What alloy for subsonic .308 127-gr PB bullet?

[Buck Shot]

I'm a new guy to cast boolits, getting ready to cast my first batch of .30 caliber 127-grain plain-base bullets to use in 30-06 over maybe 10 gr Unique or Red Dot. This is the NOE bullet:

https://i.ibb.co/g3dnzRL/NOE-311-127-FN-PB-L2-127-gr-308-bullet.jpg

I bought a bunch of different alloys (and "super hard" for alloying) from Rotometals, but I'm not sure what alloy to use for this.

It'll just be for our local 100-yd walk-and-paste matches so I'm looking for something subsonic, and the bullets won't have gas checks, so I want something that won't erode too bad at the base/heel, I guess. And I suspect they'll be jumping a fair distance in my old Colombian FN M98 before they engage the throat.

Can anyone recommend an alloy for this? (Sorry if this is a really basic question, but the amount of info out there is almost too much to sift through, it seems like sometimes.)

Thanks in advance.

[Outpost75]

First off, your proposed load is way too much to avoid leading with a plainbased bullet.

You want to keep velocity in the range of 900-1300 fps. Reduce your powder charge to about 6 grains of Red Dot or 7 grains of Unique and you will be MUCH happier. No filler is needed. Stick to soft 8-10 BHN alloy, such as 1 to 30 tin-lead, or 50-50 plumber's lead and wheelweights, with a wee bit of tin added, if needed to get good fill-out. If the report gives a distinct "crack~!" try reducing the charge another grain to remain subsonic.

[Buck Shot]

Thank you for your help, Outpost75. So if my math is right, and assuming plumber's lead = 100% lead, and wheelweights are 2% Sb and 0.5% Sn, then I want something about 99% lead and 1% tin and 0.25% antimony ... up to about 3.2% tin (30-to-1) ...

Part of my confusion is that I don't know what linotype, wheelweights, Lyman #2, etc., are, so I need to look up those formulas first and then do the algebra ...

On another front...I wonder how fast I could push a bullet like this if I used a harder alloy, and still get acceptable precision (say 3 MOA)...I guess there's only one way to find out.

Thanks again.

[Outpost75]

Plainbased bullets, regardless of alloy hardness, begin to lead and fail in accuracy above about 1350 fps. In a slow twist, very smooth barrel, using a grease cookie to protect the base, you might get 1450 fps, but in a ten-inch twist military surplus barrel don't expect anything close to normal accuracy above 1300 fps.

In a good '03 Springfield with soft bullets which fit the throat and are well lubricated, you should he able to shoot ten-shot groups around 2 MOA and maintain that for a long series without cleaning.

The Fouling Shot #267 has a detailed article on shooting cast in the 03 Springfield. If you want to PM me with an email address which can accept a .pdf file of about 3MB I can send you a sample copy.

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[Buck Shot]

That's great information. Thank you sir!

[popper]

7 gr unique is a good starting load BUT you can go much faster with proper lube (PC) and alloy. Drop down to ~5gr unique if you do want subsonic - unique is not the best powder for this. When looking for sub loads, start hot and work down, be prepared for stuck in the barrel bullets. Chrony definitely helps.

[yeahbub]

I'm curious. In the thread name, you mention .308. Were you intending to size and lube t .308 diameter? The general practice is to size the boolit to throat diameter so it will be centered and supported in the throat without having to reach waaay out there to make contact, as well as letting the throat size the boolit to groove diameter on firing for a good seal in the bore. In most chamber drawings, a .30-06 chamber throat is shown to be cut to taper from .310 at the chamber end to .308 in the rifling. Sizing it large enough to chamber freely, and setting OAL to have slight resistance on closing the bolt will pay dividends in accuracy over a boolit that is small and/or unsupported out front. Early in my cast boolit experiences, I could only get commercial cast boolits and they were inevitably sized to .308. The accuracy and leading with them was dismal and not helped at all by my lack of knowledge and experience. As others have often noted, with cast, boolit fit is king.

