Seating depth - Bullet engagement in the neck

[Rich S]

I'm looking for recommendations for minimum bullet engagement in the neck. I'm getting ready to order a reamer for a 223 project. I'm wanting an all around gun for Prairie dogs and occasional 600 yd shooting. I sent dummy rounds to JGS with 55 grn and 80 grn bullets seated with 0.170 of neck engagement. Basically there is 0.036 difference between the free bore required to touch the lands between the 2 bullets. I'm trying to figure out if it is better to give up some neck engagement with the 55s or seat the 80s slightly past the neck shoulder junction. I plan to jump the 55s at least 0.010 to avoid the potential of pulling a bullet in the field. If the reamer is made for the 80s, the 55s would have ~0.144 engagement.

Thanks,
Rich

 

[Richard Coody]

rule of thumb one bullet diameter in neck. i say as long as you have enough to have adequate neck tension give it a shot.

as far as seating bullets where the base is past the neck shoulder junction. it is done all the time with these long skinny high BC projectiles. just limits case capacity and leads to compressed loads.

 

[243winxb]

Do this

seat the 80s past the neck shoulder junction.

Its done all the time in AR15 rifle with 69gr Sierras and the longer Hornady bullets.

Hodgdon lists a COL of 2.550" for a Sierra 80 MK. This may give you an idea. The Berger 82 gr is 2.375" Measure head to ogive on the bullet of your choice.

Go to the Hodgdon load data, look at the maximum powders listed. If you see a C for compressed loads, just pick a different power.

To little bullet shank in the neck may result in a crooked bullet on loading into the chamber.

 

[dolek]

Do this Its done all the time in AR15 rifle with 69gr Sierras and the longer Hornady bullets.

Hodgdon lists a COL of 2.550" for a Sierra 80 MK. This may give you an idea. The Berger 82 gr is 2.375" Measure head to ogive on the bullet of your choice.

Go to the Hodgdon load data, look at the maximum powders listed. If you see a C for compressed loads, just pick a different power.

To little bullet shank in the neck may result in a crooked bullet on loading into the chamber.

Great pics for comparison,thanks for posting. 68 grain Hornady has my attention,I have always used the 69 SMKs.

 

[Rich S]

Thanks for the input. I was leaning toward going with the shorter free bore and seating the 80s past the shoulder neck junction.

I should have stated COL isn't an issue as this will be a single shot.

 

[243winxb]

Bullet length data base,
http://www.jbmballistics.com/ballistics/lengths/lengths.shtml

Website also has a twist rare calculator... Berger has one also.

 

[Brians356]

The "one bullet diameter" rule of thumb is tiresome and useless. I wish it would die. Some of my most accurate 223 Rem loads have had only about 0.1 inch of neck engagement. (E.g. 40-gr BT touching the lands.) I've read similar reports from others on this forum and elsewhere.
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[Rich S]

The "one bullet diameter" rule of thumb is tiresome and useless. I wish it would die. Some of my most accurate 22 caliber loads have had only about 0.1 inch of neck engagement. I've read similar reports from others on this forum and elsewhere.
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The 223 case falls a little short to begin with. I believe max SAAMI is 0.203 neck length and most new cases are a little shorter. One of my concerns for varmint loads is having enough neck engagemet to handle the trip. Hopefully only one way loaded. Think for this build Ill go for 0.170 neck engagement for the 55 grn. If it doesnt work well for the 80s maybe chamber another barrel for them latter. Guess I better get something ordered as I have the barrel and the reciever should be here this week.

 

[243winxb]

View attachment 1028550

Think for this build Ill go for 0.170 neck engagement for the 55 grn.

This is enough.

How much neck tension? I like .002"

 

[jepp2]

The "one bullet diameter" rule of thumb is tiresome and useless.

I agree. However you can have too little bullet seating depth. And the cone of a BT bullet doesn't count. With .204 Ruger and a slow burning powder, I have had the powder fail to light with 1/2 diameter seating depth. Just shoved the bullet into the lands.

 

[243winxb]

I like the front of the bullet to seal the bore, before the base of the bullet exists the case mouth.

In my mind, this keeps the hot gases from blowing past the bullet, causing extra throat erossion.

Long bullet and short throats/leade, less erosion.

 

[Brians356]

I like the front of the bullet to seal the bore, before the base of the bullet exists the case mouth. In my mind, this keeps the hot gases from blowing past the bullet, causing extra throat erossion.

That's most likely to happen with bullet seated into the lands. If there's much jump at all, the neck will have expanded before the bullet seals the bore, and those hot gases move fast.
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[Metal God]

This topic is above my pay grade but if I were reaming my own chamber . I'd first have a bullet or type and weight in mind to cut for . I then would cut for minimal jump . Not sure what the numbers would be but my point is to be planning for throat erosion . I'd think my throat would be cut to where the bullet would be seated deep allowing me to seat longer and longer if needed as the throat erodes . Rather then starting out long and if I need to be seated in the lands I'll end up not having enough bullet hold if I do end up having to chase the lands .

 

[Rich S]

This topic is above my pay grade but if I were reaming my own chamber . I'd first have a bullet or type and weight in mind to cut for . I then would cut for minimal jump . Not sure what the numbers would be but my point is to be planning for throat erosion . I'd think my throat would be cut to where the bullet would be seated deep allowing me to seat longer and longer if needed as the throat erodes . Rather then starting out long and if I need to be seated in the lands I'll end up not having enough bullet hold if I do end up having to chase the lands .

Thast what I did. If only loading for 1 bullet Id just seat above the neck junction and the decision would be easy. However I was trying to optimize for 55 and 80 grn. The throat for the 55 grn dummy round I sent JGS ended up realy close to the Wylde and JGS drawing 0518. Several people recommended the JGS 0518. Appears Im probably just reinventing the wheel.

 

[dcali]

It's a balancing act between erosion and case capacity. The "minimum" is whatever will hold the bullet straight and tightly enough, and that doesn't take much - maybe 1/3 a caliber assuming reasonable neck tension and bearing surface. But if you ream a new chamber expecting to seat the bullets at that minimum depth, you'll soon be out of luck as the lands erode and you need to seat out further. If you get too conservative, you're just wasting valuable case capacity.

I'm not sure how you'd predict the optimal starting point, except to ask others for experiences with the cartridge of interest.

 

[Richard Coody]

don't expect throat erosion to be much of a factor in a .223 especially with the lighter projectiles.

now if it were a .22-250......

if you are trying to build a tackdriver i would think the compromise trying to chamber for both bullets will hurt you.