Is IMR 4064 forgotten?
- Thread starter armednfree
- Start date
IMR4064 is nowhere near dead. Federal still uses it in their Gold Medal Match .308 ammunition and in the Mk. 316 Mod 0 sniper ammo they developed to improve on M118LR and eliminate the peaky pressure problems they had in the desert with RL 15 (used in M118LR) and ball powders. It's true they order special lots, with things like flash suppressant added for the military ammo, but given their resources, if there was something noticeably better for .308 production ammunition accuracy (where you can't work up the load separately for specific guns) I think they'd have identified it by now.
In the 1995 Precision Shooting Reloading Guide, Dave Milosovich described an experiment in which he loaded IMR 4064 and 4895 to specific velocities for a .308 bolt gun firing 180-grain bullets. He found that for velocities below 2400 fps it took a lighter charge of 4064 than of 4895 to reach a specific number of fps, suggesting to him that 4064 was faster burning. At 2400 fps the charge weights were the same (within a tenth of a grain). Above 2400 fps it took more 4064 than 4895 to reach a given velocity, suggesting to him that at higher pressure 4064 burned more slowly.
If you make a graph of Milosovich's data, what you see is simply that it takes a bigger change in the charge weight of 4064 to get the same velocity change you get with 4895 in the .308. This limits upper velocities with it, but also means anything that changes pressure and velocity, such as a charge weight error or a change in temperature, is going to produce less velocity difference with 4064, making it effectively more stable for a wider range of conditions.
Varget, which was originally intended to compete with 4064, changes pressure per grain of charge change even less than 4064 does in .308. This has a plus and a minus. The plus side is even better temperature and charge weight error immunity. The minus is less barrel time and velocity tuning range. If you have a good Varget accuracy load it should stay good through a lot of conditions, but in some guns and bullet weight combinations, you might not find such a load within the range of velocities Varget can produce. Indeed, I think this explains why you see some people find Varget the best thing since sliced bread, while others are unimpressed by it.
One other factor in the .308 is 4064 bulk density. Federal GMM loads with the 168 grain Sierra bullet that I've pulled down are all very slightly compressed; about 0.5%. This means that compression tends to lock the powder in place at loading, so it doesn't settle during transport. In the same 1995 PSRG as Milosovich's information, Dan Hackett made mention of having loads he'd developed that worked fine when he loaded them at home, but that caused sticky bolt lift and other pressure signs if he loaded them at the range. He finally traced it to the fact the vibration of transporting the loads from home to the range was changing the packing density of the powder in his cases, lowering the effective burn rate. This is the one area where spherical propellants have an edge over stick powders: sticks can rearrange themselves with more difference in how they pack, so their bulk density is changed more by vibration, drop tube length or anything else that affects powder packing. This is one reason finding a load that fills cases and locks in place by slight compression will keep its performance more consistent as you ship it around the world, as Federal does.
That tendency to pack under vibration is the reason grain cutting in drum measures can be an issue for 4064. It isn't the cut grains themselves that matter, but the fact the powder measure is jerked by the sharp movement of cutting grains. That motion causes powder in the hopper to settle so the next charge thrown is heavier than those unaccompanied by grain cutting. There are solutions. The JDS Quick Measure does not cut even 4064 grains at all. The Lee wipers in their Perfect and Deluxe Perfect and the now-discontinued Classic powder measures cut grains much less frequently than standard measures and are another way around the problem. If I get grain cutting in a powder measure, I put the next two throws back in the hopper on the assumption they'll be heavy. Afterward, they go back to what was set up originally.
IMR 4064 is a long-time favorite in the Garand, going back to John Clarke's Garand loads from the 1980's and before. This is, in part, because it fills the big .30-06 case better than IMR 4895. It is mainly used with the 168-grain and heavier match bullets, though. For 150's I get even better case fill and consistency with Vihtavuori N135 and have moved to that. Very generally speaking, though, any single-base powder whose maximum .30-06 bolt gun load is 53 grains of powder or less, will also not produce excess gas port pressure in the Garand.
In the 1995 Precision Shooting Reloading Guide, Dave Milosovich described an experiment in which he loaded IMR 4064 and 4895 to specific velocities for a .308 bolt gun firing 180-grain bullets. He found that for velocities below 2400 fps it took a lighter charge of 4064 than of 4895 to reach a specific number of fps, suggesting to him that 4064 was faster burning. At 2400 fps the charge weights were the same (within a tenth of a grain). Above 2400 fps it took more 4064 than 4895 to reach a given velocity, suggesting to him that at higher pressure 4064 burned more slowly.
