Seating depth and the cannelure

[88E30M50]

Hey folks, I could use a bit of advice regarding reloading rifle rounds. These are 300 Blackout specifically and the issue I'm struggling with is the seating depth of the bullet per reloading spec and what I'm coming up with in QuickLoad. Specifically, I'm using a mix of Hornady and Barnes brass and 150g Hornady FMJ bullets. The powder is H110 and the initial charge is 15.2g. Per the reloading data provided with the Lee dies and the Hogden website, the COL should be 2.235 with this load. The issue is that this leaves the bullet hanging out the end of the case with very little case contact between the beginning of the boattail and case mouth. The cannelure is quite a way outside of the case. To get the bullet seated in enough to bring the case mouth to the cannelure, the COL is all the way down to 1.990. Per the QuickLoad app, this is safe for 15.2g of H110 under a 150g Hornady FMJ boattail bullet. But, it's way off of the published data.

So, would you go with the published data that has very little case contact with the bullet sitting with the cannelure sitting well outside of the case mouth or would you trust QuickLoad and seat it as low as it takes to bring the case mouth to the cannelure to allow proper crimping? The published min OAL for the loaded round with a 150g bullet over H110 is 2.235. With other powders, the 150g bullet is as low as 2.140.

How important is it to seat to the cannelure? Is it important at all?

 

[bstewrat3]

If you are using an AR I would probably seat it deeper to get more bullet in the neck, but if you are using them in a single shot or bolt gun I would not be near as concerned with the seating depth. I will be doing some 150gr flat base in the Blackout for an AR pretty soon, so keep us informed on what you do and your results. I plan to seat my bullets to have the base at the shoulder/neck junction and crimp with a Lee factory crimp die regardless of the cannelure location.

 

[88E30M50]

This will be loaded for an AR pistol. The first batch will be seated to 2.155 and crimped short of the cannelure. I'll let you all know how it goes.

 

[71silverbullet]

I don't know if this helps but the Hornady manual states that for that bullet the COL is 2.220.
What I'm more concerned with is that 15.2gr of H110 is very near their max load of 15.9gr. They have a starting load listed of 12.3gr

 

[padawan]

I don't know if this helps but the Hornady manual states that for that bullet the COL is 2.220.
What I'm more concerned with is that 15.2gr of H110 is very near their max load of 15.9gr. They have a starting load listed of 12.3gr

I'll second that... If this is your first load for 300 start on the low end and work you way up. All the 150's in the Hornady manual for H110 have a COL of 2.220.

 

[Broom_jm]

Sounds like you are mixing components and data a little too freely. Wherever possible, use the data for the exact bullet you are loading. It's fine to cross-reference other data, but in this case, the Hornady OAL is what you should go with, not the generic recommendations found in the Lee dies leaflet or on the Hodgdon website.

Double-check your starting charge weight.

 

[sht4brnz]

seating and crimping at the cannelure is not important.
The important factors to consider: when you reduce oal of a specific cartridge recipe, you increase start pressure. This is visible in your quickload program on the graph
The other factor that also raises start pressure is neck tension and crimping. this value is not adjustable in quickload.
Start at the books published recipe and make incremental changes while looking for pressure signs.

 

[88E30M50]

Thanks guys. Per the Hodgen website reloading data for a 150g Hornady bullet, the low end load is 15.0g, which is why I thought I was starting low at 15.2 and working up to the max at 16.2. In the past, I've found the QuickLoad app to be a pretty good way to check loads out and they have normally coincided with the published load data. This is the first time I've had trouble matching the predicted results in Quickload with the published data. When I punch the numbers into QuickLoad using the Hornady bullet and the Hogden load data, I QL gives a CUP of 30,131 where as the Hodgen load data for the 150g Hornady bullet over 15.0g of H110 shows an expected CUP of 38,000.

I'll have to assume that the QL data for H110 is inaccurate in predicting results here. My main concern was the contact area in the neck of the case. With the Hornady bullet, given a boattail length of .150, that leaves only .106 contact area between the end of the boattail and the case mouth. I was uneasy with that little bit of contact area, which is why I was looking to seat the bullet deeper into the case. With a CUP of 38,000 and max of 55,000 on the 300 BO round, I was thinking there was room to work. I was trying to confirm that with QL, but am getting bad results there.

Does .106 max contact area sound reasonable if crimped? If so, then I'll start at the published spec and work from there.

 

[ryknoll3]

Thanks guys. Per the Hodgen website reloading data for a 150g Hornady bullet, the low end load is 15.0g, which is why I thought I was starting low at 15.2 and working up to the max at 16.2. In the past, I've found the QuickLoad app to be a pretty good way to check loads out and they have normally coincided with the published load data. This is the first time I've had trouble matching the predicted results in Quickload with the published data. When I punch the numbers into QuickLoad using the Hornady bullet and the Hogden load data, I QL gives a CUP of 30,131 where as the Hodgen load data for the 150g Hornady bullet over 15.0g of H110 shows an expected CUP of 38,000.

I'll have to assume that the QL data for H110 is inaccurate in predicting results here. My main concern was the contact area in the neck of the case. With the Hornady bullet, given a boattail length of .150, that leaves only .106 contact area between the end of the boattail and the case mouth. I was uneasy with that little bit of contact area, which is why I was looking to seat the bullet deeper into the case. With a CUP of 38,000 and max of 55,000 on the 300 BO round, I was thinking there was room to work. I was trying to confirm that with QL, but am getting bad results there.

Does .106 max contact area sound reasonable if crimped? If so, then I'll start at the published spec and work from there.

You typically want one bullet diameter's depth into the case for decent neck tension. So you'd want at least .308 depth into the case mouth. Another guideline for 300BLK is to take a USGI magazine and seat the bullet so that the place where the projectile is .250 in diameter sits right at the center of the deep rib inside a GI magazine when it is loaded.

Your exact question was answered over on ar15.com. They also talk in that thread about the seating depth I mentioned.
Does this 300 BLK COL leave enough bullet in the case or is it too long for this bullet? - AR15.COM

 

[Cemetery-man]

seating and crimping at the cannelure is not important.

This ^^^

 

[88E30M50]

Wow, the info on reloading 300 Blackout is all over the place. The discussion over on AR15.com seems to be in direct contradiction to what has been discussed here. The discussion over there offers the idea that the load data published for 300 Blackout is built around bolt rifles, and not around use in an AR. I did find a reference on one of the reloading pages that offers a 13.5 starting load for 300 Blackout which is different than I've found in most published reloading data that starts at 15g of H110. Right now, I'm thinking about trying the COL based on the .250 ogive point with the 13.5g load and then working north from there.