Replication of Federal GMM in .308

S

Stats Shooter

New member
So in previous threads I said I was going to try and duplicate the results of Federal GMM ammo in my AR 10. The factory 175 Grain bullets grouped best in my gun so that is the bullet I used.
Recall I dissected several 175 Grain factory loads and found 41 g of IMR 4064.

Here are the components I used.
BR-2 primers
Imr 4064
175 grain SMK'S
Federal once fired brass (from the same federal GMM factory loads)
Seated to the manuals COAL
Trimmed to minimum.

Recall that Factory federal GMM avg velocity in my gun was 2395.

Accuracy tests with my handloading showed accuracy nodes around 40.2 g IMR 4064, 41.1 g , 42.8, and 43.5.

Max load from Sierra manual is 42.7, from Lyman it is 44 and hodgdon is 45.6. I found 43.5 to be hot with flat cratered primers and the primer dent from the firing pin was protruding outward.....So though there was an accuracy node around 43.5, I did not chronograph it because that load would likely be hard on brass.

Here are the velocity readings using IMR 4064
41 g 2370fps ... Extreme spread 20 fps
41.1g 2382 fps....Spread 16 fps
41.2 g 2400 fps.....Spread 31 fps
41.3 g 2412 fps......Spread 36 fps

42.7 g 2492 fps..... Spread 21 fps
42.8g 2504 fps...... Spread 16 fps
42.9 g 2511 fps...... Spread 14 fps

I didn't calculate the standard deviation because the standard deviation of a 5 shot population is meaningless ( i am an economist and statistician for a living) so I gave the spread between the most extreme velocities.

What I found was that indeed, using around 41g IMR 4064 , the same bullet, a match primer, and the same brass will duplicate the velocity and accuracy of Federal GMM.

Federal GMM factory loaded ammo is supposed to be around 2600 fps, however I'm using at 16.125" barrel. So I was about 200 fps below the published information. But my relative velocity was the same as what I got with the factory Ammo's 41+/- 1/10 gr of powder .

My personal federal GMM clone will be using the 42.8 g load. The reason being that it groups about the same as the 41(+/-) load but safely gets the velocity up around 2500 fps in my gun. If the relationship holds true, in a 24" barrel, the 42.8 gr load would get you another 100 fps or so above the factory load.

If you plan to try and go hotter than that, work up slow because 43.5 and above looks like it would be awfully hard on brass.
 
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"...and found 41 g of IMR 4064..." You found 41 grains of some powder that isn't necessarily IMR4064.
You need to work up the load for your rifle. Velocity is not as important as accuracy and the apparent ladder test you did doesn't tell you anything about the accuracy of a specific load. It only tells you where shot hit in relation to other loads.
41 grains should be that much less that Hodgdon's start load that's .5 less, either. Mind you, their data is out of a 24" barrel. No mention of what barrel length Federal used.
43.5 of 4064 shouldn't be showing pressure signs. Even the different primer shouldn't cause that.
 
T oheir
It's IMR 4064.... Everyone seems to know that but you. Federal Made the federal GMM using 4064 for years, then switched to RE 15 but the Match teams complained about temp sensitivity so they went back to 4064.

You need to work up the load for your rifle. Velocity is not as important as accuracy and the apparent ladder test you did doesn't tell you anything about the accuracy of a specific load. It only tells you where shot hit in relation to other loads.
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Thanks for the news flash....This was a specific project with a specific purpose....I did a full ladder , also measured group sizes center to center (5 shot).. The best groups in my gun were at the charges I said below with the 42.8 g load around 1/2 moa and the 41 g load around 3/4 moa.

As for the pressure, hodgdons data and Sierras max load are 3 graines apart. 43.5-44g is a full 1.5-2 g above Sierra. And Lyman has the max at 44. So it looks like Sierra was a bit too conservative, hodgdon was too hot...Lyman just right.
 
Mississippi,

You've hit upon one of the well publicized "accuracy nodes" for the 175SMK and IMR4064. Stick with that load, it'll do you well.

My load for my semi-auto 308s is a 173gr FMJBT (the old M118SB or M72 match bullet) over 41.8gr IMR4064 in LC LR brass. I also like BR2 primers, but Wolf LR are starting to win me over on performance and price. When I run out of those old FMJBT match bullets, I'll probably start buying the Nosler 175 CCs in bulk.

Good shooting!
Jimro
 
Yes, Federal orders 4064 specially made to their specification (flash suppressant added) for Mk. 316 Mod. 0 sniper ammo and you can find this in ATK presentations on line. It's no secret.

