Pulled down Federal GMM in .308

[Stats Shooter]

So I pulled some Federal Gold Medal match bullets to see what they are using in their 175 grain and 168 grain .308 loads. I pulled 4 of each to check consistency . I found the following.

Both 168 & 175
COAL 2.80 +/- 0.0015
Case Length : 2.0088 +/- 0.0010
FC case
Fed 210M primers
Bullets Sierra Match King BTHP

168 Grain
Base-Ogive: 2.2200 +/- 0.0010
Powder 43.5 Grains

175 Grain
Base-Ogive: 2.2300 +/- 0.0020
Powder 41 Grains

I have been informed that Federal GMM used to use IMR 4064 for both loads but switched at some point to RE 15. The military made them switch back to IMR 4064 due to temp sensitivity.

The Sierra manual says the max charge for IMR 4064 in 175 grain is 42.8, and in RE 15 it is 41.3...For the 168 grain load, Sierra says a max load of 4064 is 43.4 and for RE 15 the max charge is 43.6.
The question is: which powder is Federal using? Hodgdon says the max load of 4064 for 168 gr is 45.9(C) and 45.6(C) for 175 gr bullets. Lyman says the max is 44.8 and 44.3 gr RE 15 for 168 and 175 gr bullets respectively.

I guess it may not matter. I intend to use IMR 4064 and BR-2 primers so my load may be a bit different. I will update this thread tomorrow morning after I test the velocity for both bullets but that may not mean much given my AR-10 is obviously going to be different than anyone else's. Previous testing at 200 yards indicated my gun preferred the 175 grain bullets with groups under 3/4" at 200 yards. The 168 grain bullets were decent also grouping at 1.5-2" at 200 yards but not as tight, or consistent, as the 175 grain load....1:10 twist barrel



Update: 2391 FPS for 175 gr GMM at 40 degrees F (8 shot average)
2504 FPS 168 grain GMM...same conditions and 16.25" barrel
Box says 2600 for 24" barrel 175 grain
2650 for 168 grain

[T. O'Heir]

Base-ogive measurements mean nothing. Cartridges are not measured that way for OAL. OAL is measured from the point bit to the flat part.
No manufacturer publishes what powders or how much they use. Cartridges are loaded to give a specific velocity and a specific pressure. One powder lot can give a different velocity and pressure with different amounts of powder.
And every manual will reflect the conditions on the day of the test only. Hodgdon, for example, used a 1 in 12, 24" barrel. Back when Lyman did their tests for their 45th Edition published in 1978, they used a 26" 1 in 12 barrel on a universal receiver.
Your "groups under 3/4" at 200 yards" is the only thing that matters anyway.

[Stats Shooter]

Base of cartridge to ogive mean nothing? That statement is false. Base to ogive tells me the distance from the lands once I have measured my chamber. It means nothing to other people probably due to chamber and throat differences, so I guess it's pointless to post that figure, but I do it because it is more consistent than COAL....and btw COAL only matters as far as fitting in the mag, if you single shot, COAL is irrelevant.


I agree the group consistency is most important. But velocity matters in some instances.

[nvcnvc]

I think Mississippi is correct. If you use brass fire formed on your gun, base to ogive as well as base to datum point on the case are more important than COAL as measured from base to tip of bullet. By adjusting the base to ogive length you control the jump to the lands. Base to datum point is extremely important to be a few thousands less than actual headspace so that the cartridge fits properly and allows the case to expand enough to seal the chamber.
The tips on my Nosler custom competition bullets are all the same, so when I measure COAL i get differences from bullet to bullet. However the base to ogive length is consistent for all of them.
I am fairly new to reloading, and I mean no disrespect to the more experienced members here, but that is how I understand it. Am I off base here?.
Thanks

[Stats Shooter]

. By adjusting the base to ogive length you control the jump to the lands. Base to datum point is extremely important to be a few thousands less than actual headspace so that the cartridge fits properly and allows the case to expand enough to seal the chamber.
The tips on my Nosler custom competition bullets are all the same, so when I measure COAL i get differences from bullet to bullet. However the base to ogive length is consistent for all of them.

You are not wrong....COAL is imprecise. Sierra match kings may have tips that vary by as much as 0.0050. Furthermore, bullets in most presses are seated via ogive rather than pressing down near the tip.

But I digress, this thread is intended to give a component breakdown of Federal GMM so that no one else has to do it if they want to try and imitate them.

