Concentricity Effects of Sizing Dies

[camac]

I agree Mark, thanks to all the valuable comments (not only on this thread but on a couple of other related ones). A big part of accurate shooting is accurate loading. It is great to get some other views on these topics and it has challenged me also to rethink a lot of my ideas. After many years of reloading and trying to work it out with limited feedback from friends and small talk at the range. it is a revelation to get such input from a large body of experience. I have a bit of renewed energy to try out some of the posts/concepts and or quantify my own to determine if it is rubbish or not. This is all spearheaded by some great articles by German - keep it going - fantastic stuff. Perhaps a follow up article that includes the 1 step custom FL dies (and maybe even tapered bushings?) ? We can only hope?

 

[GermanS1]

Camac, I received the neck reamed .308 and .30-06 dies yesterday. Today I fired a match with my neck-turned Winchester .30-06 brass (I really only shoot matches to empty the brass so I can reload it again ;D). This coming week I'll size it with the one-piece 0.331" neck diameter Redding FL die.

I'll keep careful records of the results of the sizing (before and after) and we'll see how it goes. I am definitely planning a follow-up article because it's the best way to force myself to keep good records and try things out. Without that, I tend to fall into the "always done it this way" routine and that's neither interesting nor productive.

 

[camac]

Thought I would help a little German, considering you are doing all the work for us. I also had 30 fired shells from last match in 6.5x284. I went for my Forster FL die which I have custom ground the neck out to .289 (slight lead in taper) and base out to chamber size (so that shells line up with bore using base of shell and base of neck). The second die was a Forster Neck bushing die. I favour these now as they are a bump die and neck die all in one and a little quicker to change (or flip) bushings. I have a 0.289 bushing tapered at one end for it too. So the below comparison was ten shells of each 1) straight from chamber 2) FL custom die, 3) factory neck bushing in one step sizing 4) Factory neck bushing with tapered lead into opposite end and two step sizing (one with taper, then flipped).
A few notes even though the chamber is fairly round and concentric I believe powder residue, after repeated firings starts to build up in neck and can lead to a bit of runout in the unsized necks as per the one with 1 thou reading. I checked, cleaned and checked it again. still one thou.
Also on the readings, These were done on a home made V block design similar to RCBS. V Blocks placed about 1/4 inch up from base of shell and just below shoulder. A few shells were checked for "roundness" at shoulder and base with no noticable needle movement on any. Neck Runout was measured about 1/16th of an inch in from top of neck. The accuracy of the gauge is only one thou. I can read roughly to 0.0005 but below this I gave them a 0.0002 (random) if there was a needle flicker but less than 0.0005. Only on one unsized shell could I see no needle flicker whatsoever.
unsized fl sized 0.289 tapered
0.0002 0.0002 0.0010 0.0010
0.0010 0.0002 0.0010 0.0002
0.0002 0.0002 0.0015 0.0010
0.0002 0.0002 0.0005 0.0015
0.0002 0.0002 0.0010 0.0002
0.0002 0.0002 0.0015 0.0002
0.0002 0.0005 0.0010 0.0010
0.0002 0.0002 0.0015 0.0010
0.0000 0.0002 0.0020 0.0002
0.0002 0.0002 0.0015 0.0010
AVG 0.0003 0.0002 0.0013 0.0007

Conclusions: No doubt the FL die was most accurate with most shells only showing a flicker. The tapered bushing was next, with 9/10 results under 1 thou. The standard off the shelf bushing and one step resizing was last and consistently gave readings in the 1-2 thou range.

ps In my humble opinion although the FL die produced the most concentric shells, it is not as good as it sounds unless the FL die matches your chamber (at least at base and neck or shoulder). The shell needs to sit in chamber in allignment with bore as well. It is not much good if you have a straight concentric bullet only to have the tail end drop a few thou, sending the bullet out of allignment with bore.
Also another side note the tapered bushings seem to work better on my 6mmBR shells with a longer neck and longer lead in taper to help align.
Cam

 

[bsc4444]

Viperdoc
I think you are trying to stablize to heavy a bullet with a 1-9 twist barrel. In my AR with a Shilen 1-9 the 50 and 55 V-max's and 52gr A-max shot great. I use WW brass,WW primer and 25.7gr. of Varget with the 55 V-max. Also 23.5gr of 2460 works great. Both loads shoot in the 2's. With the 52 A-max 26.5 bl-c2 was my best. I would feel good popping a coyote at 500 yds with any of these. Try the lighter bullets I think you will find you and your rifle will be happier with your accuracy.

Brad

 

[GermanS1]

Camac, that's a terrific test, thank you! As you note, the 6.5-284 has a relatively short neck; nonetheless, your results are worth studying for any cartridge as they indicate an improvement over standard bushings with the taper.

Our match shooting season is winding down here as it becomes too hot to shoot on open ranges without a roof until late October. We have a couple of 500 yard ranges with a roof that we use during the summer, but nothing longer. However, less matches means more time for experimenting and testing, so I hope to get some interesting work done on this over the course of the next month or so.

Thanks again for the data!

 

[camac]

No worries German - inspired by your testing. It was surprisingly a very easy thing to do and only took a short time. I may replicate with the 6BR or 308 when I too "empty" some shells. As you said it is good to "make you think about it" and more importantly test the theories that are often started by rumour but never tested.
Cam