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A "primer" on primers!
SMALL RIFLE (.223/5.56) PRIMERS?
The .223 Remington or 5.56mm NATO round is commonly found in semiautomatic rifles and also has special primer considerations using Small Rifle-size primers. Some recommendations follow:
Primers used for .223 Rem. loads should have heavy cups to resist perforation at the high pressures normal for this round. Military 5.56mm primers have a cup thickness of about 0.24", compared to .020" or so that was traditional for the standard small rifle primers. Federal 205, 205M, Remington 7 1/2 BR, Winchester WSR, and CCI BR4, 450, #41, and Wolf/Tula SRM (
QQQSRM or KVВ-5,56M) primers have cups of about the same thickness as military primers, and are the best to use when reloading the .223.
The Remington 6 1/2 and 7 1/2 are essentially the same. The 7 1/2 cup metal is thicker so that the primer can stand up to higher pressures... cup thickness is 25 percent greater... BRIAN PEARCE (quoting Remington), Pg. 14, HANDLOADER, October 2006.
The Remington 7 1/2 BR primer was developed for the hot, high-pressure 4100 fps. .17 Remington round and also used in .223 loads. When Freedom Arms transitioned the .454 Casull case to use the small primer, they picked the Rem. 7 1/2 BR because it gave reliable ignition and easily withstood the 65,000 psi generated by the hot pistol round. It is highly recommended for .223 AR15-type loads.
CCI states: "The CCI 400 primer does have a thinner cup bottom than CCI 450, #41 or BR4 primers. The appropriate primer for an AR15 platform is the CCI #41 primer, which helps to prevent slamfires. With this primer there is more 'distance' between the tip of the anvil and the bottom of the cup." [as per: Linda Olin - CCI/Speer Technical Services]. Despite this, it seems that most AR15 reloaders have experienced no problems using the BR4 and 450 thicker cupped primers in rifles in good condition. The #41 gives the greatest safety margin however.
The experts at 6mmBR.com have this to say about AR15 primer choice:
For use in semi-automatics and AR15s, we advise that you stick to CCI and Remington primers. These brands have harder cups and are much less likely to pierce primers. Also, the AR15 has a free-floating firing pin that dents the primer on loading. This creates a risk of slam fires. So you want hard primer cups. The latest generation of Winchester primers, with brass-colored cups, should be avoided for AR15 use. The old silver Winchester primers worked fine, but the current WSRs are soft and can be pierced more easily than CCI or Rem primers. A poll of Highpower competitors (mostly shooting ARs) showed that Rem 7 1/2 primers are the most popular (33.23%), followed by CCIs (25.78%). The majority of CCI users favored the CCI BR4s, but both CCI 400s (small rifle standard) and CCI 450s (small rifle magnum) were also popular. Only 10.25% of Highpower shooters polled used Federal primers (either 205M or 205). At the time of the poll, many shooters reported using WSRs, but this was the older version with silver cups.
Wolf/Tula also makes two small rifle primers that are suitable for 5.56 loading. First is their Small Rifle Magnum SRM primer (not the Standard). They have this to say: "If you are loading for an AR15 or Military Style semi auto rifle, or are loading high pressure cartridges in any other type of rifle ,we recommend you use the Magnum Small rifle primers. Both primers use the same amount of compound. The only difference is in the cup hardness. The WOLF/TULA Standard Small Rifle Primers have an all COPPER CUP, which is a little more sensitive than the brass cup magnum primers." Second is their newer Wolf/Tula Small Rifle 223 SR223 "This is the newest primer available in the Wolf/Tula line. It is ever so slightly hotter than the small rifle magnum primer and it comes with a brass colored thick cup. This primer can be used in place of the SRM primer or used when a different powder is used that is hard to ignite."
Primers recommended for use in .223 Rem/5.56 semiautomatic rifle loads:
CCI #41, 450, BR4
Federal 205, 205M
Remington 7 1/2 BR
Winchester WSR
Wolf/Tula SRM
Wolf/Tula SR223