The primer is the one thing that's not a match. Federal uses their own 210M, and like Jimro, I've found the Russian KVB7 (sold as Wolf and Tulammo LR primers) and KVB762 (NATO sensitivity spec primer) to produce even lower SD's than the Federal 210M, which is better on this score than most, already.

One interesting thing to read in the Norma manual is the Federal 215 primer doing better than other makes at different temperatures in a small closed bomb test (1 cc). So, it may well be worth trying the same load with these other primers to get a comparison and then trying them in different temperatures to see how they hold up.
 
One interesting thing to read in the Norma manual is the Federal 215 primer doing better than other makes at different temperatures in a small closed bomb test (1 cc). So, it may well be worth trying the same load with these other primers to get a comparison and then trying them in different temperatures to see how they hold up.
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I may do that Nick, I won't do a full ladder or workup, but I may buy a sleeve of 100 FED215 primers and try the same load around both accuracy nodes +/- 0.2 grains on either side.

There really isn't anything else I can do do get the velocity spread lower....Maybe annealing every other time. Because I trickled each powder charge, camphered, trimmed and dry lubed the bullets when seating.
I don't really think Federal Premium brass is anything too special, when this stuff wears out I will probably use Lapua....That may help.

Federal 210M might or 215 may lower the velocity spread some. However, 1/2 moa out of an AR-10 isn't too bad, especially at 2500 fps and with the relatively High BC of the 175 Grain smk.

I would not hesitate to use this load for my next 600 yard AR slow fire match (in fact I probably will).
 
. What did you use to dry lube the bullets??
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A light dusting of graphite around the base of the ogive....Very light dusting. I do it because I wet tumble my brass which gets the necks very clean inside...Too clean ......creating too much friction. I have found it reduces velocity variability in some instances by up to 50%
 
Why do you think the cases are two clean creating to much bullet hold ? I understand what you mean but factory ammo uses vigin brass , that's got to be pretty clean right . Does Fed lube there GMM bullets before seating ? I personaly use bushing dies to controle my bullet hold .

I know you did some bullet lube test but Unclenick was saying something about the density of the powder in the case can change all thoss results depending on how you transport your ammo .
 
. Why do you think the cases are two clean creating to much bullet hold ?
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It isn't the bullet hold... Practically speaking, I don't think there is such a thing as too much, especially if you aren't crimped.

The lube thing was because, after I tumbled my brass with a wet tumbler, the inside of the case and neck is squeaky clean. I began to notice on some brass I had to use a lot more force to seat some bullets. So I pulled some I had seated and noticed I was scraping off some of the jacket even after a good campher. .....This was not a problem on cases I had not tumbled , I suspect because there is some residual sizing lube in the neck even though I swabbed them with alcohol.

So, long story short, I decided to try and use a lubricant of some kind and it appears to have worked. It also reduced the standard deviation on my velocities..
One other option I am considering is using a wet lubricant that drys fast to swab the inside of the case necks....Let them sit overnight, then add powder and seat bullets. The graphite works fine but takes a long time and makes a mess.

I think this "issue" is only a problem for people who use stainless steel pin, wet tumblers. If you use walnut, or corn Cobb, or don't tumble at all, I don't think this will do anything useful for you.
 
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I could ask if there is a member here that has run an expander into the neck of a case while measuring the effort required to expand the neck.

into the neck of a case
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Or pushed an expander through the neck or out of the neck. The only time I could have a problem with the neck of the case is when I have a failure with the neck to expand.

F. Guffey
 
Or pushed an expander through the neck or out of the neck. The only time I could have a problem with the neck of the case is when I have a failure with the neck to expand.
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Mr Guffery is a man who likes as much neck tension as possible AND a good jump....And there is absolutely nothing wrong with that. I didn't mean to start the neck tension conversation again, I don't have the setup to test it anyway. I was just saying I have done everything I know to do to get the most consistent velocity.

But I want to add this, I have created loads that had consistent velocity and horrible accuracy. When I was trying to use the 300 Grain berger VLD in my .338 LM, I had a spread of 7 fps with a muzzle velocity of 3028 fps!....That's pretty consistent and yet the best I could get for groups out of that bullet in my gun was 1.5 moa.

On the other hand, 300 Grain scenars had a spread around 17 fps if I remember correctly and made 1 hole at 200 yards.....3/4 MOA at 1k yards.
 
