.308 workup questions

[osirus82]

So I'm getting ready to hit the ground running, but to where? I decided the best starting point is to find out what podwer my fnar prefers, I will be getting 1lb/ varget/ imr4895/rl 15- and working up loads with LC brass- 168gr hpbt, and federal LR primer- problem is I only have 100 bullets to test with, Im looking here in my layman 49th looking for the bullet specs and only find a listing for varget sugg-41.0gr to max 45.7. hodgdon site-shows imr 4895 sugg-41- max45.4 and found data from Reliant showing no sugg stating or max only 45gr recipe.

is there any difference in 168gr hpbt from speer or sierra? ,bought at the Tanner show?
is there any other suggested powder to test with?
should I buy some different bullets to test with? I also have some 178grAmax figured id save those for hunting loads.
What percentage should i increase the grains during workup?-- 1% is .43grains which is about right- the last group of rounds would be 45.58 grains.

I was going to use about 30 shells per powder-5 shells per test, so about 6 different loads per power, this is the first load that i will be figuring out, is this enough for testing? should do 10 round tests/3 different powder weights?

anyone have a print from quick load for suggestions.

[allaroundhunter]

The Amax is not a hunting bullet. It is a match/target bullet just like your 168 gr HPBT.

And as to are the Speer and Sierra the same? No, they aren't. However you can still start at the starting load and work your way up and be fine as long as you are watching for signs of excessive pressure.

If I were a betting man, I would put money on either Varget or RL15 turning out your best groups.

I increase charge weight by .3 grains from my starting load, and then once I find a load that shoots well I test around it in .1 gr increments. Once I am good there, I experiment with the OAL. And during my first stage of testing I shoot groups of 3 usually.

Now, another suggestion is to search OCW test.... It may be faster.

[Brian Pfleuger]

You should read and consider Dan Newberry's OCW load development.

[Unclenick]

And try IMR 4064. It's the powder Federal originally loaded in their Gold Medal match ammo under the 168 grain SMK, and is the one that they load in M118 LR Mk. 316 mod. 0, under the 175 grain SMK. This replaced Reloader 15, which Lake City used after they gave up getting adequate accuracy using WC750 powder. Varget may do as well or better for you. That seems to depend on the individual rifle, as do the performance of the other powders you mentioned.

Speer's 168 grain .308 match bullet is basically an almost-copy of the Sierra design, as is Nosler's. I just don't recall ever hearing of a match being won with them. I note that despite ATK owning both Federal and Speer and Alliant, that Federal has not changed from the Sierra bullets to the Speer bullets in their Gold Medal Match Ammo, the way they changed from 4064 to RL15. Buy some of each and see how they compare in your rifle. I don't expect them to keep up with the Sierra's but sometimes these things don't work out as expected in a particular gun.

[Bart B.]

If you're running an OCW test, I would use 1 grain increments of charge weights as 3/10ths of a grain typically won't tell you much about two adjacent loads. They're too close together. Several adjacent loads' bullets will print on top of each other. You would have to shoot 20 to 30 shots per load to find the group center for comparison with any reasonable degree of accuracy.

Here's data using a 175-gr. Sierra 30 caliber HPMK with IMR4064 powder testing at 300 yards:

42.2 grains, 2500 fps, 26.65" drop
44.4 grains, 2600 fps, 24.65" drop
2.00" (.67 MOA) drop change for a 2.2 grain change in charge weight.

Same bullet and powder charges, but at 600 yards:
42.2 grains, 2500 fps, 137.34" drop
44.4 grains, 2600 fps, 126.12" drop
11.22" (1.87 MOA) drop change for a 2.2 grain change in charge weight.

How much drop difference does a 3/10ths grain charge weight change make at each range?

Other powders with approximately the same burn rate will have different drop differences per 3/10ths grain change in charge weight, but not much.

[jwrowland77]

I recently did a workup for my .308 and used IMR4895. Grouped very well. I started at 40 then 41, then I started going by .5 grain increments up to the max I wanted to test, and then picked my best one. I did all those in three shot groups.

I'll take my three best loads and work around those, probably in 5 shot groups.

[Unclenick]

The OCW instructions recommend 0.7% to 1% maximum steps. If you've got a combination that will hold tight accuracy over a charge span of a grain or more, that is most desirable, as it's likely to be more immune to changing conditions and load variations than is one that demands the charge weight be tight. In the OCW stuff, Newberry suggests that he looks for 3 groups in a row with the same POI that cover a span of about 0.6 grains (three 0.3 grain steps), so that must be a common finding for him. However, if he can consistently find three in a row, he could be, in some instances ± 0.3 grains from the actual center, making the actual sweet spot spans more like 0.9 grains.

Also, how long and how heavy a barrel you have will affect both the time it takes a muzzle to whip during firing and the amount of that deflection. These, in turn, will affect how big a step in charge weight you can take without skipping over a sweet spot. In general, the longer the barrel the wider the sweet spot, but there's too much interaction going on to make it a law.

I once worked a 168 grain SMK load up in an M1A in 0.5 grain steps, which was almost 1.2% of the final load, using IMR4895 in Remington cases. The groups held very steady at about 1.4 moa until I hit a sweet spot at 42.5 grains where they suddenly dropped in half. Half a grain higher and they were back to 1.4 moa. In that particular case a whole grain step would have jumped right over the sweet spot, but a half a grain worked OK. That gun had a standard weight barrel, though the flash hider acts like a light tuner weight, adding a little time to the periodicity of the muzzle deflection. I wish I'd gone back and found the actual outer edges of that sweet spot load in smaller steps, but twenty years ago I still took what worked at the moment and crossed my fingers.

[osirus82]

for all to consider id be working with 20"heavy barrel. 1/12 twist.

thanks for all the suggestions, I did go over OCW page and am interested~ anything to find a great working round.

I will add imr 4064 to the list of rounds to produce.

[Jimro]

For years Sierra's accuracy load was around 41.5gr of IMR4064 under a 168gr SMK. Some folks report that 42.2gr is the magic number.

Either way, no need to go for speed unless you don't get accuracy around that range with 4064.

Jimro