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Powder Bridging for Kiwi Nate & Tang et al

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  #8  
Unread 02-19-2010, 04:19 AM
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Re: Powder Bridging for Kiwi Nate & Tang et al

Well, I can qualify my 7mm RUM experiences as being consistant if thats any help. Thing is, this was a .200" freebore chambering rather than the factory .400" freebore. I forgot to mention this in the beginning and I am very sorry about this, I had forgotten. I am not one to BS people so- my bad.

The range testing went like this (velocities are rounded to nearest 50fps):

162gr SST 86gr Retumbo 3100fps
162gr SST 86gr Retumbo 3300fps bolt jammed.
I thought that I had stuffed up my reloading so fired another shot:
162gr SST 86gr Retumbo 3100fps
Then another:
162gr SST 86gr Retumbo 3300fps bolt jammed.
Went back to the bench, cleaned the scales (thinking that they must be sticking). Loaded another few rounds:
First shot 162gr SST 86gr Retumbo 3300fps bolt locked up. No further testing done at 86gr- lesson (finally) learned.

Increased load to 90 grains Retumbo 3200fps. Max pressure, poor case life.

Freebore was increased to .400" as per factory specs and I started again with 91 grains Retumbo. Muzzle velocity was 3235fps.

Current pet load: 91gr Retumbo 180grVLD 3184fps. Groups .5MOA without brake, .3MOA with brake. I shoot it without the brake as I can't stand the noise and gas/ground debris blow back (spiral ports).

As for H50BMG. 94 grains behind the 162 grain bullet yeilds 2800fps, safe load. Can only guess that it could be reduced to 91 grains for 2700fps with regard to testing 162-180 grain bullets at reduced velocities. Would still have to take a 300-400 yard shot to duplicate 1000 yard shots.

It takes 102-104 grains of H50BMG to get the 7RUM up to pressure/ accuracy. Unfortunately, at these charge weights, its no different than hitting the bore with a gas cutting torch.
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  #9  
Unread 02-19-2010, 09:18 AM
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Re: Powder Bridging for Kiwi Nate & Tang et al

The lightest charge I've run in my 300 RUM is 83gr of RL22 behind a 180. That is around 89% load density.

I think Im going to try 97gr of Retumbo behind a 180 Interlock, and see where accuracy goes.
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  #10  
Unread 02-19-2010, 09:32 AM
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Re: Powder Bridging for Kiwi Nate & Tang et al

Quote:
Quote:
Originally Posted by Tang View Post
I think Im going to try 97gr of Retumbo behind a 180 Interlock, and see where accuracy goes.
I would work up to that. 97.5 gr of Retumbo is max behind my 180 E-Tips.

-Mark
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  #11  
Unread 02-19-2010, 01:37 PM
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Re: Powder Bridging for Kiwi Nate & Tang et al

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Originally Posted by Kiwi Nate View Post
. lesson (finally) learned.
3 seems to be the magic number for attempts. I think that's all the good Lord gives us.......
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  #12  
Unread 02-22-2010, 12:26 PM
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Re: Powder Bridging for Kiwi Nate & Tang et al

Try US869 for the 7mmRUM.
You won't have a bridging problem and will get good velocity as well.
It fills the case well and is very consistent.
My buddy has a 7mmRUM and we have been working up loads with his rifle.
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  #13  
Unread 02-22-2010, 01:29 PM
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Re: Powder Bridging for Kiwi Nate & Tang et al

Quote:
Originally Posted by royinidaho View Post
It sounds as if I may inadvertently experience some severely adverse results by downloading to simulate 1K impacts at 100 yds.

Me thinks I'll just pay the price of safety and shoot the full load at the 1k mark.

Starting to get some valuable information.

Kiwi, keep it coming.
What do you think about using an inert material on top of the reduced load for short range long range testing. Like corn meal, to keep the powder column from laying down in the case.

Just a thought.

Steve
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  #14  
Unread 02-22-2010, 01:51 PM
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Re: Powder Bridging for Kiwi Nate & Tang et al

Quote:
Quote:
Originally Posted by RockyMtnMT View Post
What do you think about using an inert material on top of the reduced load for short range long range testing. Like corn meal, to keep the powder column from laying down in the case.

Just a thought.

Steve
I'm glad it's just a thought
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