Would someone mind explaining something to me?

[Mylhouse]

I picked up my first precision bolt rifle, (gun snobs, don't laugh) a 10FP 24" .308 w/ Accutrigger.

I've recently read somewhere that neck sizing isn't the way to go for ultimate precision. I keep hearing about "bump" sizing using a FL size die.

Would someone be so kind as to describe (in detail if it's not too much trouble) the process, the how-to, and the why behind this "bump" sizing technique?

Thank you!

 

[Grump]

It's a short-sizing technique involving backing the FL sizing die out a tiny bit at a time until it barely changes the case shoulder...called a "bump"

The theory is that the taper of the case body (which is less in .308 and .30-06!) results in less reduction in the case body diameter. You get a more snug fit in the chamber, more consistent alignment of the cartridge assembly with the bore, and presumably some extra accuracy.

In my rifle, the chamber is a hair tighter than nominal, the die resizes a hair longer than minimum headspace, and the whole setup pretty much "bump" sizes as is.

 

[PaulS]

Mylhouse,
It has been my experience that you can use either a full length die or a neck sizing die to size just the first 2/3 of the case neck with the result that the case (once fired at least) will center in the chamber because the body is left untouched and the unsized portion of the neck centers it in the neck of the chamber. This gives the best alignment posible for the case. If bullet run-out is held to minimums and the load is developed for this use it will be as accurate as possible.

Will this process guarantee accuracy with any give load? NO! It still takes the tuning of each load to develope it maximum potential - and out of the 20 or so possible powders only a few will give accurate results with any given bullet weight in any given velocity range.

PaulS

 

[Mylhouse]

Thanks guys!

I will give it a shot this weekend.

I have a Dillon FL size die and a Redding neck size die (the $22 regular neck die, not the expensive bushing one).

So I can bump the shoulder with the neck die also, while sizing only part of the neck?

 

[yankytrash]

Sure, just keep backing it off until a loaded round won't chamber.

For kicks and giggles, make sure to check a round loaded with your favorite compressed charge too, to make sure everything's crammin up in there fine.


Technical reloader's jargon....

 

[Delmar]

Is this possible/recommended to do with a Lee collet neck sizing die?

 

[dakotasin]

take a magic marker and color the neck/shoulder area of your case before you run it through the sizing die to see exactly what is being sized and by how much.

i don't know if it will work w/ a collet die...

 

[Lucky Jim]

Savage 10

I think the Savage rifle is a great shooter. I have a Model 10LE, 20" barrel in .308. I FL resize every time. I have read about and heard about all kinds of techniques in sizing to enhanace accuracy. I guess some of them are worth the time and effort. This is a group, not outstanding, at 100 yards shot from my rifle. The brass had been fired 3 times, full length sized each time. I am using 41 grains of IMR 4064 and 168 grain Sierra HPBTM bullet. I have tried several different primers which had little to no effect on grouping using the same powder and bullet. I have seated my bullet .010 from rifling and so far so good. I guess you could test until you were blue in the face trying to find that perfect load. I certainly have. The perfect load is one story and the perfect rifle to shoot it in is another. The Savage 10 shoots pretty well for me but I am positive there are other rifles among us that will make the Savage look sick but probably at a higher price. Try lots of tricks, powders, bullets, primers, OAL and all the rest until you and rifle are happy with a load. I am happy with mine.

 

[Johnny Guest]

Don't sell those Savages short!

Mylhouse & Lucky Jim - - -You both mention the attitude some brand name slaves seem to have about certain rifles. So what? If YOUR rifle shoots for YOU, why worry. Lucky Jim I know a lot of guys with "super rifles" who only wish they could shoot groups like you illustrated.

I also know at least one tac team sniper who is furnished a finely tuned, very expensive, Remington 700 with custom barrel, custom stock, and huge optics, who is trying to get permission to use his personally owned Savage .308 for duty call outs. He is ready to demonstrate proficiency with the Savage which equals or exceeds the 700.

Best,
Johnny

 

[Poodleshooter]

Is this possible/recommended to do with a Lee collet neck sizing die?

I don't believe so, delmar. The Lee collet die uses a collet to squeeze the neck back to size, and never touches the shoulder or body of the case, if I remember correctly. The process being referred to is simply "minimum full length sizing"; bumping the shoulder back just enough to easily chamber. You'd need a full length sizer to accomplish this. I've been doing this for years with my bolt guns, but I've found out the hard way that my AR doesn't tolerate it very well.

 

[blades67]

My HK91 doesn't care for neck-sizing either.

 

[John Galt]

I'm no expert....

For the semi-auto rifles, you always full length resize. The main point for those is proper function.

For bolt rifles, most dies are made for the semi-auto rifles and thus create lots of slop. Resizing the brass wears it out much faster. So, for bolt guns, you back off the FL die some and try that. If that makes the bolt hard to close, move the die down a spec. If not, move it up a bit. Once you have the right amount, leave it there! Each brand / model rifle has a slightly different chamber size. The brass will last longest and shoot best when just a tad smaller than the chamber.

Neck only dies don't resize the body at all. You can use just the neck die several times and then lightly push back with the FL or body only die when the brass grows enough to cause trouble closing the bolt.

** Don't study too much! I have and instead of spending $50 on great dies, I spent $150 + brass prep tools, etc, etc, etc!

* Back off the FL die a bit. Pick just two bullets (hunting and target), make up several loads for each to find the accurate load. Use the same brass for each rifle. Go shoot your rifle!

 

[mark mcj]

Yeah, screw the "bumping" and collet stuff. If you don't have a "match' chamber, neck size only and you should be fine.
I have 5 firings on brass and haven't had to trim yet. All my shooting misses are my fault.

edited for; I found the floating decap stem/sizing bushing to be a nice addition to a good set of neck sizing dies.

 

[Mylhouse]

A thanks again to all that have answered this thread!