Are these Factory FGMM velocity variations normal?

[Otero51]

So this Saturday I had a chance to get some velocity measurements out of my rem 700 aac-sd to get an idea of where I was. This is a 20", 1-10 twist, 308. Currently I'm shooting factory FGMM in 168 and 175. These are the numbers I got:
168gr -
shot1: 2508
shot2: 2546
shot3: 2518
shot4: 2527
shot5: 2495

175gr-
shot1: 2572
shot2: 2564
shot3: 2527
shot4: 2521
shot5: 2530

Now I used a chrony to get these measurements (set around 10-12 feet away from muzzle). Is this variation in velocity expected for factory ammo? I don't have much knowledge on chronos, so don't know how accurate chrony brand is. Temperature at the time was 81.4 degrees. Barrel was warmed up at the time I took these shots and I didn't waited to much in between shots (around 1-2 minutes in between).

 

[17874]

Looks about right to me. FGMM gave me a standard deviation of 17 which is horrible. It did shoot consistent .6 MOA out of my rifle.

 

[RobertB]

How does it shoot/group at distance? Thats what matters. I don;t even trust some of the good cronos now a days. I just look at the targets.

 

[gstaylorg]

In my hands, using several different rifles, FGMM175s typically give ES values from 40-50 fps with SD values of 15-20. Although every rifle is different and must be evaluated independently, your numbers look pretty close to that.

 

[GhostFace]

How it shoots is all that matters, goes to show you that you really don't have to weigh each and every charge to make accurate ammo. All you need to do is hit an accuracy node and call it good. With that I still weigh every charge....

 

[Bear24]

In my hands, using several different rifles, FGMM175s typically give ES values from 40-50 fps with SD values of 15-20. Although every rifle is different and must be evaluated independently, your numbers look pretty close to that.

that's about the same that I have seen as well

 

[thrusty]

Those velocities you've listed are typical and close to what I've seen FGMM shoot. SD and ES on FGMM is horrible, however, it seems to shoot good/decent in 95% of rifles - which was Federal's goal: to produce factory ammo that can shoot good in a variety of firearms.

So, don't fret too much on what the info the chrony is telling you...just worry about AVG velocity and whether or not you are getting good groups.

 

[Grump]

Believe the bullet.

There is a mathematical reality that, *all other things being equal*, a velocity difference of 50 fps between two shots will result in a point of impact "such and such" higher or lower than the previous shot. This becomes more important at 600 yards and beyond, IME and IMO.

Don't worry about it unless the ammo won't do what you want it to at YOUR chosen distances. All other things are NOT always equal.

Some, if not most, of the people here CAN shoot "better than the rifle" if the ammo sucks. So it's really shooting better than the ammo.

Trust your call. Believe the bullet. Relying on one without factoring in the other (including the cone of dispersion) is playing with half the deck.

 

[RonboF117]

I shot some 168 FGMM about a month ago and had an SD of 8. I'd have to look up the velocity and environmentals but if you want them, PM me.

 

[clmayfield]

As is mentioned above, velocity variation doesn't matter much at short range. It is why short range bench rest folks throw charges as opposed to weighing them. Farther than 600 yards in 308, it starts to matter. At 1,000 yards it matters a LOT, which is why FGMM is not great for those types of distances in 308.

 

[40xs]

That's probably not too unusual. Remember that they are loaded by a machine without the benefit of minutely trickling added granules to equal each load. You would get the same results if you just "threw" your charges and seated the bullet. I double weigh my charge; I trickle to the balance point, then lift the tray and set it back down to see if it goes to the same zero, usually, the second weigh is heavy, so I know where to stop just under the zero point to obtain a uniform weight. This brings my SD down to about 5-6. It makes a big difference at a grand.