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#3241126 - 04/08/20 10:39 PM Cfe blk in 18" arp 6.8 wont run and seems sensitive
varminter .223 Offline
Die Hard Member III

Registered: 03/01/10
Posts: 2590
Loc: south central Illinois
Started by single feeding 90 tnts at 29 and 29.5 grains of cfe blk. 29 strung and 29.5 was sub 1 inch for 5 shot but I always have inadequate neck tension to hold the tnts so I gave up until I had a smaller bushing in hand. I believe .300 would be the normal bushing size and I wanted to go a thou or two smaller but .297 was all Midway had and a buddy was ordering so I had him get one.
After the bushing made it I loaded some of the same 29.5 grain loads and 1 of them just hammered the case head and flattened the 450 primer. The gun was short stroking as well. I swapped bolt carrier groups and I still had the same short stroking problem. GB is a non adjustable stoner and it is aligned properly.
Next step I ordered some 90 gold dots which seemed to have ample neck tension when run through a regular sizing die.
I had taken the scope off the gun so when I put one back on it I decided to use three leftover .297 bushing 90 TNT loads to get rezeroed. I shot three of them while adjusting the scope and noticed things were not tracking right. The third one jams the gun and after I open it I see it blew the primer out and it was caught jamming up the next round in the mag. I pick up my other two cases and the primer had blown out of them as well.
So one shot completely destroys a case head bending the rim portion down leaving the parts that line up with the extractor an ejector in their normal positions. Case head measure .009" wider as well as the case growing .004" extra width just below the extractor groove area.
I can't understand why some with the greater neck tension would have pressure and some don't.
Some of these I may have pulled the bullet on testing neck tension and resize twice.
I'd say I'm going to move to 2200 or h4198.

Has anyone experienced any odd problems like this with cfe blk? I've seen on other forums where 18" barrels did have short stroke issue however these case heads look scary.
Hornady brass and .005 to .006 should bump btw



Edited by varminter .223 (04/08/20 10:52 PM)

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#3241248 - 04/10/20 02:38 AM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: varminter .223]
reb8600 Offline
Global Moderator

Registered: 10/13/04
Posts: 10959
Loc: Morgan, Utah
I have not tried the BLK in my 6.8 yet. I will have to watch when I do. Mine is a 16" barrel. When I had my Black Hole barrel I could not get the TNT's to shoot so went to the Sierra 90 gr with Benchmark. Shot real good with 30.5 grains of it. I am using BLK in my 17 Hornet with out any issues.

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#3241258 - 04/10/20 08:24 AM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: varminter .223]
varminter .223 Offline
Die Hard Member III

Registered: 03/01/10
Posts: 2590
Loc: south central Illinois
I shot some near 90 gold dots with a near max load of 2200 yesterday and the brass looks great and the gun cycles well. Seems like 2.270" oal is where oal needs to be but I gotta fine tune my powder charge yet.


Edited by varminter .223 (04/10/20 08:25 AM)

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#3241730 - 04/14/20 08:04 AM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: varminter .223]
varminter .223 Offline
Die Hard Member III

Registered: 03/01/10
Posts: 2590
Loc: south central Illinois
After switching to 2200 powder I was able to get 1.25" or so groups with 90 gold dots. I then went back to the 90 tnts with the .297 bushing and was able to put 8 at or under an inch with 31 grains at 2.260.
30 grains was still same group but slightly bigger. Given 2200 may be be temp sensitive I'm hope this load will still work in cooler weather. Case heads are just starting to get occasional swiping and a marks but primer pockets seem to be holding up. I'd say I won't use any more cfe blk in this rifle.


Edited by varminter .223 (04/14/20 08:05 AM)

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#3241812 - 04/14/20 10:55 PM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: varminter .223]
Catdog1 Offline
Die Hard Member

Registered: 02/17/16
Posts: 566
Loc: Prarie ghost
I'll keep this in mind also. I just picked up some cfe blk but haven't tried it yet. My current barrel is a 20" Green Mountain that I'm sending to a friend tomorrow to have it shortened to 12.5". Hopefully all goes well.

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#3242061 - 04/18/20 01:33 AM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: varminter .223]
SnowmanMo Offline
Director/Moderator

Registered: 09/23/08
Posts: 3513
Loc: Phoenix, Az
Originally Posted By: varminter .223
After switching to 2200 powder I was able to get 1.25" or so groups with 90 gold dots. I then went back to the 90 tnts with the .297 bushing and was able to put 8 at or under an inch with 31 grains at 2.260.
30 grains was still same group but slightly bigger. Given 2200 may be be temp sensitive I'm hope this load will still work in cooler weather. Case heads are just starting to get occasional swiping and a marks but primer pockets seem to be holding up. I'd say I won't use any more cfe blk in this rifle.


I used cfe in my 17 Rem once...once. First round out went way high. So I decided to see if they'd group at all. Second round destroyed the bcg. Blew the bottom off the bcg, blew out the mag. That was with the recommended min load.

Thought it had to be my reloads...took them home, broke them down...powder measured what it should have on two scales. Forget it...didn't need another blown out gun. CFE went bye bye.

For what my two cents are worth...seems like you were getting over pressure like I was. Stick with what's working for you.
_________________________


Mama always said, coyotes are like a box of chocolates...



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#3242076 - 04/18/20 09:34 AM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: varminter .223]
willy1947 Offline
Die Hard Member III

Registered: 11/20/11
Posts: 3144
Loc: Ohio, Ohio


I started handloading with my Father when I was 12, I am 72 now.
I still hand load but when I bought my (Old Company) Bushmaster 6,8mm 10 years ago
I bought a supply of Silver State ammo for it.
I shoot 8 to 10 Yotes a year when I have the time.
I still load my 220 Swift. It is my day gun and my AR is my night gun.
I learn from my Dad don't reload for semi-auto rifles.
I bought a 338 win mag to elk hunt with and two boxes of shells'
Over the years I have killed 4 elk and still have a box of shell left.
It does not make sense to reload when you do not have too.
My 2 cents.
_________________________
Writing in this blog is like guessing, the color of a pig in a poke. You are wrong a lot more than you are right.
"No one plans to fail; we only fail to plan!"
NRA Life Member

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#3242081 - 04/18/20 10:30 AM Re: Cfe blk in 18" arp 6.8 wont run and seems sensitive [Re: SnowmanMo]
GLShooter Offline
PM Sponsor

Registered: 01/09/05
Posts: 5063
Loc: AZ
Originally Posted By: SnowmanMo


I used cfe in my 17 Rem once...once. First round out went way high. So I decided to see if they'd group at all. Second round destroyed the bcg. Blew the bottom off the bcg, blew out the mag. That was with the recommended min load.

Thought it had to be my reloads...took them home, broke them down...powder measured what it should have on two scales. Forget it...didn't need another blown out gun. CFE went bye bye.

For what my two cents are worth...seems like you were getting over pressure like I was. Stick with what's working for you.


That is certainly eye opening.

I've blown up two AR's over the years. One just like yours. The load used was one I have used for literally thousands of rounds. Looking at how it blew out with what looked like a square window in the case web area I felt something was structurally wrong with the case from forming. Because I track all my brass in lots of 100 I was able to trace it back to one specific batch I bought from Alexander Arms. The other pieces of that went in the scrap bucket and all was good in Shooterville after that.

Greg
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