Should I Outside Neck Turn My Brass?
October 25, 2018 Sierra Bullets

Should I Outside Neck Turn My Brass?

By Paul Box

This is a question we get just about every week. Should I neck turn my brass? Well, the answer can be yes….and no. Let’s look a little deeper into it.

Naturally, if we had our favorite gunsmith chamber a rifle with a “fitted” neck we’ll have to neck turn in order for it to fit our chamber. But what about a standard SAAMI spec chamber? This all depends on the quality of your brass. Namely your case neck thickness variation. What I do is take a ball Mic and check the case neck thickness at “8:00 o’clock, 12:00 and 4:00 o’clock points. If my thickness variation is .001” or less, I wouldn’t outside neck turn. Unless we’re shooting 1,000 yd. benchrest I don’t think you’ll see any difference in accuracy if this thickness difference is any smaller than that.

Our main goal in outside neck turning is to give our seating die it’s best chance to seat a bullet with good concentricity with as little of run out as possible. This puts our bullet in better alignment with the center of the case body and in a squared and trued action, more perfect alignment with the bore.

Brass that has a neck thickness difference that’s more than .001″can be turned down to this spec and will shoot fine. They’ll also have the advantage of not being too thin, which will give early case neck splits and short case life.

Comments (10)

  1. Frank Haertlein 5 years ago

    Outside neck turned some once fired Lapua cases in a 22-250 Ackley Imp, big mistake. My groups opened up to more than 2 inches at 100. The un-turned, once fired cases produced ragged one holers once I reached the Accuracy Velocity of the barrel (http://www.orionite.com/accuracyvelocity.htm) . Do not turn case necks unless you have really bad brass and even then this is an iffy proposition. If your cases are so bad that you need to neck turn them you are better off throwing them away and going with quality produced brass.

  2. Chuck 5 years ago

    What is a good case concentricity gauge. Most of my stuff is RCBS but Im not married to them.

    Lewiston, MI

  3. Dan 4 years ago

    Properly performed neck turning on any brass will result in truer, more consistent ammo. Loss of accuracy as noted by Mr. Haertlein was likely the result of his load not having enough tension to keep the bullet from moving and aligned with the axis of the bore through the process of loading. If necks are turned for brass to be used in a semi-auto, it is important to be able to keep a solid grip on the bullet to prevent movement and neck tension is best controlled with the use of neck dies that have bushings that can be changed to give the exact tension needed to provide the optimum results. Taking a lot off of the necks while turning and using factory dies with no bushings will often leave insufficient neck tension.

  4. Usedguns 4 years ago

    I truly appreciate this article post.Much thanks again. Much obliged.

    • Royce 1 year ago

      I neck size and get great accuracy with an occasional flyer. I’ve been on hiatus due to lack of components. These days supplies are more readily available. If I recall, when using my calipers the inside and outside of my 30-06SPNG necks are right on the money. I also run through a trimmer just in case of any stretching. Here in Wyoming I do have to stretch a shot just under 550 yards. Should I use some other guage to check if the necks could use some turning?

  5. Chuck 3 years ago

    Neck turning my be required when full length sizing brass from the parent .308 to a sub cartridge of that family of brass. The case neck brass my be to thick and turning would be done to allow expansion room in the chamber to reduce pressure and failure of the firearm due to no expansion room. Don’t do it if not needed. Read manuals on this subject and expect a good sum for the tools and measuring devices.

  6. Marty Pyke 2 years ago

    I have box of Sierra game changer .277, 150gr, for a rifle with twist rate of 1 in 8″. If find a good load with this bullet, will I be able purchase more of those bullets in the future?

  7. DAVID LAWTON 2 years ago

    Yes, indeed always something to learn.
    For the unsatisfactory points mentioned it just might be that in the process of that specific neck turning job there may be, could be a glitch that was not realised or identified.

  8. Clint 2 years ago

    Some years ago I bought a case of American Eagle .308 with 150 grain bullets. Accuracy was horrible. I just figured the Savage 110 heavy barrel rifle was at fault. I purchased a Ruger .308 precision rifle. Same deal with groups. 1.8″ average. I turned the necks of these same cases and groups dropped to .7″ average with all of my bullet choices. I am using L.E. Wilson hand dies to load.
    I recently bought 100 Llapua cases. I’m hoping to get good accuracy with them without having to turn them. Stay tuned. This truly is a great sport.


  1. […] would reduce variation in the case necks to less than .001″, which this ballistic tech from Sierra Bullets says is the […]

Leave a reply

Your email address will not be published. Required fields are marked *