This can't be good!

CBS

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May 21, 2008
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we need more details . so it's a 7 rem mag , 168 berger , how much retumbo ? and what's your COAL measured off the tip ?


retumbo is a slow powder for this combo . it will be hard to get enough in the case to get the pressure up .


I'm guessing you're in the 70 - 71 grain with 48000 - 50000 psi
3.77" oal 69 gr retumbo
 

sedancowboy

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3.77" oal 69 gr retumbo

Something is really wrong here! A COAL of 3.77 would have the boattail completely out of the case. .3.290 is SAMMI. 69 Grs of Retumbo would net pressure around 45K with bullet seated to 3.377 and a velocity of 2800 fps. According to QuickLOAD. All signs and info so far leads me to the conclusion that you have low pressure with a slow powder. Or maybe a combo of things hard brass + low pressure + bad Chronograph. I would not continue to use this load until the cause is resolved. Don't get hung up on Low ES and wanting a load to work when it will not. Nosler does list Retumbo as the slowest powder for a 168 gr bullet but it has more bearing surface than a Berger which would create more pressure than the Berger.
 

del2les

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I have seen this with long throats and excessive bullet length not allowing for a sufficient bullet-neck tension and proper ignition of a slow powder that results in low pressure ignition, leakage and then pressure spike. Since you were testing bullet seating depths and this was your longer one "3.77 (?)", this could have been the case. Hard necks from lack of proper annealing can also contribute to this phenomenon.
 
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What is going on? I didn't think this was a hot load. I've seen these before but never had one happen to me and never knew what caused it.
I have had this exact thing happen. Too little neck tension. The primer and early burn push the bullet out of the case before sufficient pressure to seal the chamber exists. The bullet lodges in the lands, and the pressure gets on the outside of the case. The case crushes, and a secondary pressure spike pushes the bullet down the bore.
I cured thus in my 257 weatherby by using a lee collet crimp die. This held the bullet until a uniform pressure developed and all the problems and crushed cases stopped.
 

Indian7953

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Feb 15, 2015
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Hodgdons load data for a 170 [no 168 data] starts at 71grn & max is 75grn [compressed]

Bergers Data max load is 71.2grn at 106% case capacity.

You need some RL25 or H1000

Too low pressure & too slow of powder to get anywhere near the max load.
How many of these cartridges did you shoot of the same overall length and powder charge? If you fire multiple ones and this was the only one that did it you may have had a light powder charge in that particular case.
 

twister

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that charge weight is very close to what i use with a 195, you probably want something a bit faster burning or heavier bullet.
 

CBS

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Sorry guys the OAL was 3.57 not 3.77.

Primers were actually quite flat. That could be from the awkward pressure I guess.

Time to start over. Might be time for a new barrel anyway. I've hot rod this one for a few years, shoots small 100yd groups with more powder but the es is so high that at longer ranges it doesn't group very good and is hard on brass.

I have less than a lb of h1000, but lots of rl26, rl22,

Anyone in n. New Mexico want to trade for retumbo? I have about 9#s to trade.
 

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twister

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Try and find some heavier bullets and stick with the Retumbo. The 195 at sealevel is 24 Moa to 1000 and 1766 FPS , and altitude helps it a lot.
 
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