300 blackout die for forming brass from 223

[Wreck-n-Crew]

Have an issue with ( myself for one) with my formed 300 BO brass. I used a Lee sizi g die and somewhere in all the reading prior to forming my own brass from cut down 223 i missed this http://www.300blktalk.com/forum/viewtopic.php?t=89334
So in my boggled mind i was trying to figure what is causing my double fires and started thread in Gunsmithing here...
https://www.thehighroad.org/index.php?threads/ar15-double-fire-help.839507/

As i mentioned i. The thread there i found some issues with my brass and loads. I feel like a big dummy right now. I am usually up to par on things of this nature. Anyhow im looking to get a sizing die that will form 300 BO brass from cut down 223.

So which FL 300 BO dies work well enough to insure.my brass will fit into my 300 BO cartridge gage and pass?

 

[Walkalong]

I would have thought that the Lee would have.

I have Forster and Hornady 300 BLK FL sizers that both work great.

 

[Walkalong]

That said, my case gauge is a Wilson and they don't measure diameter, just shoulder position. The Sheridan is cut to chamber specs. Which gauge are you using.

 

[Wreck-n-Crew]

Forgot to mention that Walkalong im using the hornady gage.

 

[Walkalong]

Does it measure diameter? Or does it work like the Wilson, a hair generous in the body, but measures shoulder position?

 

[greg_r]

All of my 300 BLK brass has been formed from 223 brass using the Lee dies. They work in all three of my blackout rifles. I usually remove the expanding plug, size the brass, cut to length, install the expander plug, size again and trim to length. I have formed it just by cutting 223 brass to length running it through the Lee sizing die and trimming. It really seems to work just as well.

FWIW, I form 6.5 Grendel form 7.62x39 with Lee dies as well. No issues there either.

 

[Wreck-n-Crew]

Does it measure diameter? Or does it work like the Wilson, a hair generous in the body, but measures shoulder position?

It is a min max gage and it doesn't measure diameter. It goes or doesn't. It has a step on the top for min and max. Here it a link to it...https://ads.midwayusa.com/product/7...8EWosE9GOWJ-xFGhm9ejvYzoBolWTHfhoCUfUQAvD_BwE

 

[Wreck-n-Crew]

All of my 300 BLK brass has been formed from 223 brass using the Lee dies. They work in all three of my blackout rifles. I usually remove the expanding plug, size the brass, cut to length, install the expander plug, size again and trim to length. I have formed it just by cutting 223 brass to length running it through the Lee sizing die and trimming. It really seems to work just as well.

FWIW, I form 6.5 Grendel form 7.62x39 with Lee dies as well. No issues there either.

My die is screwed down to max sizing and a hard cam over on the press. Still have many cases that wont pass and most of the 25 rounds i have loaded.

I did note that i had no problem with function on the first 25 rounds but when i went back with 100 loaded rounds is when my double fires began.

It seems that i need to fix my issues with loads before i can feel comfortable moving forward with mass loading.

As noted earlier i did find one where the military crimp was not fully removed and the primer was high in the remaining 25 rounds.

 

[Wreck-n-Crew]

One.more note worth mentioning. I had the same issue as far as feeding with the previous 223 upper using Lee dies. Many failed hornady gage i had for it. However i was able to fix my issues by culling some brass that was roughed up and had 100% reliability thanks to the Hornady gauge.

Majority of my brass was range pickup. 25% was from factory rounds i fired from my gun on the 223 upper.

 

[BSA1]

Before spending any money I would give LEE a call tomorrow and talk to their Tech Support. They stand behind their products.

I have a 7.62 x 54r die set that the sizing die was leaving the case neck too wide leaving the neck without enough tension on the bullet. I called LEE, talked to a very knowledgeable lady who quickly identified the problem as the die having the wrong size expander plug and sent me the correct size at no charge.

 

[cfullgraf]

My die is screwed down to max sizing and a hard cam over on the press. Still have many cases that wont pass and most of the 25 rounds i have loaded.

When you say the cases do not pass or fit the case gauge, what does not pass?

Generally, these gauges measure shoulder position relative to top of the neck and to the bottom of the base.

The base of the case should be flush with the base of the case gauge when the case is inserted. If the base of the case sticks out, the shoulder has not been moved back far enough.

The top measures the overall length of the case, assuming the base of the case is flush with the base of the gauge, but also the length of the neck from the shoulder.

Most of the commonly available case gauges are cut generously in the body diameter dimension, Sheridan being an exception as mentioned by Walkalong. If the case won't fit in the gauge because the body diameter is too big, you have a serious sizing issue with your sizing die.

A bit more information on what your gauge is telling you would be helpful in troubleshooting the problem.

 

[Wreck-n-Crew]

Of the 25 rounds loaded 8 come within 1/8" of making it into the gauge, 14 only come within a 1/4" or more. Of the 3 that pass one passes easily and the other 2 are pretty snug.

