160gr Matrix

[MontanaRifleman]

Using 5000' elevation and 40* in Paradise Valley yesterday, the Berger twist/stability calculator shows the 160 Matrix SF was 1.45 @ 3100 fps and the 140 VLD (Match Target?) was 1.49 @ 3300 fps (guessing) out of your 9 twist 264 WM.

I would guess your 140's are on the edge of stability in the 9 twist.

 

[rooster721]

Using 5000' elevation and 40* in Paradise Valley yesterday, the Berger twist/stability calculator shows the 160 Matrix SF was 1.45 @ 3100 fps and the 140 VLD (Match Target?) was 1.49 @ 3300 fps (guessing) out of your 9 twist 264 WM.

I would guess your 140's are on the edge of stability in the 9 twist.

Yah, lol.. I used that same calculator while waiting for my 160's to come in the mail. My numbers are 1975 elevation, and actually shoot the 140 Hunting vld's. Using those numbers and a 9 twist (@ 3135/140vld) I was getting 1.3-ish stability. With the 140's. If I recall off the top of my head, about 1.16 or 1.2-ish for the 160's.. crossed my fingers hoping that's be close enuf, but no sir... I also plugged in a bunch of numbers out of some bench-rest articles using velocities, twists & bullets they were shooting thru 6.5x284's and noted that the 8.5 twists (and their load info) was giving stability numbers on that calculator also in the 1.3 range* ..would think those boys would have good reason using 8.5 and 1.3 stability numbers to shoot 1000y matches. Compares nicely to my 140 numbers thru my 1:9.. obviously tho, not so nicely with the 160's. And my targets prove the fact*

Interesting either way* Definitely need more than 1:9 in this case for the 160's.. that info should help "some guys" anyway!

 

[elkaholic]

If you are ordering a barrel, I wouldn't order anything but a 1:8 for the 160's. Looks like a real thumper in the .264 mag though. That's where the big capacity case really gets a chance to stretch it's legs!........Rich

 

[BrentM]

Got mine now. Plan to measure the bearing surface, sort, lot, and prep for shooting. Hopefully they are uniform enough it does not matter and I can shoot them.

If timing works out I will shoot either Friday or over the weekend. Would like to shoot some wet newpaper for side by side comparisons. Bear hunt coming up so perhaps, like others, the bullets will get used on game.

 

[Rizla]

These bullets sound awesome! I've been waiting for someone to make something bigger than a 140gr. I'm planning on getting a real big .264, something along the lines of the Allen Mag or the new 6.5mm Prometheus I read about on here recently. I was wondering though, is there a reason the 160gr isn't a rebated boat-tail like the other Matrix bullets tend to be?

 

[BrentM]

Do you guys mind giving me some advice on where you think I should start powder level wise. Right now I am shooting 56.5 Retumbo behind a 140 pill. I can shoot 57.5 but 58 is getting a little hot.

This is in the 6.5-284.

I assume the extra weight of the 160 and possibly a longer bearing surface will bring the pressure up some. I have not shot anything but 140's in it so I am unsure of what to expect.

 

[elkaholic]

Do you guys mind giving me some advice on where you think I should start powder level wise. Right now I am shooting 56.5 Retumbo behind a 140 pill. I can shoot 57.5 but 58 is getting a little hot.

This is in the 6.5-284.

I assume the extra weight of the 160 and possibly a longer bearing surface will bring the pressure up some. I have not shot anything but 140's in it so I am unsure of what to expect.

You will probably be close with 3 grains less than the 140's.......Rich

 

[BrentM]

OK. I will reduce and work back up from the point. Thanks.

 

[gunwalker]

I found my best accuracy at 3 grains below just like rich said.

 

[BrentM]

Thanks again guys.

 

[BrentM]

Wow. Just measured these bullets and compared to the 140 vld BIG difference. Bearing surface is .580 vs .680. Base to ogive is huge too. Hope they will fly well with small jump.

 

[BrentM]

I did find a few hours to go out and test. My 6.5-284 wound up liking 52.5 Retumbo, .100 off the lands, estimated via drop at 2850 fps. Might get up to 53 and 2900 ok too. It shoots .50 moa with combo.

 

[elkaholic]

Lookin good Brent. That should put a hurt on something!.......Rich

 

[CliffM]

Looks pretty good at that speed.
What is your COAL ?
Cliff