Should I Turn Necks?This month's Question of the Month comes from Lance who is in a very common situation, wondering if neck turning will be a benefit as his scores improve and he's looking for the next step up.
For long range I shoot a 6 Turbo (plan on acquiring a bolt gun for next year). The rifle shoots well. Last fall at 600 yards I shot a pair of 199's with 14X's on one string so I know the load I use works. I gave up X's and the two 9's due to, I believe, a shifting cheek piece on a CSS tube stock. This isn't Gary's design flaw it was my fault as I didn't realize the set screw on the stock is not meant to be loosened to adjust the cheek piece (duh!). The load I am using is Lapua 6.5 Grendel brass with BR4's, 30.5 of R15 under a Hornady 105 Amax.
Anyway, I plan on shooting a few of the long range matches at Camp Perry this year and after reading your post on the daily bulletin on the K&M neck turner this got me thinking about their being any benefit to neck turning the little neck on the 6mm Turbo? I know neck turning is usually more of a bench rest technique for bolt guns. I don't use many bench rest loading techniques as I am primarily a SR/ JCG match shooter. Do you think there would be any benefit in turning the necks on my ammo? The necks on this cartridge are about 0.170" long.
That's a good question. The most important reason for a Highpower shooter to consider neck turning is to equalize neck tension within a set of brass. Consistent neck tension is one of those small factors that add up to low standard deviation of muzzle velocity and thus to less vertical dispersion.
You mentioned a couple of good scores and those are excellent scores anywhere. The important question, however, is: what is the average score? Do you tend to lose points or X's to uncalled shots high and low? If all of the shots that you call as good ones fall within the elevation of the X ring, then the load is fine for the distance used. If not, then the load could use some attention. Let's have a quick look at the various elements of a good load.
Neck turning falls fairly low on the list of items to look at when trying to improve a load, especially if you're using good brass as you are. First and foremost is the bullet. The AMAX you're using is one that I see a lot of service rifle shooters use both in their service rifle and in their match rifle when they make the switch. However, it isn't one that you'll find a lot of dedicated bolt gun shooters using, at least in this part of the country - sometimes there are regional preferences. Sierra and Berger really dominate the bolt gun ranks here and it might be worth trying a box or two. My personal preference is the Berger 105 VLD but I have had good results with all of the appropriate weight Berger and Sierra bullets in that weight range.
Your choice of powder is the same as most good 6BR shooters and the 6mm Turbo has essentially the same capacity as the 6BR so let's leave it aside for the moment. The charge weight is also right in line with most 6BR loads, I use 30.2 RL15 with moly-coated 105's, for instance.
Primers are my area of special interest and they are definitely a significant factor in reducing SD. The CCI BR4 is a good primer in this regard, but if you can get your hands on some Wolf small rifle magnum, I think you'll see an improvement. Make sure to get the magnum, the standard small primers have a very thin cup which will blank in this cartridge.
Now we're finally down to the necks. I left them for last because that's about where they fall in the relative scheme of importance. I don't know if you're currently set up to turn necks or not, so here's a good initial way to analyze your brass. Take 15 or so loaded rounds, and measure the neck diameter with an accurate digital caliper or a micrometer, ideally a blade micrometer. For these purposes, a dial caliper as shown in the picture is too hard to read accurately but will do in a pinch. Measure the neck diameter on each one in two places (measure, rotate 90 degrees, measure again). Write these measurements down in two columns on a sheet of paper. Be careful in your use of the calipers, make sure to use very consistent pressure as it is easy to affect the reading through varying pressure.
Now take a look at those numbers. If the brass was neck turned there would be essentially no variance in them. How much are you getting? If you see more than 0.001" between different necks, then the necks could benefit from turning. If you see that much within single necks, then they definitely need turning. When I say they can benefit from turning, I mean there will be a small improvement in SD, not a dramatic change in the overall performance of the load. Let's keep in mind that we're talking about the lowest item on our priority list and that these small gains can be hard to see at 600 yards, although they become more apparent at 1000 yards.
If you decide that neck turning will be worthwhile, then some better measuring equipment and technique are in order. I use a tubing micrometer to check neck thickness and check each neck at three points after turning to make sure they came out right. The caliper method I described above is just a quick and dirty way to check now if you don't have a tubing micrometer but won't really do for neck turning.
Remember that an unturned neck never caused a 9 at 600 yards. We shoot all of our own 9's; all good ammo does is get us more X's. Of course when you're in the X ring, you're further away from the 9 ring and have increased your margin of error and that's very worthwhile to me. As you know, I shoot the .30-06 a lot and am able to shoot scores with it that surprise a lot of shooters who have low expectations of the .30-06. The key to those good scores is attention to all the finer details of reloading and shot execution and those lessons apply equally to your cartridge and any other. As we herd the shots closer in to the center, we get fewer strays out there in the 9 ring where we don't want them!
Measuring the Case