Pressure signs

243winxb

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Joined
Sep 9, 2016
Messages
612
Location
USA
Oil on brass will cause hard bolt lift, pressure signs. The head to datum measurement will be longer then measured before. No spring back of the brass.
Just oiled one 6.5 CM factory ammo to see what happens. Not a good thing.

PressureSigns.jpg
 

NVGuide

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Jun 24, 2021
Messages
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Location
Searchlight, NV
When I was doing load development for my 6.5 PRC, I seemed to develop o heavy bolt lift too early. I went back home and cleaned the chamber with alcohol and it resolved my heavy bolt lift.
X2 here. Was developing a load for a friends 7mm REM Mag and had stiff bolt lift from word go. Inspection of fired brass showed signs of problems inside the chamber at the shoulder. Turned out to be leftover contaminates from a barrel cleaning that had hardened over time. Thorough cleaning of chamber and a quick polish made all the problems go away.
 

Ucsdryder

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Jan 23, 2016
Messages
323
I’m pretty sure my issue is brass because in the same range session I used virgin and 1x fired. The virgin was fine. I’m going to try and bump the shoulders slightly more to get closer to the virgin brass.
 

MagnumManiac

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Feb 25, 2008
Messages
3,941
I’m pretty sure my issue is brass because in the same range session I used virgin and 1x fired. The virgin was fine. I’m going to try and bump the shoulders slightly more to get closer to the virgin brass.
This is not a good idea. This will only give you too much head space.
Your issue may have absolutely nothing to do with your brass…if you haven’t measured it, then you have no clue.
You may have a rough chamber, burrs left over from chambering or even machining marks left in the chamber.
Measuring your fired brass will tell you a lot.

Cheers.
 

Ucsdryder

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Joined
Jan 23, 2016
Messages
323
This is not a good idea. This will only give you too much head space.
Your issue may have absolutely nothing to do with your brass…if you haven’t measured it, then you have no clue.
You may have a rough chamber, burrs left over from chambering or even machining marks left in the chamber.
Measuring your fired brass will tell you a lot.

Cheers.
I have virgin and 1x fired on hand. Besides length at shoulder what should I be measuring? I have neck measurements, base to shoulder and overall length measured. The base to shoulder on the 1
All good info so far.
To eliminate possibilities, you now need to take measurements.
First off, measure these points on a NEW piece of brass.
.200” up from the base, you can use you caliper to scribe a line there.
The neck diameter, without a bullet, and with a bullet.
The shoulder position with a set of headspace comparators.
With a fired case, measure all of these again.
Regarding neck clearance in the chamber, it should be a MINIMUM of .003” LARGER than a neck with a bullet in it. My personal max is .005”, but I see many at .006”.
The measurement at .200” up from the base is critical, it should not be more than .005”. And, it should measure the same ALL THE WAY AROUND THE CASE DIAMETER. If it changes, your chamber is an egg shape. I use a micrometer accurate to .0001” for measuring case diameter, a caliper is not accurate enough.
Check how a fired case feels when you chamber it after firing when the case is cold. If there is resistance, then your chamber may not be round. In that case, use a sharpie and colour in the entire case and carefully chamber it and carefully remove it, I normally do this with the firing pin assembly removed and the plunger ejector, if one is fitted.
Look to see if only one side or the ink rubs off.
Give all this a go, and get back to us with before and after measurements, the answer lies there somewhere if it truly isn’t a pressure issue.

Cheers.

Here are the measurements. The rl26 was 59.1gr and the h1000 was 62.6. I hit pressure with h1000 at 64.5. The 1.635” on the shoulder is whats getting me the sticky bolt.
 

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