Neck Runout Question

[sithlord6512]

I just watched a video on youtube on case selection (video by ammosmith.com). On this video, it states to divide your maximum and minimum measures for neck concentricity by two to get the amount of neck runout.

E.g., Max measure = .005'; Min measure = .000 on the RCBS casemaster gauge means a neck runout of .0025 (i.e., (.005-.000)/2 = .0025').

Is this how neck runout is determined? I would have said neck runout was .005. If I am wrong, then I have mistakenly scrapped a lot of brass (I have been only keep brass with less than .004 variation between the max and min values as I have been told neck runout greater or equal to .005' is not recommended if good hunting load accuracy is the aim).

 

[kraky]

Most people talk about runnout as the total "swing of the gauge needle". In reality the real runnout is 1/2 of that as you have a center axis so to speak. If you had .005 needle swing you would be .0025 off a perfectly centered bullet.
Some people go crazy over runnout. I'm sure perfectly straight ammo can and will win long range competitions. Others get really great groups without paying any attention to it. It's real possible that runnout affects different guns way more than others.
Over at "longrangehunting.com" a guy reported that when making cases for his 338 edge the cases were coming out with .025" runnout(yes 25 thousandths) . Yet in his accurazed long range rig he was able to shoot groups inder 1" at 300 yds and could barely tell the diff between that wobbly brass and brass that had made the "fireform" and was concentric.
It's almost like a chevy vrs ford argument or blonde vrs redhead....what works for one guy doesn't for the next.

 

[ArmyCW]

I just watched a video on youtube on case selection (video by ammosmith.com). On this video, it states to divide your maximum and minimum measures for neck concentricity by two to get the amount of neck runout.

E.g., Max measure = .005'; Min measure = .000 on the RCBS casemaster gauge means a neck runout of .0025 (i.e., (.005-.000)/2 = .0025').

Is this how neck runout is determined? I would have said neck runout was .005. If I am wrong, then I have mistakenly scrapped a lot of brass (I have been only keep brass with less than .004 variation between the max and min values as I have been told neck runout greater or equal to .005' is not recommended if good hunting load accuracy is the aim).

Finding out this is acceptable runnout for hunting ammo. What caliber are you loading? I've checked some factory ammo and it's all very close to the .005, all it shoots okay. Biggest errors are shooter, work on your shooting skills, IMHO you get bigger rewards than trying to work on runnout... been there done that..
Not trying to be a Smart A**. Also look at buying new brass to start, some of the stuff I bought on ebay and gunbroker is without a doubt alot or runnout cause not shot in my gun..
I have a Douglas Premium barrel in 1903 A3 receiver.
Please start with good loading stock, you'll be rewarded..

 

[sithlord6512]

I am loading for a .300 WSM Remington 700. I haven't actually fired a single round for accuracy (partway throught barrel break-in process). I am new to reloading and find the attention the details such as neck runout "fun" (I am a scientist by training).

 

[steve4102]

I have mistakenly scrapped a lot of brass (I have been only keep brass with less than .004 variation between the max and min values as I have been told neck runout greater or equal to .005' is not recommended if good hunting load accuracy is the aim).

Don't scrap your brass due to neck runout. Neck runout doesn't necessarily transfer into "bullet" runout. Neck runout is measure on the outside of the neck. If you are not turning your necks, checking the out side of the neck walls tells you very little. It's the inside of the neck that will determine the amount of Bullet runout.

 

[rick smith]

You need to determine where the run out is coming from and correct the problem. Many times it is the expander ball on FL or neck dies. Check run out on a fired unsized case, that tells you if it is caused by your chamber. Then check after sizing, again after bullet seating.Rick.

 

[ArmyCW]

I am loading for a .300 WSM Remington 700. I haven't actually fired a single round for accuracy (partway throught barrel break-in process). I am new to reloading and find the attention the details such as neck runout "fun" (I am a scientist by training).

Rick & Steve are right on. Take a look at/ clean your Full Length resizer
the expander ball etc. Are you using new brass? Shot once brass in your rifle? Rem 700 is a very nice rifle in 300 WSM. How many shots fired
now? Break in a barrel shouldn't be more than 20-40 shots.. I think varring opions on this. Cleaning during break in is a must to remove copper fouling.... I've found Bore Tech Eliminator to work wonders...about
5 patches come out blue after every 15 shots..
Also check for runnout on new factory loads to see if brass or bullets
at canalure have runnout. My 06 is + or - about .005

 

[sithlord6512]

Thanks for the info - much appreciated. The brass is new, but was resized in an RCBS FL die (to remove dents in neck). Also, I am 2/3rd through my barrel break-in process (e.g., 1 shot+clean for 10 cycles, 3 shots+clean for 5 cycles, 5 shots+clean for 3 cycles. I am using Barnes CR-10 (BTW - I think I ruined my recoil pad - a little bit of the CR-10 got on the top portion of the recoil pad and seems to be eating away at it despite my best efforts to "wash" it off).

I did not check the neck thickness before I ran it through my die. I am beginning to think that I am getting a little carried away with going to "advanced" reloading techniques before having a basic foundation. For example, following a "tip" made by David Tubbs on the Sierra advanced reloading video, I took a little off my expander ball (about .002) - perhaps this may have affected the neck somehow. I guess I will have to wait until my new brass gets in the check the neck concentricity/neck thinkness before and after running the new brass through my die.

 

[steve4102]

Loading new brass, sized or not, will usually produce a ton of runout. The best way to get your die set up and check actual runout is with brass that has been fired in your rifle.