What Outpost75 says about alloy and plain base velocity and pressure limits is on the money. At the velocities you intend, alloy hardness can range widely, just keep it consistent. If, at some point, you decide to step things up a bit, you can apply plain base gas checks to your existing boolit when you size/lube them. https://www.sagesoutdoors.com/

That 127gr looks interesting as also being a good candidate for use as a paper patched boolit in .30's and in 8x57. Cast of an expandable alloy and wrapped in a paper jacket, it could be driven to much higher pressures and velocities for hunting purposes.

[405grain]

For a sub-sonic load with a plain based boolit even reclaimed range scrap alloy will do. Since your just starting out I'd suggest that you try your initial experimenting with the cheapest alloy at your disposal. Save that superhard for better alloys in higher performing boolits. Once you gain more experience it's very likely that you'll want to step up to gas checked designs at higher velocities. Welcome to casting!

[dh2]

the sub sonic thing is not something that I normally get in to, I am not seeing where that light a bullet in the 30-06 twist will be stable I would expect a lot of key hole bullets in the target,
But what would Trail Boss do as the powder in this, I see a lot of sub sonic stuff using it

[oldblinddog]

That’s a 311465 copy and it will stabilize perfectly well in that ‘06. Try 3.2 grains of Bullseye if you have any.

[Cosmic_Charlie]

I had good accuracy in my 30-30 with Unique and a plain base 165 gr. Ranch Dog boolit until somewhere over 7 grains. Tight group and Bullseye worked well too.

[Buck Shot]

Thanks for the replies, everyone. I appreciate all the help.

@yeahbub, I was going to size them to .309" ... I bought a .309" sizing die and hope that will work.

I also have a 311332 GC mold but I'm hoping I can get a decent plinking load with these lighter PB bullets.

[yeahbub]

A .309 die is a good place to start and should put you right in the middle of the throat taper. Hopefully your barrel hasn't been rode hard and put away wet in its military life and the throat is in good shape. Just for grins, seat an unsized boolit in a sized case and see if it chambers freely. If it does, play with seating depth to get throat engagement just as the bolt closes. It could be you can get away with pan-lubing boolits en mass and load/shoot without sizing them. Given the preferred subsonic velocity you're after, minor lube variations won't matter. Shake-and-bake powder coat is also an option and it eliminates lube considerations.

Keep us posted on how it's going for you.

[Cosmic_Charlie]

My well shot .308 needed a .311 sized boolit. My 30-30 uses a .310

[Larry Gibson]

Any alloy from 40-1 to linotype alloy for subsonic will do. However, some softer alloy will probably do better. I suggest a binary 20-1 alloy or a ternary alloy close to 97/1 12// 1 1/2.

As mentioned, you might try shooting them "as cast" w/o sizing if they cast nice and round. Tumble lube in LLA or similar TL lube with a light coat and let thoroughly dry as in Outpost75's picture. Load over 3.2 gr to 4 gr Bullseye, Red dot, WST, etc. or similar fast burning powder. I do not find Unique, which is slower burning than the powders mentioned, to perform as well for such sub-sonic loads with such lighter cast bullets in the '06.

[popper]

#1 do you really want subs for 100 yd shoot?
#2 almost any soft alloy will work slow but I prefer 13-1400 fps for 100 yds. I shoot 30 cal PB and accuracy is fine. I'm with Larry, Alox or Ben's Liquid Lube - that stuff is great.
#3 you only need tin for fillout problems. Yes it is used for other purposes but not yours.
#4 you only need hardness to hold to the rifling. Add Sb (super hard) to get ~2%, should be fine. Keep tin LESS than Sb. Soft alloy is smaller dia than harder from the same sizer dia. !

[Outpost75]

Subsonic is fine to 200 yards and more accurate because you are not fighting transonic buffeting as velocity decays below the speed of sound. Less wind deflection also.