300 RUM, 240 SMK, US869 Initial Results

[Jon A]

Well, now I feel really silly for not having the chronograph with me last time.

This barrel must be slick as snot. For a sanity check I clocked my old 200 AccuBond load with 95 grains of Retumbo. That load gave 3186 in the old 26" barrel. In the new 26.7" barrel it gave 3139. It looks like this barrel will take at least 2 grains more just to get back up to the speed of the old one.

I chronographed 7 rounds of 100 grains of US 869 behind the 240 SMK. Average velocity, 2879 fps. OK, I was being conservative, careful, etc which I'm all for...but now it's time to add some more powder!

It all makes sense now, the tiny bit of "feel" chambering the empty case from 102 grains before...that's what's normal. You ought to at least be able to feel you're chambering something. It's just all the rest were running at starting load pressures. That's what I think, anyway.

Time to start adding powder until I find the ceiling.

 

[Eaglet]

Jon A,

[ QUOTE ]
I chronographed 7 rounds of 100 grains of US 869 behind the 240 SMK. Average velocity, 2879 fps.

[/ QUOTE ]

Not bad at all! I like that. 2875 f/sec is the max veloc. Hodgdon is calling for the 220 gr. SMK.

Thanks for sharing. Keep us posted!

 

[Jon A]

Yeah, but keep in mind that's at 55,200 psi (same as the starting loads for other powders) and with a 24" barrel--just scratching the surface of its potential. I ain't givin' up yet.... /ubbthreads/images/graemlins/wink.gif

 

[jwp475]

[ QUOTE ]
just scratching the surface of its potential. I ain't givin' up yet.[ QUOTE ]



Determination I like that!!!!!!!!

 

[Fiftydriver]

Jon A,

Not uncommon to see the Lilja 3 grooves drop pressure significantly with these long bullets compared to factory barrels. Even in spite of the tighter chamber and throat.

Keep us posted as to where she tops out.

Kirby Allen(50)

 

[Stormrider]

I get 2980 with the Berger 210VLD and 94 Retumbo out of a 26" barrel seated magazine length and it seems to group about like yours at 100. Haven't worked with it at longer ranges yet.

 

[Jon A]

Round II is complete. I chronographed one round each at the below charges. It was right at 70 degrees, chronograph was a Oehler M35 about 18' from the muzzle:

102 2971
103 2978
104 3023
105 3075 (slight pressure signs)

I shot one three shot group at 103 grains:

Average velocity, 3007 fps.

While I was surprised with the slickness of the new barrel, in the end this powder performed exactly as I had expected (or hoped) it would for this application. It'll easily match the speed, consistency and accuracy of H870. It'll beat Retumbo by a good 100 fps with this bullet. If it's nearly as temp stable as advertised, that will be a very valuable bonus (one reason I've shied away from WC872). The density is great of you've ever tried H50BMG--even the with the 104 grain load, the powder would still shake in the case even with the long 240 stuffed down to a 3.60" OAL (with fireformed cases this time). In short, a perfect replacement for H870. It's everything H870 was but better (H870 was pretty temp unstable), at least in this application.

I'd expect the typical 26" 300 RUM to top out around 99 grains in the 2950-2975 fps range with this bullet.

Now, the only piece of the puzzle that is missing for me is some heavier, higher BC bullets from Richard. I figure I can do around 2925 or so with a 250. If Richard can make one with a BC that blows away the 240, which is very possible, it'll take the old 300 RUM to the next level at extreme ranges. Of course, the 240 @ 3000 is no slouch in the meantime.

 

[Eaglet]

Jon A,
Good Job! Thank you!!
JOM

 

[Eaglet]

Jon A,
What is opinion of the would be performance of that powder (US869) with the 210 grains Berger?

 

[Jon A]

I think this powder will definately be at its best with 220+ bullets. But there's only one way to find out. I think it's possible you may get some impressive velocities with it from the 210. The problem is stuffing all that powder into the case, seating a bullet on top and maintaining your accuracy.

Like what I did with H870 and the 200 AccuBond--3250 fps easy. But accuracy sucked. Maybe with a bit more care I could have fixed the accuracy problem, but with bullets that light Retumbo came close enough in velocity and was so much nicer to deal with I figured it wasn't worth trying anymore.

 

[bailey1474]

Looks like you have a winner. I might have to try a little of that stuff w/the 240s. Your getting 150 fps more than I am w/Retumbo.

Eaglet,
Too slow for the 210s. Like JonA said, speed was great but accuract sucked!!

 

[Fiftydriver]

Jon A,

Looks like a good load! Congrats. Now time to stretch her out. Played with some US869 this weekend in my 338 Kahn and had some good results but will post those on another post.

Let us know how she does down range!!

Kirby Allen(50)

 

[Eaglet]

Thanks friend, I was really suspecting that!

 

[jmden]

Very nice. Keep us posted.

Heard any timeframe on Richard's heavier .308 bullets?