quick question over partial resizing

[whitenup11]

quick question. could one of you reloading gurus explain to me the pros and cons if there are any cons to partial resize. Also I have partially resized the some cases of 7mm wsm and I can see the line where my resize went down. that distance is approximately 3/4 of an inch down from the case mouth. Would that be too short, too long, or doesnt really matter as long as i can stick that empty cartridge in my chamber and bolt it down. if it is hard to bolt down do I need to go ahead and resize a little further down? anyway thanks for your help and if you have any more tips on partial resizing im all ears! thanks

 

[ZombieMonkey]

By partial resizing I am assuming you mean using a FL die to size the case just enough to get it back to your chamber dimensions, correct? If so, you need to get yourself a set of comparators to determine if you are doing enough or too little. By the sounds of it you are not doing enough.

 

[whitenup11]

ok, you mean like calipers? I have those and measurements are within specs around the neck and are barely over .002 below the neck. My understanding though is once the brass is fire it expands to the size of the chamber and the tighter the fit the less margin for error and better accuracy. am I wrong?

 

[dsnipe]

You are correct in a way. When you fire your case it does expand to the dimensions of your chamber. Depending on caliber you can get by with neck sizing only for an X amount of firings until the brass will not chamber. Problem I have found with that is in a bench only type rifle it is acceptable but if you use your gun in the field, tac matches, nasty conditions etc any slight buildup in the chamber and you will run into not being able to close your bolt. Get yourself a comparator set so that you can measure your shoulder on fired brass. Once you have this dimension you can then adjust your full length sizer to size the entire neck and bump the shoulder back. Most of my rifles I bump shoulder back around .0015 to .002 and I have never had a problem with chambering. Everyone has there own method so you will get plenty of good info here. I have been using this method for several years on all my rifles with great success. Here is a link to the comparator set, this one is from Hornady but there are several companies producing them. Best of luck brother.
Hornady Lock-N-Load Headspace Gage 5 Bushing Set Comparator

 

[Xtremegunnr]

take a piece of brass that you fired that will not feed. Take the ejector out of your bolt (can leave in too but its nicer with it out) and keep bumping your die down a bit until it closes. After it closes, give it another few thousandths

Its though to do this thought if all of your brass fits....

 

[dauntedfuture]

Partial sizing is when you deliberately back off your FL die so that it does not bump the shoulder back. In theory, this produces a "partial neck sizing effect" without a neck die. I along with most high-power shooters have found that proper FL sizing is the way to go. By proper I mean bumping the shoulder back .002 or so, or a sized brass with a small piece of scotch tape on the shoulder will chamber, or measure with a case mic. In theory neck only sizing will make your brass last longer. My experience is that primer pockets are the first thing to go before anything else.

 

[ksthomas]

Partial Sizing is a euphemism for saying you're not Full Length Sizing correctly. As others have said, get yourself a case gage or bump gage, and use that to set your die to where it's only setting the shoulder back .001"-.002", and now you're correctly Full Length Sizing. Chambering (and extraction) will be easy, your brass will outlast any other method of sizing (including N/S) and you'll be almost guaranteed to see improved accuracy. What dauntedfuture said about primers is spot on; you'll likely lose the cases due to expanded primer pockets before you see a head separation in a bolt gun if you're sizing properly.

 

[gewehr]

My neighbor does it on all of his 270s and though bolt close is a little hard he has had great luck with accuracy and brass life.


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