Black Hills are only 3.1 and 3.4" respectively for me.

 
#5
Re: FGM 168 Ballistics Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DirtyRod</div><div class="ubbcode-body">I'm at the other end using factory 168gr. At 200 yards I'm only 2.8" low out of a 26 inch barrel as opposed to the advertised 4". Remington and Black Hills are only 2.1 and 2.4" respectively for me. </div></div>

Weird. Wanna trade ballistics?
wink.gif
 
#7
Re: FGM 168 Ballistics Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: inGobwetrust</div><div class="ubbcode-body">Weird. Wanna trade ballistics?
wink.gif
</div></div>

Actually, I went back to verify and I was reading the wrong data. I'm about 1.8MOA or just over 3.7" @ 200 yards with FGMM 168gr. Sorry for the confusion.
 
#8
Re: FGM 168 Ballistics Question

With Federal GM308M I'm at a loss as well. Having shot M118 7.62 for practically all of my career I can't seem to get correct dope worked out from the Federal 2010 Ammunition software download. At 300 yards (with a 100 yard zero) it shows a drop of 15.2 inches but when shooting I've had to drop down from 5 moa to 4 moa to be dead on, is Federal under rating the muzzle velocity (2650)?
 
#9
Re: FGM 168 Ballistics Question

I haven't shot it over a chroney, but i'm only at 3.5 at 200 and like 12.5 at 300 which doesn't jive with any ballistics data I've ever seen this is with a 26'' barrel.
 
#12
Re: FGM 168 Ballistics Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ajwcotton</div><div class="ubbcode-body">that is why I shoot as many yardages as possible to get real life dope, in inches and in the respective corrections

</div></div>

I think we all do that, what we're pointing out is the inaccuracy of Federals published ballistics. When my shooting conditions mimic theirs as published I would expect a closer starting point to begin from.
 
#15
Re: FGM 168 Ballistics Question

Okay, went to the range again, checked all screws, everything. SAME RESULTS! I don't get it. This last trip the temp was about 30 degrees warmer than the last time so it has nothing to do with that. I'm just plain old stumped.

This is the rig:

PSSright-1.jpg



 
#17
Re: FGM 168 Ballistics Question

Why is this such a big deal?

Shoot at 100, 150, 200, 250, 300, etc. and write down your dope. Use it.

That's how we did it before the cheap ballistic computers.

You may have a slow barrel or some other harmonics may be going on.

As long as you got a GOOD zero, then just understand that your rifle is acting different and gas on. FGMM runs fast in my barrel. I recorded the difference over a chrony at the temp I had I drove on.
 
#19
Re: FGM 168 Ballistics Question

I put 168Gr FGMM through my AW - 26" barrel. Never chrono'd or used a ballistic calculator but here are my come-ups worked out "the old way"
wink.gif


100yds = 0
200yds = +3/4 MOA
300yds = + 3 1/4 MOA
500yds = + 9 MOA
600yds = + 11 3/4 MOA

These tend not to deviate that much from batch to batch once re-zero'd...maybe a click or so but never more.

 
#20
Re: FGM 168 Ballistics Question

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Why is this such a big deal?

Shoot at 100, 150, 200, 250, 300, etc. and write down your dope. Use it.</div></div>

I think it's because his numbers deviate so radically from the norm. I'd be wondering too. That said however, there really is no other way. Gotta go out and shoot the dope (
laugh.gif
). Every ammo brand I use or handload has its own proven dope table for each rifle.
 
#21
Re: FGM 168 Ballistics Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MSG Janoski</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ajwcotton</div><div class="ubbcode-body">that is why I shoot as many yardages as possible to get real life dope, in inches and in the respective corrections

</div></div>

I think we all do that, what we're pointing out is the inaccuracy of Federals published ballistics. When my shooting conditions mimic theirs as published I would expect a closer starting point to begin from.</div></div>

I don't think what you are seeing is Federals inaccurate ballistic charts, what you are seeing is Federals inaccurate manufacturing process in which some lots got out that were understrength. It doesn't take much. A little weak on the primer or a grain or two less of powder. Maybe a weak lot of powder?

The ballistics they publish, and what you find on ballistics calculators, is going to always be close. Never dead on. But, it isn't going to double. Most everything no matter what BC coming out of a barrel @ 2650 fps is going to drop about 2MOA @ 200. For the guys just under 2MOA drop using 26" barrels that makes sense. Your bullets are coming out maybe 50-100 fps faster due to the added barrel length.

As noted, grab a box of something else and see what it does. You got a bad lot of cartridges I'm guessing. Chrono it if you can. If you can shoot all the way out to 500 see where it hits then compare it to one or two ballistic calculators.

I'd sure figure that one out before I took it out to depend on it.
 
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