Seating depth blackout

[Morne]

Here is my latest project. These are 130 grain projectiles of .308 diameter for my 300 blackout. I am wondering if I have seated them deep enough, or if I should go all the way to that groove?

[JustaShooter]

If I'm loading bullets with a cannelure then I generally seat them to the groove unless I'm loading a rifle cartridge long for accuracy (sometimes loading the bullet out close to the lands can give better accuracy). Especially for a semiauto where I'm really just looking to plink and / or don't care about accuracy beyond what the load provides without tweaking, then there is no need to seat them long and I'll seat to the groove.

[Morne]

Even at this loaded length I am under the max OAL for 300 BLK.

I am just wondering if any of the data from these will be useful? After all, if I go back and seat deeper next time with the same powder loads I will probably have to work it all back up again, right?

[JustaShooter]

Even at this loaded length I am under the max OAL for 300 BLK.

I am just wondering if any of the data from these will be useful? After all, if I go back and seat deeper next time with the same powder loads I will probably have to work it all back up again, right?

Certainly the pressure curve will be different - likely a good bit higher - with s shorter OAL so yeah, any results won't carry over to the new seating depth.

Are these bullets designed for the BLK? If so, I wonder why they would be that much under published MAX OAL when seated to the groove...

[Morne]

They're .308 barrier round pull downs.

[BobK]

Morne, since you seem to come up with some interesting handloading combos, you may very well appreciate QuickLOAD software.

When I was working up an unusual .44 Mag load where I could not find matching published loads, a friend of mine ran my parameters through his copy of the software and gave me the results.

I am most impressed. If you want to know something like the impact of various seating depths on recommended powder charges, pressure levels and external ballistics, this software is very impressive.

If I ever start to get into handloading anything more exotic than I am now, this is on the definite buy list.

[Morne]

Bob,

Thanks!

I guess it doesn't hurt anything to load it a little longer, right? So long as they chamber and cycle the AR then it's all good, right?

For the record, I used the Lee Factory Crimp Die (FCD) on all of these. Thus, I'm not worried about needing to hit the cannelure for purposes of neck-tension.

[JustaShooter]

I guess it doesn't hurt anything to load it a little longer, right? So long as they chamber and cycle the AR then it's all good, right?

For the record, I used the Lee Factory Crimp Die (FCD) on all of these. Thus, I'm not worried about needing to hit the cannelure for purposes of neck-tension.

Yup, no worries with seating long as long as they load in the mags, chamber and cycle properly. And as you said, with the Lee FCD you won't need to worry about neck tension or having the bullet change depth due to recoil.

[Morne]

Well then I will quit worrying. These are about 2.100" COAL. I've shot factory ammo that was 2.250" and hand loads as short as 2.000".

On the next bullet/load work up I do I will seat to the cannelure. I've got some 163-gr slugs for that.

[Sevens]

I'll tell you up front that while I load like a house afire in straight wall revolver and pistol stuff (high volume, many calibers), I merely dabble in bottleneck rifle rounds. I can make decent ammo but I simply don't do a lot of rifle and while I'm comfortable making ammo for myself, I don't tend to get in to deep discussions about it because I don't have a lot of experience in it -- and it's just not really a hobby.

With that out of the way, it's been said many times that while we watch COAL in stubby handgun rounds for the purpose of internal combustion space and going shorter basically leads us directly to higher pressure, it seems the opposite is true in bottle neck rifle rounds. Certainly, the combustion space is reduced, but in a cartridge case THAT large, it tends to be a smaller percentage (than in, say, 9mm! ) but by seating the bullet out further... you don't give the loaded round the space the bullet typically enjoys for a run before it hits the resistance of the rifling. The net result is HIGHER pressure, and the opposite of what we see in tiny handgun rounds.

And keep in mind that while measuring and absolutely logging the COAL you use in everything you build is a must... comparing one COAL to a loaded round with a different bullet simply does not tell you all you may need to know when the bullets are of a different shape. This is why folks buy & keep a bullet comparator, and use it in concert with their caliper. I don't happen to own one.

I wish I could help further, I can only suggest you chase down more (and far better ) information on this subject.

[JustaShooter]

True, if you are out near the lands then you will get higher pressures than if you are well off the lands - but in morne's case he is already under published MAX OAL so that shouldn't come into play.

[Morne]

Thanks for all the input!

One thing I will do is as I shoot these I will post pictures of the primers. I've loaded these 130-gr bullets with five (5) different stepping up loads (even the highest is comfortably under published maxima). I have ten (10) rounds of each, so I can chrono through both the AR pistol and carbine. But I really would like y'all's review of the primer appearance so that I can start to better understand how they should look. Assuming all of these are safe I might try inching my way up a little higher.

Mmmmmm....data....

[JustaShooter]

Please post pictures of the necks as well - since you are at the lower end of the load spectrum it can help tell if you are too low...

[BobK]

Mmmmmm....data....

Mmmmmm....software to crunch that data....

[Morne]

What does the neck tell you and how? I'll post pics of necks, too, since you suggest it.

Too low? I figured that aside from a barrel blockage or a failure to cycle too low wasn't an issue.

FYI - 130-gr OTM Lil' Gun loads (in grains):
15.1
16.5
17.9
18.5
19.0

Published max is 20.0-gr (Hornady 9e) or 19.5 (Hodgdon online).