some 358 Win advice needed

[Jevyod]

I have not cast recently, am planning on getting back into it since bullet prices keep creeping up. I will be casting for a 1:12 twist (what I was told) 358 Winchester rebored from a 243. This gun shoots well with jacketed, ~3/4 inch 4 shot groups at 100 yards. I plan on casting the great 35-200fn bullet out of close to a 3-3-94 alloy and powder coating and adding gator gas checks. I have a few questions and would like some advice.
First, with a 12 twist and my alloy, where would you expect that my groups start opening up beyond acceptable accuracy? I will not be shooting this beyond 200 yards at deer, so ~ 2-2.5 inches at 100 yards should be fine. If I calculate the RPM threshold correct, I am thinking I should be able to get to 2100 or so, which I believe should do just fine for what I need.
Second, I am trying to figure out where to start with powder. I have read some that a slower start for cast may be better. I have some R7 and 4198 on hand, and traditionally those have seemed to be good powders for cast. I do also have several lbs of Win 748 that this gun has seemed to like pretty well with jacketed. I was shooting the 200 Hornady Spire points to 2475 fps with my best 4 shot group coming in at just slightly over a half inch. But I fear I won't be able to safely slow the load down enough with that powder to make it viable for cast. Thoughts? Comments?

[waksupi]

I shoot heavier bullets, but find I can keep them under an inch if I do my part. Mine average 2170 fps. with a 290 gr., which if you look at any reloading chart, you will find this is above expected velocity for the bullet weight. That gives you point blank to 225 yards. My best powder has been WC 852(F).

[gwpercle]

Lyman Cast Bullet Handbook #4 has 358 Winchester Loads for two boolits .
Lyman #358430 195 gr. RN and Lyman 358315 204 grain RN GC - with loads for RX7 and 4198 powders .
It would be better to use Lyman data , for cast boolits than trying to figure out how to use jacketed data for cast boolits .
If for some reason you don't wish to obtain the Lyman #4 manual ... I will be glad to post the min./max load data for those two powders and the 204 grain boolit .
The 195 grain boolit doesn't list those two powders.
Gary

[Jevyod]

Lyman Cast Bullet Handbook #4 has 358 Winchester Loads for two boolits .
Lyman #358430 195 gr. RN and Lyman 358315 204 grain RN GC - with loads for RX7 and 4198 powders .
It would be better to use Lyman data , for cast boolits than trying to figure out how to use jacketed data for cast boolits .
If for some reason you don't wish to obtain the Lyman #4 manual ... I will be glad to post the min./max load data for those two powders and the 204 grain boolit .
The 195 grain boolit doesn't list those two powders.
Gary

If you would post the min/max of the 204 grain that would be most helpful. I did expect that I would need to use 1 of those 2 powders.

[Jevyod]

I shoot heavier bullets, but find I can keep them under an inch if I do my part. Mine average 2170 fps. with a 290 gr., which if you look at any reloading chart, you will find this is above expected velocity for the bullet weight. That gives you point blank to 225 yards. My best powder has been WC 852(F).

What mold is that from? And I don't recall seeing that powder, who makes it? Thanks

[Harter66]

I have a 1-14 . The RCBS 35-250 runs 2100 fps sub MOA on an off the books load of I 4350 .

I tried H322 , h4198 and Unique under the Lee version of the 200 . Unique was good not so much with the other 2 .

[gwpercle]

Lyman Cast Bullet Handbook 4th edition
358 Winchester , Lyman #358315 204 gr. RN , #2 alloy . sized .359"

RX7
starting load: 27.0 grs. @ 1618 fps / 16,500 c.u.p.
maximum load : 32.0 grs. @ 2018 fps / 27,300 c.u.p.

IMR 4198
starting load : 25.0 grs. @ 1643 fps / 16,500 c.u.p.
maximum load : 30.5 grs. @ 1981 fps / 27,600 c.u.p.

Jevyod ,
Hope this helps you out .

Good news is it looks like you can use both the powders you already have .
Lyman indicates the best accuracy was with 5744 powder but looking at the data it gave no higher velocties than RX7 or IMR 4198 ... it's top velocity was 1975 fps , which ain't bad...
You may want to look for 5744 , it is useful in cast boolit loads .
Good Luck Loading ,
Gary

[Silvercreek Farmer]

I’ve had good luck (1.5 MOA or so, 1/12 twist) with RX7 and the Lee 200g boolit cast from 49% ww, 49% pure, 2% pewter running 2300 fps. Expansion/retention is excellent.

[lar45]

WC852 is a surplus powder that used to be available.

[rintinglen]

Try 36 grains of 748 and work up to a max of 40 grains with an RCBS 35-200 FN. I used it with complete satisfaction in my old Remington.

[gwpercle]

I’ve had good luck (1.5 MOA or so, 1/12 twist) with RX7 and the Lee 200g boolit cast from 49% ww, 49% pure, 2% pewter running 2300 fps. Expansion/retention is excellent.

Like the 50/50 COWW & soft lead for a hunting/shooting boolit ...
RX7 powder may be just the ticket !
Gary

[Silvercreek Farmer]

I’ve had good luck (1.5 MOA or so, 1/12 twist) with RX7 and the Lee 200g boolit cast from 49% ww, 49% pure, 2% pewter running 2300 fps. Expansion/retention is excellent.

Forgot to mention the boolit is powder coated!

[cwlongshot]

I shoot a bunch of different bullets and loads. Most all shoot good enough to de what ever Id need.

But one thats specail is a load of rl7 to hit 1900 fps under a MP 359-220hp mold cast COWW+tin. Shoots just over a inch @ 100 makes it good inside 200 yards a d everything Id ask of the load.

I have a 230 NOE WFP thats another good one with 748 & a 245g Saeco and 3031 powder as a heavy.

I have a 270 & a 310 that Im playin with but when I need them I have a Whelen and a 358 Norma Mag that do better with them.

CW

[waksupi]

What mold is that from? And I don't recall seeing that powder, who makes it? Thanks

That is the custom run Bator Heavy, a close copy of the .358009. The powder came form Jeff Bartlett, GIBrass.