22CM & 6CM Primer Pocket Size

[Mike in Oregon]

I need to make up my mind on what size primer pocket to go with for varmint hunting on both my 22 & 6 Creedmoor. I will be shooting light bullets in both, if that matters.

Mike...

 

[357Mag]

I need to make up my mind on what size primer pocket to go with for varmint hunting on both my 22 & 6 Creedmoor. I will be shooting light bullets in both, if that matters.

Mike...

Mike -

Howdy !

Small rifle primer pockets in midsize cases are thought to prolong case life, as there is more brass materiel surrounding the primers; and the cases can be fired more times before primer pockets become “ loose “. Primer’ contribution to load accuracy aside, competition high-volume shooters often find increased brass life to be a positive thing; especially when high-end cases cost $$$. Beyond that, some shooters don’t enjoy doing a lot of brass prep.

In light of all that, there’s nothing wrong with using LR primers in a mid-sized case varminting application ( IMHO ). LR primers arm not a death sentence on obtainable accuracy from a varmint rifle.


With regards,
357Mag

 

[LVLAaron]

Small magnum

 

[Mike in Oregon]

Small magnum

Preference?

 

[LVLAaron]

450's are my favorite.

 

[jpjulian]

I don't have a 22CM but do have 2-6MMCM's. I use both large and small primers. BR-2's, 200's, or GM's in LRP, 450's in SRP. Note that I have had some hang fires using small primers. I have not seen any measurable difference in accuracy with either LR/SR.

 

[msalm]

I had hang fires with a 22 Creedmoor SRP Peterson brass with 60gr Sierra TMK’s and I believe R17 or H4831sc? A relatively slower powder anyway. Problem was solved by opening the flash hole from the .060ish to .080” with an internal flash hole deburring tool. I could hear the firing pin fall, a distinct ’ting’, then the rifle fired. Problem disappeared w/ the larger flash hole. Food for thought. Pretty sure that was with cci 450’s.

 

[6.5 forever]

450's are my favorite.

I only use Cci450. Over the past 5 years they have been more available than large primers. The large primers are making a comeback.

 

[47WillysGuy]

There could be problems made in manufacture of CCI-450 primers. Human fallibility!

I have fired many many thousands of CCI-450 primers and rarely if ever had a hang or misfire with that particular primer. If did I’d look to my primer seating process or case sizing process, if I did. Or even carboned up flash holes before blaming the primer.

Enviromentals are also a factor when using SRP’s. I wouldn’t use them hunting mule deer in ND.

 

[M-61]

Note that I have had some hang fires using small primers.

A hang fire is very unusual and very dangerous.
By chance do you mean FTF. ( failure to fire?)

 

[msalm]

Okay, how about the term ‘delayed ignition’??? And when I say ‘delayed’ it was extremely short time, meaning I could hear and feel the firing pin fall before the round fired, but just barely. I did not have a single misfire. This wasn’t a primer issue IMO, it was the flash hole in the brass being too small and a slower rifle powder. At the time I remembered getting some Starline 6.5 Grendel brass in that was small rifle primer pocket but retained the .080” flash hole so I figured might as well try opening up the Peterson. It worked, instantaneous combustion.

 

[jpjulian]

A hang fire is very unusual and very dangerous.
By chance do you mean FTF. ( failure to fire?)

Nope, hang fire. There were some powders I was trying that just didn't work. Accuracy was great, velocity was low, but there were some "click bangs". RL-15 and 7 1/2's in Lapua SRP brass were the worst combination.

 

[msalm]

Nope, hang fire. There were some powders I was trying that just didn't work. Accuracy was great, velocity was low, but there were some "click bangs". RL-15 and 7 1/2's in Lapua SRP brass were the worst combination.

Open up the flash hole a bit and I bet that disappears…Lapua has the smallest flash hole of them all.

 

[STOMP442]

I can't shoot the difference between the two accuracy wise. I use both large and small in my 6XCs. My hunting rifle uses large rifle primers in Norma Brass and has probably six reloads on those cases and still fine. One of my target rifles uses Peterson with small pockets and I have four reloads on those cases with no problems either. Long story short I don't think it matters. Both rifles shoot extremely well and when loaded properly cases should last a long time. If you load hot and push things, the pockets will go, I don't care what size the pockets are.

 

[Kracken McGraw]

To the OP’s original question, it will depend if your firing pin and it’s sleeve is small enough to handle the srp.

 

[msalm]

To the OP’s original question, it will depend if your firing pin and it’s sleeve is small enough to handle the srp.

Ah yes, that is VERY true. If the rifle is based on the Win 70 action with a .080+++” firing pin tip, shoot large rifle. If not you will blank every small rifle primer you shoot. Even mild loads punch a perfect circle in your primers. Been there done that on a 6x47 Lapua. After bushing bolt face to .070” or so and turning firing pin to match all was well again.

 

[Mike in Oregon]

I have decided to go with SRP on both the 22 and 6CM and use the CCI 450 Magnums. I'm not shooting in extreme heat or cold. The hang fires or whatever you have decided to call them sort of is a concern though.

Thanks guys!

 

[Charlie-NY]

I use CCI450 primers in 22 Creed and 6.5 Creed. The 6.5 Creed brass is Lapua, and the 22 Creed brass is Alpha. I have never experienced a hang-fire or delayed fire of any kind. I've probably load tested at least a dozen different powders in these cases without issue. I can't speak about sub-zero temperatures because when it gets that cold, I've got my feet up by the fire and a cocktail of the day in hand.

 

[STS]

I've had plenty of opportunity to test ignition characteristics in cold temperatures with both Lapua 6mm necked to 22, and Alpha 22 Creedmoor brass, as well as with 450's, 7.5's and 205's. The only time I have ever had a delay in ignition is when I failed to change the primer seating punch from large to small in a Sinclair primer seating tool. The large punch would bottom out on the case head and not seat a small primer to the bottom of the pocket. I live in southwest Montana and it gets DAMN cold around here at times. I also do a lot of coyote calling so cold temp performance is important.
Mid December of 2023 we had a morning when it was -38F so I decided to do a primer test with CCI 450's, Rl 26 and Lapua brass. By the time I got to the range, it had warmed up to a balmy 23 below zero. I put my front rest, bag, rifle and ammo on the bench and retreated to the pickup. After a 30 minute soak in that temp, I shot 2 groups of 5 shots and chronographed all 10 shots. They were about 50fps slower that normal but all of them went bang and had a SD of 12 if I remember correctly.
I have come to believe that cold weather issues are more rifle ignition performance related, than ammo related. I work pretty hard at testing and making sure there is as little drag in the firing pin and spring, as well as the cocking piece and trigger sear. I have found issues with some rifles that certainly didn't appear to have any problems with only a superficial examination. If you want to get an eye opener, take the firing pin spring out of the mechanism and reassemble without it. Put the bolt in the action and push the cocking piece forward with your thumb so that it loads the trigger sear. Then pull the trigger. You may find out that things aren't quite as rosy with your action as you thought.

 

[jpjulian]

Open up the flash hole a bit and I bet that disappears…Lapua has the smallest flash hole of them all.

That would remove a primary reason for using Lapua brass.