300 Ultra 220gr SMK data with RL25 and Retumbo from Sierra

[Brent]

If you need it here's a reference. Probably will be listed in the new manual next year but this is what Paul at Sierra gave me for a start.

RL25,

72.3 - 91.5gr
89.0gr was an accurate load for them.


Retumbo,

78.2 - 95.0gr

A 26" barrel produced 3000 fps too.

 

[Jon A]

Anybody have the new Sierra manual yet? If so, is that 95 grain Retumbo load the one they list?

Oh, and while you have it open, what do they list for the 200?

Thanks.

 

[Brent]

I haven't looked at their website or their new manual, but I wonder also if they go that high in either.

I never made it past 89gr with Retumbo and the 220 without stiff bolt lift, even though pressure on the Oehler 43 indicated I was at about 63k psi. 88gr is what I settled on.

I have yet to go back and check to see what kind of stiffness and psi I get with FL sized cases, but the 178 A-Max showed psi signs down low too, accuracy with both sucked using Retumbo at those charges. I still have the pound of powder sitting there waiting to check some more 220's when I get some.

Let me know what you come up with Jon. My OAL was 2.710"... .050" off the lands.

 

[Boyd Heaton]

I got to 86gr of Retumbo with a 220 in mine.Velocity was 3122 in a 30" barrel

 

[Tim Behle]

Finally, something I can use this new manual for!

The loads Brent listed are the same ones found in the book.

For the 200 gr. they list:<UL TYPE=SQUARE><LI>IMR4831 73.4-82.7 <LI>XMR310076.3-86.5 <LI>H4831SC 73.8-84.0 <LI> MagPro 76.3-86.8 <LI> RE-22 73.4-85.0 <LI>WXR 74.6-86.2 <LI>IMR7828 76.6-89.0 <LI> AA8700 94.0-110.0 <LI> H1000 79.8-93.5 <LI> Magnum 79.2-91.8 <LI> RE25 76.0-92.0 <LI> Retumbo 79.3-95.7 <LI> H870 87.5-102.7 <LI> Viht N170 81.0-97.0 [/list]

Accuracy load in the book is H4831SC 80.6 for 2900
Hunting load is XMR3100 86.5 for 3050

I did my best to avoid any typo's, but you should probably double check the numbers for yourself.

Tim

 

[Jon A]

Thanks a bunch, Tim! What was the highest velocity listed for the 200? Was it a 26" tube?

I know, I'm cheap.

 

[Brent]

Thanks Tim.

I only got to about 87gr with RL25 and the 220 SMK without heading over about 68k psi. No stiff bolt or any other psi signs with RL25 though, groups were showing promise at 87gr too.

Interesting that H870 and AA8700 are so different in max load charge weights...

This data of Sierras here, it's one more reason to work up to max, starting from well below it too. My first time out was with a starting load of 88gr RL25, I think I made it to 89gr, went home and pulled all the rest that went up to 92gr, that always bites!

I do admit, not too often anymore that this really happens with loading manuals... you never can know though until you start working up a load.

 

[Brent]

Here's a reply from Paul at Sierra concerning the early pressure signs with Retumbo. I don't really know what to make of it, but FWIW;

Hi Brent,
I think that in some case capacities Retumbo can reach a point of having pressure spikes.Especially when combined with certain jacket hardness.This isn't something that I can prove all that easy,but the data I passed along to you was from our new 5th edition manual where we went clear to 95.0 grs.This is something we're looking into now and should have more info later down the road.Thanks for letting me know about this.
Paul &gt; Hi Paul,

 

[Tim Behle]

Jon,

They used a 26" Savage 116 with a 1-10 twist.

The highest speeds listed were 3100 fps with the max loads for IMR7828, AA8700, RE-25, Retumbo, H870, and N170