In the process of getting a 6.5mm - 300 Win Mag built. It will have a 1-8 twist barrel & be finished in the 24 1/4 - 24 3/8 range. Neck is throated to have a COL with a 140gr Accubond of 3.550.

Looking for powder suggestions & load charges.

Retumbo, RL25, H870, AA8700 & US869 are the slowest powders I have in the cabinet.

For those of you who shoot this cartridge I'm looking for a good baseline.

This will be a deer hunting rifle.

An accurate 3150 - 3200 FPS with a 140gr is my goal.

Thanks

sounds like you wanna duplicate the 264 win mag with a wildcat whose parent is of the same maker. i believe the 264 win mag was right around 3100 at its tops, but anyway, you should have a real screamer there, good luck with it. i don't have anything valuable to put in, will be interesting to hear about.

This project started life as a 264 WM. After finally coming to the conclusion that this rifle was only going to run the 140gr bullets in the 2950 - 3000 FPS range. I decided to have it opened up to the 6.5 - 300 WM.

My gunsmith pulled the barrel to confirm there was nothing wrong with the build which turned out to be the case. Being he had the 6.5 - 300 WM reamer & this wildcat is a simple neck size which doesn't require any major fire forming, I figured I'd open it up. Plus he cut me a great deal on the re - chamber job.

I owned a 264 WM before this one that would easily run 3200 FPS with 140's & a charge of H870. That was my goal with this one, such was not the case. Sold the old 264 rifle because it had a Magna Port & I hated the noise. To chop the barrel down on that one would have left me around 23"'s to boot. That barrel copper fouled something fierce but it did shoot good.

I am sure a 6.5 - 300 WM will be capable of more than 3200 FPS, but I will be very happy with an accurate 3150 - 3200 140gr & no pressure issues.

A guy who has one was what turned me on to the cartridge. He says he can go 3300 FPS with a 140gr, but his best accuracy is in the 3150 -3200 Range. Bingo, that's what I am looking for. Didn't like the 6.5mm STW because of the length & the fact I'd have to seat the bullet deeper than I like. With a 300 WM parent case I can seat the bullet out to 3.550 COL & still fit nice in my 3.600 Mag box.

Here is how they stack up beside each other.



It's done! It finished at 24 1/2" barrel length. .298 neck. Simple neck size & trim to form brass from 300 Win Mag. My wife picks it up for me tomorrow. Now to find the magic load. A pressure free 3200 FPS with a 140gr should be easy now

I hope she is good now. On his test fires he ran it up to 65gr IMR 4350 which is 9gr over max 264 WM data. Bolt lifted fine & primer was just starting to crater, so things look promising.

What is max case capacity ?

I believe it is 86grs but I am not sure.

Well it was -31 this morning when I put it to paper. Today was our last day of Whitetail season, so I wanted to load it with something accurate & fast enough so I could just put it to paper & continue on my day hunting.

Last night I pondered where to load this thing at. I decided on 79gr H870. Why? I figured this would be enough powder to get me some speed & not get me in trouble. I also sized & loaded the two test rounds after the build to see if I was going to have a once fired issue again. Bot rounds fired & extracted no problem. Here is what it did. Keep in mind it was -31 & the shooter may have rushed a bit. Mind you I do like what I see



Top shell was the 2nd shot after a horizontal & vertical adjustment. The first shot hit the target beside this one (not shown). The next 2 were fired after another correction & the last three were after another adjustment. I am not sure why the rifle wandered a bit back to the left? There was no wind it was just bloody cold. After the 3 shot group I made one more correction to the right & fired at the other target (not shown) & it was dead center of the top dot. Good enough to go hunting. Man what a muzzle flash though

The chrony did not work in the AM, but I did set it up when the sun poked out for 1 cold bore shot. 15 feet from the muzzle gave me 3274 FPS Judging by the group I think I may be pretty close. Some tweaking when it is warmer out & we should be in the ballpark.
I did neck size one round when I got home and put a primer in the case. Primer pocket still very nice & tight. Not like some reloads I have done over the years The re-sized shell goes back in the chamber like nothing

Here is the load details

Hornady 300 WM brass necked to 264 & trimmed to 2.610
Federal 215M Primer
79gr H870
140gr Accubond
COL 3.530. 20 thousandths off the lands.
.295 neck before firing & .298 neck after firing.
.514 at the expansion ring.

Nothing to shoot at today, not even a coyote Had one doe tag left, but in -31 weather it was going to have to be big to get my hands dirty.

So far all looks good.

Let me see what I can do for you..... When I get home

In the long run, I believe your going to wish you had a 26 inch barrel on that magnum rifle for getting the most of what you mix up in loads.

I once did a .277 (.270 cal) on a .300 Win mag using a 26 inch tube. It shot very tight groups with 160 grain Nolser Partition bullets, under .700-MOA off the bench.

I loaded it up with 150's to hunt spead goats with years ago and my bullets were going 3180fps and shooting into groups under .775-MOA. It was a fun rifle to shoot and hunt with and different than most hunters were packing in those days. Good Luck!

For the type of hunting I do I'm glad I shortened it a bit. I do have other rifles with 26" barrels & like them too. I have already exceeded my goal with this rifle in speed, so it is even better than expected. Now for some fine tuning & I'll be set.

Here are some updated photos of my 6.5mm-300 Win Mag. It now sports a 4.5x14x40mm 1" DPLX with CDS. The stock will be painted in a spiderweb paint finish in the new year. I may have the barreled action powder coated also.

I wanted to bump this to the top and ask, who makes dies for the 6.5-.300WM?

Couldn't find them in the Redding catalog.