What is your opinion between getting a full length bushing die vs an expander mandrel die for neck tension? Also, do you try to achieve .0002 neck tension for reloading?
2 thou neck tension is pretty standard. On some shorter necked cartridges like a 7 SAUM it could be smart to get a bit more or the ammo would be a bit fragile with not much friction holding the bullet in.
I am pretty ambivalent about bushing vs expander ball. Most of the time I use a bushing but have had good results both ways.
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I need to do some testing, but from a broad overview of neck tension tests on yt and forums, it seems like the ideal neck tension is where the brass holds on to the neck through elastic tension, where if you were to pull the bullet after seating, the neck would return to its original diameter. Forcing the neck to stretch permanently during seating seems to be what leads to inconsistency.
To measure and repeat this properly would probably require a set of mandrels and pin gages, which is why the 0.002" mantra is repeated a lot.
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Jordan, have used both.
- expander mandrels are more exact
- the Redding Match Precision Die - Full Length w/ bushing is what I use
- do still use a standard RCBS full length sizing die a lot
a. mandrel for precision and less working of the brass
b. bushing gives you flexibility to use multiple sizes, because…wait for it
c. each type of brass will have a different neck thickness, so the bushing you use for Winchester, or Lapua, or Federal to reach that .002 will change the bushing used.
Finally, if you are gonna hunt primarily, I would use a standard RCBS or the Redding Precision Die sets, having a micrometer seating die is nice. But just like with a lot of this stuff, unless you are chasing group sizes where thousandths matter in the application (hunting vs benchrest), then some of the cost and time are not worth the gain. Becomes your personal preference on what you are trying to achieve.
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Thank you, that’s very helpful. This all came about because I have some new ADG brass and I’m trying to figure out how to load it precisely. I’ve always bought factory ammo, shot it, and then reloaded it. I wasn’t impressed with how many firings I got out of my Hornady factory brass. That has led me on a search to take things up a notch but for some reason, new brass is intimidating to me.
John, I think you nailed it when suggesting to start by determining your application. Of course, I want the “most” precision. That was part of why I started handloading. I had a rifle that just wasn’t grouping very well and I wanted to see if I could work up a load it would like. There was also the cost, learning ballistics, and just because it’s cool. I have gone down so many rabbit holes and have been very thankful to have the community here at Backfire as a resource when I had questions.
I am sure I will probably go down many more rabbit holes as I am still realtively new to reloading. That said, I have realized that the use case matters. I am loading for hunting and recreational benchrest shooting. I don’t even have a range near me that goes out to 1000 yards. I probably won’t shoot past 300-400 in a hunting scenario.
For that rifle that wasn’t shooting, I am now getting groups under an inch. Huge improvement since I was starting at 1 1/2+. I’m a happy camper with that result. What it means for me is to have decent equipment and develop a highly reliable process that will consistently turn out that level of performance. If my intent was for long range precision shooting it might make sense, but for what I am doing, the value proposition just isn’t there to get all the fancy and expensive tools and dies. I do plan on upgrading some things as I go.
I’ll just chime in that the best balance of precision and ease of use for me has been a bushing die with a SAC bushing, this is mostly because it works the brass much less than an expander ball, and doesn’t require an extra step in the process like a mandrel. It takes far less force than an expander ball on the upstroke which is a really nice bonus. For my target rifle I’m now all in on the rabbit hole by both controlling the neck diameter in the die with a bushing (as a standard full length die shrinks it far too aggressively for my tastes) as well as setting final tension on a mandrel I’d agree that this is overkill for most applications, but its highly satisfying when the neck diameters are so perfect they form airtight seals with the pin gage 
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Thanks William! So if I’m shooting a .284 diameter bullet, should I get a .282 diameter bushing? I’ve heard people say it depends on the thickness of the brass. I just bought ADG brass and I’m just unsure of the whole process as to how to measure neck tension with my new brass and know which bushing I need to get.
Measure a few loaded rounds at the case neck with some calipers, subtract 0.002" to 0.003" for a starting point. When you size your necks you’ll typically get 0.0005" to 0.001" of springback; this is actually one of my pet peeves with people discussing this problem, whether they mean before or after springback. From my own experience and watching other people test neck tension I don’t think the exact amount is a big deal* as long as its reasonable and consistent.
*For most people.
Sorry for all the questions…so if I have loaded rounds using Hornady brass and I measure the neck, wouldn’t my measurement be different with ADG brass since the brass thickness might be different? Is there any way to figure out which bushing I need for new brass if I don’t have a loaded round with that brass? Thanks in advance.
Yeah you can measure the thickness of the neck with some calipers and add 2x that amount to the bullet diameter to get an estimate of what your diameter will be, then subtract 0.002" from that to get a bushing size. Also yes, if you have different brass your outer diameter will likely be different (whether its different enough to see downrange is an open question). If I’m loading a new brass/bullet combo I’ll usually just sacrifice a case and projectile to fiddle around with dimensions and seating depth on. Those come in handy when I’m fiddling with magazines and feeding issues too.
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Jordan, google Accurate Shooter Neck Tension, and you will have articles come up that are well written and with pictures. Accurate Shooter is a great source of knowledge in my opinion and I went there often in my learning days of reloading once I found it. Great source.
John
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Ok guys one more question. As I mentioned, I have some ADG brass that I haven’t reloaded yet. What are your thoughts on simply using my full length sizing die without a bushing or mandrel? I’ve spent a lot lately and not sure I want to drop a couple hundred bucks right before hunting season. Do you think accuracy will be significantly different?
I clocked a .2 moa improvement when I ran brand new brass through neck sizing with a mandrel vs without (~20 shot sample size).
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