Home Forums Hunting & Shooting Ask The Gunwriters Remington 7-1/2 primers question

Remington 7-1/2 primers have been around since the mid-1960s. One of the primary reasons for their introduction was a heavier cup, in order to contain the pressures of newer cartridges that used small rifle primers.

But have also heard and seen them called 7-1/2 Magnum primers, though I can only recall them being called Bench Rest primers. Does anybody have any older boxes of 7-1/2's that say "Magnum" instead of "Bench Rest" on them? Or know of any references to that effect? I can't find anything firm on the subject in my reference library, or on the Internet--except somebody recalling when the boxes said "Magnum."

Remington 7 1/2 Small rifle Benchrest Primers are the labels of the 2 bricks I have 2-3 years old. I vaguely remember them being labled magnums. I usually use ww or cci as they are more availible around here. Mb

Thanks.

Yeah, the 7-1/2s I bought just before the Great Obama Panic are labeled Bench Rest.

All that I have are labeled benchrest. Mine span from 2 years old to about 12 years old

Here's an ad for an empty Rem 7 1/2 primer box that has neither benchrest nor magnum on the box:

.ad for empty 7 1/2 box with no special designation

That doesn't answer the magnum question, but perhaps it's a piece of the puzzle.

Speer Number Ten reloading manual has a table st the button of Page 32 that lists Rem 7 1/2 on the Small Rifle Magnum line along with the Federal and CCI small rifle magnum primers. That's not necessarily definitive, but it's one reference.

Yeah, I saw that--but one thing that complicates all this is the CCI 450 Magnum primer (which appeared about the same time as the 7-1/2 in the 1960s) was NOT a "hotter" primer when first introduced. Instead it simply had a thicker cup, to withstand the pressures of newer cartridges.

Until then, no American cartridge taking small rifle primers had a SAAMI Maximum Average Pressure much more than the .22 Hornet's--which is pretty mild. Today, of course, most SAAMI pressures are rated electronically in PSI, and even the .222 Remington's MAP is 50,000 PSI, only 1000 more than the Hornet's. Many other small centerfires, such as the .25-20 WCF, developed even lower pressures. Consequently small rifle primers had relatively thin cups compared to large rifle primers.

But when the .222 Remington Magnum appeared in 1958 its MAP was 55,000 PSI, as was the .223 Remington's when it appeared in 1964--and the .221 Fireball, introduced in 1963, has a MAP of 60,000 PSI. Plus, many benchrest competitors who used the .222 (the most popular BR round back then, along with variations) hot-loaded the round, to help resist win-drift. The standard SR primers of the day didn't hold up well at 55,000 PSI or more--which is why the first CCI 450 "Magnum" primers only had a thicker cup.

But eventually CCI added more priming compound to the 450, and in the early 1990s changed to an even hotter mix. So there have essentially been three versions of the 450. Which is why I started wondering about the 7-1/2.

I suspect the first 7-1/2s, which appeared around the same time as the CCI 450, simply had a heavier cup. But did later versions actually use more priming mixture, or a hotter compound? The typical photos of primer flames that some experiments have taken tend to show 7-1/2 with more flame than some other SR primers--though as one primer manufacturer remarked to me during an interview a few years ago, flame length doesn't necessarily have anything to do with flame temperature, which is more important when igniting powder. (He suggested chronographing the same load, in the same rifle, using different primers as a far better indicator of primer "hotness.")

So I'm wondering whether the 7-1/2 went through any actual changes after its initial introduction, or has only the name been changed? There hasn't been the same continuity in production management at Remington as there has been at CCI, and I haven't encountered any Remington worker who has any firm answers.

Ken Waters lists max loads of IMR4198 at 21gr, whether with the 6 1/2 or 7 1/2 primers, so I doubt if they were "magnum" primers. Thicker cups, yes. In my .222, 21gr flattens the 6 1/2s, so I use 20.5gr with them. Accuracy is the same with either primer or powder charge, right around 1/2" at 100yds with 50gr Blitzkings.

I have a box of primers like the ones in the ad/auction. I also have an older box of UMC 7 1/2 primers in a red box. That box doesn't say magnum of benchrest on it either.

I don't recall ever seeing them with a magnum labeling. I do recall the anvils changing from 2 prong to 3 prong or vice versa.

I bought a carton of 5,000 a couple of years ago. The designation is "BR".

Well, I finally decided to run a shooting test, using the same .222 load with three different primers: Remington 7-1/2, CCI 450 (latest version with the hotter priming compound), and Winchester Small Rifle. The WSR is supposed to be somewhere between a standard and magnum SR primer in brisance. Also decided to use Ramshot TAC, as hotter primers tend to make more difference in velocity etc. with spherical powders. Will report on the results.

Look forward to hearing your results as always. I have always used 6-1/2 for 222 remington never pushed it though. The 7-1/2 I have say small rifle bench rest. They're not 20 but over 10 for sure.

Good luck and shoot straight y'all

FWIW, I've used thousands of Rem. 7-1/2's over the years...starting in the '90's when they were about the only thing that would hang in there on the .17 Remingtons and other big cased .17's I was working with. Eventually, bushing the firing pin hole and profiling the pit tip got ahead of those issues to where any quality, thicker cupped SR primer was viable.

Though I've heard them referred to as Magnums, I've never seen any 7-1/2's actually labeled as such from Remington.

Good shootin'. -Al

For a different look at your question, you might take a look at the Remington catalog nomenclature from the period you're looking for. The cartridge collectors have an online pdf library you can peruse;
https://www.cartridgecollectors.org/ammunition-catalogs/Remington

FWIW, in 1979 there were referred to as "Small Rifle Benchrest".

Mine, between fifteen and thirty years old (purchased at different times) are all labeled as "Benchrest". GD

like full3r, i have several boxes of 7 1/2s of various ages all labels say bench rest.

the primer labeling thing is interesting though. i have some winchester wlr boxes that say standard or magnum and some that just say standard
was there a change in primer compound in these similar to what you describe in the cci's ?

Chris,

Thanks very much for the link. It has answered most of my questions. Apparently 7-1/2 primers were introduced in 1965, "Specially designed for .221 Rem. Fireball, .222 Rem. Magnum and .223 Rem. Cartridges."

In 1978 it was specifically mentioned for use in the then-new .22 BR Remington, as it was "designed to withstand higher pressure loads." It first listed as the 7-1/2 "Small Rifle Benchrest" primer in 1980.

So far I haven't found any mention of it being listed as a "magnum" primer, but the Large Rifle 9-1/2M showed up in 1968 "For use in Belted Magnum Cartridges, .264 Win., 6.5mm Rem. Magnum, 7mm Rem. Magnum, .300 Win. Magnum, .350 Rem, Magnum, .375 Win. Magnum, .458 Win. Magnum." (I found it interesting that Remington didn't include the .338 Win. Magnum--and listed the .375 H&H as the ".375 Win. Magnum.")

Am still going to run a shooting test to compare velocity results with other primers, especially the CCI 450 Magnum--the present version which has a hotter priming compound.

John

Have you considered adding small pocket 308 Win. brass loaded with a ball powder to the test?

I looked at my primer supply. I had a wooden box of primers I've had since 70's, the 7 1/2 boxes say bench rest.

As I recall the 222 Remington used 6 1/2 primers way back when. I bought a 1,000 of the 6 1/2's last summer on the way back from PD shooting. I promptly lost those primers. I had planned on using them in 17 Hornet, 256 and 222.

I believe the 7 1/2's were brought out for the higher pressure than the 222. The magnum moniker may perhaps have referred to usage in the 222 Magnum? That is my guess.