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300BLK sizing issues! Need help


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I finally got my cases today and they are already formed/processed. I went through to use my gauge to see if I need to resize any brass and 3 out of 10 need to be resized, not that big of a deal. 

 

I set my dies up and some cases are sized and fit great in my gauge AND barrel. Then there’s some cases that I sized but still don’t fit in my gauge AND barrel! I properly set my dies in my press but still don’t know what the deal is. 

 

I’m using a hornady gauge and Lee dies. I’m also using imperial die wax for lube.  All the brass is already sized and processed 300BLK brass. 

 

Any ideas?

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Word on the interweb Lee sizing die does not work very well. This appears to show up more with freshly converted 223 to BO brass. Now once its "fire formed" it works fine.

You need a "under size" die to fix this.

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If it is mixed brass of 223/5.56 brass that was converted to 300 Blackout I have read in a couple of Forums that NATO 5.56 wall thickness creates issue when trimming or cutting it to make 300 blackout brass.  I have heard you only want to convert brass from the US to 300 Blackout brass.  I cannot remember where I read that but maybe a rabbit hole to go down.  

 

I have to say I’m not 100% sure that was exactly what I read but fairly certain that info is accurate to what others had experienced through reading various forums.  

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If you sort out the brass .223 from 5.56 and check the neck thickness.   You may have to turn the necks for all the brass to work.    

 

.334-.308/2=.0125  trim to .010 to .011  

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One thing I found, depending on who did the processing, is that the cases may need to be deburred on the outside from trimming. I had a ton not passing and couldn't figure out why. 

 

Noticed some sharp edges, deburred all the case mouths, and now they all pass. 

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On 1/12/2021 at 10:29 PM, NOSHMJ said:

Try a SB resizing die.

I just ordered a SB sizing die. Hopefully this will solve the issue cause I’m gonna be pretty disappointed if it doesn’t lol 

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55 minutes ago, Tom Freeman said:

 

Any particular headstamp not chambering?

 

What bullets are you using?

 

What is the OAL of the brass?

Haven’t put a bullet in cause the brass isn’t sized right. It’s a mixture head stamp 

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15 hours ago, sstephns said:

One thing I found, depending on who did the processing, is that the cases may need to be deburred on the outside from trimming. I had a ton not passing and couldn't figure out why. 

 

Noticed some sharp edges, deburred all the case mouths, and now they all pass. 

It’s odd cause the ones that didn’t fit, I beat it into my gauge and it still didn’t fit. 

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  • 2 weeks later...

From my limited reading and watching several videos on youtube if the brass you are using is mixed headstamp brass the wall thickness could be something you are going to want to pay attention to also....Below is a list I copied from another forum related to brass wall thickness post cut down....The extra wall thickness WILL keep certain rounds from chambering and functioning...Again youtube has several videos specifically about 300 B/O not firing and details as to why...I know because I experienced the same issue and it was related to the headstamp on the brass.....Makes no difference as to the dies you use to size your brass because this is related to neck thickness....Hope this helps...It helped me...

 

 

 

Originally compiled by tlee_20, updated with user reports. In general, the wall thickness around 1.360 inches from the base will determine success or failure. As a rule of thumb, if the wall thickness is greater than 0.014, there may be problems with the loaded diameter of the neck being too large to chamber easily. 

Neck thickness data:

Factory Blackout brass

Gemtech (factory 300 BLK) - 0.011"
PNW Arms - 0.011"
RP - 0.010"

