Small Rifle Primers For 10.5" AR 300BO

[DougGuy]

I am reading up on what's best to use for 300BO pistol with 10.5" barrel in the AR platform and CCI #41 keeps coming up. From what I found, the #41 is made for gas rifles. LGS doesn't have #41 but they have CCI 450.



This will be for a 220gr jhp subsonic with H110 powder. Would the 450 be a better choice being I am using H110?

[Ed_Shot]

While I have not tried subsonic, my experience with my 16" 300BO AR using 130 gr. boolits over W296 @1800~1900 fps and 200 gr boolits over RX7 @1600~1700 fps is that CCI 550, CCI 400 and Rem 6 1/2 primers work fine for me....certainly no flat primers. I use WSR for supersonic jacked 300BO and 223.

[M-Tecs]

There are a couple of different claims as to the differences between CCI 450 and CCI 41. Everything I read indicates the priming mix and the primer brisance is the same. The difference being either a harder cup and or design difference between the anvil and the cup to reduce the risk of a slam fire in semi autos and full autos with floating firing pins.

https://www.snipershide.com/shooting/threads/a-primer-on-primers.6936610/
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.

[lancem]

I'm with M-tec, they are all the same primer wise. In my 300 I've been using what ever I pull out of the horde without issue..

[jonp]

I've used several brands of primers in my 300BLK including Wolf and Sellier. All go bang

[Hick]

not a direct comparison, but I use small rifle primers with H-110 regularly (but its a 357 Magnum rifle)

[DougGuy]

I am reading up on what's best to use for 300BO pistol with 10.5" barrel in the AR platform and CCI #41 keeps coming up. From what I found, the #41 is made for gas rifles. LGS doesn't have #41 but they have CCI 450.



This will be for a 220gr jhp subsonic with H110 powder. Would the 450 be a better choice being I am using H110?

The difference from what I found out between CCI #41 and CCI 450 is miniscule. they both use the same .025" cup, same compound, the anvil in the #41 is set slightly higher to lessen chances of an unintended discharge in rifles with floating firing pins. I assume. And the #41 is mil spec.

About like using a heavier firing pin spring in your 1911. Sorta.

[Freeandcold]

Recommended primers for ARs have to be able to withstand high pressures and resist slam fires (however low the probability)…For subsonic, high pressures are not a concern… but, some will voice concerns of the potential for slam fires. For this reason, most would recommend primers with thicker and/or harder cups.
These would include, but not limited to, CCI 41, CCI 450, CCI BR4, Rem 7-1/2, Fed 205M AR…

CCI 41 and CCI 450 are magnum primers - differentiated by the 41 having a different anvil geometry to make slam fires even more unlikely.

BR4 have thick cups (same as 450s) and per CCI have the same primer mix/amount as 400s (not magnum).

Rem 7-1/2 are magnum and (in my experience) hotter than 41’s. Rem 6-1/2 are not recommended for ARs (pressure and slam fire potential).

Fed 205M AR are recommended by Fed for AR use (harder cup and anvil positions- like 41s). BUT, many High Power shooters use 205Ms in ARs with zero issues…

There are others, Fiocchi for example that will work (I hope anyway because I have a bunch of them to try). AND the use of say a CCI400 which is not the best choice for an AR will not guarantee an issue…. Many use them with zero issues too. Just, there is a higher probability of an issue and it does happen… occasionally… (pierced primers, slam fire…).

Hope this helps!
Chris

[Winger Ed.]

I'd grab the #450s.

The only primers I've ever heard about slam firing was some Federals.
But I've never had, or have ever talked to anyone with 1st hand experience of that actually happening.

If anything,
I'd be concerned about a primer not being seated more so than the thinness or hardness of the primer itself
and being hit by the bolt face than concerns about the inertia of the firing pin.

I talked to a guy years ago that tried to get a slam fire with the 'soft' primers.
He played around with high primers and several mild-ish loads in a Garand.
He never did get one to slam fire.

[Freeandcold]

I’ve only had one slam fire in my life… it was with Federal factory ammo… so, I’m assuming Federal primers…. It was an interesting experience… full auto! …2 round burst…

[Jtarm]

I’ve been using Winchester small rifle in my two ARs.

No problems, but I’m not a high-volume AR shooter.