Home Forums Hunting & Shooting Express Rifles and Big Bores Only First time loading 458 question

Ok long time reloader but new to anything this big. I was going to try 76gr. Min book load I have of IMR4895. under some 350gr Hornady RN Interlocks.

My question is while it does not fill the case completely it is close and with bullet seated to 3.105 it will be compressed. Book does not call that a compressed load however.

Am I ok here?

No worries.
IMR-4895 is so slow and bulky that you will not be able to get into excess pressure
with a 350-gr Hornady in the .458 Winchester Magnum.
COL when seated to cannelure on that bullet is only 2.950" with brass trimmed to 2.490",
COL is 2.960" with 2.500" brass.

The Speer 350-grainer has a COL of 3.105" with 2.490" brass crimped on factory cannelure.
77.0 grains of H4895 is the Hodgdon manual starting load for that bullet, not compressed at 3.105" COL, 24"-barrel velocity = 2419 fps, 34,600 CUP
80.0 grains of H4895 is the Hodgdon manual maximum load for that bullet, COMPRESSED at 3.105" COL, 24"-barrel velocity = 2496 fps, 38,700 CUP
All well under 50,000 psi.

IMR-4895 and H4895 are close enough to use them interchangeably here.

If you seat the Hornady 350-grainer out to 3.105" you will have more powder room than same COL with the Speer.
The Speer has a longer ogive/nose projection.

H4895 is preferred (by me) with your Hornady 350-grainer for use at either 2.950" to 3.105" COL in 2.490" brass
or 2.960" to 3.115" COL in 2.500" brass.
Use a LEE Factory Crimp Die and no need for cannelure on that bullet.
Consider 80.0 grains H4895 or IMR-4895 to be your max load, whatever the mild degree of compression may be.
I would start at 77.0 grains H-4895.

The Speer manual calls for 76.0 grains IMR-4895 minimum and 80.0 grains IMR-4895 (compressed) maximum, with Speer 350-gr FNSP Hot-Cor bullet at 3.105" COL.
Again, note that the Hornady 350-gr RN Interlock at 3.105" COL will have shallower seating depth at same COL, less compression.
Ignore compression in this load, it is minimal if any.

I have used H4895 at about 110% Load-Ratio/Net-Fill COMPRESSED after use of drop tube with 400-gr bullets.

To have any hope of getting up to max pressure you will have to use a faster powder.

Awesome... thank you for this info. I had just enough of an old metal can of IMR4895 to do the 18 350gr hornady bullets. I'll just use those to break the gun in.

I plan to shoot 500gr bullets out of this rifle going forward. Looking at the manuals the velocity increase is pretty minimal from min to max loads. I'll probably shoot for just above minium. Its only plinking and pigs. Nothing dangerous.