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How much is not enough (seating depth)

M

Monteria

Well-Known Member
Joined
Sep 18, 2020
Messages
400
Location
Texas
Because field work is my primary use, I've always subscribed to the "1xbullet diameter bullet shank in the case neck" rule of thumb.

Today I tried out a new bullet in one of my rifles. It was a completely arbitrary load, with no change to the seating stem which was set for my standard bullet and load, just to get an idea if the rifle liked that particular bullet. It did.

This evening I loaded up 5 more for verification and noticed there isn't much bullet shank in the case neck (though I didn't measure how much, I'm guessing .2"ish)

If I was a bench shooter I wouldn't care, but what do yall consider minimum bullet engagement in the case neck for your field work?
 
There are plenty of examples of cartridges that don't measure up to the one bullet diameter rule.

The 223 Rem, 6.5 Grendel, 300 Savage and the 300 Win Mag neck length are all less than the diameter of their respective bullets.

Personally I don't worry if my chosen bullet is seated less than a bullet diameter as long as it shoots well.
 
I had the exact same question/concern a couple of months ago. This group advised me not to worry about maintaining one bullet diameter of case engagement, and it turned out to be good advice. I am shooting a 7 Sherman Max and have about .240" of case engagement and it shoots exceptionally well, and even after cycling numerous rounds through the chamber and out without firing them, there was no additional runout caused by the action of cycling the round. I'm rolling with it!
 
I have a gunsmith friend who built a super long throated 257 Roberts and it has .1 of bullet shank seated, shoots great bullets don't fallout.

But here is the real test. Put a loaded round in a kinetic bullet puller, measure and it give it a light tap and measure it. Continue with successively harder taps until you see some actual movement. Then make you own determination of the likely occurrence of that amount of force occurring in the field. You could also load the magazine of your rifle (confirm your chamber is empty) and give the butt stock a few raps against the floor and see if you get any increased COAL and assess for yourself the likelihood of that amount of force occurring in the field.
 
Monteria said:
Because field work is my primary use, I've always subscribed to the "1xbullet diameter bullet shank in the case neck" rule of thumb.

Today I tried out a new bullet in one of my rifles. It was a completely arbitrary load, with no change to the seating stem which was set for my standard bullet and load, just to get an idea if the rifle liked that particular bullet. It did.

This evening I loaded up 5 more for verification and noticed there isn't much bullet shank in the case neck (though I didn't measure how much, I'm guessing .2"ish)

If I was a bench shooter I wouldn't care, but what do yall consider minimum bullet engagement in the case neck for your field work?
Click to expand...
If my set-up allows, I always go for longer than SAAMI COAL.
1733573363157.png

(SOURCE: https://www.alcobullets.com/faq/)

Below is a cut-out I made for myself. It's a .338 Thor (NMI) to show the bearing surface related to the neck junction engagement. This would be how far I would go. The bullet is a 300 Berger at 3.7" touching the lands with plenty of room in the magazine.

1733574237103.jpeg


.338 Thor with 300 Berger 3.7 COAL1.jpg

Greg addresses this relationship as well.
1733575054246.png


 
I just measured and I have .13" of engagement. I have no concern with magazine function, etc.

My concern is simply, is that enough engagement to hold the bullet strait and steady in field conditions?

I guess there is one sure way to know... MTtF study starts now.
 
Fill the box and shoot. Unload and measure to see if they have grown/shrunk. If so, maybe play with neck tension and then do it again.

Or seat deeper and see if you can find the same accuracy...chances are, you will. If the rifle likes the bullet, it likes the bullet.
 
Along with the aforementioned checks for changes in seating depth. I'd load them check alignment, feed them from the magazine and recheck the alignment. I have seen this change the run-out of my loaded ammo in some guns. One was corrected with more neck tension. Others needed a different shaped bullets etc. More bullet length (long mono's) out of the case means more leverage pressure as it's fed up the feed ramp as fed from the magazine.
 
That Thor is a good example of a bulket that has too much engagement at 3.7" - should be at keast 3.850 to get out of donut area.
 
med358-boise said:
I have a gunsmith friend who built a super long throated 257 Roberts and it has .1 of bullet shank seated, shoots great bullets don't fallout.

But here is the real test. Put a loaded round in a kinetic bullet puller, measure and it give it a light tap and measure it. Continue with successively harder taps until you see some actual movement. Then make you own determination of the likely occurrence of that amount of force occurring in the field. You could also load the magazine of your rifle (confirm your chamber is empty) and give the butt stock a few raps against the floor and see if you get any increased COAL and assess for yourself the likelihood of that amount of force occurring in the field.
Click to expand...

In a heavy recoil rifle…..those in the magazine may get pushed back into the case when the bullet tip is "slammed" against the magazine

I never had any setback (lots of bullet to case contact) but when I was shooting cup and core bullets with an exposed lead tip…..the tip was battered very badly. By the time the 3rd round in the magazine got to the top, the tip was flattened so badly……I thought that I may start seeing expansion before the cartridge was even fired! 😜 memtb
 

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