30XCB Rotometals Alloy Choice 1 in 12 308 Win

[AnthonyB]

Fellas:
I've never played the HV cast game; 1800 fps has been plenty for me. But, I would like to qualify Appleseed KD that goes out to 400 yards with a 1 in 12 twist FN rifle. The course of fire requires 4 MOA accuracy from sitting and prone; the rifle is more than capable with jacketed. I don't want to play alloying games and am willing to buy my first ever non-WW scrap alloy. What Rotometals alloy would you recommend to make this as painless as possible?
Current boolit of choice is the 30XCB from what I have read here, but have never shot it. I also have Lyman 311291 and 311284, RCBS 30-165 and 30-180SP, and an unmarked 30-(looks heavier than 180) in Magma blocks that was a gift from BD. I have discounted the flat nose hunting boolits as too wind resistant/more wind drift, but this is from no practical experience at all.
Your long range and higher than average speed cast advice much appreciated.
Tony

[Bigslug]

We discussed the process of optimizing the .30XCB at great length here: https://castboolits.gunloads.com/showthread.php?440902-The-Components-of-Going-Faster&highlight=Components+Faster

My Dad & I tinkered with 2 parts lino to 1 part Lyman #2 for a 19BHN alloy. The accuracy "wheels" fell off the wagon for me somewhere above 2,200 fps in a 1-10" twist .30-06 - you should be able to go a little faster with your 1-12", but probably not the full 2800-3000 that some of the guys are getting with their 1-14" to 1-15" barrels.

[dtknowles]

Lyman #2 or Linotype or something in between. If you want harder than Lyman #2 use Linotype and some 50-50 solder or like the previous post just mix Linotype with Lyman #2. A lot of competitors shoot straight Linotype. If you are going to order from Rotometals there is not a lot of price difference between Lyman #2 and Linotype probably just go with straight Linotype.

Tim

[243winxb]

Oven heat tread , water cool alloy with minimum of 2% antimony. Full Hardens in 2 weeks.

https://www.thehighroad.org/index.php?media/make-cast-bullets-harder-oven-heat-treating.4774/full

https://www.thehighroad.org/index.php?media/oven-heat-treating-cast-bullets-water-cooled-to-harden-alloy-must-contain-2-antimony-minimum.3749/full

[JonB_in_Glencoe]

If I was gonna shoot cast at High velocity, I'd worry less about alloy, and more about bullet fit and runout, so as to get a square launch.

First, I'd do a pound cast of the chamber.
https://castboolits.gunloads.com/showthread.php?356251-Pound-Cast-instructions-(for-rifle-chamber)

then I'd get the best fitting boolit.
https://castboolits.gunloads.com/showthread.php?67033-Defining-boolit-quot-fit-quot

As to the XCB, it was designed for the 30 XCB chamber, it may be the best for your FN, or it may not be? You need to measure the chamber.
https://castboolits.gunloads.com/showthread.php?214329-30-XCB-wildcat-from-scratch

As to alloy, if you heat treat, COWW alloy will be fine, probably get to same hardness as Linotype, but with better characteristics.

[Larry Gibson]

Lyman #2 alloy is my 1st choice for the 30 XCB. It will cast the excellent quality bullets you'll want for your 400 yard shooting. I WQ the bullets straight from the mould which gives them a BHN of 20 +/-. That is strong enough to withstand the acceleration yet ductile enough. I have gotten my best accuracy at HV with #2 alloy. The use of Hornady crimp on GCs and a good lube such as 2500+ are also highly recommended.

A medium to slower burning powder is also best with Extruded powders being the best choice. A dacron filler is recommended if load density is less than 80%. You should be able to get consistent sub 2 moa accuracy upwards of 2300 +/- fps.

[AnthonyB]

Guys;
Thanks for the responses.
I've read the 30XCB threads, but like everyone, was looking for the easy way out! I'll order the Lyman #2 from Rotometals, and the 2500+ from White Label. I've used Carnauba Red and Blue before but never tried that one.
I had not considered the pound cast idea; about to start reading now....
Tony

[Larry Gibson]

I wouldn't even bother with a pound cast. I've shot a lot of 30 XCBs and other cast bullet in many milsurp and commercial 30 caliber rifles over the las 50+ years. I used to chamber cast and measure the throats. I found most, especially commercial 30 cal chambers, do best with a .310 or .311 sized cast bullet. The .311 sizing is most common for military and commercial chambers with the .310 being the choice for tight neck match chambers. My M70 308W match rifle throat is right at .310 which is what my 30x60 XCB and 30-6 XCB chambers have. It shoots the XCBS much better than I can. Actually, all of my 30 cal rifles I've shot the XCB bullets sized at .310 in shoots them more accurately than any other cast bullet. Thus, I haven't cast or measured a throat in several years. Yes, I know "fit is king" but I think we can overdo it and/or give it to much importance.