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Hoot, I am 75 yrs old so I can identify with your last posting. guy

Well I was going to use Rem 7-1/2 primers but the place I bought them from doesn't carry them any more. I'm thinking of going with the CCI 450 primers. Hoot, Sorry to hear of bad outing to the range with the 275 XPB bullets. I was looking forward to you helping me come up with a starting load for my RAR.

CJP1 wrote:Well I was going to use Rem 7-1/2 primers but the place I bought them from doesn't carry them any more. I'm thinking of going with the CCI 450 primers. Hoot, Sorry to hear of bad outing to the range with the 275 XPB bullets. I was looking forward to you helping me come up with a starting load for my RAR.

I'd venture that with the RAR's faster twist, the 275s might actually stabilize better. Start with 38gr of W296/H110 and work up in half grain steps. I had to vibrate the cases to get the powder to pack down far enough to seat to 2.22 with 42gr charge. If you load yours longer, you may be able to start at 39gr.

Hoot

The first time I tested the 275's, I used the old blend of Lil Gun. It worked great. It wouldn't be the first time I changed to W296 to achieve the same velocity but had the groups open up. Lil Gun, even the current blend, still has the Ju-Ju. If I weren't out of 275's now, I'd give them a second chance going back to Lil Gun. Wish I had jumped on that deal for those tarnished ones but as I said, whitetails are not that hard to kill and we don't have hogs up here yet.

Hoot

Hoot , I picked up a box of rem 7 1/2 yesterday . thanks for your input. guy

Hoot wrote: ...and its not like we can test them in the 450b, even if we wanted to. Velocities are so erratic, by bottleneck caliber standards, that the impact of the primer variations would be lost in the "background noise". If there's any chance of comparing the results in this caliber, it would no doubt come from a cannelured or grooved bullet with a well regulated stab crimp, shot from a bolt action. (Yo Bob...) ...

Hoot-
Using my bolt rifles in 450B, I have not been able to reduce the variability in MV that most shooters experience using AR-based rifles. It appears to be a characteristic of the cartridge. Because bolt rifles chambered in 450B have become relatively common, I have been hoping somebody would come up an answer, but I've read of none. Please clue me in if I've overlooked some data set.

I need to find out whether other straight-wall cartridges, e.g. 45-70, 44 Mag, 458 Win Mag, experience the same variability. If not, why not.

An excellent treatise on primer selection and the results of using different primers is Chapter 3, "Rifle Primers", of John Barsness' book The Big Book of Gun Gack - The Hunter's Guide to Handloading Smokeless Rifle Cartridges. (Book is available from riflesandrecipes.com.) Spoiler alert for the chapter: It depends. It's not even necessarily true that the primers displaying the most spectacular ignition in photos are the "hotter" or most capable of igniting hard-to-ignite powders or long powder columns. Photos don't show flame temperatures.

As I recall, Hornady selected the small rifle size for the 450B because they were concerned with the possibility that large primers could loosen the bullets in the case mouth before the powder started burning well. If this is so, then the cartridge design suggests that proper ignition is a fairly narrow range between too much primer "strength" and too little.

--Bob

So Cabelas doesn’t stock the 7-1/2 and none of the local shops do either... what’s the next best option? I have some CCI small rifle primers, not the ones for an AR, but I’m loading for a bolt anyway. Thoughts?

Tag Soup wrote:So Cabelas doesn’t stock the 7-1/2 and none of the local shops do either... what’s the next best option? I have some CCI small rifle primers, not the ones for an AR, but I’m loading for a bolt anyway. Thoughts?

in my testing, cci 450's and rem 7½ gave nearly identical results, both on the chrono and the accuracy.

ive also used cci 400's, but you may not get as good of ignition in the colder months, so do some testing at your hunting temps if thats all you have. I stress *may* because that will depend both on your powder choice and your location.

400's are perfectly safe in an AR - unless you're chambering the same round over, and over, and over, and over. the floating firing pin WILL dimple them a bit, and i'm not comfortable chambering one more than around 5 times before i shuffle it to the bottom of the mag. I've never had one slam fire on me(yet), and i've burned through several bricks of them in various calibers in my ar's (223, 300 blk, 450 bm). However as noted (ie - during hunting season) i do cycle them down after 5 chamberings to prevent that possibility.

HTH