Mr Guffery is a man who likes as much neck tension as possible AND a good jump....And there is absolutely nothing wrong with that. I didn't mean to start the neck tension conversation again, I don't have the setup to test it anyway. I was just saying I have done everything I know to do to get the most consistent velocity.
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forgive, Mississippi, the neck of the case is not in the way when the bullet leaves the case, a very disciplined reloader brought me 80 7mm Remington cases he purchased from the wife of a friend that died recently. As soon as I looked at the cases I gave him notice we had to go talk to the reloader that owned the cases. He said: "too late, and then I wanted to find the proud new owner of the rifle because all of the necks were caked with carbon meaning there was no way the case neck could expand when releasing the bullet and I suspected the neck in the chamber was getting smaller in diameter ever time it was shot the rifle because of the build up of carbon.

I understand the part about the shooter liking the powder and accuracy but in my opinion the powder he was using was too slow, or the barrel was loose or the chamber dimensions were larger than the case diminutions. Most of this means the chamber neck was not being sealed at the neck but was fast enough to seal at the shoulder and body.

I don't have the setup to test it anyway.
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Reloaders were measuring bullet hold before there were tools designed to measure bullet hold in pounds. It has always been easier for me to push so I push both ways. All a reloader needs is a bath room scale, it never seemed complicated but when I want to know how many pounds are required to pull a bullet I drill the flash hole out and then push the bullet out.

I know, it sounds like pulling from the front or pushing at the back:eek:.

F. Guffey
 
The same very disciplined reloader built 4 magnificent rifles, again, he made the reamer etc. etc. and built the rifle. One of the rifles did not shoot groups, it shot patterns like a shotgun. All 4 rifles had the same receiver, barrel and stock. He asked me what I though would cause that and I said I did not know, He took the rifle to all the usual places and got no help. Later after having the chamber and bore scoped he called and wanted to know where I would start when trouble shooting. Long story/anyhow when I checked the rifle for free bore I pushed a 170 grain 7mm bullet out of the case and into the forcing cone and continued pushing the bullet until it final hit the rifling. His remedy was to set the barrel back and or replace the barrel; problem, he broke the reamer. He then asked me what would cause the problem; and again I had to say I do not know but I suspected someone was reading about R. Weatherby and did not understand what they were reading.

Back to "I do not know", we loaded 100+ rounds in groups of 5 with different bullets, powder etc. lengths with bullets deep and bullets about to fall out of the cases. Believe it or not there was one loading that made the rifle shine, groups opened up when the bullets were moved out and opened when the bullets were seated further in to the case. Increasing the powder or decreasing the powder had the same results.

I have too many ugly rifles that that shoot better than that so I do not spend a lot of time with beautiful rifles if they do not shoot groups. Again, I have the ugliest rifle ever built from a M1917. I thought the man that built the rifle knew more about building rifles than those that voted it 'UGLY'.

F. Guffey
 
Mississippi said:
So I pulled some I had seated and noticed I was scraping off some of the jacket even after a good campher. .....This was not a problem on cases I had not tumbled , I suspect because there is some residual sizing lube in the neck even though I swabbed them with alcohol.
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I've even seen scraped rings of copper at the mouths of some commercial loads. The cause is that even though the chamfer produces and oblique angle where it meets the sides of the rest of the neck, that corner is still sharp enough to do some scraping. I discovered this when I pulled some moly-coated bullets that came out looking like clean copper below the neck mouth.

I found I could eliminate the problem a couple of ways. One was to burnish the chamfer. There were several burnishing methods I tried. One thing, probably not good for neck straightness or bullet hold, but it worked, was to put the brass back in the press and run it into the sizing die just far enough to go over the expander and back again about three times. This would be a very bad idea with standard expanders, but this die has a carbide expander bead I put in that touches less brass area and, like a carbide pistol die inside out, does not require lube, though I use powdered graphite anyway. Another method that worked was to sharpen a short length of hardwood dowel like a pencil and chuck it into my drill press and push the chamfered case mouths up against is. The downside is it would need resharpening before very many cases when through. I also tried Cratex polishing tips and they worked, too, but didn't last long, either. The final solution was given to me by Bart Bobbit: use an EZ out in the drill press at low speed. The reverse thread doesn't try to enter the case. The angle of the taper is great enough that it burnishes the sharp corner left by the chamfer tool really well. You only need a cheap, brittle one for brass, and you can polish it with crocus cloth to make the burnishing smoother.

