300 AAC loading questions

[Blood Trail]

I have a 311410 MP mold that throws a 125 gr HP or 130 gr fn. these bullets are pc’d and gc’d. I’m following data from the Lee manual for a 125 gr jacketed bullet using 20 grs of CFEBLK (min load).

Those who load this bullet, what OAL do you use?


Edit: Loading, not losing

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[Dusty Bannister]

You have introduced too many variables to get an answer from a book. Try this instead.

Cleaning rod/dowel method of finding cartridge OAL

This is what I use for my guns to determine the max OAL and this eliminates any question of the crimp, incorrect case prep, or other operator induced error.

This method works well on rifles and single shot pistols as well as Semi-autos. You can use a flat tipped cleaning rod, or flat tipped dowel rod. You will also need a sharp pointed pencil, a short dowel and a bullet sized but clean, of the type you are going to load.

For Rifles
Make sure the chamber is empty. Close the bolt, and be sure the firing pin is retracted into the bolt. Insert the dowel or cleaning rod and hold it against the face of the bolt. Mark the rod at the face of the muzzle. Remove rod, open bolt and remove it from the action. Insert the bullet into the breech and hold it snug into the rifling. While in that position insert the dowel or rod again, and with it firm against the nose of the bullet, mark the rod at the face of the muzzle.

The distance between the center of those two marks is the max cartridge OAL for that rifle, with that bullet sized to that diameter.

For Semi-autos
Remove the barrel from the slide and make sure it is clean and free of leading or other debris in the barrel and chamber. The dowel or cleaning rod needs to be longer than the barrel. Hold the barrel, muzzle up, and place the barrel hood on a flat surface like a table top. Insert the dowel or rod from the muzzle and mark the rod exactly flush with the muzzle. Remove the rod and insert the bullet you intend to use into the chamber and lightly press and hold it in place with the short dowel. Place the assy muzzle up on the flat surface. Insert the rod/dowel into the muzzle so it rests on the nose of the bullet and again mark the rod exactly flush with the muzzle. Remove and set the barrel aside. The distance on the center of the two lines is the cartridge OAL. Seat a dummy round to this length, or slightly shorter and begin to apply the taper crimp until the dummy passes the plunk test. This is the optimim cartridge OAL length for this bullet in this gun.

You may need to adjust the seater to shorten the OAL if this does not feed from the magazine, but generally this will be a great fit. Remember, if you seat and crimp in one step, you might force a slight ridge ahead of the case mouth and that will screw up your seating.
Dusty

[popper]

Make a dummy rnd seated short, if it chambers, seat less deep. Try again till it is hard to chamber. Some make it long and then push shorter - which ever. Then back off seating depth about 20 thous. as PC thickness changes. Hand cycle in your gun. If it chambers and ejects OK, good.
Measure bullet base to mouth. COMPARE with the book bullet COAL for the BOOK bullet, same or heavier than yours. Look at book max load and pressure if given. If you seat deeper than book, decrease powder load to keep pressure down. You are trying to calc the load fill. QL or GRT will do that for you. Book COAL has nothing to do with their test barrel or bullet but load FILL.
You can start at min load and use a chrony to move up. Powders like H110 don't give much spread, max-min. CFE BLK likes to run 90-95 % filland can be slightly compressed..

[sukivel]

If you are loading for an AR, good luck and it doesn’t matter. I’ve seated it all the way in and out, with several powders, and several charges, and can’t get it to feed and function. The bullet is too short and you can’t seat it out long enough because of the large lube groove.

If you get it to work i would like to know.

If it’s not for an AR, I would seat to the crimp groove.


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[Texas by God]

In an AR15, seat to magazine length. If they won't chamber, try seating a little deeper. I hate it when ejecting an unfired round pulls the bullet out and spills powder into the action.

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[Blood Trail]

Thanks all. I ended up at 1.89” OAL. They cycle fine. I’ll test for accuracy today.


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[Blood Trail]

If you are loading for an AR, good luck and it doesn’t matter. I’ve seated it all the way in and out, with several powders, and several charges, and can’t get it to feed and function. The bullet is too short and you can’t seat it out long enough because of the large lube groove.

If you get it to work i would like to know.

If it’s not for an AR, I would seat to the crimp groove.


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At 1.89” they work. I popped off a few with no issues.




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[Texas by God]

Those look great. I’m looking forward to the range report.
It’s a fun little cartridge.

[Blood Trail]

Range report:

50 yards with a red dot. No magnification. Not bad for a plinking round. No jams. Two mag dumps without a hiccup. AR-15 pistol 7.5” barrel




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[sukivel]

At 1.89” they work. I popped off a few with no issues.




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That’s about where my OAL was. What powder are you using?

Was that the HP or solid?


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[Blood Trail]

That’s about where my OAL was. What powder are you using?

Was that the HP or solid?


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20.4 grs of CFE BLK. I shot a combo of both. They pretty much hit the same.


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[Krh1326]

It kills me that, we have cast boolits and their molds that have exposed lube or crimp grooves ? I know it’s just aesthetic, but it really looks stupid. Why can’t these mold manufacturers make a mold that is “supposedly” for 300 BLK actually BE for 300 Blk… ? Grooves, including crimp where they are supposed to be , in a practical spot? Why are they making these boolits to difficult COLs for feeding, battery..etc?

My rant for the day. I feel better now. Carry on….

[Blood Trail]

It kills me that, we have cast boolits and their molds that have exposed lube or crimp grooves ? I know it’s just aesthetic, but it really looks stupid. Why can’t these mold manufacturers make a mold that is “supposedly” for 300 BLK actually BE for 300 Blk… ? Grooves, including crimp where they are supposed to be , in a practical spot? Why are they making these boolits to difficult COLs for feeding, battery..etc?

My rant for the day. I feel better now. Carry on….

I agree. I tried crimping one to the top lube groove. The OAL was so short I’d thought I’d run into pressure issues due to powder compression. However, it suits my needs, so I’ll have to live with it.


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[44Blam]

I make a sample boolit and seat it as long as will fit in a magazine or max col for the cartridge and I crimp it how it will be crimped. Then I attempt to chamber it. If it goes - your done. If not pull the boolit, resize the case, bell, seat crimp again just a little shorter. You can kind of gauge on how much shorter by how close you are to chambering.
Once you have that, cycle that dummy a bit - maybe it needs to be shorter still?

[sukivel]

All this talk is making me want to revisit this again.

I seated my last bunch at 1.85, so I’ll go to 1.9 and see what happens. I was thinking that 1.85 was as long as I could go for some reason. Anyhow my notes aren’t that detailed.


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[44Blam]

OH! I remember what gave me 100% feed reliability with 300 BO. Hi-Tek.
The mold I am using is the NOE HTC310-225-RN-CE4 and I did have some occasional issues feeding when I was PCing the boolits. I started Hi-Tek coating my 300 BO boolits and I have not had any issues since.

[popper]

Just get a mould without grooves. They aren't needed if you PC or hitek. I've even used them with 2 coats BLL and no problem to about 1600 fps.