IMR4320 and .358 Winchester

[richhodg66]

I happen to have quite a bit of IMR4320 and it has been good stuff with jacketed loads in several things for me.

I'm currently working with a Savage 99 in .358 to make my main deer rifle this Fall. I've been working with the NOE clone of the RCBS 200 grain FP and so far, it's worked alright with the load I've been using, but is a little more erratic than I like.

This is a deer killing load I'm looking for, so I'm looking for good accuracy in the 1800-2000 FPS range with relatively soft alloy, say 50/50 with some tin added.

Seems like it would be a bit slow burning for this application, but my old Hornady manual shows it as a good powder with 200 grain jacketed bullets. I was thinking of starting at 39-40 grains with this RCBS bullet.

Thoughts?

[tommag]

No real world experience, but since I just got quickload, I punched in the numbers.
My noe rcbs200 wieghs 218 grs with the flat point. Your load shows 1900 at 39 grs, 1957 fps at 40 grs. The pressures are very low, using my milsurp 308 cases formed to 358, 55.9 grs water. 28641 psi at 40 grs.

[richhodg66]

Thanks. I'm gonna try a few at 39 grains and see what happens. 1900 FPS or thereabouts is what I'm looking for.

[FrankG]

Wow , this came up at right time ! Just finishing up a 358 Win on a Springfield 03A3 action with Shilen barrel.
I have a Accurate 220gr boolit mould from Tom and wanted to use 4320 also ! Seems this should be a good starter for mine too . Ill probably reduce 5% to start as the PTG reamer cut a real tight chamber and I couldn't use milsurp brass. Luckily the local shop had 100 new 358 brass !!

[richhodg66]

Well, the IMR4320 experiment is a success. It grouped tighter with 40 grains of IMR4320 than with the other loads I had been working by quite a bit. I shot a nine shot group at 100 yards (I have a small odd lot of brass I have been using for testing, hence the weird number)The first two went a bit low and were touching, the rest formed a cluster of about 2" slightly higher. The whole group was maybe 3 1/2 inches, but without the first two shots from a clean barrel, I'd say that is a good group for a deer hunting rifle.

I'll try some tweaks, but I think I have my deer load this year figured out.

107091

[35 shooter]

That is looking good! I think 4320 is one of the most over looked powders on the market. Works well over a pretty broad range of calibers really,at least with jacketed. I've been meaning to try it with cast in 35 whelen, but got side tracked with 4350, which has worked out really well too.

[richhodg66]

So far, I've been using a Lee Universal expander die and not crimping at all. I wonder if a little crimp might help accuracy?

I might try increasing the charge a grain or two, but this should be pushing between 1900 and 2000 FPS, which should be plenty for the conditions I hunt deer in.

[35 shooter]

I use a light crimp with my noe 200 gr. boolits in the whelen and it did improve accuracy and powder burn. Working with a 280 gr. now and it fills the neck and throat up so well it's shooting fine without the crimp. I've found it pays to play with crimp and seating depth too once i've found a good load. Sure won't hurt to try it.