300 BO brass not fitting gauge

[Rich22]

Going through a new die set and working on doing large batches of 300 Blackout brass. Coming across a very weird problem. Using the sheridan slotted case gauge. I am trimming the brass near min, in these 2 cases 1.353 was the actual OAL. With this length the case is still sticking out of the top of the gauge past the max length part of it between 4 and 8 thousandths. What could be causing this? If everything was correct then a trim of 1.353 would put it well below max Everything seems fine from looking at the case in the gauge. I have the die cranked very far down during the forming procedure to the point where I do not believe it safe to cam over the press any more. Only thing I can think about is the shoulder needs to move lower on the case but it is not possible since the die isnt going to go any farther down. Using Hornady dies and, for now, a lee single stage to form on. I know the real answer is "shoot it and find out" and that was the game plan for tomorrow. The bolt closes without an issue that I can tell.

Thank you

[xacex]

I found that some once fired military brass will do this. The case head expands enough that even with a proper trim length, and shoulder set back the case would protrude slightly at the top of my wilson case gauge. I found I had to go through all my brass and cull out the once fired brass that were snug in a shell holder,and it solved that problem. Some say it is brass that was fired from a machine gun (SAW) and the heat created firing sustained full auto some how expands the case web from the flow of the brass.

[BUCKEYE BANDIT]

Rich 22,
If I understand what your saying, the case is above on the head end of the gauge ?. If so,take a look at the extractor groove for a burr.I ran across this with 762x51 mostly,but have also on the 556.I use a small file to dress down the burr and wa-la the case fits the gauge.These would chamber in the M1A with no problem,but not fully seat in the gauge (Wilson ).Hope that helps .

[6bg6ga]

Reading this thread had me heading into the reloading room to pick up a pan off 300 brass the gauge and start checking. Most of my 300 brass is made from military 5.56 brass. It fits perfectly in the gauge and measures correctly in my Lyman gauge. I use the RCBS 22401 dies. If memory is correct both the 22407 and the 22401 are small base dies the difference being the 22401 are vented for excess lubricant.

[garym1a2]

Use RCBS small base sizing dies.

[6bg6ga]

I would recommend either of the RCBS dies sets the 22401 or the 22407's. Have seen rather poor results from other manufacturers die sets. I opted for the 22401's simply because I am forming both 223 and 5.56 brass and I use a lot of lube and end up with no wrinkles or problems using the more expensive vented dies.

[brass2bullets]

Second on the small base dies. I run the problem brass thru my RCBS small base die. This will solve my problem 9/10 times. 1/10 brass I just save to make 30 cal bullets. Hope this helps.


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[garym1a2]

Worlds finest trimmer is also great to use.

[6bg6ga]

You may have the problem in your sight with the Lee dies. My brass is too length and with blue shows it is formed properly. My brass= sami specs.

[Rich22]

Second on the small base dies. I run the problem brass thru my RCBS small base die. This will solve my problem 9/10 times. 1/10 brass I just save to make 30 cal bullets. Hope this helps.


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I was hoping not to have to get any additional dies but I will consider it. I guess I should have gotten them from the start. I will post a picture of the exact problem when I have a chance, it looks just like the case is too long but the OAL is a bit on the short side so that is not the problem, I am really thinking shoulder location

[Rich22]

You have to be concerned about 2 lengths. Shoulder to case head and shoulder to case mouth. Trimming to spec OAL gives approx. neck length but NOT shoulder location. If the shoulder is NOT back far enough, you can grind the bottom of the die (like I did) or try another shell holder which is really hard metal (to grind). I use the Lee die set, no problem in my AR, I don't think it is small bass. I use the small base for 308W which is MG used brass and needs it.
Maybe the sheridan is cut wrong or your rifle's head space is different. In either case, the sheridan needs to be cut to your rifle h.s. or it has no value to you.

I unfortunately have no way to mill the die down and since I will be resizing (not forming) on a progressive I really couldn't mill that down either. I am having some issue so the gauge is probably right, gun ran fine but accuracy was unbelievably bad. I will look at the small base dies

[James Wisner]

I am setting up as well to do a run of this brass for the very first time.

So I set the one Hortz mill up to saw 5.56 cases to the length in Hornady book, did a few and then set up my RCBS AR small base die.
Am checking shoulder length with a Wilson case gauge.

In my set up the case grows, in length .008 to .010"
This is because of necking the basic cut off case down to form the neck and shoulder the brass will grow in length.

Something I learned a long time ago when we used to make LOTS of odd ball ammo, yes the brass grows/moves longer when necked down

No problem, as the trimmed neck end may not be square, so I come back in with the RCBS 3 way trimmer to clean up the overall length and chamfer it at the same time. I just adjusted my sawn length so after forming I only have to clean up less than .010" off the final overall length.