The other cure is to buy Lyman M die. These traditionally were used as expanders for cast bullets, which, as you might imagine, are even more vulnerable to any kind of scraping. However, these dies have enjoyed rising popularity with jacketed bullet shooters in recent years and are now advertised for the purpose by Lyman. What they do is put a step in the case mouth for the last fraction of an inch before the mouth that is full bullet diameter plus a thousandth or a half a thousandth over. The bullet sets into this easily and is held straight up so you don't need to follow it into the seating die with your free hand as you operate the press handle with the other. Indeed, you can skip the full chamfer and just lightly deburr the inside of the case mouth if you add this step to your brass prep after resizing. You can also remove the expander from your resizing die and stop the neck tilting that pulling case over an expander can cause (though you may want to put the next smaller caliber expander in its place to take dents out of necks). You may have to set up your seating die or a separate taper crimp die to take the slight flare the die makes out again. You also may not. If you just set it to make the step with no flare, it will chamber in most guns as-is, and the very slight extra diameter at the mouth probably then actually helps center the cartridge after the fashion of partial neck sizing, but at the other end.

That added M die loading step works the case mouth a little extra so it may need annealing a little sooner. But the straight-seated bullets shoot really, measurably better than those seated by a standard seating die alone usually do. You can see the improvement on a runout gauge; as much as 4:1 when I've measured it.
 
The other cure is to buy Lyman M die. These traditionally were used as expanders for cast bullets, which, as you might imagine, are even more vulnerable
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And there was RCBS, they went through some changes with expanders, they made tons of them. Problem, there early expander had a primer punch that was integral to the to the expander and then came one of those 'and then moments'. They moved the primer punch to the full length sizing die because the #1 position was more convenient for installing primers.

The early sizing dies for pistol were not threaded for a primer punch so RCBS had to reinvent the 3 die set of dies with the primer pinch in the sizing die and the primer punch had to be removed from the expander.

And that is what makes this a long story because a reloader with shop skills could use one die body and a pile of expanders to make a kit for neck expanders of different sizes.

F. Guffey
 
Update***

I went out this morning to test the range of the IMR 4064 42.8 gr accuracy node.

I loaded, in 0.1 Grain increments from 42.6 gr, to 42.9 graines. 15 rounds each, 3 x5 shot groups.

As expected, 42 .6 wasn't that great , above moa at 200 yards.
However, 42.7 was sub moa, 42.8 produced 3/4-1" groups at 200 yards, and 42.9 was just below moa at around 1.25 ".
I didn't bother testing 43 graines since the grouping was poor at 43.1.

The point of impact change from 42.7. - 42.9 was 1/2-3/4" at 200 yards...

This works out to be a very nice load because you don't have to trickle your powder to get sub moa, and if it is a bit cool, or a bit warm, there is no need to adjust your load...Today was 75 degrees in Mississippi.

I suspect federal GMM went with the 41 Grain aacuracy node because it is perhaps more universal. 41 graines was accurate in my gun too, but with 42.8 I got another 120ish fps with no loss in accuracy.

As a side note, CCI owes me 4 BR2 primers. One of my sleeve had 4 BR4 primers in it. I didn't notice until I was seating primers on my RCBS bench feeler primer. At first I thought it was my mistake until I noticed I was 4 BR2 primers short doing a lot of 100 round from a previously unopened sleeve. Also, I don't use BR-4 primers in anything.
 
That's an unusual packaging error. Call them and I expect they'll fix it. They may want to know the lot number, too.

The point of impact change from 42.7. - 42.9 was 1/2-3/4" at 200 yards...
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How many standard errors did that work out to? Since you do stats, I expect your confidence in that shift is good, but if so, the fact there is a shift suggests the barrel is not in a flat spot even though the group is tight. Read this old thread on another board, starting with post 13 to see a flat spot as an Audette ladder shows them. You can actually get them on perpendicular axes, which is what the OCW system addresses.
 
. Nick:.expect your confidence in that shift is good, but if so, the fact there is a shift suggests the barrel is not in a flat spot even though the group is tight
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It's a small sample size.... Actually too small to assign a standard error. There is a strong possibility that the move in poi was due to the chamber temp, or wind (it was more breezy when I began than at the end). And according to my software, a modest breeze can shift poi 1/2-3/4 inch at 200 yards. (0.7") to be exact

So....I shall load up another batch 42.7-42.9 and repeat under different weather conditions and see if I get a different result.


Way to keep me honest Nick
 
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