Help - bullet runout

[crkckr]

This might seem a bit silly but give it a try. When I loaded up some .308 that showed decent neck runout but a large tip runout, I tried pushing sideways on the bullet and danged if the runout didn't move to the opposite side! Not all that hard, either. I just pushed a little less and centered the (now delicate) rounds for near to zero runout. Didn't seem to make much difference in accuracy, tho. Hmm... honestly, I'm in the least sure what, if anything, this proves. Nothing special in the accy department but that could have been the bullet/powder combo. Needs more testing to be sure. However, all of most accurate ammo has had low runout numbers all the way, so... lot's of question marks there!
Good luck.
Cheers,
crkckr

 

[4SFED]

Given your sized neck runout is OK, the culprit has to be one or more the following:
-Misaligned seating dye body
-An incorrect/mismatched seater plug.
—a defective press
-too much seating pressure due to oversizing the neck
-a bad batch of bullets.(I have experienced this!)

You're missing the point ... the neck can be centered but slightly angled. Measure the concentricity of the neck of an assembled cartridge, then check near the tip of the bullet. If the neck is on center but the bullet has runout, the neck is not straight.

 

[WalksLikeADeer]

You're missing the point ... the neck can be centered but slightly angled. Measure the concentricity of the neck of an assembled cartridge, then check near the tip of the bullet. If the neck is on center but the bullet has runout, the neck is not straight.

Have you checked a batch of bullets for run out at the tip that have not been seated in a case? Post your results...

 

[Mikecr]

Any shape can be centered, and therefore put in a concentric condition.
But if you want actual straight ammo, you'll remove any value commonly assigned to 'concentric', and focus purely on TIR.
A V-Block type runout gauge fully shows everything, and once you've removed everything, your straight ammo will also be concentric (to it's own form).

So why would you want straight ammo? It has nothing to do with any notions of alignment with bore centerline. You're chamber, throat, & ammo are rarely aligned with a bore, which is rarely straight itself. That is, while chambered, your bullet tips are not pointing at the center of muzzle.
You can have considerable runout, relative to your chamber clearances, before testing shows an affect. At some point it will, and this is due to chambered tension points caused by that runout. A chambered tension point is little different from any other tension point in a shooting system. Action issues, bedding issues, trigger issue, base issue, ring misalignment, forearm contact, your rest or hold, etc.
Straight ammo eliminates one potential here.

Where you have big chamber clearances, you're less likely to have chambered tension.
This serves many well enough, but it's also a huge contributor to the making of crooked ammo. Tight chamber clearances contribute to very straight ammo, and then your good to go again. It's relative and self perpetuating. Just understand and manage it.

 

[Mc Fraser]

Lots of good advices. Thank you all.
I also have a 300wm as well with complete set of Lee and Forster Competition with micrometer dies.
I ordered new shell holders from Redding, and brand new RCBS rock supreme press. Once they show up I'll start testing.
For the 270 Win I only have he Redding Series A dies which are the basic ones I believe. Do you think they are at the same level as Lee dies?

 

[Mc Fraser]

Finally, all my equipment arrived!
I used Redding series A dies, Lee carbide, Lee cast iron and RCBS RC supreme press. Win cases and 140 SBT Sierra bullets. To measure concentricity, I used the Sinclair gauge.
The brass was fired formed with very minimal runout; the bullets were measured as well with zero runout.
I used 10 cases for each test.
1. Lee press & Lee NS die 1-2.5 thou runout
2. RCBS & Lee NS die" 1-2.5 thou runout although more have 1.5 to 2 thou
3. Lee & RCBS press & Redding NS die 4-7 thou runout with imperial wax. Two cases were run through the die multiple times and increased the runout
4. Lee & RCBS press with Lee seating die 5-10 runout measured at the tip and close to case mouth
5. Lee & RCBS press with Redding seating die 3-5runout measured at the tip and close to the case mouth
When seating the bullet, I used some of the recommended techniques didn't seem to make a difference.