Max 308 load for 175gr Seirra match king with Varget

[mr renwick]

I have a Remington 700p with a 26 inch barrel. I just started using 175gr Seirra match kings projectiles with great success. I thought I would see if any of you guys have worked up max loads for them. I plan on doing it myself but I would like to hear what your experiences have been.

Thanks

[csmsss]

Just curious - why are you looking for a "max" load with a match target bullet? Seems to me a best accuracy load would be more useful. You're not going to get so much more velocity out of a "max" load that it will dramatically benefit the trajectory to any great extent.

For the record, Hodgdon lists a 42.0 grain starting load (vel. 2583), and a 45.0 grain max load (vel. 2690) with this bullet/powder combination.

My own personal load is 43.5 grains of Varget with Lake City 7.62 NATO brass and CCI 34 primers.

[Unclenick]

Well, the first thing you'll want are Winchester cases. They have more powder capacity than others.

You'll note the maximum load from Hodgdon in this case is the slightly compressed 45.0 grains (as Csmsss already mentioned; see attached chart) in the Winchester case in a gun with a 24" tube. You'll get about 40-50 fps more velocity from your barrel length if your chamber is as tight as theirs. The maximum load will be lower for other case brands owing to their lower capacity.

Dan Newberry lists that maximum load of 45 grains in Winchester brass as "an all around favorite", so it is pretty universally liked. Newberry comments that CCI 200's, BR-2's, and Federal 210's work well with Varget. I use the 210M's in my Steyr Scout, and it likes this load to the tune of about 3/8 moa. I have no experience with it in a 26" tube, however.

[Zak Smith]

Most people I know who have worked up a 175/Varget load (including myself) have a "final" load between 44.0 and 45.0 grains and a final velocity of about 2700 fps from a 24-26" barrel.

[nate45]

Originally Posted by csmsss

Seems to me a best accuracy load would be more useful.

Thats how I look at it. I'm fairly certain you are wanting the flattest trajectory possible, but 45 grains may not be your most accurate load.

It is always advisable to not start at max and work your way up. Moving in half grain increments is the way I go it. If it were me I would load five, or ten groups of cartridges of 43.5, 44, 44.5 and 45 each. Check them for accuracy and pressure signs as you go. If something like 43, or 43.5 gave good accuracy, I would not worry about the extra velocity gain.

Varget seems to be a very good powder for the .308, at least in my Rem 700 Varmint. I use 45.5 grains with the 150 grain Nosler BT and get sub MOA groups.

[mr renwick]

Thanks for all the info. My thoughts on trying to get the most velocity is trying cut down on drop for the 1000yd shots. I see your point on finding the most accurate load not the fastest. Something I thought was a little odd was last time I chronoed the 175grs they where at 2950fps using between 43.5 and 44. That seems to be a bit higher than most peoples fps that I have read. Is that a product of having a longer barrel?

[Unclenick]

You only gain about 20-25 fps per inch of additional barrel length at your barrel length range. The high readings are most likely due to the chronograph being too close to the muzzle blast. That can cause either high or low readings. Try 15 or even 18 feet. Make sure you are under good light conditions. 200 fps or more error can happen just from poor lighting conditions as well as from muzzle blast helping false-triggering one screen or the other.

I've shot at 1000 yards from a 22" tac rifle with the 175. The good thing about it is, unlike the 168, this newer design does not become unstable in the transonic velocity region, so it flies well even near the speed of sound. So, accuracy first.

[mr renwick]

Very interesting. That would explain why my ballistic calculator seemed to be a bit off. I will say my last batch was 1/2 moa at 100 3.5 inch group at 500 and a 15 inch at 1000.

[Jim Watson]

I load 44 grains of Varget in .308 with a 175 gr SMK. 45 is too hot in my rifle with short brass life.

2950 fps is about 200 fps higher than I get with a 28" barrel.

[Unclenick]

And again, let me emphasize that 45 grain load is only with Winchester brass, which weighs around 156 grains. If you are using, say, Lake City, which weighs around 180 grains, you have about 3 grains less water capacity and need almost 2 grains less powder to make the same peak pressure as Winchester brass sees with 45 grains. Other brands, like Remington (about 168 grains) or Lapua (about 171 grains), will fall inbetween. This assumes a mild primer, like the Federal 210M in all instances. The new Lapua Palma brass with small rifle primer may let you use a tad more powder.

[Slamfire]

Well I don't think this is a maximum load, but I chronographed this load after I used it in a 600 yard match.

It shot well. I think my lot of Varget is a slow one.

Ruger M77 MKII 26 " Barrel 1:10 twist	
	
175 Sierra Matchking 44.0 grs Varget wtd Lot 4295 W/W new cases Fed 210S
	 
30 April 2008 T =  71 °F
	
Ave Vel =	2606
Std Dev =	13
ES =	28
High =	2621
Low =	2593
N =	4
	

[A_Gamehog]

Read this article all the way down.

