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.

I'd be curious as to those results well. I believe I have some shot strings stored in my silver mountain system of 7 1/2s vs 450s in .308 lapua sp brass with N150 and a 155.5 bullet. The 7 1/2s were slightly faster if I remember correctly. I'll be able to check in a couple of days.

I do not recall seeing "Magnum" on these and I just checked my supply and they say "bench rest".

I'm looking at some old 222 loaded ammo - might of been my dad's. The primers are copper colored. I have not seen primers this color for quite a while. It may be before my time?

Remington 7 1/2s are not nickel plated like many of the others; they retain a copper color.

I'd call it more of a brass color. The only reddish copper primers I've seen were very old.

I've been using 7 1/2s since the early '90s, I have never seen any copper colored .

just some anecdotal information..
there is a NATO / OTAN paper " The Combustion of Solid Propellants" that discusses flame temperature, length and composition of various compositions in section 2.0 of the paper.

The paper seems more focused on the inner cone length than the secondary (visible) flame length (at all but the highest pressures ~100ATM), and specifically considers the two parts of the flame separately.
the pdf is 3.2 megs so I dont think I can attach it, but I could send it to you John.
looking at inner cone length might make for an interesting second look at primer flame photos....
Though I can't say for sure that priming compound fit the category of a "double base propellant"

Mule Deer:

I dug into my older primers and found a 7 1/2 box that doesn't mention magnum or benchrest. The same as what Ramblin_Razorback posted:

https://www.ebay.com/itm/Rare-Vinta...leanbore-cartridges-/124438644539?_ul=IN

I am interested in what you find out with the primer comparison

I have a few left in a box that was purchased circa 1983. Labeled Benchrest and they are indeed copper color.

Forgive me for being particular, but I'd like to be clear on what we're talking about.

Pinkish like copper:



Or "copper color" like brass:

I have been using REM 7 1/2's ever since I bought One of the first .17 cal Rem Model 700's rifles.
They were made for the .17 Rem because of the pressure. As far as 6 1/2's I never liked em even in 222 because I drove em harder than factory.
I considered 6 1/2's junk primers

I still Use 7 1/2's in .17, & 223 if loaded to 5.56 pressure because if you use the same hot loads in either caliber with most any other primers they flatten or end up pierced, & eats away at your firing pin.

. I remember back in the day{70's} Ad's from Remington showing a longer duration flame front, not hotter burning just longer lasting
compared to to other primers, that picture clearly showed the flame front while other primers were already done. That + the much harder Bronze cup.

I still have a bunch of the Rem 7 1/2's, all saying BR, or Benchrest. I don't waste these just to burn up ammo, they special. LOL.

Actually, as I mentioned in an earlier post, 7-1/2s were primarily introduced for the .221 Fireball, which appeared years before the .17 Remington. But same deal: Thicker cup than the 6-1/2s to resist higher pressures.

RP used only 3 digit lot #s back then so there's no way for me to establish manufacture date, or to remember exactly when I got these. I have a box of 6 1/2s that are surely from early 80s that are nickle plated lot #231, lot #175 of 7 1/2s marked SRBR that are copper colored (mid to late 80s), & a later lot of SRBR 7 1/2s #297 that are brass colored (late 80s/early 90s). All other RP primers in my closet are brass colored except an older lot (late 80s?) of 2 1/2s which are nickle plated. No mention of magnum anywhere on my SR stash.

Al Angerman did some work with primer photography that the late Dave Brennan published in Precision Shooting Magazine. It was subsequently reprinted as part of the Benchrest Shooting Primer.

Comparisons were the Rem 7-1/2, Fed 205M, etc. -Al

Dave Brennan also ran an article by Audette on Primers which also included photos in the 90's. IIRC it was Audette's last article before he passed away.

Yes....Al Angerman's article was a follow up to some of the work done by Rick Hornbeck and Creighton Audette. I believe the Angerman article was in '93.

After that article, I tested primers extensively in the big cased .17's, finding some definitive stuff.

Presently, both the 6PPCs and the 30BRs routinely operate in the pressure range that no small rifle primer would have survived back then......

Good shootin' -Al

Well I learned something today. I had thought 7 1/2’s we’re older than 221’s. Thanks MD.

