Closing bolt not the same feel

T

tvtv

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What would cause the bolt (to close) on my Savage 223 LRPV to feel different from one round to another. The bolt closes with a little more resistance on some rounds. Same cases, same trim, same load, same bullets.

I've separated out the cases that took a little more pressure to close the bolt, both batches of fired cases look the same.
 
Your brass is not sized quite enough. either shoulder or base is not pushed back enough. Are you full length sizing or just neck sizing ? has brass been fired many times.

Dick
 
did one full resize. then only neck. brass used about 4 times.
 
You are getting

tvtv said:
did one full resize. then only neck. brass used about 4 times.
Click to expand...

growth in your brass as you fire it. And not every case grows the same. That is one of the reasons that BR shooters, most of them, FL size every time. You must realize that FL sizing to us is NOT the same as what the "books" are telling the general public. We are using custom dies, matched up to custom chambers, and doing VERY accurate measuring to nderstand just EXACTLY how far we are sizing the cases. .001-.0015" bump on the shoulder. .0005" or so bump of the web. VERY minimal movement of the metal, but movement none the less. And we do it EVERY time.
 
I was led to believe that if the brass is being used in one gun only (mine a single shot Savage) neck sizing is the "best" thing to do.
 
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Sounds like a shoulder bump problem. You will need a Redding Body die and an RCBS Precision Mic. If the shoulder is not bumped back occasionaly it will cause hard bolt closure.
 
If you have a way to measure the distance from the heads to a circle on the shoulder of all of your sized cases, and you measure them all after they have been sized, you will see that the amount that the shoulders of various cases have been set back are not all the same, even with the same die setting. There are several variables. Differences in the amount of case lube will change the amount of bump, as will differences in the degree to which cases are work hardened and/or annealed. Once you have established the amount of variance of bump that a given lot of cases has, you may decide to adjust your die so that the one that was bumped the least, at a given setting, gives you the bolt feel that you are looking for. I have also observed that putting cases through an automatic annealer set up to stress relieve rather than a full anneal, reduces variance in shoulder bump. Keeping cases in batches that are fired the same number of times also helps.
 
Your cases need to be full length sized, and possibly have the shoulder pushed back another thousandth of an inch or so. The problem is unless you have a good way to measure from the shoulder to the base you may over size the case.
 
"unless you have a good way to measure from the shoulder to the base"....

what's a "good" way to measure from shoulder to base?
 
Hornady makes a nice set of headspace measuring tools that will fit just about any caliber out there. If you really wanted to get specific with it, you could take 3 of those rounds, send to Harrell's precision and have them make you a FL neck bushing die with a shoulder guage (headspace guage).
The ring on the shoulder that was previously referred to is called the datum line. The distance from the datum line to the base of the case is your headspace.
If you are going to try to bump your shoulder down .0005 to .001 you will want to get a set of die shims (see sinclairint.com), or the, again, previously mentioned micrometer top die. I can tell you from experience that to move the brass that little requires VERY little movement in the sizing die (1/32-1/16" and this was a rough measurement) so having those shims would be a necessity. If you do it by feel you may go too far and create excessive headspace....failed cases in your future.

Hope this helps,
Mike
 
Not sure if this will help but this is how I prepare chosen cases for best accuracy and consistently tight groups . The cartridge this applies to is the .303 British but the basic principles should remain the same.

On second firing I rotate the case 180 degrees to equalize expansion.

After second firing I neck size only the first .2" of the neck so that the now equally expanded rear portion of the neck serves to center the bullet to the throat as nearly as possible.
I use a hand turned undersized expander and don't crimp, relying on neck tension rather than crimp for an equalized and lesser level of pull strength.
Up to a point the less the pull strength, the less variation in pull strength affects accuracy.

Before the third reload and subsequent loading I put the fired cases in the chamber and use them each once for dry firing practice. The impact of the firing pin on the expended primers acts to micro size the case, making chambering easier.
This also reduces the cushioning effect of an expanded case with narrow shoulder that might otherwise induce variation in primer performance.
This is a rimmed case tapered and narrow at the shoulder, so the effect may not be as consistent with a rimless case.
Head clearance has been reduced to less than .004 by use of the extended length No.3 bolthead.

Using this method I've gotten consistent sub moa grouping from a rifle that shouldn't be capable of such a high degree of accuracy.

My best groups are single hole groups only 1/8" larger than the bullet itself .
 
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What everyone else said plus I'll go a step farther and say that for the most part I've given up on neck sizing and FL size everything. It's just a little more trouble to FL size after every firing due to having to clean the lube off the cases, but if it's done right and the chamber isn't oversized it gives the same "feel" for every round and better accuracy as well.

If you're shooting groups you'll probably notice that those rounds that chamber with more effort than others will generally throw their bullets out of the group. FL sizing cures that problem, but don't go berserk and shove the shoulder back too far. Get a Hornady "headspace" checking tool and bump the shoulders back 2-3 thousandths of an inch max. This should give some "feel" on closing the bolt on a chambered round, give good case life, and better more consistent accuracy.
 
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