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Okay guys, we have had, or seen the recomendation on the AR related forums on the advisability of using the CCI 450's as primers (or other SRM primers with slamfires being the nominated reason for the mag primers having a thicker cup even though many use the standard 400's.
Primer cup data - scroll down
http://www.radomski.us/njhp/cart_tech.htm
Now we have our own bolt rifle forum I want to ask whether the SRM primer is
necessary for the powder burn - performance, or whether the 400 will give notabley different (different being less, either in velocity or uniformaty of velocity) results in the case size we are dealing with in the Grendel. (I have a friend who says he gets 100fps faster with the 450's and CFE223 over 400's)
gruff, ive heard it both ways, more velocity, same velocity. Think it depends on individual gun. Worth a try though.
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I had meant to add that the extra velocity was in the 6.5x47 and not the Grendel and wondered if it was replicated in the Grendel.
I am using CCI BR4 primers in mine and when seated to the bottom of the pocket, in Lapua cases, they are slightly below the base of the case. No possibility of slam firing with that setup.
Anyone who seats his primers to protrude, is asking for trouble, whether it be a bolt or auto.
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08-22-2012, 09:07 AM
(This post was last modified: 08-22-2012, 09:10 AM by Von Gruff.)
To reiterate --------------------- we have had, or seen the recomendation on the AR related forums on the advisability of using the CCI 450's as primers or similar---------------
---------------------------I want to ask whether the SRM primer is necessary for the powder burn - performance, or whether the 400 will give notabley different (different being less, either in velocity or uniformaty of velocity) results in the case size we are dealing with in the Grendel.
Von,
I don't personally believe the CCi 450 is absolutely necessary in the Grendel cartridge its self.
What I have witnessed in the primer testing I have done, is that the (non-magnum) Rem 6 1/2 and the CCi 400s may provide higher velocities in compressed charges i.e. (31g CFE223 under 130g Norma @ 2.265" OAL) and give lower ES and SD. My best guess for this is, with a compressed charge of powder, the lighter detonation of a non-mag primer ignites less powder at the instant the primer detonates, providing more powder burn time as the projectile moves down the bore toward the muzzle, basically the burn rate is more linear to the rate of projectile travel.
I can't say that all powders will behave this way, but I have data showing that CFE223 does.
CCi recommends the use of their magnum primers for Ball Powders
The Rem 6 1/2 has a thin soft cup and regardless of the powder charge (when used in loads for the Grendel) will exhibit cratering, Which; I now believe to be splash from the firing pin strike.
The recommendation for a harder thick cup primer in an auto loading rifle is more in the lines of safety rather than performance.
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That is the type of tested response i was hoping for BW. I do understand the concept of burn time against the force of burn and the resulting possible difference in burn characteristics. There has been some very good data shared on the forum but most of it has been for the AR platform so it is apropriate that we start amasing some data specifically for the bolt rifles many here have or are planing. Have a few K of 400's on hand and if they are suitable I would like to use them rather than going to more component trials than is necessary.
Von Gruff,
In my testing, Wolf Small Rifle Magnum primers produced the most uniform velocities of all primers I tested. These include the CCI 400, 450 and BR4 as well as the Remington 6 1/2 and 7 1/2 and Federal 205 gold medal match. This was with IMR8208XBR and 81.5 grain Cauterucio bench rest bullets out of my Stolle Panda. I've seen ten shot strings with standard deviations of 6 fps and groups in the ones.
BW,
I believe what you are seeing with the Remington 6 1/2 primers is due to the larger firing pin hole of an AR bolt leaving a gap that the pressure can force the primer cup material into. I see this as well with my ARs but not my bolt rifles that have a very precisely fit firing pin hole in the bolt face. For these bolt rifles, as peak pressures are approached, the primer is very flat, no radius left but no cratering either.
Bob
