Help with runout

[buckbrush]

I apologize if this has been covered before. I tried a search and nothing came up.

I am getting run out on my 7mm Rem mag and I don't know why or how to eliminate it. My gun definitely likes loads with less runout. I seperated some rounds into "non-noticeable visible runout" and "noticeable visible runout" using a hokey set of v-blocks I made because I don't have a gauge.

Groups with the noticeable were 0.450" and without were 0.280" I confirmed this with three trials.

I am using an RCBS rock chuck press with Remington Brass and a Lee Collet Die set.

Where do I go from here to eliminate it?

Thanks for any help.

 

[Brain]

Yes, this has been discussed many times before, but I figure it will continue to be asked time and again until the big candle in the sky burns no more. So...I'll lend some suggestions.

You need to figure out where the runout is being induced. Is your chamber out of round? Case necks inconsistent (thickness ans concentricity)? Die misalignment in the press? Bad die? Inconsistent chamfer on the mouth? Bad seating die? Press out of alignment? Etc...?

There are plenty of ways runout can be induced, but until you measure (not visually, with an indicator) from one end of the process to the other, and between every step, you'll be hard pressed to find the culprit.

 

[Derek M.]

Check out this thread:

Bullet runout in 375 H&H - Topic Powered by eve community

 

[buckbrush]

Thanks for that link.

I don't understand why it's not consistant from case to case. Some are bad. Some are near perfect then there are those in the middle.

 

[Derek M.]

Thanks for that link.

I don't understand why it's not consistant from case to case. Some are bad. Some are near perfect then there are those in the middle.

Well, point one from your original post is that ALL rifles will shoot concentric ammo better than ammo with runout, not just yours.

In terms of continuity of runout, there are variables, some of which you can control, others you cannot. You can get a bad batch of brass.

I have found that cases from Winchester, Remington, and Hornady tend to have more runout from the factory when new, v. Lapua, Norma, and Federal. Once fired cases have less to no runout than new.

In the case of sizing, if your case mouths have even as little as a thousandth or half thousandth of asymmetry, this can cause more runout when you seat the bullet.

Do this: measure the OD of a loaded round at the neck. Compare that to a sized case neck when using the expander, and also a sized case without the use of the expander. Then measure the OD of a fired case.....all at the mid-neck.

What are all of those measurements? If it is greater than 8-10 thousandths, that is a big problem. My Redding 270 die had 17 thousandths difference from a fired case to a sized case without expanding the neck over the button. Simply put, that is overworking your cases.

Plus you really need to buy a Sinclair concentricity gauge. Straight ammo is the only way to go.

 

[3006savage]

Neck size using Lee Collet Dies. Problem Solved.

 

[Brain]

I am using an RCBS rock chuck press with Remington Brass and a Lee Collet Die set.

Neck size using Lee Collet Dies. Problem Solved.

Reading comprehension goes a long way. Problem unsolved.

 

[Quarter Round]

I am using an RCBS rock chuck press with Remington Brass and a Lee Collet Die set.

Where do I go from here to eliminate it?

Thanks for any help.

Measure and sort at each stage of the process a selection of brass. Your measurements should point to the greastest cause of runout. Eliminate the identified problem and move on to the next largest runout stage. Sounds easier than it actually is. Good luck.

 

[boomhand]

I'm a greenhorn at reloading and went thru this until I narrowed it down to how I seated the bullet. The most important thing I found was not forcing the bullet into brass (that was checked for runout) . If I went very slow and I mean slow in starting the bullet until the brass accepted it I cut my .005-.008 down to .001-.002. I can actually tell if it's going to be a good cartridge as I'm feeling it start in. I'm wondering if a neck turning tool can make this process easier. Good Luck.

 

[buckbrush]

Some bullets do seat harder than others. I am usually pretty careful when seating them and rotate 180° while seating.

Aside from the Sinclair and RCBS concentricity guages, are there any others with notable mention?

Thanks for the help.

 

[3006savage]

Sorry did not notice you were using Lee Collet dies already in my first post. Are you sizing and then rotating the shell 90 to 120 degrees per the instructions from Lee, and then re-necksizing? This is recommended to further minimize runout. I do it mainly because I felt it would provide a tighter fit when seating the bullet.

 

[buckbrush]

I confirmed that it's definitly happening during bullet seating. It's more profound with 168 gr Bergers than the 162 gr Hornady A-Maxes I seated for some reason. Are there better seating dies available than the Lee that comes with the Collet Die?

I really slowed down the seating process as recommended and rotated about 3-4 times while seating and it helped a lot. It's still not a consistant problem though. I am now getting 3-4 loads with little to no runout then one with rather than 1-2 good ones to every bad one. I think I will be able to live with it now though.

Thanks!

 

[Quarter Round]

Polish your bullet seating stem cup to more closely fit the Berger bullet and you should see improvement.

 

[3006savage]

Buck you may want to check out the Hornady seating die. I do not use it but my buddy swears by them for seating bullets and he is really particular. Bottom of page two of the attachment shows how it works.

http://www.hornady.com/media/new_dimension_custom_grade.pdf

It seems like it could be a good solution to your problem.