[Metal god]

"If" those are the only two powders to choose from as far as what's inside Fed GMM . Then it is very simple to tell which it is . If it's longer cut stick powder then it's IMR-4064 . If it's a short cut stick powder then its RL-15 .

I pulled some 168gr rounds in 2014 and it appeared they were loaded with 4064

Im not home now but will post a pick of both powders side by side later .

[Stats Shooter]

.
Metal god "If" those are the only two powders to choose from as far as what's inside FEd GMM . Then it is very simple to tell which it is . If it's longer cut stick powder then it's IMR-4064 . If it's a short cut stick powder then its RL-15 .

It was long cut, I was leaning towards IMR 4064, I have some RE 15 and it didn't look like my RE 15.

[Metal god]

Since you have RL-15 I wont post the side by side picture . How ever I do have a side by side picture of the 2014 pulled powder and IMR-4064

________Pulled from GMM on left ---------------------------------------------------- IMR-4064 on right ________

[30Cal]

Three decimal places is more than adequate at the reloading bench.

[Stats Shooter]

So based on your photos, and the bullets I pulled, the powder is most likely 4064 because the stuff I pulled Thursday night, and it was purchased last week, looked just like your picture.

One thing I noticed though, is that Federal GMM barely fits in my magazine. That means, if I want to magazine feed the rounds, there isn't much leeway in how shall I seat the bullets. But, as I said, the 175 grain GMM loads were near 1/2 moa at 200 yards so I'm not sure messing with the jump will improve groups anyway.

So, I'm going to buy 8 lbs of 4064 and 500- 175 grain smk's and see what I can do. If I can get 1/2 moa at 200 yards I'll be set.... federal GMM cost $1.50/round but I can make it for about $0.50/round, $0.30/bullet +$ 0.035/round primers +$0.16/round powder. Brass is free . So that is significant savings for match grade ammo.

[Unclenick]

I pulled some 168 grain GMM about 15 years ago that was clearly IMR 4064. 4064 grains are 0.085" long × 0.032" diameter. Also 43.5 grains. When I put the load details into QuickLOAD it predicted 2648 fps from a 24" tube. Pretty close to the 2650 claimed by Federal.

It was Federal who chose 4064 over RL15 when developing Mk 316 Mod 0 sniper ammo that uses the 175 grain SMK. M118LR, which also uses that bullet, was loaded by Lake City with RL15, but they had pressure signs with it in the desert in Iraq and attendant POI change. 4064 is more immune to temperature.

Federal gets their 4064 specially made. There's an ATK presentation you can find on line that mentions the Mk 316 4064 has a flash suppressant added. Given that the charge weight in GMM is the same has it has been in past decades suggests they are buying it tweaked to even tighter burn rate specs than the canister grade 4064 from Hodgdon is. There may be other factors.

[Road_Clam]

Good vid on FGMM reverse engineering:

https://www.youtube.com/watch?v=iDIu6Mivi-Y

[Metal god]

The interesting thing I noticed in that video is he was exactly .7gr off with both loads of what we got doing the same thing . Coincidence or is his scale off .7gr ?

[Unclenick]

Could also be I'm full of beans about the tight burn rate and the matching 43.5 grain charges for the 168 being identical over all these years is a coincidence. If so, then the 41 verses 41.5 he measured to the mentioned government load of 41.7 grains, is powder lot burn rate difference that has been adjusted for in a pressure gun.

[Stats Shooter]

Well, as I said, I'm going to try 4064. Even if it isn't the powder of GMM (which I think it is) it is still great powder for 168 or 175 gr .308 bullets. Also, as unclenick said, even if it is 4064, the batches federal get isn't going to be quite the same as what I'm going to be able to buy. So while there may be 41 grains in the 175 grain load, it may take 41.4 or 40.8 or something like that. I'm hoping to achieve the federal GMM 175 grain accuracy but add another 50-100 fps which may be possible.

Like I said, federal claims on its box 2600 fps and I got near 2400 fps out of my 16" barrel. Hodgdon says 2728 is possible in a 24" barrel with 45.6 gr 4064, which may equate to about 2450-2500 fps out of. 16" barrel. But if accuracy suffers I'll stick with the lighter load.

[Road_Clam]

Just for knowledge I tested 168 FGMM in both my 26" R700 Varmint and my M1A and neither shot this ammo with precision. The FGMM is simply over charged for my barrels. My most consistent loads are :

R700 26" Heavy contour 1-12" twist : 168 match bullet / *41.7-41.9 W748 / LC LR cases with a .025" jump approx 2540 fps

*note the two different W748 charges, W748 is a bit temp sensitive so I tweak the charge based upon the time or year, 41.7 in hotter temps, 41.9 in cooler temps.

