Runout questions....Long story.

[Mikem]

If I remember correctly, this is for an AR type auto, so you dont want the bullets too lose. And I dont think you can turn the necks, with that barrel, It must not be a tight neck chamber, or you would be doing that already.
So your question about .002 tension not being enough, may be right on.

 

[blawton]

If I remember correctly, this is for an AR type auto, so you dont want the bullets too lose. And I dont think you can turn the necks, with that barrel, It must not be a tight neck chamber, or you would be doing that already.
So your question about .002 tension not being enough, may be right on.

Its not a big deal if he is just gonna take off .001-.0015 a side to clean them up its not gonna hurt not having a tight neck chamber unless you really start to turn a more the that off.

.002 should be enough but i would not let it get any less then that for running them in your ar.

 

[Hapnin]

So what do you guys think about me sizing em without the button and then reaming them. Sizing without the button should leave the excess on the inside of the neck and a proper sized reamer should take care of the thickness. After I do that the first time, the necks should be the same thickness and I could then go back to the button for the future reloadings. Does this sound like it would work? I'm not really set up nor wanna be for neck turning at this time.
My brass measures .013-.0135 on the one side and .016-.0165 on the opposite. I'm thinking a reamer .003 bigger than the ID should be about right.
Mike..you are correct that this is for an AR.

 

[ronemus]

My reloading is for an AR, and I've never had a problem with 0.002" neck tension; remember, that's the point where bullet pull is maximum. Smaller necks will actually give you LESS bullet pull, and could contribute to problems.

You definitely don't want to inside ream if your case neck thickness varies. The reamer will follow the existing hole and you'll be left with a thinner eccentric neck. Outside neck turning will give you a constant neck thickness, and will also help reduce the oversizing of your brass. If you turn to a consistent 0.013" thickness you'll have eliminated a major source of bullet runout, and the expander won't be working the brass as much. Using the expander to bring the neck up 0.001-0.002" shouldn't produce any runout.

You might even want to turn the brass to 0.012". Ideally the ID of die neck should be 0.003-0.004" less than loaded diameter; the brass will spring back 0.001" (less when new or annealed, more when work hardened) and the expander will bring it up 0.001" leaving you 0.002" under - perfect. Since you don't have a bushing die, you'll want to be conservative now and allow a margin to cope with hardened brass. You'll need to know the ID of the neck of the die (0.001" under the sized neck diameter of a soft case is a good approximation); subtract the bullet diameter, add 0.004" and divide by 2 - that's the neck thickness you want.

If you're turning a lot of cases, you'll want to use a turning tool with a carbide cutter and mandrel; steel (especially the cutter) wears, even with lubrication, and requires that you readjust the tool frequently. This isn't a consideration for 20 cases, but needs attention if you're working up hundreds or thousands of cases.

I run a close-necked setup in my AR (0.003" clearance) and have prepped over 7,000 cases. I use a Gracey Neck Shaver, and it's really fast but the steel cutters wear and I have to adjust them every 100-200 rounds. I like the Gracey, but I had to replace the mandrel (poorly machined) with a Sinclair mandrel to get it to work well. The case necks MUST be lubricated inside and out (Imperial Die Wax works well). I wish there were carbide cutters available, but haven't found anything that might be adapted.

 

[toodogs]

And there is this tool to fix runout. http://www.accurateshooter.com/forum/index.php/topic,3743715.0.html. Simple, and it works. Less work than neck turning and so forth. And you'll always have some cartridges that have case wall variation that will result in runout when the bullet is seated. Tool works for factory ammo too. Even the higher end factory ammo can have a cartridge or three (more too) in a box with runout.

Pat

 

[blawton]

Yes a inside reamer might help the runout a small amount but its by no means gonna correct the brass if its offset from one side to another. Turning the outside of the necks is really the only way back to true if the thickness is off by more then .0005 from side to side.

 

[Hapnin]

Looks like I'm gonna be neck turning tool shopping. I also think I'll see about getting a FL die with a neck bushing made for it as well.

I really appreciate you guys sticking with this thread, it was getting pretty long and thanks for all the help. I could have struggled with this for quite a while and tried/ purchased a lot of stuff that wouldn't have helped.

Y'all take care and shoot well.

 

[toodogs]

Here is a piece I wrote that discusses case neck concentricity.
Mathmans advice regarding neck wall thickness is key here. And I do respect his input and wisdom very much!

Here is why neck thickness is key:
The likelyhood that if the neck walls are a uniform thickness means that the shoulder area and the case body walls beyond the neck/body junction are also uniform (close to the same) thickness. IMO it's the neck/shoulder region of most importance to inducing "runout" during sizing AND bullet seating functions. Visualize the neck & shoulder as a funnel. Now visualize that the "wall" or material thickness of the funnel is thinner on one side. If you apply a tensile load (pull) on the end of the spout of the funnel the side of the funnel at the spout/funnel body that is thinner will yeild while the thicker, therefore stiffer, will resist yeilding.
Likewise, applying a compressive (pushing) load on the end of the spout, the side of the funnel with the thinner walls will yeild whereas the thicker walled side will resist yeild.

What this boils down to is that during the press upstroke the case is forced into the die cavity, brass flows, and assuming die/shell holder alignment and so forth are correct, there will be zero runout of the now sized case. This is true of any sizing die.

