Which CCI Primer for 300 Blackout?

[dantiff2]

I've found that with H110 powder, CCI 450's worked the best by far with the lowest ES followed by FED 205M. Everything else was terrible for accuracy and velocity ES.

 

[Uncle Ed]

With a semi-auto rifle the greatest chance of a slam fire is when a single round is loaded and "NOT" fed from the magazine. When the round is fed from the magazine the bolt bolt velocity is slowed down reducing firing pin inertia. Both the M14 and M16 rifles had their firing pins lightened during early trials testing.

NOTE, Remington ran Lake City from 1941 until 1985 and used the Remington 7 1/2 primer in all the 5.56 ammunition. The CCI #41 primers were not used until 2001 when ATK got the contract to produce ammunition at Lake City. Winchester now has the contract at Lake City and it will be interesting to see if they use their own primers.

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS
http://www.sksboards.com/smf/index.php?topic=56422.0

Small Rifle Standard

CCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the page
CCI BR4 - match primer with a thicker .025" cup.
Federal 205 - Mil-Spec cup thickness according to Federal - okay for 5.56mm. .0225" cup thickness.
Federal 205M - same as the 205 but the match version.
Magtech PR-SR - .025" cup thickness (not much feedback yet on this new primer as to AR15 suitability but with the same cup thickness as the Rem 7 1/2 it looks good so far)
Remington 6 ½ - thin .020" cup, intended for older, lower pressure rounds Remington says do not use for the .223 Rem or other similar pressure rounds. Good for .22 Hornet, .30 Carbine.
Remington 7 ½ BR - A match or "bench rest" primer. Lyman & Nosler classify this primer as a Standard. Remington says the compound is the same as the 6 1/2 but with a thicker .025" cup.
RWS 4033
Winchester WSR - some piercing issues noted when changed from silver to brass cup. Cup thickness is a bit thinner at .021". Most say they are good to go for the AR15 despite that, probably because of the hardness of the cup. Some feel they are less resistant to higher pressures.
Wolf/Tula Small Rifle SR #KVB-223 - soft, sensitive copper cup, not recommended for AR15/military rifle use or high pressure rounds.

Small Rifle Magnum

CCI 450 - same thicker .025" cup as the BR4 and #41.
CCI #41 - commercial version of the fully-qualified DOD primer for use in U.S. military ammo. With this primer there is more 'distance' between the tip of the anvil and the bottom of the cup than with other CCI SR primers. .025" thick cup. Same primer mix as CCI 450.
* Remington 7 ½ BR - A match or "bench rest" primer. Hornady, Handloads.com, and Chuck Hawks classify this primer as a Magnum, differing from other sources that classify it as a Standard. .025" cup thickness.
Wolf/Tula Small Rifle Magnum SRM - hard, less sensitive brass cup intended for AR15/military rifle and high pressure rounds - #KVВ-5,56M.
Wolf/Tula Small Rifle 223 SR223 - #KVB-223M "This is the newest primer available in the Wolf 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."

NOTE 1: According to Speer/CCI Technical Services - Both the CCI 550 Small Pistol Magnum and CCI 400 Small Rifle primers are identical in size. Both primers use the same cup metal and share the same cup thickness. Both primers use the same primer compound formula and same amount of primer compound. They can be used interchangeably.

My comment, 296 is a double base ball powder with more deterrent coatings, and magnum primers are recommended.

Below a pierced CCI 400 primer with a thin .020 cup that was fired in a AR15 rifle.

Bottom line, the Remington 7 1/2 primer was used in the military M16 from its development until 1985 without any problems with its .025 cup thickness. And the #41 CCI primer was not used until 2001 when ATK took over at Lake City.

 

[Metal God]

FWIW the cci 400 primers has the exact same mixture as there small pistol magnum primer . The cup is specked the same as well . The rifle magnum primer has a greater chance of moving the projectile forward before the powder really gets to burning unless you use a heavy crimp . This can cause erratic SD/ES but will work .