Now to swage the primer pockets


J Wisner

[Rich22]

Worlds finest trimmer is also great to use.

That is what I currently use but I am looking for a solution to trim differently since my hands get tired quickly and I need something that leaves a perfect case mouth so I don't have to chamfer/deburr each.

[Rich22]

I am setting up as well to do a run of this brass for the very first time.

So I set the one Hortz mill up to saw 5.56 cases to the length in Hornady book, did a few and then set up my RCBS AR small base die.
Am checking shoulder length with a Wilson case gauge.

In my set up the case grows, in length .008 to .010"
This is because of necking the basic cut off case down to form the neck and shoulder the brass will grow in length.

Something I learned a long time ago when we used to make LOTS of odd ball ammo, yes the brass grows/moves longer when necked down

No problem, as the trimmed neck end may not be square, so I come back in with the RCBS 3 way trimmer to clean up the overall length and chamfer it at the same time. I just adjusted my sawn length so after forming I only have to clean up less than .010" off the final overall length.


Now to swage the primer pockets


J Wisner

I have my saw set to cut to the exact length I am wanting finished too so when it grows after necking down that is what it trims off so the trimmr only takes two seconds.

I am having to call the makers of the CH4D swager tomorrow since I am having a hell of a time getting the crimp consistently out without bending case heads

[rockshooter]

i made the job much easier by sizing /decapping using a .22 recapping rod and shaping the case mouth with a lyman "m"die. The WFT cuts very nicely if you replace the cutter with a 4-flute carbide on.
Loren

[6bg6ga]

When I make my cases I set my little saw to cut the minimun length. Once this is done I debur the cases inside and out (neck) and then I lube them and run them thru my RCBS small base full length resizing die. When I am done I check the cases with my Lyman Gauge. Now, some things to remember....not all dies are created equal. Not necessarily a Lee bashing comment here but I haven't seen ANY 300 Blackout cases run thru Lee dies that amount to anything. So, it takes SMALL base dies, a good go no go gauge and some smarts to make blk cases. Yes, the cases will grow slightly from what you started with. Want to actually check a case correctly then use some spray blue and you can see the contact pattern. When I am done with my 300 cases they end up slightly longer than the MINIMUM SAMMI specs. The head space falls between minimum and maximum and over all is within specs. I cut my 5.56/.233 cases on a mini saw with a 300 blackout jig and I use a Hornady Case Prep Trio to debur the inside and outside of the cut what will be the formed end of the case. There may be a few thousanths out of round and that will be taken care of down the line when the cases are at maximum length and I again run them thru the chop saw and deburr them again. Once again to recap here....you will set your primary cut length to obtain your finished formed length. If you find yourself at max length some sticking out of the check gauge then simply make your cases a little shorter before you form them. What your looking for with the gauge is the head space ( top of check gauge case needs to fall between minimum and maximum) and a observation on the neck end of the gauge will show you if your oversize (case will protrude from the bottom of the gauge).

[Big Dog]

if you are having too much trouble forming and getting the shoulder properly formed you need to anneal the case before forming so that it does not spring back so much

[Rich22]

i made the job much easier by sizing /decapping using a .22 recapping rod and shaping the case mouth with a lyman "m"die. The WFT cuts very nicely if you replace the cutter with a 4-flute carbide on.
Loren

This leaves a smooth ie no need for deburr/chamfer, mouth? If so, you have a part number by any chance? If I can do this without having to change tools i would be very happy until I can go to something automated.

[6bg6ga]

It doesn't make any difference what manor you use to cut the cases down. The simple fact is that you still kick up a small burr both inside and out and this needs to be addressed after the cases are cut and before they are re-formed for 300 blackout. Annealing is NOT necessary when making 300's. I really question your measuring capabilities when considering the shoulder has sprung back and I suggest a professional check a few of your cases. Anyone can pick up a pair of calipers but multiple different readings will result with people that are not capable of measuring accurately.Already I have mentioned the Lee quality issue especially with a newer caliber like the 300. Not all dies are made correctly and when it comes to something like the 300 I'll spend more money to get something reliable and accurate. I was able to do two things.... first I measured the case against the SAMMI specs and was right on and second I used blue to obtain a visual contact pattern on the cases. Both were right on. The theory about military brass not forming correctly is not true as they form and measure within a few thousands of any other case that has been formed. Headspace should be correct as long as the barrel/chamber isn't shot out and any good headspace gauge used in checking the finished 300 case should be adequate and will tell you in an instant that your formed brass will fit and function in your rifle.

[garym1a2]

I use the 5 station RCBS case trim station. 2 stages have deburers, One station to mill out the crimp primers. One station to clean the primer pocket.The case are cut on a saw, than deburg, the case forming in done with RCBS small base. WFT trims the cases.