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Build advice for a modern safari rifle

 
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  #22  
Old 12-26-2012, 07:04 PM
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Re: Build advice for a modern safari rifle

Soot on the case pretty much always means the pressure is too low. The appearance of the primer would support the low pressure theory.
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  #23  
Old 12-26-2012, 10:37 PM
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Re: Build advice for a modern safari rifle

Yup! That look like one strange case. Nice looking target rifle tho.

The only time I had close to that much soot on the case walls was from shooting a box of 375H+H in my 458 Lott. You don't have a fluted chamber on that do you.
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  #24  
Old 12-27-2012, 02:26 AM
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Re: Build advice for a modern safari rifle

My trips to Africa were both combos for plains game and dangerous game, buffalo and lion. I brought two rifles after my first trip a 375 H&H Whitworth,and a 500-450 H&H Double. The first trip i brought only my 375 which I used on a buffalo. The 375 was perfect for the plains game, but seemed underpowered for buffalo. I don't believe a couple hundred FPS extra velocity would have made much difference. My lion(tracked in Botswanna), and buffalo were all shot at 20-25 yards. At close quarters in the thick brush I prefer the bigger bores for mean guys. The difference in killing power is quite noticeable. IMHO.
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  #25  
Old 12-27-2012, 06:03 AM
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Join Date: Apr 2012
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Re: Build advice for a modern safari rifle

These are the loads I have been working on for the 7mm RUM:-
  • All loads are with Berger 180gr VLD's
I'm a big fan of Berger and I built this rifle especially to benefit from thier .659 high BC offering.

The photo is with Retumbo - (I did a bit of research and it came up as a good mag / ultra mag powder)
  • Nosler custom brass - new
  • Fed GM215M primmers - Large rifle-magnum-match
  • Berger 7mm 180gr VLD
.284" Ogive to the land was 3.3920" ~ my loads were seated 3.1410"
(251 tho freebore) this gave me what I felt was 'enough' bullet in the case mouth.

Powder Charges:-

Picutres Shown ~ Retumbo 86gr - this was the max charge!

Vitavori N170 89gr faired much the same - I carefully loaded that way over the max and still got sooting (the max was 87gr - I loaded upto 89gr and still got sooting) Velocity was also very poor - around 3000fps

I was hoping for 3100 -3200fps range (the rifle has a 32" barrel and I thought the cartridge is capable of much more - my friend loads a factory rifle in 30-06 with 180gr bullets nearly upto that speed with no issues - 2990 fps)

I did beter with Vitavori N165 but its not listed on Walts data - the fastest powder he lists is H1000 at a burn rate of 118

Powder Burn Rates:-

N170 ~123 (heavy sooting)

Retumbo ~ 121 (very heavy sooting)

Reloader 25 ~ 120

H1000 ~ 118

IMR7828 ~ 116

Reloader 22 ~ 113 (great in my .300wm loads)

N165 ~ 112* this powder worked o.k, I wanted to try some others but I may have to go back to using it if I dont get anywhere.

With regards to the photo:-
  • Crattering of the primer - is that high pressure?
  • Plunger mark on the head - is that high pressure?
  • Sooting to that level - is that really low pressure?
Is the fact the case is not expanding hard enough because of low pressue it is not gripping in the chamber and causing these misleading high pressure signs?
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  #26  
Old 12-27-2012, 08:43 AM
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Join Date: Dec 2010
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Re: Build advice for a modern safari rifle

The primer is not "cratered" and looks to have been shot in a low pressure load to me. Also, the soot on the case means low pressure to me. If you want added confirmation, look down the barrel after you shoot; if there is a lot of powder residue in the bore that is added confirmation of a low pressure load. Also, if you were shooting an excessively high pressure load, you would probably be getting a sticky bolt lift and scuffing of the head of the case from the bolt.

You seem preoccupied with Berger's data and with powder burn rate. You can have several powders with very similar burn rates and have one that will shoot better than the others. You also could use data from other bullet purveyors for 175 to 180 gr. jacketed lead core bullets with your Berger bullets.

As for "maximum" charges, take a look at different reloading manuals and cartridges. I've found instances where a maximum charge in one manual was about the starting charge in another. That is because chambers, barrels, throats, free bore, powder lots, cases and primer lots varied among the various testers. Thus, a maximum charge in a manual may not be the maximum charge for your gun and components.
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  #27  
Old 12-27-2012, 08:59 AM
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Re: Build advice for a modern safari rifle

Did you use the same primer lot for all of the tests?
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  #28  
Old 12-27-2012, 09:17 AM
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Join Date: Sep 2005
Location: Kalifornicated
Posts: 338
Re: Build advice for a modern safari rifle

I, too, have never seen that much soot, wow.....

How much NK tension? Has the brass been annealed? how many firings on the brass?

I would try a different lot of primer, but before that I would load a few up with the bullet a lot closer to the L/G's. I understand the issue with the high pressure cases, but it is accuracy you are looking for, not another 50 fps. This could also help you figure out the issue with the soot.

Nice looking rig...
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