Highest MV for 180 gr. 308 Win Load?

[haskins02]

I recently purchased a Loadbooks manual for .308 Win. Inside it publishes loads from various manuals, all for .308 Win. In the Nosler section, I was surprised to see the maximum load listed for IMR-4064, using a 180 grain bullet as: 44 grains, MV = 2,718 fps. Is this correct and not a misprint? Would this be a safe load to work up to (assuming no signs of excessive pressure) in, say, a Browning X-bolt?

I had previously thought the only way to safely get a 180 grain bullet to move at 30-06 velocities (2,700 fps) in a standard bolt action .308 hunting rifle was to buy Federal high energy Nosler Partition cartridges, advertised at 2,740 fps. Is this untrue? Can a reloader safely achieve such velocities with a bolt action hunting rifle (not just a heavy single-shot target rifle), if carefully working up to this maximum load without signs of excessive pressure? If so, is IMR-4064 the best powder available to handloaders that can do this?

Thanks for any input.

Greg

[314EPW]

I use IMR4895 .The reason being it will work with 110 gr bullets and up to 190 gr.Using the Hornady manual and Hornady bullets it states 180gr SST, bc .480 41.1 gr of this powder is MAX!FPS equals 2400.STARTING LOAD is 33.8. I get excellent results with this powder and Hornady bullets.

IMR 4064 with a 180gr SST is 41.3 gr is MAX.STARTING LOAD is 34 gr.Max fps is also 2400

[Shoney]

Hodgdon lists max for the 180 gr bullet and IMR4064 as 45.2C, @ 2683fps with a 24" barrel. It is possible to get a higher velocity using a 26" barrel and shooting that at a higher elevation above sea level than the Hodgdon site of testing.

Combinations of factors can cause great variances in velocity/pressure. Here are a few factors:

Primer: amount of striking force on primer, strength, presence of powdered metal (Aluminum & others), brisance - a measure of the rapidity with which an explosive develops its maximum pressure
Barrel: length; tightness of bore; height of the lands; distance of bullet to lands; temperature of barrel;
Bullet: bearing surface of bullet, alloy of bullet; shape of bullet;
Brass: new/used elasticity; manufacturer, volume;
Powder: new, aged, old, batch powder was from;
Weather: ambient air temp., barometric pressure, humidity
Elevation: above sea level
Other: I am sure I have not listed all.

[haskins02]

My question is whether you can get 2,700+ fps with a 180 gr. bullet in a 308 Win. by reloading. The Loadbooks Manual (refering to the Nosler Reloading Guide) says "yes", while my experience wonders if this is a misprint. Can anyone verify if it is OK to work up to 44 grains of IMR-4064 in a .308 Win case? Of course, if another powder can more easily achieve over 2,700 fps with a 180 gr. bullet, I would like to know about that too. Thanks.

Greg

[tyrajam]

I have yet to shoot a factory load over a chronograph that measured up to the published ballistics. They generally are wildly optimistic with their velocities. Combine that with the blended powders that aren't available to reloaders and some factory cartridges can outperform handloads, at least in theory.

[dipper]

I am SURE you have READ that loads you see in Reloading manuals are " safe in test barrel or safe in rifle that was used for this table" or something similar to that.
Generally speaking, you start at lowest published load and work your way up UNTIL you see pressure signs and then back off the load and be happy... IF highest velocity is what you are after.
Very often, highest velocity does not mean best accuracy.
No one here can tell you what velocity YOU can safely achieve with YOUR rifle.
Differences in chambers, twist rates, barrels, ambient temperature, etc, dictate what each individual rifle will produce.
So, just because some load states a certain velocity, don't stuff your case full of that powder and start shooting.....work your way up slowly and watch for pressure signs.
BE SAFE!!

[haskins02]

Thanks again for your input. I am aware of these safety precautions and that max pressures do not always equate with good accuracy. I was just wondering what the published upper limit of the .308 was. Of course, the safe upper limit must be established on a case by case basis.

- Greg

[mousegun]

I have a couple of Loadbooks and don't think much of them except to compare maximum charge weights from different powder/bullet manufacturers. Without a chronograph and/or a way to measure chamber pressure, a reloader is on thin ice pushing for maximum loads from reloading manual data like that; there are just too many variables.

If the Loadbook data includes a starting load for that 180 gr/4064 datum, chronograph the starting load and see if the velocity is anywhere near what they got. If not, it doesn't mean the load is bogus. With their barrel/chamber, their components, the temperature, barometer and humidity they had, they may well have reached that velocity - if their chronograph was working right. Nobody knows.

A rule of thumb to use when trying to find rational velocities for a given cartridge with appropriate propellants is to average the kinetic energies of maximum loads from published load data over a cluster of bullet weights. That average will be pretty indicative of real world performance since kinetic energy is directly proportional to average bore pressure. A faster powder will require higher peak pressures than slower powders to make the same energy levels. Convert back to velocity for the bullet weight wanted and that's the maximum rational velocity for that cartridge/bullet. Pick a powder that stays under the SAAMI maximum pressure and ya got it! Keep the CUPs and PSIs straight!

So, short answer to the OP's question: I think the load is a bad one. Kinetic energy of that load (2952 ft-lbs) is almost 300 ft-lbs over what most safe loads in that bullet weight range attain. Use it on a hot day in the desert and you may alter the headspace on your favorite model 70.