Keyhole issue

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cobra246

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Hey guys. I jus got my .223 setup for my reloading press. I loaded 10 rounds of 55gr FMJ Hornady in Lake City 5.56 once fired brass with a 26.5gr powder charge of Winchester 748 Ball Powder and CCI No.400 small rifle primers.
I fired them out of an Anderson AR15. It has a 16" barrel with a 1:7 twist, carbine length direct impingement gas system, and a muzzle break (not sure if the brake has anything to do with it).
b2b40a4afae8bfdcd8c04bdb661e3db3.jpg
Heres a pic of my recorded load data. And one of the rifle im shooting from. c9a87dcb3b9cdc936a7130bd5c4e14b2.jpg
The issue is 5 out of the 10 keyholed at 50 yards. The others hit the target. All cycled fine, and ejected fine. The primers looked a little crushed. Barrel has less than 2000 rounds through it; all previous ammo was military surplus grade 5.56 (shoots fine in my gun). Im using the Speer manual edition 14.


Anyways what could be going on? Too light? Too hot? Wrong barrel twist? Sorry im not that familiar with the .223/5.56 stuff yet. Thanks in advance!

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Ok cool. I'd say only two of those ten are flattened.

I'll have to think on the keyholes. Normally it's due to not stabilizing, but I'd figure a 1:7 would stabilize a 55gr bullet for sure.


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I'd weigh the bullets to double check them, a 1-7" twist should stabilize fine... I'd also double check the twist on the barrel.
 
Your load exceeds the maximum charges on Hodgdon site as well as the Hornady manual. I'd back off a bit and try again.
 
Huh. The Speer manual said maximum load for that weight bullet with W748 was 28C with C being compressed....but your right the hodgdon said 26.3 max in which case im over by 0.2gr

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Question, did you work up to that load or just start there? If you worked up to it, drop back to a known safe load.


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I started there because the manual said 26gr. was minimum charge and 28gr was maximum. So i figured id start with a .5gr increase from 26 and it would be fine.

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Check inside your brake carefully...it might be clipping. That's the only reason I can think of for 55's out of 1-7 to be keyholing. Driving a bullet too fast in too fast twist barrel can cause them to fly apart from the spin, but that doesn't seem likely here unless the bullets were damaged like if they were pulls.
 
Take a look at Hodgdon, one of the two 55-gr bullets they list maxes out at 25.0 grains. Hornady max is higher, but you're still a little over it. I would work up this load from a significantly lower charge than what you used.

Your Speer manual is for Speer bullets only.
 
IMtheNRA said:
Take a look at Hodgdon, one of the two 55-gr bullets they list maxes out at 25.0 grains. Hornady max is higher, but you're still a little over it. I would work up this load from a significantly lower charge than what you used.
Click to expand...
Ok so possibly start from maybe 20-22gr range?

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Hornady #7 data for 55-gr bullet and Win-748 starts at 22.7 grains and maxes out at 26.4 grains.
 
You're welcome, good luck. As someone else stated, check your brake for bullet strikes. That'll cause some problems too.
 
I have used the same bullet and powder combo with 1/7 twist 16" ar with good results. 24.5 gn was what I settled on. No key holes
 
Right im thinking i loaded too hot. I wonder why speer is that hot? Possibly becuase they used a bolt gun instead of an AR?

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I would say start at the min load and work up / never start at near or over max !
Also were these rounds left in a hot barrel or in the sun longer then the others ?
I have read that W748 can give you touble with near/over max data and tempature
Causing high Pressures and do weird stuff.
 
I'd like to add too, that if Speer is the only manual you have currently, invest in a few more like Hornady, Sierra, Lyman 49th, Nosler, etc.


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Speer is my only manual at the moment. I will invest in some more as soon as possible tho

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The Sierra and Lyman 49th are pretty good manuals.

The Lee one just takes data from other resources and puts them into one place. I'm personally not all that impressed with the Lee manual.


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