Primers for Grendel reloading

[dpete]

As an owner of a newly built Grendel I've been doing plenty of reading and digesting posts about reloading for it. One thing I have noticed is the constant mention of CCI 450 primers in handloads. Is there a specific reason it is almost universally used instead of the 400? I already load for .223 and 300BLK using CCI 400 primers. If the 450 are better in the Grendel I guess I will be stocking them too. Any well founded reasons would be appreciated.

[robertc1024]

I'd like to hear a well informed answer to this too. I load a lot of .357 mag & .44 mag rounds and have run up against std vs. mag primer shortages. I've heard the mag primers are thicker to keep from blowing out and some say they've got a hotter charge. They were posted on the internet, so they must be true - right?

[biodsl]

You might find some good info in this thread. http://www.65grendel.com/forum/showt...ghlight=primer

Post #45 on page 5 includes a link to an article and primer comparison chart that's useful.

[MrDraco]

It's not that the 450's are better for the Grendel, it's that for the AR15 (and almost any semi-auto rifle) slam fires do happen and are more common than people think. The thicker cup of the 450's reduce the chances of this happening.

[Rickc]

I actually don't use the magnum primers

I prefer cci br4's. They also have a thicker cup

[Klem]

I've used both 450's and BR4's. The BR4's are harder to seat as they are slightly wider. They are also shorter so seat shallower. Given the 450's seat below the level of the case base I don't need them any shallower.

I keep the BR4's for old worn out cases.

[m796rider]

CCI 41s work nicely as well.

[robertc1024]

You might find some good info in this thread. http://www.65grendel.com/forum/showt...ghlight=primer

Post #45 on page 5 includes a link to an article and primer comparison chart that's useful.

Awesome! I've never seen that before. Thanks for the link.

[dpete]

It's not that the 450's are better for the Grendel, it's that for the AR15 (and almost any semi-auto rifle) slam fires do happen and are more common than people think. The thicker cup of the 450's reduce the chances of this happening.

I understand that slamfires can and do happen but how often? Is there an actual empirical data reason for using a magnum primer in what definitely is not a magnum cartridge? Does it burn hotter producing a more uniform explosion and therefore better groups? My experience with my LR308 AR is that the only difference I have seen is that the powder charge can be reduced using the 7.62 designed CCI primer vs. the #200 large rifle primer. I would think a slam fire in a .308 caliber AR would be more common than a .223 given the huge difference in BCG size and moving mass. Never had one, and never have even seen a dimpled primer while ejecting bullets doing ladder tests.

[Cockednlocked]

I've been using Winchester Small Rifle primers in my Grendel, as well as my 300BLK, and I use Winchester Large Rifle primers in my M1A loads. No slamfires in over 2500 rounds.

[m796rider]

I understand that slamfires can and do happen but how often? Is there an actual empirical data reason for using a magnum primer in what definitely is not a magnum cartridge? Does it burn hotter producing a more uniform explosion and therefore better groups? My experience with my LR308 AR is that the only difference I have seen is that the powder charge can be reduced using the 7.62 designed CCI primer vs. the #200 large rifle primer. I would think a slam fire in a .308 caliber AR would be more common than a .223 given the huge difference in BCG size and moving mass. Never had one, and never have even seen a dimpled primer while ejecting bullets doing ladder tests.

Does your .308 BCG have a firing pin spring? Many of them do, because of the larger moving mass involved in a 308AR.

[dpete]

Nope, its as free floating as the firing pins in my AR15 rifles.

[Klem]

It's not just about slam fires or if magnum primers deliver more kick, it's about containing pressure. Magnum primers have thicker cups and so are able to contain pressure in hot loads.

F-Class .223 shooters use magnum primers to load over SAAMI and so reach 1,000yds with long barrels and 80gn projectiles. They also use bolts with narrower firing pin holes for more support. From all the posts I've read on this forum Grendel owners tend to load hot to compensate for the lack of velocity from a small case. Claims by posters that manufacturer data is overly conservative and it is OK to load hot because the cases seem to last and not too many bolt lugs get blown off is mitigated by using quality brass and thicker cups to contain this over-pressure. Also knowing what you are doing and being precise about it helps.

If your firing pin is reasonably free to move in the carrier you will see a slight mark on ejected unspent round. Probably an irrelevant fact to say I have never seen a slam fire because military ammunition is thick-cupped to prevent it.

[dpete]

Sitting depriming/resizing a batch of cases I thought of one possible reason to use the 450 primers. Being magnum primers they might allow a greater explosive force and resulting higher velocity from a given load of powder. Any thoughts?

[Klem]

If you want higher velocity you can always load more powder. Like I say, 450's are not about more kick, it's about containing pressure. Mitigating slam fires is an added bonus.