Tips from Brad Sauve, 2004 F-TR Nat'l Champion

http://www.6mmbr.com/308Win.html

[bamaranger]

Drop is not so much the issue, as is staying supersonic, stable, and resisting the wind. Drop can be predicted and accounted for w/ appropriate come ups. But if your bullets "go stupid", or blow all over the target, you are wasting your time.

The flattest 1000 yd .308 bullets are the 155 palma driven at well over 3000 fps from match length bbls. My mentor said they were something like 6 MOA flatter at 1000. Like 5 feet flatter. Now that is from memory, I could be wrong. But my understanding is they do not resist the wind as well as 175's driven fast enough to be supersonic at 1000. There is a photo on the internet that shows a 1000 yd, 155 gr target, shots strung horizontally, which illustrates the point well, though I cannot recall the site.

I'm thinking the bench mark is 2600 fps at the muzzle, w/ 175's to stay supersonic at 1000. (again from memory) The longer bbls will yield higher vels w/o pushing the limits on pressure and case life. I'm running a 26" 'cause I got a deal, the next will be longer.

My .308/175 load is 44 gr Varget, W-W cases, batch sorted for weight, and Fed 210M primers. If I can get that down to 43.5 and still have the accuracy and velocity necessary for the above, I will for my next match.

[Unclenick]

You need to be a little careful to compare apples to apples there, so you don't end up attributing something to the 155 that actually is due to the Palma rifle's greater barrel length. Palma rifles often are 32" tubes, while most of the rifles shooting 175's have either 22" or 24" tubes. If you run both with the same powder in the same length barrel, the velocity difference is less than 200 fps. You can, with Reloader 17, for example, pretty easily get to 3000 fps for the 155, and 2850 fps for the 175 using 32" tubes and loading close to the same peak pressure. That's 150 fps MV difference. The difference is similar in a 24" tube. It becomes a 5% bigger percentage at the lower velocities from shorter tubes because those short tube velocities are about 5% lower.

The bottom line is, whichever barrel length you choose, as long as it is the same and the powder and peak pressure are the same, you are looking at about 3 1/2 feet of drop difference at 1000 yards. Since the ballistic coefficients of the two bullets are in the same ballpark (Brian Litz measured G7 BC's of 0.229 and 0.243 for the 155 and 175, respectively), the 155 has less drop at 1000 yards simply because it takes less time to get to the target starting out at the higher velocity. That means gravity has less time to act on it.

Wind drift, though, is not directly dependent on total travel time, as drop is. Wind drift depends on the difference between total travel time and the time it would take the bullet to arrive at the target in a vacuum (at constant muzzle velocity). This difference is a measure of the effect of drag, since the vacuum causes none. So, at Camp Perry altitude (about 590 ft above sea level) for the 155 those time differences are .516 and .564 seconds for the long and short tubes, respectively. For the 175 they are .515 and .567 for the long and short tubes, respectively. You'd figure that between launching at a lower velocity and having a slightly higher BC, the 175 would have less drag acting on it and would do better, but the 175 spends more time closer to the speed of sound on its way to 1000 yards, so it is more influenced by the squirrely transonic region. But you can see the effect of BC when the the two bullets are given the same MV (e.g., 2850 fps for the 155 from a short barrel as well as for the 175 from a long barrel), you can see that higher B.C. give the 175 a slight edge:

From the QuickTARGET Unlimited 3 DOF ballistics program and using Brian Litz's measured G7 BC's, a change of 10 mph side wind moves the horizontal POI at 1000 yards as follows:

32" tube:
155, 3000fps MV, 90.8" drift
175, 2850 fps MV, 90.7" drift

24" tube:
155, 2850 fps, 99.2" drift
175, 2690 fps, 100.1" drift

So wind drift for the .308 round sees no practical difference for the two Sierra bullets at 1000 yards within the normal ability to hold on the bull, as long as the barrel lengths and powder and peak pressures are the same. If you fix velocity at one number, such as 2850 fps for the 175 and 155 for the two different barrel lengths, above, the 175 has about 9% less drift at 1000.

[mr renwick]

Wow thanks for the input. Windage is a big factor for where I shoot. We have had quite a bit of wind the last few times we have shot. I have to learn to calculate how fast the wind is going in the field before I go out next time. I re chronoed my rounds last weekend and I got an average of about 2675fps with 44gr of varget and winchester cases and primers.

[Unclenick]

That sounds like you've got the chrono technique squared away. The more accurate MV will make your ballistics program predict more accurately. If you haven't used them, the free online JBM ballistics programs work well and will let you compare with your own. There are some more sophisticated tools there than the usual run-of-the-mill exterior ballistics program.

You might want to check out this book:



Scroll down just over half way here, or look on Amazon.

Jim Owens (jarheadtop.com) also has a book with information on doping the wind. His books are short and sweet and to the point.