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excess pressure?

 
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  #1  
Old 02-07-2012, 10:59 PM
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excess pressure?

how much is too much? I have some very faint ejector marks and there is some brass specks on the bolt face with 92 grains of retumbo. This is brand new Lapua brass. I like this load but I dont want to screw anything up. How much shouldI back down from here? The mark is just below the trademark L. Ryan
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Old 02-08-2012, 12:30 AM
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Re: excess pressure?

What bullet are you shooting?
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Old 02-08-2012, 12:38 AM
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Re: excess pressure?

I am shooting 300 grain smk's in a savage 110 fcp. Ryan
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Old 02-08-2012, 02:00 AM
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Re: excess pressure?

I normally back up .2 and call it a day if Im doing my load dev, in the summer, if not then I'll back up .2 at a time as temp goes up until I'm at my max average ambient air temp with no ejector stamp
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Old 02-08-2012, 09:28 AM
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Re: excess pressure?

Not knowing anything about the cartridge, and solely based on the picture, I don't see any problem.
Is there difficult extraction?
Any issues in sizing this brass?

A little brass on the bolt face, slight ejector marks, flattening of primers(not failing),, seems normal and fine to me.
I get this with a bunch of cartridges that are NOT loaded to high pressures, and the brass is lasting forever.
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Old 02-08-2012, 09:38 AM
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Re: excess pressure?

Most everything 85% of what I shoot are savage rrifles and a lot of them will leave just a slight ejector mark, especially when they are newer and the ejector spring has heavy tension. As long as bolt lift is still easy I see no reason to change it, there are no obvious signs of pressure on the primer so I wouldn't change it. I get that mark on mild plincking loads sometimes, if you can't find anyother sign of pressure then its likely just the ejector.
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Old 02-08-2012, 10:56 AM
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Re: excess pressure?

Quote:
Originally Posted by bigry26 View Post
how much is too much? I have some very faint ejector marks and there is some brass specks on the bolt face with 92 grains of retumbo. This is brand new Lapua brass. I like this load but I dont want to screw anything up. How much shouldI back down from here? The mark is just below the trademark L. Ryan
I copied this from some site - sorry I did not make a note of where to find:

"The way to tell if the pressure is low:

1. Unburned powder in the barrel pretty much always means low.

2. Primer backed out of the primer pocket (i.e., not flattened) usually means low.

3. What does the manual say? If you're at the lower end of recommended loads, then the pressure is probably low.

The way to tell if the pressure is high:

1. Sticky ejection. If ejection is sticky in a clean firearm in good mechanical condition then the pressure is high.

2. Primer flattened clear out to the edges.

3. Loads at the upper end of those recommended in a manual.

4. Blown or pierced primers.

5. Rapidly expanding primer pockets on reloading and/or poor brass life. Defective brass can also cause these signs.

6. Group sizes that have been decreasing as a load is increased and then start to widen again.

7. Cases from a semiauto that have been landing in about the same place and then start to be thrown erratically to markedly different places.

8. Cases from a semiauto on which scuff marks start to appear on the body of ejected cases.

9. Extractor marks swaged into the case head.

I've probably missed some.

You have to know an individual gun as well because different guns and different actions types will show signs of pressure in different sequences.

Now I'm sure you've all heard about light powder charges in large capacity cases using slow powders (it can happen with fast powders as well). The result can be high pressure signs like flattened primers, splintered stocks and sticky ejection as well as hang fires. What happens is that the bullet starts to engage the bore but the pressure isn't quite high enough to push it clear through. The powder is still burning and the pressure keeps rising until it's high enough to push the bullet that was kind of stuck, out of the bore. As we all know, it takes quite a bit less pressure to get a bullet going down the bore with a little jump between the bullet and the lands than to start a bullet that is already engaging the lands. You might think of it as the closest you can get to a squib load (a load with which the bullets remain in the bore) without having a squib load.

So, in the latter case, though the load is light, the pressure is quite high. In other words, case head smearing, sticky bolt lift, very flattened primers are signs of high pressure even if the powder charge is low unless the chamber is dirty or there is some mechanical defect in the firearm."


According to my observation you do not have a high pressure sign. The primer is not smeared in the primer pocket and is not flattened. I would say this is a good pressure load given that all other conditions are favourable. Lastly when you press the primer out and you look at it with multiplyer glasses and you see a "flat-hat-top" you have high pressure, but when the top of the "hat" is still rounded, pressure is still fine.
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