338 WM Bullet Design

[BABore]

Just did a chamber cast of my T/C Encore barrel in 338 Win Mag. It's a custom 26" barrel from Fred Bullberry.

http://www.hunt101.com/img/358602.bmp

I would like to design up a 250 gr plus GC bullet with a 70% meplat. This will be mainly for hunting and plinking. I figure I will be shooting for 2,000 to 2,200 fps. I would rather keep the alloy hunting compatible rather than quest for speed. That means WW's probably heat treated. Since I plan to keep my speed down I would prefer the heaviest practical bullet. My bore slugged a tight 0.3380 at the muzzle. The breech end is 0.3392" so it is nicely choked as well as being hand lapped.

My main concern, besides not really having a clue, is the seating depth in the case. I've read in several places that you don't want the GC to go below the case neck. This means only about 0.330" can be in the case. Everything else has to be forward. To get a 250 gr. plus bullet, that means a bore rider. Since this is for a single shot, I'm not really confined to a mag length. Question is how long can you go and what is practical? Of the couple of designs I've seen, both had a tapered BR nose. Should this taper be matched to anything?

Any help will be appreciated.

This post is also on Mnt. Molds forum. I plan to have Dan cut me a mould when things are ironed out.

[45 2.1]

The Lyman 33889 is a good example of what your asking for. You have the dimensions to design a mold like that posted. Put the base of the bullet at the base of the neck and design the rest to fit. Match the bullet taper to your drawing. The nose should engrave slightly on the lands. Since you have a single shot, no more than "slightly" should be used since your thumb will be doing the pushing. A"DD" band does not work for single shots, you cannot engrave a DD nose band by pushing it with your thumb at all.

[BABore]

I looked over the drawing over on Castpics. What is a DD band?

What are your thoughts on the GC position below the case neck?

I'm assuming that if I have a 0.340 top band, say 0.100 to 0.150 long, I then taper to a BR dia. of just at or above land dia. The taper length would match the chamber cast taper, more or less. The BR nose is the only portion that actually touches. Is this correct? The land diameter is the only thing I couldn't measure accurately. Do you happen to know the proper diameter?

Now for a couple real ignorant questions. Would you keep the crimp groove? I'm assuming the twist rate is 1 in 10 or 1 in 12 (I'll find out). Do you see any stablity problems with a 250 gr bullet at 2,000 fps?

I just confirmed with Bullberry, the twist is 1 in 12".

[Bass Ackward]

BA,

Well .... you want what you want. Just design it up. But the real reason that the "don't go below the case neck" thing came about was to keep lube from contaminating the powder. If you are comfortable using a filler, then you have less to concern yourself with in the case. Beside, you can usually go down another .070 (height of the check) before the gas check groove becomes exposed anyway. So you can add that in.

But I fear that your velocity goal is going to need to be .... tamed. BruceB was supposed to be working in this area but has not reported back as of yet. Maybe he will chime in.

And you are probably going to be right on the edge of stability with a 12 twist if you make your grease grooves too wide, you could excede it.

[45 2.1]

I looked over the drawing over on Castpics. What is a DD band?

NEI Handtools uses a bearing band at the ogive point on the nose to align an undersize nose.

What are your thoughts on the GC position below the case neck?

Wouldn't care for it on a 338 Mag.

I'm assuming that if I have a 0.340 top band, say 0.100 to 0.150 long, I then taper to a BR dia. of just at or above land dia. The taper length would match the chamber cast taper, more or less. The BR nose is the only portion that actually touches. Is this correct?

Match what your rifles dimensions are.

The land diameter is the only thing I couldn't measure accurately. Do you happen to know the proper diameter?

Land = Bore, which you already stated to 4 decimal places. Again, match your rifles dimensions. If you can get Dan at Moutain Molds to cut this, let us know.

Now for a couple real ignorant questions. Would you keep the crimp groove?

No and the Lyman 33889 didn't have one.

I'm assuming the twist rate is 1 in 10 or 1 in 12 (I'll find out). Do you see any stablity problems with a 250 gr bullet at 2,000 fps? I just confirmed with Bullberry, the twist is 1 in 12".

I'm not the one to answer that, ask Felix. I have shot a Sako 338 Mag quite a bit with the Lyman bullet, very accurate with Unique, but didn't push it over 1700 fps either.

[BABore]

I was taking a hopeful shot (in the dark) at the velocity. You're right, 1,600 to 1,900 fps will probably be reality.

[45 2.1]

You shouldn't have any problem getting to your posted velocity. Just design the bullet to fit with adequate lube capacity and the correct alloy. If it stabilizes at 1700 fps, it sure won't go to heck at a higher velocity in a 12" twist. Check out the current and older Lyman manuals for what you can expect.

[BABore]

45 2.1

"Land = Bore, which you already stated to 4 decimal places. Again, match your rifles dimensions. If you can get Dan at Moutain Molds to cut this, let us know."

I guess I asked it wrong. I have the bore diameter at 0.3392". I meant the groove dia. then (I think). Anyway the smaller 0.330+ diameter. Isn't this what you design the BR nose too?

"No and the Lyman 33889 didn't have one. "

The Cast Pics picture didn't show it, but the Lyman 3rd Ed "Cast Bullet Handbook" didn't.

Please forgive the ignorance. Besides being still wet behind the ears, there's not too many (existing) 338 bullets out there.

[45 2.1]

I guess I asked it wrong. I have the bore diameter at 0.3392". I meant the groove dia. then (I think)

Yep.

Anyway the smaller 0.330+ diameter. Isn't this what you design the BR nose too?

Yes, measure it carefully and match it exactly.

"No and the Lyman 33889 didn't have one. "

Seems I CRS at times, its been a long time since I shot or cast for the 338. I think it does have one (couldn't make it out on Castpics), which I wouldn't worry to much about. Good place for a lube groove.

Please forgive the ignorance. Besides being still wet behind the ears, there's not too many (existing) 338 bullets out there.

Yep, so true and the 33889 is the only one I have.

[felix]

12 twist will work above the speed of sound quite well with a .24 meplat, .24 or better nose length, total length not to exceed 1.2 inches. ... felix

[Bass Ackward]

BA,

You simply need to narrow your focus of what you want. The best high velocity lead bullet for accuracy will almost always be the lightest bullet per caliber. This is because force increases on the base the more weight you need. Or stated another way you will need a harder bullet in a heavy bullet to reach the same velocity levels that a light one will. Not a big factor in paper punching, but definately important for hunting.

And the velocity limiter will be the bore ride design itself. Because of the lack of drive area. The more non-drive weight you add to a design, the lower overall velocity potential you will have, regardless of twist rate.

The only advantage of a heavy bore ride design is in worn throats where you need to reach out for guidance. And yours is not.

[TCLouis]

Works very well out of my model 70.

I bought a 200 grain RCBS to get the meplat to hunt with and have yet to find a load that will shoot with that bullet. Rather limited testing, but fter the 220 Lee I was expecting "easy" load development.

My most accurate "low power" loads are right in there with those produced by the 338-08.