Body sizing? A necessary step?

[Bart B]

Bart, no problem at all, and no offense intended. Besides, we're in complete agreement on the F/L vs. N/S issue. Just wanted to make clear that Sierra doesn't do anything that most serious reloaders do in turning out ammo. In fact, they do less.

Kevin, all's fine with me. And regarding what can be done to make very accurate ammo may well best described as how several thousand rounds of .308 Win. ammo was made using two Dillon 1050 progressives back in 1991.

One machine resized new Winchester brass (with near 4 grains weight spread) case necks so they would be perfectly round and hold the then new Sierra 155-gr. Palma bullet as well as seat the Fed. 210M primers. The second machine metered 45.3 +/- almost 2/10ths grains of IMR4895 and seated the bullet. 20 rounds were randomly selected for testing. Bullet runout was up to 3/1000ths inch. They were to be fired in a standard SAAMI spec chamber except for the throat being a bit shorter for the Palma bullet to just touch the lands when the 2.800 inch OAL round was chambered.

All 20 went inside 2.8 inches at 600 yards from the Win. 70 Palma rifle in Bob Jensen's machine rest. Several top long range shooters from around the world said that ammo was definitely 1/2 MOA stuff at 600 across a variety of bore, groove and chamber dimensions. Compare this to what the many-group aggregates in benchrest 600-yard matches.

Even mass produced ammo with new cases can shoot very well indeed.

 

[pyroducksx3]

I have the redding competition 3 die set, it comes with the competition micrometer neck sizer (uses the bushings), the body sizing die (it looks just like your average die minus the decaping pin and no micrometer or anything and the bullet seating die with micrometer. I also have the competition shell holder set and all the headspace (bump guages) and comparators. Is there anything else beside the innovative gauge (to size all the down to the rim) that I need? Like a different body (full length) sizer?

 

[Bart B]

Is there anything else beside the innovative gauge (to size all the down to the rim) that I need? Like a different body (full length) sizer?

Probably not. That Innovative die (it's not a gage) sizes the case all the way to the belt, not the rim. The rim is behind the extractor groove, the belt's in front of that groove. An RCBS Precision Mic is a case headspace gage to measure the head to shoulder length on cases. Use it on a fired case then again after full length sizing it to see how many thousandths the fired case shoulder gets set back.

 

[Kevin Thomas]

Bart, I remember Bob loading that ammo quite well. I was at that match, too (Palma Championships held in Raton in 1992). Just got back from the Midwest Palma in Lodi, and you'll be pleased to know that there's still plenty of the same folks in the game. Jack and Pat McCann were both shooting, and of course, Mid was there as well. No doubt several others you'd remember as well. Great crew, and Earl runs a hell of a good match.

 

[Pons]

Bart & Kevin, I enjoyed reading the last couple of pages of this thread.

Pyroducksx3, how is the reloading going? How do you like the Innovative die? (I've got one ordered)

 

[boomtube]

" ...if its already chambering easily why bump the shoulder at all."

You are correct.

 

[Bart B]

" ...if its already chambering easily why bump the shoulder at all."

You are correct.

Setting a fired bottleneck case shoulder back a couple thousandths ensures the case neck will be better aligned with it. If the case neck's not aligned with the case shoulder, the case neck won't be centered in the chamber neck when the round fires.

Proper full length sizing of fired cases, even belted ones, lets them all headspace on their shoulder. There's typically enough room on belted cases to let them headspace on a SAAMI spec minimum chamber without their belt touching the chamber belt headspace point. Moreso on longer chambers still within SAAMI specs.

When the firing pin drives the case forward and hard into the chamber shoulder, that perfectly centers the front of the case in the chamber....if the necks axis is aligned with the shoulder axis.