M1A Loaded, new production mill spec barrel : 168 match bullet / 41.6 / 4895 / FGMM cases loaded to mag length 2.800" oal. approx 2620 fps

"This is why we handload"

[Unclenick]

RC,

Your results differ from mine, but as you say, this is why we handload.

I find 4064 generally needs to be loaded closer to maximum to achieve the same barrel time numbers as 4895, but produces shorter barrel times than 748. I suspect this is what you are seeing. Your M1A likes a shorter barrel time and your bolt gun likes a longer one than 4064 produces.

The only thing in your data that is unusual is the M1A velocity. Using Hodgdon's 24" test barrel numbers for the same bullet and COL to tweak QuickLOAD to match, and then allowing for Hodgdon's use of a Winchester case and you using Federal brass (about 2 grains less water capacity in my past measurements), I did an estimate of your 168 grain MV for 41.5 grains of IMR 4895 from a 22" barrel and got 2461 fps. I am curious to learn if your 2620 fps number is measured or perhaps estimated from different data?

[emcon5]

So, I'm going to buy 8 lbs of 4064 and 500- 175 grain smk's and see what I can do. If I can get 1/2 moa at 200 yards I'll be set.... federal GMM cost $1.50/round but I can make it for about $0.50/round, $0.30/bullet +$ 0.035/round primers +$0.16/round powder. Brass is free . So that is significant savings for match grade ammo.

Keep in mind, the IMR4064 you and I buy and the IMR4064 Federal buys are not necessarily the same thing.

Ammo companies buy bulk powder by the boxcar full, which is different than the canister grade powder you can buy at your local store.

Canister grade has a much higher quality control for burn rate, so generally speaking a can of IMR4064 you buy today will be essentially the same as the can you bought last year, or 10 years ago.

Bulk powder is not like that, the ammo companies do testing on each lot of powder to meet a pressure and velocity specification, and a box of GMM you bought today may have a different powder charge than what you bought last year.

[Stats Shooter]

. Emcon
Bulk powder is not like that, the ammo companies do testing on each lot of powder to meet a pressure and velocity specification, and a box of GMM you bought today may have a different powder charge than what you bought last year.

I understand that. I plan to do a ladder just like I usually do when I develop the load. It is just that now I have a benchmark for what the 175 grain bullet is capable of in my gun with match primers and 4064 powder. So it means I won't wind up buying some bullets and powder my gun hates. And it gives my an idea of what pressure gives good results. It will be interesting to see what 8 lbs of 4064

[44 AMP]

Base of cartridge to ogive mean nothing? That statement is false.

It's not false, it's just not a complete explanation of why it means nothing to US.

It's an important measurement to you, FOR YOUR RIFLE and the way you load your ammo. For the rest of us, it's possibly interesting information, but essentially irrelevant.

First off, as you recognized, not all chambers are exactly the same, and where you set the "ogive" to be "just" off the rifling (and how much is that?) might be either further off the rifling or jammed into it, in a different rifle.

Second, "ogive" is the entire curved/tapered portion of the bullet. Stating a measurement "to the ogive" doesn't tell us where on the ogive your data point is.

If you are talking about the point on the bullet where it first reduces from full caliber width, that would be start of the ogive, and while I'm pretty sure you know what you mean, "to the ogive" wasn't clear to me what point you were referring to.

Assuming what powder is used in any factory ammo based on information coming from anyone BUT the manufacturer is a risky business. As other have mentioned, ammo makers do not use canister grade powder, and powders with drastically different burn rates can have identical physical appearance.

[Unclenick]

Yes. Moreover, the mechanical reason for tracking that measurement in rifle cartridges can be seen on many loaded rounds. It shows up as a little ring mark on the bullet ogive where the seating die pushed it to seat it into the case mouth. As a result, the dimension you actually control during seating is base to ogive and not base to tip with most rifle seating die and bullet combinations.


Emcon5,

What you say is generally true of bulk powders and bulk powders are what are generally used by commercial ammunition makers. Federal, however, says they order their GMM powders special for their purposes, so they are paying more for it and getting something more from it. Based on their own load and performance data it is being held very close to matching canister grade 4064. The fact the 43.5 grain charge weight has remained constant for over 20 years would seem to be another clue if it isn't a coincidence. Even canister grade powders for handloaders aren't held that consistent.