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Old 09-14-2014, 03:05 AM
trotterlg trotterlg is offline
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Default A "what causes pressure the most" question.

The setup: Savage 10 action, GM 1 in 12 25 inch barrel. PTG reamer, now set at .003 clearance on the necks. Zero free bore. I had the chamber cut with 45 degree lead into the rifling and seated the bullets at contact. At 30 gr of 8208 and 35gr Bergers I have slightly hard bolt lift and at 30.5gr I have sticky extraction. I think this is fairly low charge to be getting pressure problems at. So, I cut a zero FB 1 degree lead into the rifling. Haven't tried it yet. I am wondering which item, the fairly tight neck or the steep lead caused the problems. I could ream the neck another thousanths or so or just go with the 1 degree lead. Anyone have any experience with either of these things? Larry
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Old 09-14-2014, 03:26 AM
Bill K Bill K is offline
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Default A "what causes pressure ?

If this is in a 204 R. Hodgdon shows around 28 grains as max for 8208 and 35 grain bullets. That could be your issue, over load. Bill K
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Old 09-14-2014, 03:47 AM
trotterlg trotterlg is offline
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Sorry, skipped the most important part, it is a 20BR. Larry
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Old 09-14-2014, 03:47 AM
ab_bentley ab_bentley is offline
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Actually Larry it's up there. In my 22BR I max out at 32gr of XBR and a 40gr bullet.


Adam
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Old 09-14-2014, 04:11 AM
trotterlg trotterlg is offline
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Well, I will load some more of the 30gr of 8208 and see how the 1 degree lead does, bound to be a little less pressure. I burned up all the 30gr loads before I put up the crono. I will shoot some across it first to see what it is doing. could be 29 point something will be max. Larry
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Old 09-14-2014, 07:42 AM
georgeld georgeld is offline
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I'd back 'em off the lands a touch.
Tight neck will do it too as you/I found out with my NEF that
time. Every shot had been splitting necks til Paul reamed it out to .203" from .195"
Cured that problem.
Only other problem I've had so far was trying to find max and went over .1gr and blew it up breaking your fine work.
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Last edited by georgeld; 09-15-2014 at 05:59 AM. Reason: typo
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Old 09-14-2014, 08:05 AM
Chickenthief Chickenthief is offline
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Think of it this way: All Weatherbys are cut with a country mile of freebore just to keep pressures down in them overly big cartridges.
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Old 09-14-2014, 11:22 AM
wally bennett wally bennett is offline
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The most pressure problem is always the same ITS THE LOADER STARTING TO HIGH.
Hard lift and extraction is the first sign and it makes no difference if its the freebore or tight neck its still too high a charge.
Wally
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Old 09-14-2014, 04:48 PM
Daryl Daryl is offline
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I don't understand the 45 degrees notation. My leade to throat angles (Pacific) are 1.5 and 2.0 degrees, for the .17's and I think my .220 Swift IMP reamer has 3 degrees (might only be 2 degrees) in the throat.

The only 45 degree is the mean little shoulder at the end of the chamber's neck, (which is smaller than bullet diameter) running up from the 90 degree chamber end to the leade or start of the throat. I also have 0" leade on those chambering reamers.

I also think the pressure signs have more to do with starting too high with full "binding" contact of the bullet in the throat.
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Old 09-14-2014, 04:59 PM
Nor Cal Mikie Nor Cal Mikie is offline
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The biggest cause of over pressure is TOO MUCH POWDER!
Book says max load it XXX so I'll start there.
Back way off and work your way back up to a "comfortable load".
And leave yourself some wiggle room when it comes to loads.
You load and tune at 70*. Your load is at Max or damn close.
You go shooting and it's 100*+. You have to beat the bolt open.
A lower load will still get you the accuracy you're after, your brass doesn't get hammered and lasts longer. You don't have to be a rocket scientist to figure that out.
You don't have to be fast to be accurate! Your intended target won't know the difference between 3000 and 4000 FPS.
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