No no MD I don't think so, the 17 rem was introduced by Remington in 1971, the 221 fireball was not introduced until 2007.
I've read many times the 7 1/2 was created because of the .17 rem. and the fact that 6 1/2's were not going to cut it. In 71 I was interested in a .17 as soon as I heard about it. Remington said no small rifle primer at the time were recommended for the 17 rem except the 7 1/2.
Today there is some other primers that could fit the bill, not so then.

They are. By quite a few years. I think now a days some of the cci made for 5/56 and Federal AR SRP are maybe even stronger.

Copper colored like copper not like brass coloring for the old loaded rounds I was looking at.

That is way off. Try 1963.

The 221 Fireball was introduced in 1963 in the XP100. Beginning In 2002, it was chambered in both the Model 7 and the 700.

Good shootin'. -Al

17 Fireball was introduced in 2007 I believe.

German Salazar trod similar ground more recently.

IIRC, he also included spark photography (as did Audette) or long exposure photography (i forget which) to image the prime flame front.

These days you’ll ha em to be motivated to find his work as he pulled much of it from online outlets.

Yep.

Then the 221 Fireball came out a little later than the 222 Remington Magnum. The 222 Mag came out about 1958 --- I believe.

So, did the 7 1/2 Magnum primer come out in 1958 or 1963? If it came out in 1958, like I had in the back of my mind, it would make sense that Remington would have called it the 7 1/2 Magnum - to match the higher pressure of the 222 Magnum. Perhaps they changed the name to 7 1/2 Bench Rest when the 221 came out in 1963, IDK?

Just throwing it out there as I was wet behind the ears and very early into center fires in 1958. The center fires I had were the 7.92x57 and later the 6mm.

Wrong, the 17 Mach IV was. 62

Well not quite, yer over 40yrs early ,Ah whatever ! LOL The Rem Model 700 was in 62. The Model 7 was in 83.

doubleDs55,

Good to know we have you on the Campfire to straighten out history.

MD you are SO patient 😀

Not talking about when the models were introduced. Rather, when they became available in 221 Fireball.

According to Ken Waters' Pet Loads 1968, Factory 222 Remingtons were loaded with 6.5's, when piercing in both 222 and 222 Magnum factory ammunition surfaced and was eventually replaced in both cartridges (and the 223) around 1966. Ken still used and preferred 6 1/2s in both cartridges, probably because he was never heavy on the powder handle.

In his 1977 write up of the 222, Federal and CCI had introduced "Bench Rest" primers, both of which increased velocities markedly over the Rem 7.5.

Mike Venturino did a primer article for Handloader in 1979 (all SRP) and his box was the "Bench Rest" primers, 7 1/2. At that time, only CCI had a "magnum" small rifle primer of domestic make. - Wolfe Varmint and Small Game Rifles and Cartridges

Both men I would count as having a habit of seeking facts, or beyond the scope of doubleDs.....in the case of Venturino's article, he posts a picture of every box of primers used in his test.

I've got most of German's work from The Rifleman's Journal saved. He was thorough and put a lot of effort into his testing and documentation. -Al

You and Pete53 related ?

I'll shut da hell up

delete my bad

You’re gonna have to live with it.

Yep, pink like copper, not yellow like brass.

I don`t often read every post in a thread,but this one has all kinds of information.Even an old dog can learn stuff here.

Woof Woof

I checked the data I had stored in my e target and find that for 10 shot strings at 1000 yards the 7 1/2s averaged 1292 fps, SD 8.6 fps and the 450s 1290 fps, SD 12.2 fps. Statistically a tie and I would need longer strings to validate any SD comparisons. My go to loads use the 450s.

I did lookup my notes on German Salazar's testing, and with a strain gauge equipped 6XC the 7 1/2s were about 1000psi hotter than CCI BR4s. He did not test the 450s.

Thanks for the info.

Just checked some of my older testing in a .22 Hornet with Li'l Gun, and in that one 450s were hotter than BR4s--but for some reason I also didn't try any 7-1/2s..

Can't say if Star Line has done any actual comparisons, but this comes directly from the the 6 Creedmoor srp brass page:

"As with all types of cases this large with small primer pockets, it will require care in powder and primer selection in cooler temperatures to prevent hang fires. Single-based propellents are generally easier to ignite and a quality primer such as the Remington 7 1/2 BR are recommended."

I've been using 7 1/2 s with CFE223 with good results in the 6Cm, but haven't had a chance to try the load in cold weather.