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Signs of pressure?

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Signs of pressure?

Old 07-21-2007, 08:17 AM
  #1  
Spike
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Join Date: Apr 2007
Location: Rockbridge co. VA
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Default Signs of pressure?

My dad and I are going to be reloading for his 7mmRem and my .300RSUAM to start with. I bought IMR4350 to use. And looking through my reloading manuel, this powder isnt listed as the most accurate for the two calibers, but velocity between the accuracy round and the IMR4350 isnt but a few fps different. The one thing I was noticing that the manuel showed is that with the IMR4350 loaded with max grains that pressure is always slightly higher....what are some pressure signs to look for as we work up a load?

**note-we we also be reloading for his .270win and maybe for my .260 remington...is the IMR4350 a sufficient "all-around" powder? thanks
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Old 07-21-2007, 08:36 AM
  #2  
bigcountry
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Default RE: Signs of pressure?

Yea, it will work, but RL22 might be better for your two magnums. Or H4831sc.

I use 4350 for my 270win.

Don't worry about about most accurate loads and stuff in your manual. Doesn't mean a thing. You have going to see alot of differences between manual to manual.

Just make note of your bolt lift, study your primers after every shot. And work up in 1gr increments for most bullets like SST, partitions, Bullistic tips, and gamekings, but be careful with barnes X, failsafes, TSX's, and bonded bearclaws. They will build pressure quick and unexpected. Really need a barnes manual for these. Start 10% down.
 
Old 07-21-2007, 10:15 AM
  #3  
Giant Nontypical
 
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Default RE: Signs of pressure?

And looking through my reloading manuel, this powder isnt listed as the most accurate for the two calibers,
Don't put much faith in so called "accuracy loads".Those are simply the most accurate loads in one test rifle,and they may not be overly accurate in your rifle.In some rifles that I have loaded for,the so called accuracy load was the least accurate load that I tested.
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Old 07-21-2007, 10:54 AM
  #4  
Fork Horn
 
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Default RE: Signs of pressure?

Don't put too much trust in so called pressure signs either. When they show up you have too much pressure, but if they don't show doesn't mean you are safe.

Signs to look for:

Primers: The primer is completely flat. The primer has no radius left on the outer edge and has filed the whole primer pocket. You can also look for 'cratering' which is a raised edge around the primer dent. This is caused by the primer trying to flow back around the firing pin into the firing pin hole.

Brass flow: The bolt lifts hard. The case is being stretched back against the bolt. Brass has a little spring back, and so does the steel bolt. When you get too much pressure, the bolt flexes back and allows the brass to stretch longer. Then the bolt springs back and presses against the brass. Under normal pressure, the brass will spring back and still be smaller than your chamber, and the bolt opens easily. Under higher pressure, the steel chamber and bolt flex too and allow the brass to expand larger than the chamber, then the chamber and bolt spring back and a the friction makes the bolt lift hard. The brass will also flow, distorting the headstamp and making a shiny spot where the brass flows into the extractor groove. The bolt may actually have to shave off a part of the casehead in order to open.

I have seen several articles that state that many times you can be well over allowable pressures and never see pressure signs. So if you have signs, you are too hot. If you don't, it doesn't mean you have a bunch of room to play with over the max charge.

You also get false pressure signs that mean you have too low pressure. Black soot past the shoulder of the case means the pressure isn't high enough to stretch the case into a good seal on the shoulder.

Primers sticking out past the back of the case can mean the pressure isn't high enought to stretch the casehead back against the bolt and force it back in.
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Old 07-21-2007, 12:11 PM
  #5  
Giant Nontypical
 
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Default RE: Signs of pressure?

I find the most reliable pressure sign to be loose primer pockets after a few firings.As such,I usually reuse a small number of cases for a few firings before loading up any large amounts of ammunition.
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Old 07-21-2007, 12:26 PM
  #6  
Fork Horn
 
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Default RE: Signs of pressure?

ORIGINAL: stubblejumper

I find the most reliable pressure sign to be loose primer pockets after a few firings.As such,I usually reuse a small number of cases for a few firings before loading up any large amounts of ammunition.
I read an artlcle by Jack O'conner in an old speer manual that basically stated that was the best test. If your primer pockets are not loose after 6-8 firings of a case, then you are OK. I don't think that would apply to low pressure rounds like the 30-30 and 45-70.
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