New guy loosing his mind from load data

[smithjasona1978]

Ok I am a new guy. I have made several new posts lately looking for information. I have been shooting a 243 and a 300 win mag for a while now. But I am thinking about moving up to something to spend more money on. So I have a new 300 wby mag on the way and gonna send it off for a new barrel.
So this is why I am loosing my s**t a little. I ordered some Ramshot magnum, and last night I was on there website looking at load data, and saw this....

300 win mag 24'' barrel 220 gr SMK

accurate mag pro 80.1 gr 2875 63,396 psi
ramshot magnum 80.9 gr 2868 63,412 psi

300 wby mag 24'' barrel 220 gr SMK

ramshot magnum 83.0 gr 2840 62,500 psi

300 RUM 24'' barrel 220 gr SMK

ramshot magnum 91.0 gr 2870 62,940 psi


Ok it is my understanding that the MK248MOD1 round the military is using is a 220 gr SMK at 2850. And isn't that out of like a 26 or 27 inch barrel?? And that its such high pressure that the brass is not reloadable because the primer pockets are looser than my first girlfriend after the first firing.

So am I loosing it? Is this info wrong? More velocity from 300 win mag than a 300 rum?!

I know that every rifle is different. And I know companies can't conduct all of their tests on a day when the temperature is the same, but WTH???

MAYBE I SHOULD TAKE UP GOLF.

 

[Barrelnut]

I think those are the Sierra accuracy loads? They are not the max loads usually. The one for the RUM might even be a starting load...

Looked in the Nosler book and found this data.

300 RUM 220 Gr partition
Start: 91.0 gr. Magnum for 2870 FPS. (most accurate load tested)
Max: 95.0 gr. Magnum for 2979 FPS

 

[smithjasona1978]

No. Those are the max loads listed on ramshot and accurate powder website. MAX LOADS. look for yourself. Accurate and ramshot data. Not sierra. Just using 220 mk bullets.

 

[Barrelnut]

No. Those are the max loads listed on ramshot and accurate powder website. MAX LOADS. look for yourself. Accurate and ramshot data. Not sierra. Just using 220 mk bullets.

Have no need to look at it. I don't use their info. And now I don't even trust it.

 

[smithjasona1978]

Yeah. That's why I am so frustrated. Everyone harps about using load manuals and published load data. So I go to the horses mouth for the powder I am gonna load and end up with that. Who to trust?

 

[Barrelnut]

I looked at the Ramshot PDF Guide. I think the HPBT 220 MK must have a long bearing surface and therefore builds pressure quicker. The loads they have for other bullets in 300WM 300 WBY or 300 RUM seem to make more sense. It is just the MK that looks different to me.

Clip from the Ramshot guide:

200 SIERRA SBT GK 85.7 2,732 95.2 3,035 62,910 3.600
220 SIERRA HPBT MK 81.9 2,583 91.0 2,870 62,940 3.600

 

[smithjasona1978]

According to the sierra website they only have one .308 caliber 220 grain matchking bullet.
.308 dia. 220 gr. HPBT Matchking. #2240
And in 200 gr,
.308 dia. 200 gr. HPBT Matchking. #2230

 

[Barrelnut]

Oh... Your right. only one 220 gr. bullet.

Well I think it still has to do with a long bearing surface that causes pressure to max (62,940 PSI) before the case capacity is used. Seems that with the 220 MK a 300WM would be as big a case as practical for it. You're right it's kinda crazy.

 

[smithjasona1978]

Mind you I am not holding anyone to anything. I totally understand that this entire practice is based upon a gun to gun basis period. Having said that. R U saying that that data might be correct?!?!?!
A 300 win mag 24" inch barrel 1-10 twist fed 215 pr win case, 3.34 coal. 80.9 grains of ramshot magnum will push a 220 gr smk at 2868 , 63,412 psi.
And a 300 RUM 24" inch barrel 1-10 twist fed 215 pr rem case, 3.60 coal. 91.0 grains of ramshot magnum will push a 220 gr smk at 2870 , 62,940 psi.

2 fps with 10.1 more grains of powder??

And the poor wby with 2840 at 83 gr. So 28 fps less with 2.1 more grains of the same powder in the same length barrel. ???

 

[Barrelnut]

Yea, guess I'm saying that's it is probably correct. They most likely use strain gauges and load till they get max pressure. Which seems to be between 62,940 and 63,400 PSI. If the bullet has a long bearing surface you may hit pressure max before you run out of room for powder.

I think the reason the 300 RUM uses 11.9 Gr. and the Wby 10.2 Grs. more to get there is because their larger cases build pressure slower because of all the air space left in the case that gets compressed. So you have to fill the larger cases more to get to max pressure.

This is an interesting phenomenon you have recognised here. First time I have seen anything like it. I'm not a expert loader or expert on internal ballistics or anything, so I am really just trying to explain it based some rather simple basics and taking faith that the info they provide it correct.

Seems a 220 MK wouldn't be a very efficient bullet for a big 30 Cal magnum.

 

[smithjasona1978]

I was under the impression that the reason the military picked the 220 smk for their 300 win mag sniper round was because at the time it was done that was the highest bc 30 cal bullet out there.

 

[smithjasona1978]

I sure wish that some of the other guys would chime in on this. Stuff like this is what worries me. Makes me want to just live with factory ammo and a barrel tuner.

 

[Barrelnut]

Didn't say it was not a good bullet for the 300WM. It is probably a very efficient, effective, and accurate bullet for a 300WM and that is why the military uses it for a 300WM.

What I am trying to convey here is that it is not a very efficient bullet for a BIG 30 magnum like a 300 RUM, and 300 Wby. Probably would not be an efficient bullet for a 30 Nosler either.

I do load for a 300 RUM and a 300WSM. So I do have an idea about what velocities they can run.

Would be nice to hear from someone who actually uses a 220 MK in a 300 RUM.

 

[smithjasona1978]

Agreed. Pipe up guys. Who's shooting 220 smk bullets nowadays??