Full Length Dies, Runout Correction?

I got a new batch of Remington 300RUM brass. So I decided to check the neck thickness and sort by uniform batches. Holy cow. Some varied by .006". Most all were greater than .003". Thats a bunch of crap. So here I got getting busy and turned the neck to take off the high spots. Well all this neck working causes the neck runout to be pretty bad and by the looks of it, they were bad from the start. So I picked out the worst one with .007" neck runout that has a uniform neck thickness now, and pushed it thru my Full Length die. It corrected the neck runout down to .004" from .007".

How much can Full length sizer correct for? I think the die is straight. I have checked several times with out expander balls from fireformed brass.

I figured the only way for me to have dead straight brass is to now fireform. Whats the best way to fireform these badboys without loading up expensive bullets? I was reading you can use Unique and dacron, but don't know if I like that dacron burnt in my barrel.

Any help would be appreciated.

By the way, I checked the thickness of the neck of my federal 308 brass that has been once fired. Guess what? None were greater than .003".

Well, just talked to Tech Support at Sinclair and at RCBS. They said no way a FL die can correct for that much neck runout. Said I was lucky I got it down to .004". I am happy with .004 of neck runout. I can deal with that as long as my seated bullet runout doesn't exceed that.

Said the only way to get dead straight ammo is to now fire it in straight chamber.

Also suggested I stay away from fireforming with cream of wheat, cotton, dacron or anything other than a bullet.

[1mile50]

How much can Full length sizer correct for? I think the die is straight. I have checked several times with out expander balls from fireformed brass.

Is your decapper stem straight?


Doesn't pay to worry about the runout too much until you fireform them. Neck turned rounds should be fireformed anyway. Won't matter how straight you get them, your FL sized cases will banana when you shoot them, because the case walls vary so much. The best you can do is cull the worst and with the rest index the runout by marking the edge of the heads with a very small file, then shoot the rounds with the index marks always in the same o'clock position.
Once the brass has been foreformed, the amount of flexing when you shoot will be minimized. Indexing the brass will also help greatly. Hopefully, you have or can get a bushing type neck sizer. You should be able to do better than .004" then. A bump die would be great too, but I don't know if they are available for the .300 RUM. I would suggest some inexpensive bullets for the fireforming.
Pat's Reloading
Forgive my ignorance, but does anyone else make .300 RUM brass?

Is your decapper stem straight?

Yea, its straight. I have checked the dies several times. You know, taking a fireformed piece and checking concentricity, FL sizing without the stem, checking concentricity again. Putting the stem back in, and raising it as high as it will go, and resizing again. And if the neck thickness is real uniform (>.001"), then the brass will come out uniform. If my case necks vary in thickness like .005", then when I drag it thru the expander ball, the neck will be .005" out of round.

If I use my Bushing die redding, now you trade off Neck runout for inside neck runout. In other words, if you necks vary in thickness, and you run thru a bushing die, you neck runout is 0", but now your inside neck will be off and cause your bullet runout to be bad.

So, in my quest for perfect brass, I had to resort to neck turning. I was just hoping a FL sizer could knock the necks back in.

But I found out something interesting. I measured necks of 50 more new pieces of 300RUM brass that has not been worked or turned, or fired. They were bad from the start. Runout varied .001" to .006". So I sorted them, and expanded the necks, and turned the outside. Good news is the turning isn't causeing them to be anymore out of round than they was before. Bad news is these cases are junk.

Out of 150 cases I have brand new, over 40% of them are dented on the body or mouth. Some real bad. I am going to take a picture of them, and send to remington.

Yes, Federal made a batch. But only thru D and L Sports. And you have to buy by the 500.

Thanks for replying 1mile. Hope you know I am not blowing off what you say. Just have tried alot of this before.

Fact is, for a good dynamic load, runout should not matter so much. For example. My 308win load is 46gr of Varget with 210 primer and 165gr Gameking. I sorted 50 loaded rounds last year by bullet runout. I got 1.1" grourps very consistently with ones with runout less than .002". Some groups were .5" at 100 yards.

With ones with runout >.005, that opened to 1.5". A few groups had flyers. Some were still .6" groups.

Bottom line, it made a miniscule difference. But these RUM's with free bore are like Weathby's and bullet comeing out of the brass as high speed and then freeboring .2", you want it to be staight as possible. Unlike my 308 where I am .01" from the rifling.

