Bring Back the 5mm Rimfire Magnum Part I by Eric A. Mayer

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If you are a regular visitor to the rimfire forums available on the internet, then you have probably seen the posts asking about Remington’s 5mm Rimfire Magnum. Even now, 30+ years after the Remington 591 & 592 rifles were discontinued, folks are still fans of this caliber.

Introduced in 1969, Remington hoped to bring a caliber to the table that could challenge the .22 WMR introduced by Winchester a decade earlier. The factory cartridge was impressive by 1969 standards. It consisted of a 38 grain “Remington Power-Lokt HP” 0.2045″ diameter bullet with a factory listed muzzle velocity of 2100 feet per second. Remington released two rifles chambered in this caliber; the 591 and the 592 . The Remington 591 consists of a 24″ barrel with a 1 in 12″ twist, using a 4 round magazine. The same configuration is standard in the Remington 592, with the only difference being a tubular magazine holding 10 rounds. The stocks are not fancy, but what they lack in looks, they make up for in weight and fit. I have always disliked the thin stocks and forearms on many of the “modern” rifles; the stocks on these guns remind me why. The trigger-pull is very heavy and not easily adjusted, which can lead to a squeeze that seems to last for hours! Both rifles came with open/iron sights, but scopes can be mounted on the receiver for those who prefer that option. All in all, it was a nice rifle for the period, albeit based on a rimfire model which tended to diminish the capabilities of the cartridge it was chambered for. Approximately 51,743 of the 591/592 rifles were made. Thompson also produced a 10″, octagon barrel for their Contender pistol in the 5mm, releasing about 30,000 of them before discontinuing production.

The ammunition was produced for a decade after the rifles were discontinued. Eventually Remington stopped production, making any leftover cartridges instantly valuable with prices topping $60.00 dollars for a box of 50 on some of the gun auction sites.

The 591/592 rifle owners were able to dust off their guns years ago when Lowell Kenney wrote about the 5mm Craig Centerfire (5mm Craig Centerfire) here within the pages of This gave a viable option for folks who didn’t want to search for, then spend top dollar for a box of the Remington 5mm Rimfire ammunition. It also brought a fun round back to life.

Now that you have the brief history of the caliber, let me explain to you a bit about the performance. If you have read my articles, I don’t sit down and print out a bunch of info gathered while sitting at a shooting bench. Instead, I give you real life hunting situations and back my thoughts up with visual proof of a hunting round’s capabilities. So, I will keep the technical information short and then move on to the good stuff!

I borrowed’s Technical/Gun Editor, Tim M.’s, Remington 592 still chambered in the Remington 5mm Rimfire Magnum (no Craig conversion on this gun). I was lucky to pick-up 4 boxes of the Remington 5mm Rimfire ammunition in the “Green Box” (the first rounds released were in a white box) at a reasonable price ($30.00 a box). The rifle is topped with a Parker-Hale 6 power scope with a crosshair a bit finer than your standard duplex.

I first sighted in the rifle at 50 yards, making sure that the rifle was on after the 4000′ elevation climb from Tim’s home. We noticed quite a difference in the POI, so I adjusted it to shoot approximately 1″ high. On the second trip I made out to the field, I was able to shoot for groups and was pretty impressed with the 592. It printed well at 50 yards, with the first edge to edge group being a touch under 0.4075″ (0.2045″ subtracted from 0.612″). I set up the chronograph to verify the 2100 fps that had been published in all the old hunting magazines. This chart shows a comparison with the 17HMR and the 22 Magnum:

