Safe amount of bullet in neck ?

[Okumacaptain]

I have a few 6BRs that have freebore for 105s. I remember like .14 or .104 , something like that . Anyways , I’ve changed to lighter FB bullets and of course they are much shorter . Just wondering as throat erodes , How far can the bullets be outside the neck ? Or inside I should say ? .05 , .1, .15 ? I’ve heard Berger say about 1/2 bullet dia. But I’m sure with the 68g bullets that I only have about .08 in the neck . So is there a safe standard ? These are being loaded single , no mag .

Thx

Mark

 

[6ShotsOr5?]

Can you clarify if you mean safe as in “not dangerous” or safe as in “will not diminish accuracy”?

 

[JEFFPPC]

I have shot with I would guess sbout .1 in a PPC and in a 6BRXwith no problems but required very careful handling of the ammo. Guns shot very well. Not a preferred method but it can work, I have done it.

 

[Mark W]

As @JEFFPPC says, I have a shot out 6.5-284 that still shoots great, but I have to be very very careful handling the loaded ammo because there’s not much bullet in the neck.

 

[Okumacaptain]

Can you clarify if you mean safe as in “not dangerous” or safe as in “will not diminish accuracy”?

I’m interested to know both . Safe and accuracy !

 

[gunsandgunsmithing]

If the bullet doesn't fall out, I fail to see the safety aspect, outside of safe loading procedures. IM?E, if the bullet stays in the case, it's safe, in a single shot action, being single fed with common sense. I've shot quite well with bullets that were barely in the case at all.

 

[Okumacaptain]

If the bullet doesn't fall out, I fail to see the safety aspect, outside of safe loading procedures. IM?E, if the bullet stays in the case, it's safe, in a single shot action, being single fed with common sense. I've shot quite well with bullets that were barely in the case at all.

Thank you sir !

 

[Ned Ludd]

In this scenario, there may be a few things you can to help optimize loads and the handling thereof with a relatively small amount of bullet shank seated in the neck (i.e. < 1/2 caliber). For example, you can vary neck tension (interference fit). Selecting from bullets sorted base-to-ogive those with the longest BTO dimension may throw a few extra thousands in your favor. Little things like that may be sufficient and help you get everything working to your satisfaction. Obviously, if you could fins a suitable FB bullet with a bit longer BTO dimension, that also might be beneficial.

One thing I would suggest that might ease your mind a bit is simply to load a few dummy rounds with your bullet of choice seated close to where you think they will end un in this particular setup. You can easily do this with varying neck tension/interference fit (.001". .002", .003", etc.). Then try to move the bullet in the neck with only your fingers. You might be surprised at how tight they will be gripped in the neck, even with only a small amount of bullet shank seated below the case mouth.

 

[divingin]

As an alternative, you can also look for a seating node further from the lands. When I was testing the Berger 108 BTHP's, they shot well at about .015" off, and at around .115" off. Ran out of them (and haven't found more) before I made any hard conclusions though.

 

[Straightshooter1]

As an alternative, you can also look for a seating node further from the lands. When I was testing the Berger 108 BTHP's, they shot well at about .015" off, and at around .115" off. Ran out of them (and haven't found more) before I made any hard conclusions though.

Hmmm??? Because freebores vary widely, how far you're off from the lands really doesn't tell anyone the seating depth or how much of the neck is holding the bullet. Now if we were to know the COAL and the case length, then we would have a better idea of what you're actually dealing with.

 

[Okumacaptain]

Hmmm??? Because freebores vary widely, how far you're off from the lands really doesn't tell anyone the seating depth or how much of the neck is holding the bullet. Now if we were to know the COAL and the case length, then we would have a better idea of what you're actually dealing with.

6BR
Case length 1.56
Bullet length .922 Berger 80FB
COAL 2.315

Case length 1.56
Bullet length .84 Berger 68FB
COAL 2.315

Both bullets .02 in the lands .

