Need Advice on Concentricity Problem

[LoneTraveler]

I had thought of the suggestion AZshooter suggested, but did not put it in my post. Measure the body of the case right at the shoulder before and after the bullet seating in several points the shoulder may be giving a couple thousandth on one side and it tilting the bullet. Good Luck in a fix.

 

[BCMAG2]

Thanks for the neck tension ideas, guys.

The loaded ammo measures .310" at the neck. The sized unloaded cases measure .308" with both the unfired Nosler Custom brass and the same fired Nosler brass that has been resized by the RCBS FL sizer. However, the unfired Nosler Custom brass is a noticeably tighter fit on the first load than after being fired and sized, as the brass when new causes tiny flakes of glitter to shear off the surface of the bullets during seating. I attributed that difference in neck tension (even with the same exterior dimension) to a slight thinning of the neck wall thickness after firing and trimming on the reload. There is no noticeable difference in bullet run out between the tighter first loads as compared to a batch of second loads.

I have ordered a .307" bushing, anticipating a thou of neck diameter spring back, since I wanted to end up with a .308" neck. It sounds like I may need to order a .308 and .309" bushing if too much neck tension is the source of the problem.

 

[BCMAG2]

As an update to my concentricity battles...

I marked the tip of a loaded LRAB round with inletting ink and seated it into the Redding competition micrometer die fully. I then took the seating stem out and examined it and the bullet carefully. The tip of the bullet is definitely not coming into contact with the seating stem.

I also received my Redding type S bushing FL resizing die today. I was sure that would be the answer to my prayers. It wasn't. The Redding does not quite resize the brass enough to allow the bolt to close without resistance like the RCBS does. Worse yet, the brass neck run out was far worse (up to 4 thou) than the results I was getting from the RCBS FL resizer (1.5 or less). I ignored that ominous sign and proceeded to load a few rounds. What a waste of good bullets that was. Bullet run out ran as high as 8 thou. So I put the RCBS FL sizer back into the press and resized all the Redding brass. That straightened out the necks to 1.5 thou or better. Proceeded to reload some ammo, turning partially seated rounds 180 degrees as suggested, and was right back to my old concentricity of 1.5 to 3 thou of run out at the ogive. And since its not a problem with the bullet seater stem, and the more expensive Redding FL sizer only made matters worse, I'm pretty much out of ideas at the moment.

 

[Canadian Bushman]

What is the outside diameter of your necks after firing?

 

[idaho elk hunter]

I would call Redding and see what they have to say. I can assure you that if the bullet is not matching the seating die it will not shoot. Neck tension is the overlooked #1 accuracy problem.

I do want to add that Nosler brass is decent brass in its own right. It is horribly expensive and most of the cost is in marketing and packaging. They want to compare there selves to Lapua and Norma. You will not see them in heavy competition due to the fact they are run of the mill normal brass that is massed produced by.....FEDERAL! They have Federal make it and then weigh sort it out to make it "better". I can tell you I have had a lot better luck by doing it the right way. Take you desired brass. Size it, cut the primer pockets, trim it if needed, debur the flash hole, and check the neck thickness. THEN WEIGH. If its weighed first it is just wrong. A amateur mistake.

 

[BCMAG2]

CB....I don't have any fired unsized brass at the moment to measure the necks. I did roll several fired cases on the Sinclair digital gauge and concentricity was excellent, about half a thou.

 

[Canadian Bushman]

CB....I don't have any fired unsized brass at the moment to measure the necks. I did roll several fired cases on the Sinclair digital gauge and concentricity was excellent, about half a thou.

Thats pretty typical, most brass runs pretty true right out of the chamber.

You said earlier that pre loaded necks measure .308 i believe.
If your fired brass's necks measure >.005 of this value, try sizing it back down in steps. Not to exceed .005 change on the diameter with each sizing. Ive had good luck with this process.

 

[BCMAG2]

That's interesting...never heard of that technique...but to tell the truth, I was so disgusted with the Redding bushing die that I already shipped it back for a refund.

 

[Canadian Bushman]

That's interesting...never heard of that technique...but to tell the truth, I was so disgusted with the Redding bushing die that I already shipped it back for a refund.

One thing i noticed about reddings bushing dies is that if the bushing has a little slop inside the die its best to keep the lock screw loose than tighten it down. Sometimes it will lock down just a bit off center and translate that into your brass.
I make most of my own bushings so i run into this problem from time to time.

If some of you guys saw how loose i leave certain parts of my dies you would probably think im an idiot.
The other alternative is to place o-rings under everything. This has the same affect.

 

[BCMAG2]

The Redding instructions say to first swab out all the packing grease, which I did, then drop in the bushing, run the stem down to make contact with the bushing, and then back it out 1/16 of a turn, and lock it in place. So according to Redding too, the bushing should not be locked down by the depriming rod stem. I did all that, resized some cases with bad results, took the die all apart, and repeated the set up process. Then I resized more brass with the same poor neck run out results, and decided that I was better off with the RCBS, and sent the Redding back.