What do you guys think of this boolit design?

[O.S.O.K.]

I have a new 338-06 Savage rifle - actually it started as a Stevens 200 .270 and I've switched the barrel, added a rifle basix trigger and replaced the plastic trigger guard with a steel one.

Here's the pic of the "new" rifle with the old barrel:



Did all that myself, so I am not a complete chimp when it comes to gun stuff... but, I've never designed a boolit mold and know only the basics when it comes to the desired parameters.

Anyway, I'd like to try some cast boolits in this puppy - about 1950-2000 fps - for hunting.

250 grains - gas checked.

Needless to say, there's no factory molds so I'm looking at the Mountain Molds...

Here's the drawing:



Specs:
255 grains with ww+2% tin
Bore Riding Tangential Ogive
as cast diameter .340"
driving bands .340"
2 bands - .010" wide
nose length .825"
meplat 60%
crimp groove .055"
bore ride bottom diameter .333"
bore ride top diameter .331"
bore ride length .070"
.3275" step shank for Hornady GC
shank length .110"
groove to band ration 1.0
groove angle 55%
Brass 2 cavity
screw and setscrew hinge

rifle throat length .115" (I have no idea if this is good or what)
length inside case .398" (this is for a .338-06 so this should be good)
suggested twist 1:11 (rifle is 1:10")
sd .315
groove diameter.308"
ogive radius 3.257" (?)
ogive length .64" (should keep it off of the lands when seated to the crimp groove?)

I measured the nose length of the jacketed .338" bullets that I have on hand to get an idea of proper nose length in order to keep OACL correct, so I'm pretty sure that's OK.

I started with a heavier boolit but found that the nose length and inside length wasn't going to work - I want the base of the boolit to sit flush or slightly up into the neck when seated and the ogive of it to not dig into the lands - though, that wouldn't be a problem...?

So, what do you guys think?

Please don't worry about insulting me - I really have no idea what I'm doing here - just using my limited knowledge and common sense in setting these parameters...

[geargnasher]

Do a search on this site regarding "impact slug" procedures involving a fired case filled with soft lead up to half of the neck, then "seat" a soft lead boolit cast from your heaviest mould on top, force it to chamber, and pound it down with a steel rod wrapped in electrical tape.

Take careful measurements of your impact slug which will give an accurate and permanent impression of the chamber, chamber neck, throat, ball seat, and the first part of the rifling.

Design a boolit that will fit these dimensions as closely as possible for FULL boolit support under launch. No excessive gaps or unsupported features that the boolit can distort into upon firing.

Gear

[JIMinPHX]

That looks like a nice design to me.

[O.S.O.K.]

impact slug = alternative chamber cast?

makes sense. That would show the exact dimensions... as long as the boolit isn't over maximum OACL and fits in the magazine...

[GabbyM]

My preference would be for a longer percentage of bore ride length.
However I've seen long unsupported nosed bullets before. Veral Smith sell lots of them.
Seams to me with that much unsupported nose the bullet would have to be cast hard to resist slumping? But I don't know that for a fact.

BRP has a few 338 molds you may want to look at. http://www.brp.castpics.net/R1.html

That’s' a great clambering. IMHO.

[geargnasher]

impact slug = alternative chamber cast?

makes sense. That would show the exact dimensions... as long as the boolit isn't over maximum OACL and fits in the magazine...

Si'.

Gear

[Ben]

I don't own a .338 right now. However, my cousin shoots a 338 Fed., a 338/06 and a 338 Win. Mag. He wanted a heavy weight mold in .338 also.

I recently found for him an NEI mold ( made by Walt many yrs. ago ). It cast a .3405" dia. bullet weighing 262 gr. bullet, it is g/c'd and is extremely accurate. We size .3395"
I cast and size his bullets, he does the reloading.

Here are photos of the bullet and mold.

[nanuk]

When I compare Ben's NEI boolit to the "Theoretical" boolit made from the MM design software, the first thing I notice is the MM boolit has a long unsupported portion of the nose.
it appears almost 40% of the nose is unsupported, Whereas Veral's boolit has about 25-30% unsupported.

I wonder, is that long nose going to stress the bearing surface and cause boolit yaw? that is a lot of leverage

just thinking out loud here

[geargnasher]

Nanuk, depending on lots of factors, slumping of the fairly large unsupported portion of the nose could indeed happen.

Gear

[O.S.O.K.]

Thanks for the links. I have to admit that I kind of like the idea of having my very own OSOK design mold

And the unsupported portion of the nose would be remidied if I extended the width of the bore-ridder band right? So move extend that forward...

What about the width of that? Does the top and bottom width look right?

[nanuk]

it would seem to me that making the bore riding portion move forward up the nose would do two things
1) make the nose more supported and a longer bore rider like a xxx299
2) either make the nose blunter/rounder, or widen the meplate.

I'm sure the experts on here can direct you as to how much unsupported nose would work without issue.

things to think about, how long is the magazine of your rifle and how close can you get the nose to the rifling.

guys that design boolits, (We have a couple on this site), understand these relationships.

[O.S.O.K.]

I measured several jacketed bullets to get their dimensions and nose length, etc. They are designed (and do) fit standard magazines and such.

[waksupi]

I would add another lube groove, and shorten the nose. I did a similar design, and they tended to tip slightly when the barrel heated up.

[swheeler]

2 bands - .010" wide
What am I missing here?? You ain't going to get much traction.

[waksupi]

Here is the design I ended up with. Just shot these this morning out in the rain. I had went up the mountain last night shooting, and was not hitting. Realized I had taken the scope off last fall, and put the aperture back on without re-sighting, so had to check zero. This has been a very accurate boolet for me, being close to a Loverin design.
Boolet is sitting on a sighter hole. Dropped the sight two clicks.
100 yards.

[O.S.O.K.]

Good shooting!

Hmmm.

[Bret4207]

Take a look at the NEI mould Ben pictured and try and copy it. Note the rear band is nice and thick and strong. Note the "bore ride" shape, rather abrupt, not long and unsupported. Long, unsupported bore riders can work, but alignment becomes more and more critical as the unsupported length increases. Any misalignment/runout can cause an unbalanced boolit and the heavier the charges the more it gets magnified.

[O.S.O.K.]

Yes, I see what you are saying now. I've gone back and played with the parameters some more... I'm waiting for a closing on some land before I go ahead and make the final design and order...

I do want a heavier boolit though - 260 ish would be fine. Seems that 250-270 is about the optimal for the caliber as going beyond seems to push the base down into the case, and I don't want that - I want the gas check to sit in the neck.

[O.S.O.K.]

How about this:


this is the drawing from the Mountain Mold site.

With WW+2% tin:
Bore ridding tangential ogive

251.8 grains
as cast diameter: .240"
front band diam: .339"
front band length: .150"
nose length: .750"
meplat: 65%
crimp groove: .055"
bore ridder bottom diam: .332"
bore ridder top diam: .331"
Bore ridder length: .200"

base is .3275 straight shank for Hornady gator .338, 3 gr. gas check
Groove to band ratio: 1.0
Groove angle: 55%
2 band, 1 groove .0828" bands
OAL: 1.148"

length inside case: .398"

[nanuk]

now that there is a nice looking boolit

Any one have thoughts on Lube in the 338?