Converted brass

Good:
ADI - 0.012"
Aguila - 0.012"
A USA - 0.012"
FC - 0.013/0.014" [Note 1]
GFL - 0.012" (Fiocchi) Some GFL may have different thickness
HB - 0.013"
Hornady (223 headstamp) - 0.011"
Hornady (nickel 223) - 0.012"
IK03 - 0.012" [Note 4]
IMI - 0.012" [Note 4] Listed on both lists, but seems like more often good than bad.
IVI - 0.013"
IVI ('85) - 0.012" (runs great)
LC - 0.011"
LC (converted blank) - 0.012"
M193 - 0.011/0.012"
Norinco 223 - 0.010"
NOSLER - 0.012”
PERFECTA 223 rem. - 0.012"
PMC - modern "bronze" and "X-tac" are good, older PMC with small letters may have problems
PS - 0.011/0.012"
PSD - 0.011"
RA - 0.013"
RA ('69) - 0.012"
RP .223 - 0.011"
SSA - 0.012"
TAA - 0.013-0.014" [Note 4]
Tula - 0.0115"
TW 67 - 0.012”
TZZ - 0.012"
WCC - 0.010/0.011" (Some less common WCC headstamps run thicker, but the majority are good to go)
Winchester - 0.011"
WIN NT - 0.011"
WMA - 0.011" (Winchester Military, equivalent to WCC)


Thick neck wall, bad without neck turning:

AB 556 - .015" to .016"
ATI - 0.015" [Note 3]
CBC - 0.014/0.015"
CJ6 - 0.015"
CJ 8 - .014"
DNL - 0.016"
FNM - 0.016" [Note 3]
FRONTIER - 0.015"
GECO - 0.015/0.016"
Hot Shot - 0.014" [Note 3]
HRTRS ( Herters?) - 0.017"
ICC - Reported as bad
IK03 - 0.015" [Note 4]
IMI - 0.015" [Note 4]
IVI - 0.015"
KFA .223 REM - 0.015"-0.019"
L2A2 - Reported as bad
MKE13 - Anecdotally reported as troublesome
MPA - 0.015"
Norma - 0.015"
NPA - [Note 3]
PMC (old headstamp) - 0.015"
PMP - 0.015"
PPU - 0.014/0.015" [Note 3]
RAM 223 - .014"
RORG - 0.015"
RWS - 0.014-0.015"
S&B - 0.015/0.017"
SADU - 0.014/0.015”
TAA - 0.013-0.014" [Note 4]
T - 0.015
SADU 5.56 - 0.014-0.015"
Wolf Brass .223 - 0.014"

General notes:

There's no consistent difference between "5.56" and "223" when it comes to brass.

Many manufacturers may use different sources for casings at different times. This means that even within the same headstamp, it is possible that a particular batch was from a different source and may be different. Treat this list as a rule of thumb, and double check before processing a large quantity.


Note 1:
"FC" brass includes several types of brass that don't seem to come from the same factory. Most of them are good to go, but the "thin web" FC that turned up a few years back tends to have thicker walls and will cause neck thickness problems. Some FC that runs thicker is the newer stuff. Has beautiful annealing marks on it. Has FC @ 12:00, numbers @ 3:00 and/or 9:00 (May have both, could just have one), and the year @ 6:00


Note 2:
NPA is very low quality brass, with a super small flash hole, and is likely to cause broken or stuck decapping pins, or other problems.

Note 3:
The brass marked with this note may require extra sizing force, and machine flex may cause them to headspace too large if the machine is not set up specifically to do this "harder sizing" brass. This is due to thicker brass, alloy variations, or variations in factory anneal. This isn't always universal within a headstamp, for example, some older PPU had the problem and others did not. 

Note 4:
This brass is included in both the good and the bad list based on differing user reports. It is important to keep in mind that sometimes a single headstamp can be made at multiple factories on multiple differing manufacturing processes. Other times a manufacturer that has their own brass factory might bring in brass from another manufacturer during times of high demand or to fulfill a large contract.

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4 hours ago, Sigarmsp226 said:

From my limited reading and watching several videos on youtube if the brass you are using is mixed headstamp brass the wall thickness could be something you are going to want to pay attention to also....Below is a list I copied from another forum related to brass wall thickness post cut down....The extra wall thickness WILL keep certain rounds from chambering and functioning...Again youtube has several videos specifically about 300 B/O not firing and details as to why...I know because I experienced the same issue and it was related to the headstamp on the brass.....Makes no difference as to the dies you use to size your brass because this is related to neck thickness....Hope this helps...It helped me...

 

Thank you for passing this along.

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