They are too fat somewhere. So i measured them to compare to SAAMI specs and of the ones that fail the problem is behind the shoulder where it is formed. Everything else is within SAAMI spec. Also the ones that pass are good behind the shoulder where the others failed.

Edit to add: i may need to use my 700 degree tempilaq and anneal them. The problem is my tip on my torch is not the one i need but it sufficed for longer cases like 308. Im afraid it may heat this shorter case up too far down. Maybe im overthinking this. I have a tip that splits the flame into 3.

 

[berettaprofessor]

I had the same issue resizing 223 to 300BO using Lee dies (Hornady gauge). RCBS Small Base 300BO sizer die worked great as a solution.

This one: https://www.midwayusa.com/product/261325/rcbs-ar-series-small-base-2-die-set-with-taper-crimp

 

[Wreck-n-Crew]

Update and fixed. I did not anneal enough. When i used my tempilaq on newly cut cases sized ( formed ) and trimmed my cases drop in with ease.

Guess this is a lesson for me. Seems some of the brass bounced back too easily but proper annealing allowed it to form enough in the Lee fie to pass.

Thanks for all the responses.

 

[RussellC]

I would have thought that the Lee would have.

I have Forster and Hornady 300 BLK FL sizers that both work great.

My Lee 300 BO die does self cut off LC 223 brass just fine. I remember it took a little practice to get it down, but once figured out, not further trouble.

Russellc

 

[Blue68f100]

Of the 25 rounds loaded 8 come within 1/8" of making it into the gauge, 14 only come within a 1/4" or more. Of the 3 that pass one passes easily and the other 2 are pretty snug.

They are too fat somewhere. So i measured them to compare to SAAMI specs and of the ones that fail the problem is behind the shoulder where it is formed. Everything else is within SAAMI spec. Also the ones that pass are good behind the shoulder where the others failed.

Edit to add: i may need to use my 700 degree tempilaq and anneal them. The problem is my tip on my torch is not the one i need but it sufficed for longer cases like 308. Im afraid it may heat this shorter case up too far down. Maybe im overthinking this. I have a tip that splits the flame into 3.

Glad you found the problem.

Normally when a case is bulging just below the shoulder it's due to crimping. In most cases the die body is screwed down too far, buckling the are just under the shoulder.

There is no reason to crank a sizing die down so far that it's heavily loading the press. If it can be sized with 1/2 turn or less something is wrong, normally 1/4 turn. Once the die is contacting the base/shell holder there is nothing else to be gained.

 

[jmorris]

My Lee die won’t form them from 223 but will resize them just fine.

I use a GSI die along with a Dillon trimmer to form them and final trim, so I never bothered to see why the Lee works fine for reloading them but wouldn’t form them.

I built a couple machines to rough cut the cases too. This is the 2nd best one.

 

[Wreck-n-Crew]

My Lee die won’t form them from 223 but will resize them just fine.

I use a GSI die along with a Dillon trimmer to form them and final trim, so I never bothered to see why the Lee works fine for reloading them but wouldn’t form them.

I built a couple machines to rough cut the cases too. This is the 2nd best one.

Your posts of your builds are inspiring jmorris. Thanks for sharing them.


Update: after 2 boxes of factory loads and 30 of my reworked reloads gun ran 100%.

 

[243winxb]

From lee

Forming vs. Sizing
Posted by on 19 January 2017 11:08 AM
Case forming dies are usually cut to size the case slightly smaller than the minimum SAAMI (Small Arms Ammunition Manufacturers Institute) dimensions, to account for the brass case's tendency to spring back after sizing.

Our full length sizing dies are cut to size the case closer to the middle of the SAAMI dimension, because that is where most rifle's chambers are made, and to size to the minimum would shorten case life. Whether or not our full length sizing die will work as a case forming die depends upon the chamber dimensions of your rifle, and how much spring back there will be when sizing the case.

Forming 300 AAC Blackout Cases
Posted by Steph @ Lee Precision on 20 June 2012 08:36 AM
Should you choose to make 300 AAC Blackout cases from 223 Remington or 5.56 cases, you may have to ream the case necks to obtain a maximum loaded case neck outside diameter of .3340". The reason for this is that the case wall thickness of a rifle case is tapered, being thinnest at the case neck and thicker towards the case head. When you trim the longer case to the shorter dimension, you are getting into a thicker case wall. The maximum allowable case neck wall thickness is .013" when seating a .308" bullet. Because of the taper of the case, wall thickness at the case neck mouth may be .013" but could be thicker just above the shoulder. The thicker wall in this area will cause the loaded case neck outside diameter to be in excess of .3340". This will cause the bullet to be pinched by the case when the round is chambered, which may result in dangerously high chamber pressures.

http://leeprecision.net/support/index.php?/Knowledgebase/List/Index/13/product-support

 

[Capt.Roll]

Your posts of your builds are inspiring jmorris. Thanks for sharing them.


Update: after 2 boxes of factory loads and 30 of my reworked reloads gun ran 100%.

Awesome!! Glad you found the issue and with a few tweaks to your process you are getting the expected results.