Alloy for 308 development

Hey folks, I have always cast for modest velocity pistol and revolver plinking rounds, or similar levergun ammo, so I've never used anything besides 50/50 WW/Pb and it's always been fine for what I want. However, I want to start trying to develop a load for the 308 and I'd like to try to get to a decent velocity and accuracy, like mid 2k fps and close to MOA. The boolit is an NOE 310-165-FN-H3 gas check for the 30XCB. I'll be experimenting with powder coat and White Label Lubes' Carnauba Blue (not at the same time). Intended rifle is a Steyr Scout.

I've got lots of COWW, pure Pb, and lino. I've got a little bit of Sn solder. What's a good alloy for this application that will get me up to 2400-2500 fps with a gas check? Or is 50/50 powder coated good enough? I'd like to not use too much of my Sn or lino if I can avoid it because I can't easily get more.

What twist does the barrel have?

Lino, casts well and strong enough for the power level you are trying for.

If you have a lot of lino then I would just cast straight linotype for what you are doing.

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Originally Posted by Larry Gibson

What twist does the barrel have?

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Supposed to be 1:12 although I haven't verified that.

I'll give a try with the linotype, thanks.

If it's a 12" twist then you may get very good accuracy in the 2300 fps range +/- given the short barrel length. It will probably not ne MOA, particularly past 100 yards. If using a "scout scope" of minimal power then that further will hinder obtaining consistent moa accuracy.

I define "accuracy" as what the rifle is capable of day in and day out with a particular load out to the maximum range the rifle will be used at. That is not with the occasional 3 or 5 shot group at 50 or even 100 yards. But what the rifle load will do consistently, shot after shot at the maximum range it is to be used.

My own 12" twist .308W match rifle with a 26" barrel will give 1 1/2 moa at 2450 fps with 10 shot groups consistently at 300 yards with the 30 XCB bullet. A search for my thorough testing of high velocity cast bullet loads, including 10, 12 and 14" twist 308Ws will give you a lot of information. I use Lyman's #2 alloy WQ'd for such loads as I've found linotype to not be the best alloy for such HV loads.

That's great Larry, thanks so much. I definitely read your threads when I was researching which mold to get. I had forgotten about them though in the meantime. I will go back through those. Thanks again.

Mix up as close as you can to Lyman #2.
It's pretty much the bench mark, and what the loading books compute their data with.
If it isn't perfect for ya, it'll get you pretty close.

I wouldn't change your alloy. I would quench them, water drop or even oven heat treat. Even water dropped is going to be harder than air cooled linotype.

Hardness of the alloy is but one aspect. The #2 alloy will cast bullets which are a lot more uniform in size and weight.

bcr

Note; I don't PC, hoping to see some decent results from your testing.

50 lead
50 lino

Quote:

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Originally Posted by Larry Gibson

Hardness of the alloy is but one aspect. The #2 alloy will cast bullets which are a lot more uniform in size and weight.

bcr

Note; I don't PC, hoping to see some decent results from your testing.

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I don't use 50/50 COWW and lead alloy, but it's not that different from what I'm using. Do you think it is from too low a tin content?

Yes, it has too low a content of tin. It may be an okay alloy for many applications, handgun level especially but it is still no the best to use. You want a balance of antimony to tin not to exceed 5% of each. They then form a submetal which will stay in solution in the lead and not harden at a different cooling temperature. If you want to use the same alloy add 2% tin to your COWWs before mixing 50/50 with the lead. I use that alloy for many of my hunting bullets that are shot at 1900 - 2100 +/-fps. That alloy is good for holding very good with 7 - 10 shots out of a clean barrel but fouling soon will decrease accuracy at that velocity level. I don't know if PC'd bullets will do better.

However, even when WQ'd or HT'd that alloy will still be too soft for the velocity/accuracy level the OP seeks. At a minimum try the COWWs + 2% tin WQ'd or HT'd. Better yet is to mix up some #2 alloy.....can't say enough #2 alloy will be the best for him to use.

For 30 cal. rifles ... 308 , 30-06 , 30-30 , 7.5 Swiss and even the 303 British ...
I like to start with - 9 lbs. COWW + 1 lb. Linotype , shoot some loads and see if the mix needs to be harder for the velocity I'm trying to hit .
This is basically just a sweetened COWW metal ... but is a good place to start .
Gary

You can get away with using softer alloys when you powder coat because the powder coating acts as a jacket. That being said, I think you might have problems if you try to powder coat this bullet. Check the print for the 310-165-FN-GC-H3 on the NOE website. You'll notice that the nose diameter just ahead of the forward driving band is .310". At .1105" ahead of this the diameter is .305". At .221" ahead of the forward driving band the diameter is .299" Doing a traditional shake-n-bake powder coating can add up to .002" to a bullets diameter. If you end up with a bullet that has a nose diameter of .307" over a tenth of an inch ahead of the forward driving band, there's a better than even chance that you won't be able to close the bolt on these cartridges, and they will not chamber. I do a process where I powder coat the driving bands, but leave the nose bare, but for most folks that is just too much of a PITA.

Also, even though you may be able to reach 2400 to 2500 fps with hard cast, water quenched, gas checked bullets: it is not reasonable to expect MOA accuracy with those velocities. Expert, world record holders might be able to approach things like these, but not us mere mortals. You can expect much better accuracy in the regime of 1800 to 1900 fps. Even at those velocities you'll need to visually inspect each bullet for flaws, then weight sort them, if you want MOA accuracy with cast bullets. I'd recommend that you water quench your alloy & use conventional lube to see how that works before trying powder coating. If you do want to powder coat, just do one bullet, then use that to make up a dummy round. Use the dummy round to see if you're going to have chambering issues. This might save you from casting up and coating hundreds of bullets that don't fit.