small rifle vs small rifle MAG

[7mmtcu]

Has anybody done any cronagraphed testing to see if a mag primer gives you a little more speed I am running cci sm rifle, with 28 gr of ar comp under a 107 tmk getting 2728 out of a 24 inch bbl.just wondering if a cci sm rifle mag will give a few feet faster? thanks HORDE!

[Lemonaid]

There was a post on the forum that had results that the CCI 400's actually gave more velocity than the 450's. I have seen this happen as well with my 1-7 twist 6PPC, got about 35 fps more on average.
Unfortunately, the 400's are best suited for mild to medium pressure (40,000 to maybe 45,000? psi.) and I have had primer piercing twice or three times with powder still 2 or more grains under max listed. Your experience may vary, and I've had better luck with the Grendel than with 6ppc or 6 arc.
I would definitely stay with the 450's or other primers with the thicker, stouter cups if any were to be had.

[grayfox]

The deal for the 400's is that they have a thinner cup material. Most primer studies look not for any absolute speed advantage, but for relatively better/lower std deviations. I did some testing of that in a couple of my rifles a couple years ago (not grendel) and observed that one primer would usually give you better, tighter MV groupings than the others.
In grendel, I find slightly better bolt gun performance (or at least as good as) with the Federal 205M vice the cci450... which is a good thing b/c it spreads my usage out to incorporate the 205's I have on hand.

LA, I've followed your experiences with cci 400's and, while the 400 is better suited to milder pressures, how much Milder may be subject to discussion IMO. I have used them in the past pretty extensively in my 223 loads, both bolt and AR, and while not pushing any max's I'm pretty sure the pressures were above your 40-45Ksi range... so there might be a bit more ## they can handle... My guess (I wasn't measuring pressures at the time) is they should be ok up to maybe 50Ksi... but it's just a guesstimate. My ARs have not had any slam fires with 400's, but I have since shifted the 223's (AR) over to cci41's or 450's just to be on the safe side.

[Oso Polaris]

Primers - Impact on Accuracy (ES & SD), Impact on Performance (velocity), and Compatibility (pressure).
I believe the following two articles will give you the information that you are looking for.

Laurie Holland did an in-depth review of primers (performance by type/brand). He is a frequent contributor on Accurate Shooter Forum.

http://www.targetshooter.co.uk/?p=2662

James Calhoon did a nice study on Primers (pressure and cup thickness)

http://www.jamescalhoon.com/primers_and_pressure.php#:~:text=PRIMERS%20AND%20PRESSURE%20by%20James%20Calhoon%20%28First%20Printed,reloaders%20know%20that%20primers%20have%20different%20pressure%20tolerances.

[Lemonaid]

The deal for the 400's is that they have a thinner cup material. Most primer studies look not for any absolute speed advantage, but for relatively better/lower std deviations. I did some testing of that in a couple of my rifles a couple years ago (not grendel) and observed that one primer would usually give you better, tighter MV groupings than the others.
In grendel, I find slightly better bolt gun performance (or at least as good as) with the Federal 205M vice the cci450... which is a good thing b/c it spreads my usage out to incorporate the 205's I have on hand.

LA, I've followed your experiences with cci 400's and, while the 400 is better suited to milder pressures, how much Milder may be subject to discussion IMO. I have used them in the past pretty extensively in my 223 loads, both bolt and AR, and while not pushing any max's I'm pretty sure the pressures were above your 40-45Ksi range... so there might be a bit more ## they can handle... My guess (I wasn't measuring pressures at the time) is they should be ok up to maybe 50Ksi... but it's just a guesstimate. My ARs have not had any slam fires with 400's, but I have since shifted the 223's (AR) over to cci41's or 450's just to be on the safe side.

I agree. It seems CCI 400's and the .223 has much fewer primer piercing issues than other calibers. It might be due the pressure curve or the smaller amount of powder or something like that. The firing pin shape and amount of protrusion could make a difference as to when a primer pops.
I should have stocked up on the 450's back in the good old days.

[Happy2Shoot]

Just a quick test with a random charge.

223 Rem, 55gr, PPV 26.5gr

CCI#400 2885 fps, 31sd, horizontal oval shape group

CCI#450 2918 fps, 23sd, vertical oval shape group.

[Happy2Shoot]

Edit to the above post.

Mixed my group values.

Cci400 2870 fps 5 sd

Cci450 2933 fps 8 sd

2% increase in velocity.

[grayfox]

I agree. It seems CCI 400's and the .223 has much fewer primer piercing issues than other calibers. It might be due the pressure curve or the smaller amount of powder or something like that. The firing pin shape and amount of protrusion could make a difference as to when a primer pops.
I should have stocked up on the 450's back in the good old days.

Right... you know one other thing occurs to me (maybe)... with the grendel there is more force exerted backwards to the bolt per shot due to the larger surface area... for a given psi of shot pressure. This might make piercing of a grendel primer more likely. (disclaimer, not an engineer...lol)

[7mmtcu]

thanks to all for the info i will read the articles. it will report back after it warms up a little in Wisconsin and I put some mag loads over the lab radar again THANKS

[VASCAR2]