 

[Straightshooter1]

6BR
Case length 1.56
Bullet length .922 Berger 80FB
COAL 2.315

This configuration appears to give you .167" of shank seat depth (the amount of bearing surface being held by the neck), which is just fine IMHO. I've gone as low as .143 with my .308 cartridges using 168 SMK's with a COAL of 2.929 (obviously, a much larger bullet) and they did very well. . . even when feeding from a mag.

Case length 1.56
Bullet length .84 Berger 68FB
COAL 2.315

Both bullets .02 in the lands .

With this bullet and configuration you're getting about half as much shank seat depth at .078". It's doable, but I'd probably be a little uncomfortable feeding it from a mag as I would expect the feeding would very possibly alter the concentricity substantially. I'd be ok with handfeeding and even more so if the cartridge was touching the lands. .078" isn't much to hold concentricity.

 

[divingin]

Hmmm??? Because freebores vary widely, how far you're off from the lands really doesn't tell anyone the seating depth or how much of the neck is holding the bullet. Now if we were to know the COAL and the case length, then we would have a better idea of what you're actually dealing with.

My post does tell you that, in my rifle, those bullets shot well at one point, and with a tenth of an inch difference in seating depth. Which was my point: You shouldn't limit yourself to one depth simply because that's where everyone else seats. It wasn't my point to reference how much of my bullet was in the neck; just that not being able to reach the lands doesn't mean you have run out of options.

 

[Straightshooter1]

My post does tell you that, in my rifle, those bullets shot well at one point, and with a tenth of an inch difference in seating depth. Which was my point: You shouldn't limit yourself to one depth simply because that's where everyone else seats. It wasn't my point to reference how much of my bullet was in the neck; just that not being able to reach the lands doesn't mean you have run out of options.

OK, though it didn't answer the OP's question(s), you're absolutely right on.

And along that line, if the OP hasn't read the series of articles on the bullet jump research done there, it's a really good read:

Bullet Jump Research: Executive Summary & Load Development Tips

This is the last post in a series of articles focused on bullet jump research that has been conduct...

precisionrifleblog.com

I recently discovered with my .308 what Wade Stuteville did with his 6x47 mentioned in the article . . "He discovered on his 6×47 rifles he could start off jumping the 105 Hybrid’s around 0.080” and never have to change the seating depth over the entire life of the barrel and it’d perform great the whole time. Wade explained, “Over the life of the barrel, my jump might change from 0.080” to 0.130” or something, but it never really comes out of tune. And I’ve had a lot of cartridges that have been that way in the past.”

It makes me inclined to think of the importance of finding a good seating depth for accuracy over worrying at all about bullet jump.

 

[JMayo]

Just an fyi. Most small bullet shooting rifles need 0 freebore for this reason.

If it'll stay on the case .. shoot it.
But don't eject a live round !

 

[divingin]

And along that line, if the OP hasn't read the series of articles on the bullet jump research done there, it's a really good read:

Bullet Jump Research: Executive Summary & Load Development Tips

This is the last post in a series of articles focused on bullet jump research that has been conduct...

precisionrifleblog.com

That is an excellent article. I read it a few months ago, and realized there's a lot of experimentation in my future...

 

[243winxb]

Slow Powder may not burn correctly with little shank in the case neck, combined with a long free bore jump to the rifling. https://forum.accurateshooter.com/threads/strange-dent-in-fired-case.4016999/

 

[dcali]

It's good as long as the bullet isn't falling out or being inadvertently pushed in/out. 1/2 a caliber is plenty - conservative even.

 

[divingin]

It's good as long as the bullet isn't falling out or being inadvertently pushed in/out. 1/2 a caliber is plenty - conservative even.

Kind of depends what you're doing, IMO. For range work, yes. For something like a mag-fed field gun that may get loaded and unloaded more than fired, or the spare ammo may get jostled around a bunch, maybe not so much.