For die that has an expander stem, on the downstroke of the press, where the case is drawn down and the die "expander" button engages the now undersize neck I.D. a tensile load is induced upon the case. Say the shoulder/neck walls are of non-uniform thickness, the shoulder/neck junction will yeild a bit while the expander button is pulled through the neck. Runout, or think of it as the neck axis is now "crooked" out of alignment with the case body axis, is the result. If the wall thickness is fairly uniform the tensile load will induce little mis-alignment of the neck/case body axis. Note: it's a real GOOD practice to lube the inside of case neck, being sure to get lube at the shoulder/neck junction.

Also, bushing and Lee collet dies do not typicaly induce runout during sizing. However, when the too large neck is forced into the smaller neck sizing region of the die residual stress may remain in the case neck/shoulder region which will cause the neck to shift a bit out of axial alignment when the case is drawn out of the bushing or collet die. Most affected are case that have a large difference in wall thickness.

Ok, bullet seating. Potential problems here too. Typical interferance (press) fit of bullet/neck is 0.001-0.003". Assume that the bullet axis will be aligned perfectly to the case axis and case neck mouth is square to the case axis. If the shoulder/neck walls are uniform thickness, during the applied compressive load of bullet seating no yeild of the shoulder/neck junction will occur. The now seated bullet should result in a loaded cartridge that has near zero runout.

If shoulder/neck wall thickness is not uniform, yeild may occur, and the cartridge will have "runout", or a non-concentric condition of the bullet axis in relation to the case body axis.

So, result is that some cartridges will have near zero runout, some will have unsuitable runout. Myself, I have noted better accuracy from carts. that have little runout. Whole set of conditions enter that discussion though. Tight chamber-vs-loose chamber, and so on.

JMO though.

Pat

 

[Hapnin]

What you say makes great sense and I don't doubt that you and the others are absolutely correct.
Would you think that necking down a cartridge may also influence neck thickness variations? Like when you squeeze down the neck, the excess brass does not get spread evenly around the whole neck? That is what I suspect is going on with my cases. The brass is not " spreading" evenly during the necking down process and then the expander pulls the thin side out of round.
Is there another way I could neck down without this occurring or should I just neck turn after the sizing? I might end up with a "truer" round by going this route?

 

[toodogs]

ronemus has good input in his post above. I use 0.002-0.003 neck tension for my AR ammo (223). I use 0.002 for my .308 ammo in a bolt f-tr gun.
Hapnin, if you know what the diameter of your chambers neck is that will be helpful for the neck turning you may do. Last thing you want is too little case neck to chamber neck clearance. Apples and oranges, but my f-tr chamber is 95palma, meaning that with heavier walled cases I can still do no-turn necks and have 0.002 clearance per side. Too little neck clearance is not desirable due to not enough room for neck walls to expand while bullet is being released. Could be some bullet base obturation occurs too and is part of the equation. If I had a tighter necked chamber I'd need to consider turning neck OD of thicker walled brass.
So, if you know what your chambers neck dia. is, step 1. Next, size a case, expand the neck ID to get it 0.002-0.003" smaller than bullet dia. (step 2). Measure neck OD. (step 3). What is the case neck dimension compared to the chamber neck dimension? That gives you a basis to decide how much (if any) to neck turn. Remember that 0.002" (0.004" total) chamber neck clearance is kinda tight IMO, so you might want a clearance number like 0.004" per side (0.008 total) Others here could give good advice to that dimension. A tighter chamber in general shoots better, however????
It's been my experience that brass flow from the firing events has not moved circumferentially, thus evening wall thickness. On cases I've made runout during bullet seating, and measured neck wall thickness after firing, the thinner side is always there on subsequent loading firing cycles.
my 2 cents anyhow.

 

[Hapnin]

I'll get ahold of the smith that chambered my barrel and see about getting a chamber and/or reamer print and go from there. My brass only differs by .003" from the thin to thick side.The thin side is .0135" so it looks like I could clean up the whole OD of the neck without hurting anything. It just seems strange to me that I know people neck down brass all the time and don't seem to have this problem. I'm not even going down a whole caliber. Is this problem normally associated with necking down brass? What about making 22BR from 6BR? Or is this just a side effect of the original brass? This brass is not so expensive that I couldn't/ wouldn't just scrap it if I thought it would be less hassle.
I'm just trying to understand what might be the cause and learn to correct it in the future.

Thanks again for all the help. Maybe after visiting this site for a few more years, I'll be able to help someone as much.

 

[infantrytrophy]

In one of his excellent and well-researched posts in his "Rifleman's Journal", German Salazar performed tests to determine the effects of the seating die on cartridge runout (see link below). He cleverly designed the test to separate the effects of runout inherently due to the brass vs. runout induced by the seating die.

While many will interpret this article to conclude that a certain brand of die might be better that others, the real lesson is that all of the dies tested are good and that the more prominent effect on bullet runout is the quality of the brass. I think that Toodogs has made the same point here.

See this link: http://riflemansjournal.blogspot.com/2009/09/reloading-seating-die-runout.html

Randy Sikes

 

[Hapnin]

I'm beginning to agree. I just measured both neck wall thickness and runout on my "parent" brass ( brand new ) and have both thickness variations and runout. New brass is on order. I'm still curious if necking down in general will cause neck wall thickness variance.

 

[toodogs]

I don't think so, just my uneducated opinion though.

Pat