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Question on sizing belted mag brass

 
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  #1  
Old 05-28-2013, 05:50 PM
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Question on sizing belted mag brass

I hope someone knows what I'm doing wrong. I am building a load for a 300 win mag and a friends 7mm rem mag. Both guns are having the casings stick in the chamber after a shot. Bolt opens fine but have to put a heck of a pull to shuck the shell out. This is even at the minimum load. I am using RCBS full length dies and Winchester brass. Am I doing something wrong in sizing them? Thanks for any help.
Dennis
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  #2  
Old 05-28-2013, 06:53 PM
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Re: Question on sizing belted mag brass

Try a factory load and see if it happens.

Look at the area directly in front of the belt for shiny marks. This is the area that I have had troubles with.

I used the Innovative Collet die to resize cases back to original specs. but it didn't solve the problem(it helped other things though).

I ended up "fixing" the problem by polishing the chamber in the area directly in front of the belt.

It also could be a lack of "primary extraction" in the rifles(where the bolt "cams out" from the receiver "camming" the bolt handle back at the top of the bolt lift).
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Old 05-28-2013, 08:38 PM
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Re: Question on sizing belted mag brass

Thanks for the response. On the first firings through these cases I had no extraction problems, which makes me think I'm resizing them improperly. I seat the die to the shell holder and give an extra 1/4 turn like my other reloads, so not sure what to do differently at this point.
How do you polish a chamber?
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  #4  
Old 05-28-2013, 10:47 PM
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Re: Question on sizing belted mag brass

Quote:
Originally Posted by imohunting View Post
Thanks for the response. On the first firings through these cases I had no extraction problems, which makes me think I'm resizing them improperly. I seat the die to the shell holder and give an extra 1/4 turn like my other reloads, so not sure what to do differently at this point.
How do you polish a chamber?

I had a similar problem with a RCBS die and a 7mm Rem mag. The shoulder of my brass raised up with my set of RCBS dies. I called RCBS and they had me send them 5 fired cases to them and my dies. They sent back a 7 RemMag small base die for free and said I needed this die for my Browning Abolt. Apparently Abolt chambers are "differernt" and it is a know problem. The small base die worked the area above the belt better but the shoulder still raised up after sizing it (instead of being bumped back). I bought a regular redding die and it did the same thing. I tried a set of regular LEE dies and I finally could get the shoulder to bump back. But I also now need to use the Innovative technologies belted magnum collet die every shot. A "russian character" wants me to cerrosafe the chamber. I should but I have it shooting so good with the technique Im using on this gun I don't want to change anything. I do get case head seperation around 10 rounds.

Have you checked to see if the shoulder is being bumped back?

I worked my way down 1/8 or less and could never get the shoulder back with the RCBS dies.

What gun?
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  #5  
Old 05-29-2013, 06:49 AM
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Re: Question on sizing belted mag brass

If the resized cases fit ok in the chamber and are not too long there shouldn't be an extraction problem.

Different dies resize the cases differently, my Lee dies will push the shoulder back .020"+ which results in cases head separations in 3-5 loadings. I set the die now to push the shoulder back a .002-.003"

None of the regular dies will resize the area directly above the belt very much, a small base die resizes that area more. A body die or the Innovative collet die will size that area back to close to factory dimensions.

In my rifle the cases fit easily in the chamber after resizing in the Innovative die(which only resizes the lower case body). Before polishing the chamber the cases fit easily but after firing showed bright spots directly above the belt. After polishing the cases no longer show the bright spots and extract easily. The dimensions of the cases fired in the chamber before and after polishing are virtually the same.


I resized a case then turned the belt off of it in a lathe, then drilled and tapped the base for 1/4nc and mounted it on a piece of threaded rod. I applied a small amount of valve grinding paste to the area directly above the (now gone) belt, lubed the shoulder area and spun the modified case in the chamber for a short time. I then cleaned out the grit and repeated with some FLitz(JB bore bright or jewelers rouge might be better).

There may be better ways to polish the chamber but the theory is that cutting off the belt ensures there is no change in headspace(belted cases were intended to headspace from the belt). The valve grinding compound may be a little rough but it ensured the job would get done in a short time in a limited area( the longer the case is spun in the chamber the more other areas are affected).

My rifle is a 1990's Winchester Laredo 300WM. It worked pretty well for a long time but developed sticky extraction sometime during the time one of my Buddies owned it. I was going to either fix the problem or re-barrel it. I may sometime re-barrel it anyway but I use it now for practice and it functions fine with pretty hot loads. This rifle seems to only shoot decent groups when loaded towards the top of the pressure curve and not too great even then(slightly sub moa with 180BT's and a 75.5g RL22).
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  #6  
Old 06-05-2013, 07:13 PM
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Re: Question on sizing belted mag brass

Even a min load can be too little, go up a bit, maybe say 1 gr and see what hapens. As for a belt, just size it according to the ( distructions) and work from there. Slowly sizing less and recording each movement of the die to the left as you back it out.
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