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Excessive headspace=lower muzzle velocity?

 
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Old 12-31-2011, 07:35 PM
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Excessive headspace=lower muzzle velocity?

Hi everyone first time poster so go easy one me. My question for you all is, does excessive headspace cause a slower muzzle velocity? Yesterday I went out to do some shooing at 700 yards. Using the same amount of elevation I always use I shot about three rounds at some steel. I noticed that the rounds were hitting about 7-10 inches low. I didn't give it much thought just dialed up some more elevation and started shooting again. Used this new dope for the rest of the time and was on target. Later that night I was cleaning up my brass and noticed that almost all of them had signs of thin wall around the case head. Brass had only been reloaded twice before. Checked some of the rounds that I had not shot yet with a hornady headspace gauge and notice the shoulders had been pushed back to far and causing to much headspace. Unfired brass was a little over 0.010" shorter than the fire cases. I reset my sizing die to fixed this issue. Anyway I got to thinking and was wonder if the excessive headspace caused my rounds to go low. I was thinking that since the brass and to expand more to fill the chamber that it would cause a loss in pressure resulting in a slower muzzle velocity. Am I thinking straight or just making excuses? Thanks.
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Old 12-31-2011, 07:38 PM
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Re: Excessive headspace=lower muzzle velocity?

I think you have it right. Energy spent stretching that case was not spent on pushing
the bullet.
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Old 12-31-2011, 07:51 PM
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Re: Excessive headspace=lower muzzle velocity?

temp will also play havoc on your velocity even using extreme powders. did you use a setting from a summer (warmer) velocity reading and now shooting in a colder enviroment? I lost 50fps in my edge from 75-80 degrees to now 35-45 degrees.
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Old 12-31-2011, 08:12 PM
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Re: Excessive headspace=lower muzzle velocity?

Excessive headspace = Blowed up gun. :(
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Old 12-31-2011, 10:00 PM
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Re: Excessive headspace=lower muzzle velocity?

Quote:
Originally Posted by PapaChunk View Post
Yesterday I went out to do some shooing at 700 yards.
What caliber and was the brass new brass, once fired or fired multiple times

Quote:
Originally Posted by PapaChunk View Post
Later that night I was cleaning up my brass and noticed that almost all of them had signs of thin wall around the case head.
What signs, do you have pics and how did you determine the signs

Quote:
Originally Posted by PapaChunk View Post
Checked some of the rounds that I had not shot yet with a hornady headspace gauge and notice the shoulders had been pushed back to far and causing to much headspace. Unfired brass was a little over 0.010" shorter than the fire cases.
.010" is not un-normal for an unbelted case going from a new case to a fired case. My Steyr 30-06 is .011". When you say the "shoulders had been pushed back too far", what was the difference in the measurements between the cases with the shoulders pushed back too far and a new case? A little more info

Quote:
Originally Posted by PapaChunk View Post
Anyway I got to thinking and was wonder if the excessive headspace caused my rounds to go low. I was thinking that since the brass and to expand more to fill the chamber that it would cause a loss in pressure resulting in a slower muzzle velocity. Am I thinking straight or just making excuses? Thanks.
Normally it takes so little pressure to expand the brass case in comparison to the pressures inside the chamber that it has little to no effect on pressure and velocity.
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Old 12-31-2011, 11:08 PM
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Re: Excessive headspace=lower muzzle velocity?

Quote:
Originally Posted by woods View Post
What caliber and was the brass new brass, once fired or fired multiple times
.308 Win
twice fired winchester brass


Quote:
Originally Posted by woods View Post
What signs, do you have pics and how did you determine the signs
Shiny ring around case head.




Quote:
Originally Posted by woods View Post
.010" is not un-normal for an unbelted case going from a new case to a fired case. My Steyr 30-06 is .011". When you say the "shoulders had been pushed back too far", what was the difference in the measurements between the cases with the shoulders pushed back too far and a new case? A little more info
Brass fired from my rifle measure 1.625" before resizing. My sizing die was pushing the shoulder back roughly .010" to 1.616". Normally I like to bump the shoulder back only .003"-.002" to avoid over stretching the brass. New winchester brass was measuring 1.616"



Quote:
Originally Posted by woods View Post
Normally it takes so little pressure to expand the brass case in comparison to the pressures inside the chamber that it has little to no effect on pressure and velocity.
This was what I was really wanting to know. So you are saying that difference in headspace will not affect my point of impact.

Thanks for the replies.
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Old 01-01-2012, 12:53 AM
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Re: Excessive headspace=lower muzzle velocity?

In my experience any change will very likely change POI especially at longer ranges....Imagine changing your seating depth .010...let alone case capacity...
IMHO,
Randy
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