168gr Amax Development

[Unclenick]

That moves the QL prediction numbers just slightly. 67,000 psi, 2825 fps.

[browninghunter86]

interesting that 2825 was calculated. that is what JBM velocity is to get 1.5" high at 200 and the 2.5" high at 100yards ***Sorry mis-posted it earlier stating it was 2.5" at both 100 and 200 yards***

But that pressure is extremely high isn't it? SAAMI is 62,000PSI correct?

But I did not see any pressure signs with the loads though...... No flatened primer, no hard bolt lift, pressure ring measured same as factory ammo brass

[Unclenick]

CAUTION: The following post discusses loading beyond currently published maximums for cartridges. Rely on the information AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

62,000 is correct, but it's for a standard SAAMI test that averages the peak pressures of just 10 shots. They allow 4% standard deviation and 20.6% increase as the extreme variation with 99% confidence. In other words, you could run over 74,800 psi for one shot in 100 and still be keeping SAAMI happy. These are all below the 83,000-89,000 psi proof load range.

Most handloaders can hold down pressure standard deviation below 4% pretty easily, allowing them to aim higher than SAAMI MAP without physical danger. Figure that 4% SD is equivalent to close to 2% powder charge error, or ±0.9 grains out of 45 grains in a .308). This is one reason many handloaders get away with higher average pressures than SAAMI specs would allow.

On the other hand, there is a price to be paid in wear and tear on the barrel and on bolt lugs and all other parts subjected to the forces of pressure and friction. Figure a barrel at 67,000 psi might have half the throat life of one fired at 57,000 psi, and one at 47,000 psi may last half again longer than one at 57,000 psi. For a .308 we might be looking at 47kpsi, 57kpsi, and 67kpsi as having around 5000, 3500 and <2000 round life, respectively (and depending on powder choices and barrel cooling between shots and whatnot), before fliers started appearing on targets. For match rifles these are possible kinds of numbers.

[browninghunter86]

hopefully some people will get alot out of these threads. I know I have learned alot.

I am wandering too Nick if I could switch powders and get pressure down with enough velocity range.

[Unclenick]

It looks to me like Reloader 15, a popular .308 accuracy powder, has enough energy to give you about the same velocity and barrel time you have without exceeding the SAAMI MAP.

[browninghunter86]

You had mentioned previous thread that 4895 was also a good accuracy 308 powder. Been looking online trying to figure out pressure/velocity differences in these powders.

is there a "most accurate" burn rate chart out there? All seem to vary some

[Unclenick]

No accurate one. In general, while 4895 is pretty good, I know of almost nobody who ranks it best. Most versatile, perhaps. 4064 usually produces better precision because of its greater bulk filling the case better, but it won't get you to the highest velocities possible. Reloader 15 was chosen for the military M118LR sniper load rather than the 4895 they used in older M118SB and in M852 because its accuracy loads give them more velocity with the 175 grain SMK bullet.

Lot to lot burn rate variation causes powders to change position on the burn rate charts from one batch to the next. I think the better way to organize charts is to group powders by application, as this GS Custom chart tries to do, but you'll see it ranks Reloader 15 and 4064 together with 4320 faster than 4064, which I've never seen anywhere else, and puts 4895 down closer to Varget, which I do see on other charts. This doesn't quite agree with the measured numbers used in QuickLOAD's database, but it's perfectly believable that particular lots might be this way and it depends on the actual load level.

I've repeated John Feamster's data here before that shows that 4064 doesn't rise in burn rate as fast as 4895 does as load density goes up, and QuickLOAD's model doesn't show that, so it's still possible 4064 could be a good choice, too. But based on the military choice, I'd try Reloader 15 first.

[browninghunter86]

would I still have decent velocity at the 42.5gr area? I am going to load some tonight and go shoot tom hopefully if weather is good

[Unclenick]

QuickLOAD thinks about 7.5% slower. That's still at or over regular .308 match ammo velocity from a 22" M14 barrel, depending where your real velocity is. So, yes, you could still shoot 600 yard targets with it just fine.

[browninghunter86]

then if I found a node at 44.5ish that should almost get me out to 1000 although some say this bullet will destabilize around that distance

[Unclenick]

It's got the same near 13° boattail that the 168 grain Sierra MatchKing does, and that's credited with destabilizing the 168 gr. SMK in the transonic reason. I've had that happen with the SMK at around 700 yards. I don't have any experience with the A-max at that range, though. The different nose shape may affect it. At any rate, if I wanted to go to 1000 yards I'd do what the military did and move to the 175 grain SMK with it's 9° boattail or to the 155 grain Palma SMK or the 155 grain Lapua Scenar.

[browninghunter86]

Finally dloaded OnTarget to help me with my targets. Pretty cool program

[browninghunter86]

Got out and shot the lighter charges and still the rifle shot pretty well. Started at 43.3 and went up in 0.3gr incraments. Shots with X through them were after I knocked rifle over and it lost zero. Luckily it was only my last 3 shots of the day

[Unclenick]

Seems pretty stable. I'm still curious what happens when you go in the other direction to see if anything stands our around 42.5 gr.

[browninghunter86]

where would you start? 42.0 and go up to 43

[Unclenick]

Yes. Just continue your last target down to 43, 42.7, 42.4 and 42.1. I don't see wasting more ammo on that unless, as you have at the right side of your last target, the left end shows you might be getting into a tight cluster. If you wanted to check Long's 2% rule, I suppose you could go down two more steps to 41.5. You've already shown about +2% from 42.5 is pretty tight with the performance of the 43.3 gr load, so it may be the actual node.

[browninghunter86]

I think 43.9-44.5 is where my barrel likes to shoot. Although this 43.9 group was not as tight as yesterday it still had same POI as 44.2 and 44.5. I will try the lighter charges too Nick to see what happens. Also gave gun a good scrubbing lastnight and first shot today out of cold clean bore was right on POI which is good thing I think

[Bart B.]

Folks shooting 3 shots per test group may want to check out:

http://fuzzylimey.net/coachtalk/groupanal.html

It's based on the age-old engineering and statistics standard of "If you don't get the same number each time you measure something, your ruler's either broken or not being used correctly."

Best example in the shooting sports is when someone shoots four 5-shot groups, measures the extreme spread of each, then averages them. The answer they get's a lot smaller than if all 20 shots were fired in a single group. And that 20-shot group's larger than the biggest 5-shot one.

No wonder there's several thousand "favorite" loads for a given cartridge and bullet. The popular reason is "Every barrel's different." I'm convinced there's a much, much greater spread in variables elsewhere.

Just food for thought.........

[browninghunter86]

Anyone using Power Pro2000 MR? Was reading on their website and on some online forums but not sure if this is going to lower pressure while maintaining velocity as compared to Varget