If you make a graph of Milosovich's data, what you see is simply that it takes a bigger change in the charge weight of 4064 to get the same velocity change you get with 4895 in the .308. This limits upper velocities with it, but also means anything that changes pressure and velocity, such as a charge weight error or a change in temperature, is going to produce less velocity difference with 4064, making it effectively more stable for a wider range of conditions.
Varget, which was originally intended to compete with 4064, changes pressure per grain of charge change even less than 4064 does in .308. This has a plus and a minus. The plus side is even better temperature and charge weight error immunity. The minus is less barrel time and velocity tuning range. If you have a good Varget accuracy load it should stay good through a lot of conditions, but in some guns and bullet weight combinations, you might not find such a load within the range of velocities Varget can produce. Indeed, I think this explains why you see some people find Varget the best thing since sliced bread, while others are unimpressed by it.
One other factor in the .308 is 4064 bulk density. Federal GMM loads with the 168 grain Sierra bullet that I've pulled down are all very slightly compressed; about 0.5%. This means that compression tends to lock the powder in place at loading, so it doesn't settle during transport. In the same 1995 PSRG as Milosovich's information, Dan Hackett made mention of having loads he'd developed that worked fine when he loaded them at home, but that caused sticky bolt lift and other pressure signs if he loaded them at the range. He finally traced it to the fact the vibration of transporting the loads from home to the range was changing the packing density of the powder in his cases, lowering the effective burn rate. This is the one area where spherical propellants have an edge over stick powders: sticks can rearrange themselves with more difference in how they pack, so their bulk density is changed more by vibration, drop tube length or anything else that affects powder packing. This is one reason finding a load that fills cases and locks in place by slight compression will keep its performance more consistent as you ship it around the world, as Federal does.
That tendency to pack under vibration is the reason grain cutting in drum measures can be an issue for 4064. It isn't the cut grains themselves that matter, but the fact the powder measure is jerked by the sharp movement of cutting grains. That motion causes powder in the hopper to settle so the next charge thrown is heavier than those unaccompanied by grain cutting. There are solutions. The JDS Quick Measure does not cut even 4064 grains at all. The Lee wipers in their Perfect and Deluxe Perfect and the now-discontinued Classic powder measures cut grains much less frequently than standard measures and are another way around the problem. If I get grain cutting in a powder measure, I put the next two throws back in the hopper on the assumption they'll be heavy. Afterward, they go back to what was set up originally.
IMR 4064 is a long-time favorite in the Garand, going back to John Clarke's Garand loads from the 1980's and before. This is, in part, because it fills the big .30-06 case better than IMR 4895. It is mainly used with the 168-grain and heavier match bullets, though. For 150's I get even better case fill and consistency with Vihtavuori N135 and have moved to that. Very generally speaking, though, any single-base powder whose maximum .30-06 bolt gun load is 53 grains of powder or less, will also not produce excess gas port pressure in the Garand.
I still have a good quantity of IMR4895, I bought 32# of it about 10 years ago when I started loading for both the M1 and my M1a... so I'll keep using it until I run it dry, but after that, I may just drop it from the roster and switch to IMR4064 in my M1. I don't shoot 168grn bullets in the M1, just 150's at a reasonable velocity, I'm sure 4064 can push them right along as well.
Roadkill2228
New member
The .220 swift is the pickiest cartridge that I’ve ever loaded for (not that I’ve loaded for more than 10 or so). 38-38.5 grains of 4064 and a 55 grain flat base bullet seems to be about the only sure bet in this cartridge. It just works. I’ve heard it said by shooters and loaders more “seasoned” than myself that if the swift won’t shoot with that combo it probably won’t with any.
What a great thread! IMR4064 forgotten? Not hardly. When I had my 22-250, I used the Sierra 55gr bthp[#1390?] and 35.0gr IMR4064, Superb accuracy, just forget the fps.
In one of my 30-06's, using the Hornady 150 Interlock FB, 52.0gr of IMR4064 gives me 2900+ MV and again, superb accuracy. Forgotten? No way.
In one of my 30-06's, using the Hornady 150 Interlock FB, 52.0gr of IMR4064 gives me 2900+ MV and again, superb accuracy. Forgotten? No way.