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Primer backout problems

 
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  #15  
Old 09-12-2005, 06:32 PM
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Join Date: Mar 2004
Location: scotland
Posts: 174
Re: Primer backout problems

i have no idea what a wilson headspace gauge is like, however, i set my dies up using a stoneypoint headspace gauge so that i am bumping no more than a thou. maybe you want to get one and check between a fired case and a sized case to see how much bump you are getting.

federal brass is a little on the soft side, but 3 - 5 thou is not gonna appear with just loose primer pockets. if the case is only bumped 1 thou after firing, primer should only protrude by about 1 thou i'd say. someone correct me if i am wrong here please.....

why not get a seasoned re-loader to check over your set-up and see that you are going about things the right way. i am not trying to insult your intelligence here so please don't take that the wrong way. i have seen people who have been loading for years do some really scary things in the past. everyone can learn something from someone after all.

i'd offer but i am a little too far away from you....

i still say you have headspace problems though, and it's something you need looking at unless you want a seperation? and these are a real paing in the ass at the best of times and there is no reason to have them if all is good and well.

good luck

derek
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  #16  
Old 09-12-2005, 10:35 PM
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Join Date: Nov 2004
Location: GF Montana
Posts: 467
Re: Primer backout problems

[ QUOTE ]
<font color="purple"> I would love to see a test design on this, as there is no doubt that you are creating an incredible amount of bolt thrust. Meaning the case is not able to grip the walls of the chamber, so the entire case is able to push back against the bolt face with much more thrust than is normal. With a heavy load, this "Has the potential" to be a disaster. </font>

[/ QUOTE ]

There is (at least an excellent FE model) (My area of mathematics).

.243 Win
Coefficient of friction u = 0.55 (Very rough chamber, rough reamer finish) Maximum bolt load = 4435 lbs Radial thinning near the base = 0.006504"
Coefficient of friction u = 0.11 (Probably not possible: Polished chamber, polished brass with grease) Maximum bolt load = 4787 lbs Radial thinning near the base = 0.004481"

Finite Element Analysis of Rifle Chamber Surface Finish and how the resulting friction effects brass cartridge case stretching and bolt face loading.
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  #17  
Old 09-13-2005, 09:02 AM
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Join Date: Jun 2001
Location: Potomac River
Posts: 5,059
Re: Primer backout problems

I will look tonight and see if we still have my son's 8th grade science fair project on the affects of viscosity on reducing static and dynamic friction between two metals. We went all the way up to 90Wt rear gear lube.

What I do remember is WATER. You would not believe what a good lubricant water is. A very thin coating of water will reduce friction way better than oil (cold oil). Warmed up oil is a different subject. You are right, there is a safety lesson here.
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  #18  
Old 09-13-2005, 11:44 AM
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Join Date: Jan 2005
Posts: 260
Re: Primer backout problems

FWIW--for hunting ammo I usually set up about .003" headspace. I think it's best to have a little cushion for possible dirt, debris, water, ice, what have you. Also I've had it happen where the expander has dragged a little more than usual and pulled the case neck up and when that happens it was good to have a little margin for error. Also some brass may or may not have some spring back and again a little margin for error is good in my opinion.
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