Runout and bullet jamming

[jambau]

I'm loading 140gr. Bergers for my 7mm-08 and they exhibit runout. Enough that I can easily see it when rolled across a piece of glass. They are seated way out in order to be seated into the lands which means minimal purchase inside the case mouth. Since I am neck sizing only I'm wondering if some of that runout is being corrected during chambering due to the fact that the body is supported and the lands are centering the bullet to it's axis. Is this possible? I have never had a stuck bullet in the throat upon extracting live rounds and they are super accurate.

Your thoughts,

Tikka09

 

[MALLARD]

Re: Runout and bullet jamming

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tikka09</div><div class="ubbcode-body"> Since I am neck sizing only I'm wondering if some of that runout is being corrected during chambering due to the fact that the body is supported and the lands are centering the bullet to it's axis. Is this possible? I have never had a stuck bullet in the throat upon extracting live rounds and they are super accurate.

Your thoughts,

Tikka09 </div></div> i believe what you wrote is possible ,but if the bullet doesnt get stuck in the lands then i dont think your lands will center the bullet , or , if your getting small blemish marks on your bullets , then maybe.some guys do that.

what kind of dies are you using ? brass ? , you know , without a runout gage of some sort , i dont think you should worry about runout , i think eyeballing runout is hard, if your accuracy is good then it doesnt matter right ?

 

[jlow]

Re: Runout and bullet jamming

I think the rule of thumb is to have at least one caliber length of contact inside the neck, and this does not include the boat tail area, are you getting this?

Logically speaking, the shorter the length of the bullet sitting inside the neck, the greater the chance for run out.

 

[BBeyer]

Re: Runout and bullet jamming

If you have enough runout that you can see it rolling the ctg. you have way too much.

 

[jambau]

Re: Runout and bullet jamming

Here are the specifics:

Winchester case (neck turned to about 90%)
Neck sized on Lee collet dies.
140gr Berger VLD seated to OAL of approx. 2.795 (no tools to measure from ogive)seated with RCBS dies

I can't get an exact measurement but there is about 1.5mm of purchase on the bullet.(yes I know this is insane)

I've tried different seating depths and got less runout but lost accuracy.Also these are not my hunting rounds.

Thanks again,

Tikka09

 

[flashhole]

Re: Runout and bullet jamming

Why not go to the equivalent flat base design and get more neck surface on the bullet.

 

[Lumpy Grits]

Re: Runout and bullet jamming

Glass is NOT flat. Don't depend on it to be either.
Buy the correct tool. Sinclair has about the best one out there.
You want a T.I.R. of .003" or less.
Cheers,
LG

 

[jlow]

Re: Runout and bullet jamming

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tikka09</div><div class="ubbcode-body">I can't get an exact measurement but there is about 1.5mm of purchase on the bullet.(yes I know this is insane)</div></div>

So my guess is that you already know the source of your problem. Having only 1.5mm of contact point gives you a knife edge to pivot on and so any lateral pressure is going to immediately give you runout – its’ not a workable solution.

The flat base idea is good as long as the bullets are still long enough to reach the lands.

This is a bummer but I hear a common problem with commercial guns – the chamber dimensions has been dictated by the legal department to avoid problems from folks who neglect to trim their neck to length.

 

[Fuzzball]

Re: Runout and bullet jamming

"they are super accurate...Your thoughts,"

I strongly doubt that touching the lands lightly does very much for runout in common ammunition but if what you're doing is "super accurate", what difference does it make? It's seems more likely that your bullet runout is being limited by a tight chamber and leade.

 

[bohem]

Re: Runout and bullet jamming

A highly competitive tactical and F-Open shooter that I know ran some tests on this topic.

He loaded some ammo and purposefully introduced 0.015" of angularity runout (measured at the bullet tip) and tested the ammo jumped and then using his normal jam.

Jumping them there was no reduction in the runout upon insertion and extraction.

Jamming them the runout was eliminated.

This was all performed from a match grade, Warner Tool cut chamber on a 7 WSM with 180gr Berger VLDs.

The group size change when jamming was non-existent. For the jumped loads the group sizes grew substantially (due to bullet seating depth, and then again with the runout ammo).

 

[725franky]

Re: Runout and bullet jamming

I wouldn't worry about it if they are performing like you want (and they're safe).

 

[jambau]

Re: Runout and bullet jamming

Yeah, I guess I'm being too anal about it. They are shooting great. Better to leave well enough alone. I do have another load using the speer 130gr SP's. These are my hunting loads and they are quite accurate as well. However, I'm going to give F-Class a try and thought the 140gr VLD's would be better. Any other 140's out there I can try for longer range?

Thanks again,

Tikka09