Checking Runout ?

[Derek M.]

I have a question related to this....

Depending on what device you use to measure runout, the case body can determine what results you get?

I use a sinclair runout gauge. The case body rides on roller ball bearings. If there is a high spot or bump on the case body where I am rolling it, it will show on the gauge. I have to really pay attention to make sure I am not getting a false reading.

I use the gauge from Sinclair also. To be honest, I was doing it wrong for the first year. I cradled only the brass case and had the gauge on the bullet. This is wrong. I always wondered why I was getting 3-6 thousandths in runout.

The rear of the case is cradled but the bullet where it meets the case mouth sits in the front cradle with the gauge on the top side. My runout went to virtually zero and most are less than .0015. I spoke with a guy at Sinclair today and he told me this was the correct way to do it.

In fact, ever since I had my sizer die's necks honed, runout is about zero.

 

[nheninge]

Neck turning, culling bad brass with increased runout from the start, avoiding sticky expander balls all work. Use high quality brass and bullets. High quality seating dies are a must. If I have a case with high runout, I cull it. Putting a bullet in a case with high runout only seems to amplify the problem. I strive to never develop runout, not to reduce it... However, there is even a swiss machine that claims to be able to reduce (not eliminate) runout by bending the neck. Never tried it though.

 

[Shawn Carlock]

DerekM,

If you put the bullet on the front cradle and measure straigth above it you are measuring nothing to speak of. The whole purpose is to send the bullet down the bore straight. Assuming that the chamber is square with the bore you want the bullet in the center of the case and pointing straight. The method you have described will not identify neck runout issues or bullet runout issues. The neck must be straight with the axis of the case and the bullet must be straight with the axis of the case to allow it to go straight down the barrel coming from a square chamber. The two cradle points should be on the body of the case as far apart as is practically possible. The indicator point should be on the bullets forward baring surface as far as possible but not out on the ogive. This will give you the true bullet run out based on the axis of the case. If you have excessive runout you can move the indicator to the neck to check the neck runout. You have to get little to no neck runout before you can get good bullet runout. If you put the forward cradle on the neck it will eliminate the ablilty to read the neck runout in the total, if you put the cradle on the bullet and the indicator above it you are reading nothing. Your original method was correct now you need to see if you are starting with neck runout before seating the bullet by running out the necks.

 

[Lookinforlunkers]

Hornady has a new tool to measure and correct runout. I have not tried it yet but would love to here if anyone has

 

[WildcatB]

DerekM,

If you put the bullet on the front cradle and measure straigth above it you are measuring nothing to speak of. The whole purpose is to send the bullet down the bore straight. Assuming that the chamber is square with the bore you want the bullet in the center of the case and pointing straight. The method you have described will not identify neck runout issues or bullet runout issues. The neck must be straight with the axis of the case and the bullet must be straight with the axis of the case to allow it to go straight down the barrel coming from a square chamber. The two cradle points should be on the body of the case as far apart as is practically possible. The indicator point should be on the bullets forward baring surface as far as possible but not out on the ogive. This will give you the true bullet run out based on the axis of the case. If you have excessive runout you can move the indicator to the neck to check the neck runout. You have to get little to no neck runout before you can get good bullet runout. If you put the forward cradle on the neck it will eliminate the ablilty to read the neck runout in the total, if you put the cradle on the bullet and the indicator above it you are reading nothing. Your original method was correct now you need to see if you are starting with neck runout before seating the bullet by running out the necks.

??? Shawn, this is what you are talking about, correct? This is from Sinclair's website:

Paul

 

[Derek M.]

Shawn, I put the indicator not directly opposing the cradle but up the ogive. I rechecked a bunch as in the photo how I have done it in the past and they still read the same. Just finished 75 rounds. I know exactly what you are saying though.

 

[elmerdeer]

DerekM,

If you put the bullet on the front cradle and measure straigth above it you are measuring nothing to speak of. The whole purpose is to send the bullet down the bore straight. Assuming that the chamber is square with the bore you want the bullet in the center of the case and pointing straight. The method you have described will not identify neck runout issues or bullet runout issues. The neck must be straight with the axis of the case and the bullet must be straight with the axis of the case to allow it to go straight down the barrel coming from a square chamber. The two cradle points should be on the body of the case as far apart as is practically possible. The indicator point should be on the bullets forward baring surface as far as possible but not out on the ogive. This will give you the true bullet run out based on the axis of the case. If you have excessive runout you can move the indicator to the neck to check the neck runout. You have to get little to no neck runout before you can get good bullet runout. If you put the forward cradle on the neck it will eliminate the ablilty to read the neck runout in the total, if you put the cradle on the bullet and the indicator above it you are reading nothing. Your original method was correct now you need to see if you are starting with neck runout before seating the bullet by running out the necks.

I have the Neco concentricity gauge and from the pictures in the manual on how to check runout, it shows one v-block on the back of the case .025 away from the end of the head and the other v-block just off the neck on the bullet and the dial indicator right in front of where the ogive starts, with the bullet tip touching a flat surface. So I am assuming this is the corect way to check for runout.
Elmer

 

[Shawn Carlock]

If you place the forward cradle on the neck it will not allow you to read the neck runout into the total runout of the bullet. The Sinclair picture posted above is the correct way to read total bullet/case runout. If you place the cradle on the neck and the indicator on the bullet all you are reading is bullet/neck runout. If you have no neck runout this is fine. The important part is to insure the bullet is going straight down the bore, bullet/neck runout is only part of the the total bullet case runout. Since we are using the chamber to hold the case/bullet square with the bore we need two things:
1. A square to the bore chamber.
2. The bullet square in the case.

If you measure bullet runout against the neck and the neck is offset or crooked with the bullet to neck runout at .000" you will get readings of .000 If the neck is offset or crooked .003" and you test runout with the cradle under the neck you will still get .000" If you test as pictured above you will get the proper runout of .003". The bullet has to spin in the center of the case, just because it spins in the center of the neck may not mean it is straight with the axis of the bore.

 

[Mikecr]

I agree with Shawn. The Sinclair setup shown is the only CORRECT setup.
That NECO setup described is completely wrong.
And any of the adjusting type tools pinning the bullet tip and case head are also very wrong.

The neck and bullet, one end, must be free to measure