Seat to cannulure or to COL?

[Grunt]

So, I got a bunch of .30-06 and 7.62 NATO brass that needs to be reloaded for my Garand and 7.62 NATO rifles. I want to duplicate the M2 load data for the .30-06 and M80 load data for the 7.62 NATO ammo.
The problem comes in when I am trying to use a bunch of Hornady 150 grain FMJ/BT bullets I have on hand. The COL for the .30-06 is listed as being 3.340” and the 7.62 NATO is listed as being 2.800”. The problem is that the cannulure of the Hornady bullet. On the .30-06, the middle of the cannulure is .125” past the end of the case mouth and on the 7.62, it’s .070” past the case mouth.
On the one hand, I think I should seat the bullet down to the cannulure grove and crimp it in place there. On the other hand, I am concerned about higher pressures with the deeper seating length as well as free bore travel seating them that deep. The pressures shouldn’t be that big of a concern as I’m running 47.5 grains of IMR-4895 in USGI cases with the .30-06 and 43.0 grains of IMR-4895 in the 7.62 NATO loads. How much of a proble can I expect from free bore? Both USGI .30-06 and 7.62 NATO ammo chambers fine in their perspective rifles with the longer length.
So any suggestions as to where I ought to consider seating these bullets?

 

[Demi-human]

As far as seating them deeper, there won't be a marked difference like with a straight taper cartridge. The bullet is not reducing the volume as severely. One hundred twenty thousanths would make a difference in a Nine Millimeter.

If it will fit and function in the magazine at either seating depth the only thing is to see which is better. I don't crimp any of my rifle loads and am unsure how rough a Garand is on loading, but if so seat to the cannelure, crimp them and see. Some bullets don't mind a long jump, some do. And that in its self will also depend on the barrel's throat and lead and such...

Only one way to know.

 

[Stew0576]

I'm testing this with my .270, so far it seems following the Hornady oal I've been able to reduce powder usage, but I'm still testing, Hornady book shows shorter oal than Speer or Sierra

 

[cfullgraf]

You do not have to seat the bullet to the cannelure although to some folks will look at it as a bit strange. Don't worry about that.

If you want to seat the bullet to the cannelure, reduce the powder charge a bit and work it back up again.

For my Garand, I do not use bullets with cannelures nor any crimp. You do have to make sure the neck tension is sufficient though.

 

[Slamfire]

If you are shooting your ammunition in a Garand, don't seat the bullets longer than 3.30", as you are too close to magazine length. The cannelure is only important if you are worried about the cartridge sliding around, and you are concerned that the bullet will be jammed back into the case. With something like a 30-06, the recoil is not enough to jam a bullet back in the case neck. On a big boomer, maybe 458 Win Mag, it might. I think bullets were jammed back in the case with my 375 H&H, but that was long ago.

If you are shooting multiple 30-06 rifles, it is best to adjust the COL so that the round chambers in all of them, without the bullet being jammed into the throat of one of them. Bullet jump is a contentious issue, it makes a difference if you are shooting heavy target rifles off a rest. The target guys monitor throat erosion and seat the bullet out as the throat increases. However, if you are shooting a lightweight hunting rifle, the group size difference will be in the noise. If you are shooting a rack grade Garand, you won't see anything related to cartridge OAL, unless the round is too long to go in the magazine.

And if you are putting rounds down range in a military barrel, you probably won't see much of a difference between military ball, and target bullets.

 

[cheygriz]

I seat to the middle of the cannelure for ball ammo.

 

[MEHavey]

NOTE: Hornady bullet ogive designs are very unforgiving (read: jam into the lands) if/when seated past the Hornady-listed OALs.
(Ask me how I know).

Stick with the Hornady data (i.e., the cannelure) -- especially in gas guns -- unless you have done some real distance-to-lands measurements.**





** worst case/rule of thumb:
- Lightly hold a bullet into throat with a short pencil/eraser and run a flat-tipped cleaning rod down the muzzle to meet it. Mark the rod.
- Remove bullet/close action/run rod down to bolt face. Mark it.
- Measure the difference for approximate/absolute Max OAL.




.

 

[Charlie98]

I found that as well...



L to R: Winchester, Prvi, Hornady.

It is now my understanding that the Hornady bullet was designed for the 7.62mm, not necessarily the .30-06... but I didn't know that at the time and loaded them for my M1 anyway. I'm loading over 47grn IMR4895 which is a mild load, I wouldn't worry about seating the bullet deeper in the case over a similar charge. You might see some accuracy differences seating the bullets deeper... increasing the jump to the rifling... but if you are just loading generic blasting ammo, it's not that big of a concern.

 

[1KPerDay]

For the garand ignore the cannelure and seat as long as will fit in the magazine and reliably feed (without jamming into the lands) with the hornady this will leave the cannelure exposed above the case mouth. IME.

 

[Lee Q. Loader]

Hornady bullet ogive designs are very unforgiving (read: jam into the lands) if/when seated past the Hornady-listed OALs.
(Ask me how I know).

OK....How do you know?

 

[MEHavey]

Because I started loading for a Win Model-70 that I was SURE had to have a defective chamber/throat after finding HNDY jammed into the lands on everything that I tried to load.

Then I looked/measured how far up the bullet shank the "straight" section went . . . .

 

[gifbohane]

This is an excellent question. I load 223 Hornady in an AR 15 and if I use the Hornady data will leave me below the cannelure in OAL.

I have been using the middle of the cannelure (somewhat short per data.)

Any thoughts?

 

[Charlie98]

If you look at the picture of those three bullets above, if the bullet is seated to the cannelure, the ogive of the Hornady will be further back from the rifling vs the other two, based on the cannelure position and the shape of the bullet ogive. I'm not saying this is the case with your instance... you may have been using a different bullet.

 

[brasscollector]

I seat the 30-06 garand loads to the same OAL that hornady suggests for the 165s/178s, I believe is 3.24". I loaded the suggested OAL for the 150s in the M1/garand section of the book (3.185") and accuracy was not good. This will put you out of the cannelure. For my 308 gas guns I load to the OAL suggested in the book which is 2.70". I've worked out to almost 2.8" and accuracy was the same or worse. YMMV