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#12260030 - 09/09/17 unexpected result  
Joined: Apr 2017
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ohio_jeff Offline
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ohio_jeff  Offline
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Here's the situation:
gun: Browning A-bolt, .338WM, 26" barrel
load: 225gr. Barnes TTSX, 71.0gr. Reloder 19, WLRM primer, R-P case, COAL 3.370 which is 96 off the lands, chronos at 2830.

I have been shooting this load for over a year, it has been at the range several times and hunting more than once. Never any sign of
pressure issues. Accuracy has been excellent.

I decided to try to develop another load for same rifle:
load: 200gr. Accubond, Reloader 19, WLRM primer, Nosler case, COAL 3.366 (same off the lands as the TTSX).
I loaded a powder ladder from 71.0 to 76.0 in steps of 1.0 up to 74.0 and 0.5 after that.
Nosler powder range for that load (7th edition) is 72.0 - 76.0.
Hornady, Lyman, Speer and Lee all have similar max loads (althrough Lee is a bit more optimistic at 78.0).

The first shot, 71.0gr., gave a normal report and chronoed at 2799, slightly lower than the 225gr. with the same charge.
Upon inspecting the fired case, I observed a very flat primer with some black residue around it. There was no cratering
and no bolt impression in the case head.

I would call that an early high pressure indication. So I put that load away for the day.

Now, powder charge is well below the expected maximum, and the same charge that behaves well with a heavier bullet.
Also, the lighter 200gr bullet seems to be flying slower than the heavier 225gr. in a similar load.

I am using a different case. Nosler brass may be enough thicker to cause somewhat higher pressure, but this much
of a difference?

What am I missing here?

CMG 300 BP

#12260169 - 09/09/17 Re: unexpected result [Re: ohio_jeff]  
Joined: Feb 2014
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SEM Offline
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SEM  Offline
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Posts: 814
Golden State
several factors, not enough powder in the case can cause pressure spikes just as much as over charges, incomplete burn or even complete burn early before bullet has cleared the rifle, You already suspect the brass I suspect the charge, The bullets you are comparing are also quite a lot different bearing surface is one, just a thought

sorry I forgot to ask, you fired only one round ?

Last edited by SEM; 09/09/17.
#12260401 - 09/09/17 Re: unexpected result [Re: SEM]  
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ohio_jeff Offline
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ohio_jeff  Offline
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Posts: 24
Thank you SEM, very interesting. Yes, the bullets certainly have a different bearing surface. I fired the first three shots of the ladder (71.0gr, 72.0gr. and 73.0gr.) All three fired cases looked essentially the same. I stopped there.
I ran the load through QuickLoad, which estimates that 96.5% of the powder (at 71.0gr.) should have burned. I weighed the bullets to make sure they weren't in a mis-labelled box: 199.9 - 200.2gr.

I also backed my TTSX load off 2gr. and loaded 69.0, 70.0 and 71.0gr in the new nosler cases (in stead of the re-loaded R-P cases I have been using). In that load with the TTSX, the fired nosler cases look just like the fired R-P cases (no excessive flattening and no black powder on the head), suggesting the case is not the issue.

However, I do notice that the nosler cases are shorter than I expected. Out of the box new they are 2.484 - 2.489, consistently under the "trim length" for the cartridge. I have been keeping my R-P cases in the 2.491 - 2.499 range. Could that be a factor, I wonder?

#12261152 - 09/09/17 Re: unexpected result [Re: ohio_jeff]  
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SEM Offline
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SEM  Offline
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Golden State
cases being short should not make that much of a difference even if the jump was a little longer, well when you figure it out let us know

#12261241 - 09/09/17 Re: unexpected result [Re: ohio_jeff]  
Joined: Mar 2005
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alpinecrick Online content
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alpinecrick  Online Content
Campfire Kahuna

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Western Slope of Colorado

My first guess is soft Noz brass. The Noz brass I have for two different cartridges (30-06 and 243) flows into the ejector with minimum loads.........

Casey


Casey

Not being married to any particular political party sure makes it a lot easier to look at the world more objectively...
Alpha

#12261411 - 09/09/17 Re: unexpected result [Re: ohio_jeff]  
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antelope_sniper Online content
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antelope_sniper  Online Content
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Colorado
Sample of one doesn't tell you much.

You need to shoot a few more so you actually have some data to assess.


Nobody spends somebody else’s money as carefully as he spends his own.
The U.S Government has a unique capacity for getting things upside down.
Milton Friedman.

Go quiet or full tilt, just don't get caught in the middle of the stupids. DD

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