Length issue on finished reload of 300blk

[x101x ARES]

Hey everyone,
New member here. I am starting to adventure into reloading 300 blackout.(dummy round) I took one LC 223 brass case, cut it down in length, chamfered and deburred, resized to 300bulk, trim to length (1.360), seated the projectile(150 gr. Spitzer bt w/cannelure). My issue is my overall length is 2.144 and load data says overall length should be 2.260. The length of the projectile is 1.096. The middle of cannelure is 0.035 away from case mouth. With my calculations, that puts my projectile seat depth at approximately 0.315. After a few moments of sitting with my thoughts on this I decided to try chamber the round, threw the dummy round in a Mag, chambered the round just fine. Any and all help will be greatly appreciated from those who have insight or have had this issue.

[rjacobs]

There are VERY few projectiles that will actually run at 2.260.

MOST of the load data out there states 2.260, which IMO is complete horse shit because we all know that most of the bullets wont run that long. If you call the manufacturers on it(I have) they say "oh we do all load development/testing in single shot bolt actions and 2.260 works for that"... Problem is 90% of 300blk is shot out of AR's and magazines where 2.260 doesnt work.

Start low on the load data for powder and work up because with the bullet seated deeper, your pressures will be higher.

[golfindia]

Seat bullet so that the 0.25" wide portion of it contacts magazine rib and proceed to safely work up load. If you don't come across an accuracy point at that depth, adjustment may be necessary. Longer may cause feed issues, shorter can too.

Just treat 2.26 as max.

[x101x ARES]

I figured as much when the dummy round chambered just fine, just wanting to make sure since I never ran into this issue before when reloading. Now my question is do I seat the projectile a little deeper to meet the cannelure and crimp?

[TMD]

Ignore the cannelure, the bullet your using wasn't designed for the .300bo is why its not in the proper place.

[x101x ARES]

OK makes sense. Thanks alot for your help!

[5kcstq]

Hey everyone,
New member here. I am starting to adventure into reloading 300 blackout.(dummy round) I took one LC 223 brass case, cut it down in length, chamfered and deburred, resized to 300bulk, trim to length (1.360), seated the projectile(150 gr. Spitzer bt w/cannelure). My issue is my overall length is 2.144 and load data says overall length should be 2.260. The length of the projectile is 1.096. The middle of cannelure is 0.035 away from case mouth. With my calculations, that puts my projectile seat depth at approximately 0.315. After a few moments of sitting with my thoughts on this I decided to try chamber the round, threw the dummy round in a Mag, chambered the round just fine. Any and all help will be greatly appreciated from those who have insight or have had this issue.

I have to load a particular sub-sonic projectile clear down to 1.945 to get it to chamber right, and those run fine in my AR, so you should have no trouble at all. Like everyone else has said, just adjust your charge accordingly.