Educate me

ChetStafford

Explain to me neck reaming and turning to get the run out of the case neck. Thanks in advance

jonk

Neck reaming and turning both essentially do the same thing. Reaming does it from the inside, turning from the outside.

Case necks aren't uniform in thickness all the way around. The idea is, you take off the high spots until they are. It also helps uniform all your brass to 1 thickness to allow for consistent bullet release drag.

45Kimber

When you resize a cartridge you are pulling a round resizing ball back out to make the inside "hole" round. The case's walls are not the exact same thickness around that hole. By shaving off the thicker parts of the wall you make a perfect hole outsice of the hole. If the walls are not the same thickness, as the brass expands after the round is fired, you have spots, the thick ones, that put more drag on the bullet canting it as it leaves the case. I do not practice this but at some point I will give it a try. Adds lots of time to case preperation.

ChetStafford

I loaded some .223 Rem to night and was getting .003 to .005 run out in some of the rounds. I just want to make the ammo the best I possibly can.

shoff14

Try competition seater dies and lap the bullet you want to use to the die.

bpost

Are you getting bullet runout or are you getting neck runout? There is a difference.

Bullet runout can be helped by partially staring the bullet then rotate the case 90 degrees as you seat the bullet. A competition seating die guides the bullet into the case during seating keeping it aligned with the case mouth. I have Redding Competition seating dies and appreciate the quality of their product.

Case runout can be neck consintrisity (sp?) issues, varying neck thicknesses or a sizing die with the runout machined into it. A lot of case runout happens from the expander ball being off center causing a slight off-kilter to the neck.

ChetStafford

quote:Originally posted by bpost1958
Are you getting bullet runout or are you getting neck runout? There is a difference.

Bullet runout can be helped by partially staring the bullet then rotate the case 90 degrees as you seat the bullet. A competition seating die guides the bullet into the case during seating keeping it aligned with the case mouth. I have Redding Competition seating dies and appreciate the quality of their product.

Case runout can be neck consintrisity (sp?) issues, varying neck thicknesses or a sizing die with the runout machined into it. A lot of case runout happens from the expander ball being off center causing a slight off-kilter to the neck.



I haven't worried about the out side of the case because it hasn't caused any problems I have been getting .200 groups until this new brass. Then with this brass I started getting A lot of runout in my bullets.

I kind of figured that if I was going to ream necks I would go ahead and get the neck turning fixtures as well.

I use a Forster case trimmer and they make all the attachments for neck turning and reaming.

Who knows if I get these cases down to a uniform amount of neck tension and low amount of bullet run out the rifle may shoot bug holes.

Rocky Raab

Brass that's notably thicker on one side of the neck is thicker down that whole side of the case - and the likelihood it will shoot bug-hole groups is minimal whether you trim/turn or not. The thin side of the case will always size differently and expand in the chamber differently, thereby obviating any modification you make to the neck. In short, it'll always be a bit off-kilter.

I've never tuned necks for two reasons: one, it is horribly tedious; two, it almost never helps for the reasons above, and especially so in a typically loose factory chamber. If I had a custom-chambered, tight-neck benchrest gun and premium brass I would turn necks, but that's the only time.

JustC

here is the tool used to determine the neck thickness variances


you will also note the neck turning tool on the bench to the right.

once variances are noted, and are outside the realm of acceptability for your purposes (mostly benchrest and match chambers with tight neck tolerances) you can set the trimmer to shave off the "high spots" which will bring the neck uniformity to much tighter tolerances.

here is a turned neck


dies which utilize bushings for exact neck tension are then used


and you can use a bullet with lapping compound on it, chucked in a drill, to lapp in the seater plug in your die


in a factory chamber, I doubt you will ever see much of a difference, except at long ranges.

grandman

Justc, Explan your last photo. I have been loading for a long time and don`t understand what it is that you are saying about the seater die. I have in the past turned my necks when I shot high power rifle but did not see a great difference in the ones that I turned and did not turn,. I am starting to load for medium and long range shots now and are going to start to turn my necks for .308, 6.5 x 55 and 30-06. What kind of tool is that that you are measuring the necks with?

JustC

The last photo is of a 140gr 6.5mm amax shoved into the seater plug from a set of redding competition dies. The bullet was coated with lapping compound and chucked in a drill. The bullet was then turned in the seater plug until the internal dimensions of the seater plug, more closely resembled the shape of the VLD design of the amax bullet. This allows for less runout due to better bullet-to-plug fit. This was done because the rifle is ready for competition and I will be using only VLD bullets. Anything not VLD, and it won't matter since they won't be used for long range target work anyway.

The tool pictured for neck thickness measurements is the Sinclair Neck thickness micromoter. It measures down to the .0001"