Issue with forming 300 BLK from 223

[cwlongshot]

When manually seating a case the ejector must snap over the brass. This can seem difficult as you have no momentum. When the bolt slides forward it has its mass and enough momentum to achieve this seemingly effortlessly.

Could the resistance you feel be just the ejector?

CW

[madmosche]

When manually seating a case the ejector must snap over the brass. This can seem difficult as you have no momentum. When the bolt slides forward it has its mass and enough momentum to achieve this seemingly effortlessly.

Could the resistance you feel be just the ejector?

CW

Yep thanks that makes sense. I tried the same thing in another AR (chambered in 5.56) and I had the same resistance. The reason I was asking is because the guy at RCBS called me back today, and we discussed the issue at length. One of the things he asked was whether the cases that are sticking up a hair over the gauge will still chamber in my gun. When I manually chambered some cases, it took a bit more force on the BCG than I was expecting. Same with factory (unfired) 300 BLK. So I cannot really tell using my gun whether the formed or resized cases chamber the same, because I have to use a good amount of force every time which will force them into the chamber anyway.

RCBS asked me to send them a few fired cases straight from my gun, I guess so that they can measure them and make sure the chamber dimensions match up with their die dimensions. I don't have a headspace comparator tool for my calipers or I would be able to measure my fired cases and compare to the headspace of the formed/resized cases (that was a suggestion from them as well). He said that if I'm pushing the shoulder back to at least fire-formed dimensions then they would work fine in the gun regardless of failing my Lyman gauge. Anyone have thoughts on this?

[dellet]

Where are you located?
maybe some one is close enough to help

Did you ever get the ram to sit flush against the shell holder when sizing?

[madmosche]

Where are you located?
maybe some one is close enough to help

Did you ever get the ram to sit flush against the shell holder when sizing?

I'm in North Florida. Yes, the shellholder is making good flush contact with the bottom of the seating die.

[Sig220]

Wish I were closer......we may be talking about splitting hairs. But at least we could compare our split hairs to each others....

[dellet]

Do you shoot or have access to 9mm. 380, 38 spl brass?

If so you have a workable comparator we can get some numbers from?

you can also cut off a 223 or blackout case below the shoulder and trim it square

[madmosche]

Do you shoot or have access to 9mm. 380, 38 spl brass?

If so you have a workable comparator we can get some numbers from?

you can also cut off a 223 or blackout case below the shoulder and trim it square

Actually just ordered the Hornady headspace kit and bullet comparator kit yesterday so I can get some good measurements from fire-formed brass. As long as the sizing die is pushing the shoulders back below my fire-formed brass then I should be good to shoot them (even if they fail the gauge).

[dellet]

Do you shoot or have access to 9mm. 380, 38 spl brass?

If so you have a workable comparator we can get some numbers from?

you can also cut off a 223 or blackout case below the shoulder and trim it square

Actually just ordered the Hornady headspace kit and bullet comparator kit yesterday so I can get some good measurements from fire-formed brass. As long as the sizing die is pushing the shoulders back below my fire-formed brass then I should be good to shoot them (even if they fail the gauge).

Yeah, but we want answers NOW

Any of the cases mentioned, sized would be best, you want an inside diameter of .350-55, .352 would be ideal, the Hornady insert will be .350.

You will want the shoulder around 1.070" minimum

[Snozzelquaf]

I actually ordered a sharidan headspace/case gauge and I must say it is very nice, i will be ordering for al my cartridges.

Does anyone have anything to say about the Lyman 300 AAC "MSR" dies? I keep seeing everyone say, RCBS "SMALL BASE" Dies but as also mentioned in the post above, my shell holder is rather sloppy..

The shell holder just spins freely and is only rigid when making up to the bottom of a die.. and even then I'm not sure its flush.

My Lyman all american 8 turret press seems to have some give when overcoming (slight overcam). Enough for me to physically move in the z axis (up and down)..

Should i be alright with this configuration?

[madmosche]

Hey everyone, wanted to update on this issue and my findings. I purchased a Hornady headspace comparator which attaches to your calipers and has different inserts to measure directly from the case shoulder to get accurate headspace measurements.

I measured 10 pieces of fire-formed 300 BLK brass shot from my AR (max variation 1.5 thousandths), and zeroed the calipers on the longest piece. I then measured my resized factory 300 BLK, and my chopped-down 223 formed to 300 BLK. All of the resized and reformed brass had the shoulder pushed back between .008 and .013 inches (8 thousandths to 13 thousandths). There was no significant difference between the resized 300 vs chopped-down and formed 223, they were all measuring between 8 and 13 thousandths more headspace than my fire-formed brass.

I also measured factory new (unfired) 300 BLK rounds, and they had around .012 to .014 inch less headspace than my fire-formed brass, only slightly more than my resized brass. So this tells me that my resized and reformed brass is acceptable and will fire without issue, despite the minor variations in how they index in a Lyman headspace gauge. In fact, I could probably back out my sizing die a little bit since I only need to move the shoulder back .002 or .003 to fire these all in the same rifle. They are currently being resized to almost factory ammo specs and would work in any 300 BLK gun.

I still can't figure out why some of them stick up higher in my Lyman headspace gauge. Even when I have 2 pieces of brass and measure the headspace with calipers to be exactly the same, one of them sticks up a hair higher in this gauge. But I'm basically just going to ignore the Lyman gauge and verify them with my calipers and start loading & shooting them.

I will update this thread if I discover any issues firing them (wish me luck haha). THANK YOU to everyone who provided advice or suggestions! My biggest takeaway from this learning experience is that being able to accurately measure your fired cases and resized cases for headspace (and compare them) will help a new reloader greatly. I also recommend reading the "Reloading and Bullet Accuracy" preface section in the Hornady 10th edition reloading book, it helped me understand a lot more about what cases do when fired, reloaded, and fired again.