Split case necks on .223


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jeff.cain
March 8, 2010, 05:48 PM
I have a 12" barrel LMT ar15. Just learning to reload. When working up my loads up I started getting split case necks.

I'm using
PRVI once fired brass (fired by me)
CCI small rifle primers
Ramshot TAC powder
Hornady 75 gr HPBT bullets.

Per Ramshot data Min load = 21.2 gr powder / Max load = 23.7 gr.

No problems shooting 21.4 gr or 22.0 gr . When I got upto 22.5 gr of TAC, 5 out of the 10 rounds I fired split the brass case necks. Factory new PRVI chronos the same velocity (2305fps) in my gun with no brass problems.

Since all Ramshot test data is with a 24" barrel vs my 12" barrel, I have no real velocity data to compare. Why the split necks? and What are overpressure signs I should look for when I can't use velocity from the data sheet due to short barrel? Thanks for any help!

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243winxb
March 8, 2010, 05:56 PM
PRVI brass would be my guess as the problem.No problems shooting 21.4 gr or 22.0 gr Then dont load any hotter. Look thru pages here for pressure signs. http://www.photobucket.com/joe1944usa Lots more good reading here http://www.6mmbr.com/223Rem.html

rcmodel
March 8, 2010, 05:58 PM
Be my guess too.

Nothing to do with pressure or a short barrel.

The only other possibility is you have a really over-size chamber neck in your gun and they are just expanding way more then they should.

rc

straitnate14
March 8, 2010, 07:14 PM
I have problems with privi brass to, I have problems with my rifle tearing chuncks out of the rim of the brass, I would say half of the privi I have shot gets tossed before I even reload it. I have aslo had more neck splitting from privi than with other makes.

janobles14
March 8, 2010, 08:44 PM
is the brass .223 or 5.56? the throat length might have an effect if it is .223. just a passing thought.

243winxb
March 9, 2010, 04:14 PM
Pressure Signs
The bolt will be hard to open when you are over pressure(bolt actions). The primer will not have a rounded edge. The web area of the brass has expanded. Some LC brass that has an expanded web is roll sized to bring it back in to spec. Some say this weakens the 5.56 brass, causing head seperations, i feel this is true.:confused: There is an ejector mark on the brass head. Case head separation. Primer flowing into & around firing pin. On an Auto gas operated rifle, i am not sure if the case would stick in the chamber:confused: It might be possible that the extractor would try to rip the head off the body of the brass :confused: Hopefully others with more experance will add to this. If the case head comes apart near the primer or extracter groove, an AR can be damaged. Bolt actions are much more forgiving and contain pressure better on head seperations. Here is a good thread with peoples thought on handloading and reading pressure. http://www.thehighroad.org/showthread.php?t=375160

rcmodel
March 9, 2010, 04:17 PM
is the brass .223 or 5.56? the throat length might have an effectThe throat has nothing at all to do with the case neck.
.223 and 5.56mm cases are the same length.

The throat is in front of the chamber to make way for longer bullets to get a running head start before hitting the rifling.

rc

Slim Pickens
March 9, 2010, 08:27 PM
Per Ramshot data Min load = 21.2 gr powder / Max load = 23.7 gr.

No problems shooting 21.4 gr or 22.0 gr . When I got upto 22.5 gr of TAC, 5 out of the 10 rounds I fired split the brass case necks. Factory new PRVI chronos the same velocity (2305fps) in my gun with no brass problems.



Jeff,

From your post I can't be sure if you loaded 21.4, 22, and 22.5 gr sequentially into the same set of brass and then had split necks, or if you had split necks with 22.5 gr in once-fired brass.

You really shouldn't have problems when you are 5% below published max loads with an LMT barrel (I assume that has a 5.56 chamber?).

What kind of dies are you using? In my experience, split necks are caused more by repetitive sizing stresses than by high pressure.

I would measure (with a micrometer) the OD of the neck on fired brass, and then measure the neck on brass resized both with the expander ball and without the expander ball. Sometimes commercial dies reduce the brass diameter more than necessary before expanding it. If the brass is thick in the case mouth it can really get a workout and cause premature splits. The cure for this is a bushing die, and case annealing if you really want to get into that.

Balrog
March 9, 2010, 09:28 PM
is the brass .223 or 5.56? the throat length might have an effect if it is .223. just a passing thought.

I don't think its thoughts you are passing.

janobles14
March 9, 2010, 10:56 PM
hey i never claimed any expert status here! no need to get grumpy womanly there balrog! :O) glad i know what the difference is on this now though. learn something new every day

WmCC
March 11, 2010, 08:02 AM
Short answer: Properly anneal the case necks.
"Split necks" is NOT an uncommon problem, especially with 22 CF and many wildcat cartridges, regardless of the brass manufacturer. The problem is normally with work hardening of the shoulder and neck during the manufacturing process followed by resizing... not with the load, chamber or die, per se.
Many years ago when the various .30's were in use by the military, virtually all of the civilian 22 CF brass was perfectly annealed as a final step after being formed. I have some old Speer DWM in 222 Rem that has been reloaded probably 20 times without annealing. I have no hard proof but I suspect that most of the current production 5.56 and 223 is not being annealed "in the same manner" due to the presumption that it will be left on the ground after being fired (and to possibly save a few bucks or increase brass/ cartridge production rates).

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