.308 shoulder bumping

berger

berger

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As I posted in another thread, I am new to reloading rifles, and I have started with the .308 for my Savage 10TR. I have been reading and watching a lot of videos, 8541 Tactical in particular, on the subject and decided to neck size (Lee Collet Die) my Savage once-fired brass only. I understand why one neck sizes (correct me if I am wrong), as the brass is already formed to the rifle it was chambered and shot from and it will create the "most accurate" cartridge. I do know that the shoulder should still be bumped occasionally. So my question is this, is it okay that the shells I have neck-sized are very snug in the chamber (bolt does close and extracts brass)? My understanding is that this is the reason to neck size. Should I bump the shoulder slightly with the FLS dies just to allow a looser fit?

I am only shooting off a bench at this time.

Thanks again guys!
 
if its snug but not excessive force to close the bolt, then you are fine, when youve got to use the palm of your hand and really giver then better bump that shoulder..

i use a redding body die to bump my shoulders back.
 
I've fired some ammo and had the bolt get pretty stiff to extract the spent brass. When i neck sized the case, the empty cases were still fairly snug to chamber. I ended up just FL sizing and trimming those cases if needed then neck sizing after that without problems.

That Redding die UM pointed out is pretty cool. I might have to look into one later down the road. :)
 
I use a Redding Type S bushing die. I have it set to bump the shoulder back .002". I also have a Redding body size die just in case:( It has saved me from pulling a sh!tload of loaded ammo several times because they were too tight to chamber in a 4 lug action.
 
When you full length resize your cartridges case the case itself has less effect on alignment or misalignment of the bullet. The rear of the cartridge case is supported by the bolt face and the bullet is being supported by the throat. The case sidewalls, shoulder and neck are not "normally" touching the chamber, until the firing pin drives the case forward and the shoulder of the case contacts the shoulder of the chamber.

We do not live in a perfect world and no cartridge case has perfectly uniform case and neck thickness and "zero runout". By full length resizing you eliminate any cartridge case misalignment errors caused by warped cases due to uneven case wall thicknesses. *(called the warped banana shaped case after firing)

chamber-neck-diagram-with-cartridge2x_zps7395df40.jpg


Below is Kevin Thomas of Team Lapua USA, and he is quoting the late Jim Hull of Sierra Bullets Testing and Quality Lab and one of my favorite sayings about full length resizing. "The cartridge case should fit the chamber like a rat turd in a violin case" meaning Jim got his best accuracy by full length resizing and "NOT" neck sizing.

KTLapua-b_zps8d1abc2c.jpg


The Rifleman's Journal
Reloading: Partial Neck Sizing
by Germán A. Salazar (Mr Salazar also knew Jim Hull and shot competitively with him and supported the full length resizing concept for accuracy)

"A full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.

In conclusion, I believe that allowing the bullet to find a relatively stress-free alignment in the throat by full length sizing (including the neck) and turning necks to enhance concentricity gives the bullet the best probability of a well-aligned start into the rifling."

http://riflemansjournal.########.com/2010/06/reloading-partial-neck-sizing.html

The Rifleman's Journal
Index of Articles
http://riflemansjournal.########.com/p/articles-index.html

*See the NECO case gauge below
runout_zpsfe87d011.jpg
 
Thank you very much for that post. My understanding, and in part the other reason I chose NS, was because of brass longevity. I guess I have some more research to do.... :)
 
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