[1mile50]

If I use my Bushing die redding, now you trade off Neck runout for inside neck runout. In other words, if you necks vary in thickness, and you run thru a bushing die, you neck runout is 0", but now your inside neck will be off and cause your bullet runout to be bad.

bigcountry,

That's why most folks use dies with expander balls.
To use a bushing NS die properly, you must turn off the high spots on the neck, after FL sizing with your expander ball type die, which will put the high spots toward the outside.
The cases must then be trimmed equally, before the neck turning. The full length sizing and the trimming means that the necks should all be of equal length, the high spots outward and the shoulders set to equal dimensions, relative to the datum line.
This ensures that the necks are all cut equally. A proper neck turning should result with the cut going slightly into the shoulder, at the juncture of the shoulder and neck. This helps delay formation of the "dreaded doughnut", an inside thickening of the brass in that area. Also, because of the way brass is drawn, many times there is a thickening in that area to begin with. This "dreaded doughnut" is restrictive and it affects the gas flow, impedes performance and accuracy. Ken at K&M Services sells an optional fluted carbide mandrel for his neck turners. Upon the intial firing after the neck turn, the aforementioned cut will mostly disapear, the brass under it will flow and fill it. But as time progresses, the "dreaded doughnut" will return. Ken's fluted mandrel is for shaving it off from the inside.

The main purpose of a bushing type neck sizer is not to improve runout. The main purpose of a bushing neck sizer is to provide for an consistant specified neck tension, round to round. After the high spots are turned off, 70%-80% of the neck should at least be cleaned up. The average neck thickness should be very close. If you load a projectile into that case, the diameter of the neck will be projectile diameter plus (neck thickness x 2). If you chose a neck sizer bushing that is, let's say .003" smaller than that loaded neck diameter, all of your rounds, given that the prep was done consistantly, should have about .002" consistant neck tension. P + (NT x 2) - .003" + .001" springback =.002" neck tension. To really take advantage of this, the necks must be annealed, this gives true consistancy. If eveything else is done right, consistant neck tension gives consistant velocities, with a good load that = accuracy.
As far as runout and accuracy, you are right, runout is not the final word. It's a detail, and an excruciating one at that. The best way to eliminate it is to get the best quality brass, sort it and cull as necessary. You can correct runout to a good degree with a FL die. If your die is custom made to your chamber, made from the same reamer. You can size, turn the case 120 deg.,size again, repeat this, if necessary. With a regular FL die that has an expander, you would of course ruin the necks in no time flat.
There is a tool that I am interested in for correcting bullet runout in loaded rounds. See this link for the
Bersin tool
Some of the knowledgeable shooters at the range where I shoot at rave about it, but I'm skeptical. It is supposed to be able to correct runout accurately to .001". I'm thinking of asking Santa Claus for one. If I do, I will do a review and post a link to it.

bigcountry,
Now please don't think I'm blowing you off. I don't know much about .300 RUMs, but I know someone who is doing much better than 1.1" at 100 yards with his .300 RUM. More like around 2.5" at 565 yards. Don't feel bad, he is an R.O. at the range I go to, he gets lots of practice. I have not seen Bob lately, as he travels a lot, and now we are coming into hunting season. If you are interested, I will ask him what he has been doing with his rig next time I see him. Don't hold your breath, I may not see Bob for quite a while. But, I'm sure he has talked about his .300 RUM with another of the R.O.s, and I'm going to that range on the 19th.
Good luck!

No 1mile, my 300RUM don't get 1.1. It gets like .5", but you have to cull the brass, and cull your loaded rounds to get it. Its basically a target rifle with target scope and all. Just very tempermental over runout and temp it seems.

but in the end, it was a bad choice for a long range thrower. It is what it is.

I am talking about my browning Medallion in .308 hunting gun that get consistent 1.1".

When I talk accuracy, I talk about consistent accuracy. Or my worst group. As I think most should. I was shooting with this guy last weekend, and he got two rounds touching for a slug gun. Later he told everyone his 870 was a one hole shooter. So I yelled, and told him I would be lunch its not. Guess what, its more like a 3MOA shooter. And I got a real nice angus berger out of the deal.

[1mile50]

My 308win load is 46gr of Varget with 210 primer and 165gr Gameking. I sorted 50 loaded rounds last year by bullet runout. I got 1.1"

My mistake. I missed the reference to the .308. But, the rest of my post I'll let stand as it is.