5mm Rimfire Mag
Remington Arms
38 gr.
2043 FPS
60 FPS
.22 Win. Magnum
40 gr.
1910 FPS
.17 HMR
17 gr.
2657 FPS
50 FPS
The rounds I was shooting were a full 60 FPS on average less than the published velocity. It was a bit surprising, but I assumed the age of the ammunition or the elevation had something to do with the difference. I wasn’t going to worry too much about it, as I wanted to get to the hunting! Luck would have it, as we sat at the bench a cottontail rabbit decided to wander down a hill and into the brush pile a few feet behind the target we were shooting at. I tucked behind the gun and aligned my shooting bench so I could be ready for when it popped out. I waited for what seemed like an hour watching the rabbit’s head peaking out from behind a large branch in the pile. Finally, after much mental prodding from me, the rabbit moved out to an open spot allowing me a perfect shot. So, that should be it, right? Nope, I pulled the trigger and missed. I swear I heard a groan from Tim’s body. He was probably wishing he was behind the gun so the tension could be over, but there was no way I was going to pass on this opportunity! Thankfully, the rabbit moved directly behind a small pile of branches, leaving me with a small opening in order to shoot through. I waited a bit, hoping he would make one more little hop. He didn’t, so I put the crosshairs on the only part showing, a small bit of neck. This time I took my time squeezing the trigger. At about the time I was wondering if I had left the safety on, the rifle cracked and so did the rabbit’s neck!! The bullet had hit home and hard. My first kill with the Remington 5mm Rimfire! Wow, was I excited! We immediately walked over to the rabbit so we could see the damage. I took a picture as the rabbit lay, nothing more than a trickle of blood flowing from its neck. Tim flipped it over for another picture and we saw the exit wound. Not huge, but destructive enough to kill the rabbit immediately, with not even a twitch.

My adrenaline was definitely flowing at that point. I had to shoot another, just to see if the instant death was a fluke. A few minutes later, not one, but two cottontails gave me the chance to try again. This time would be different. The shots were a bit further out, but they were partially hidden behind some dead grass. The first was facing away from me, quartering away. I could see the body and head through the grass, but no clear shot presented itself. I decided to shoot and see what would happen, as I relayed to Tim later this was the biggest problem I had with the 17 HMR, its inability to penetrate any small amount of foliage in front of your intended target. I pulled the trigger and we heard the “pop”. After the rabbit dropped out of sight, nothing moved; it was stone dead!

This first picture shows the way the rabbit ended up. The bullet traveled most of the way up the body, stopping in the chest cavity. Afterwards, when I was cleaning it, I saw the destruction the bullet left. It was dynamic! The second picture is a shot of the grass I shot through. Granted, the rabbit was visible and not completely hidden. Don’t try this shot with the 17 HMR!

A few moments later, we caught more movement in the area. It took me a bit to find it, eventhough it was only a few feet away from the first one. This rabbit gave a much better target, with most of its body showing within a clear shooting lane. I aimed for just below the head at the lower neck-line. Once again the crack of the gun was echoed by the crack of the rabbit’s neck as the bullet struck home. Like the others, it was dead instantly. The damage was more than the other two, with a splash of blood coating the grass a foot away. The 5mm had misted it, blowing out the exit leaving a large hole with guts hanging out (see pictures below).

The rabbits must have heard that the 5mm was out killing their friends because after that we didn’t see many of them within a reasonable shooting distance. We did spot a few ground squirrels; one which was lifted out of its hole by Tim. It was the longest shot of the morning and put the squirrel to sleep!

My first outing shooting the Remington 5mm Rimfire Magnum was quite a learning experience. When I left that morning, I was already itching for targets so I could test it some more. I would get my chance, two long weeks later.

The second outing with the Remington 592 came on the last day of my hunting lease. I had gotten up early and headed up to the ranch, only to find myself shivering from the mid-50’s morning. So I sat in my vehicle listening to the radio and reading a book my wife had left. The wait was killing me, so as soon as the sun hit my vehicle I was back out setting up the shooting bench and targets. I shot the 5mm and printed the group I listed above. After that, I put the 592 aside so I could sight in my new 17 HM2. I was happy with all my groups that morning. For me that’s rare!

I packed up the guns and headed to an area I had hit two weeks before. It was a long, curvy dirt road that split a small canyon. This allowed me to drive 100 yards or so and shoot at targets in any direction. One side allowed shots out to 100+ yards and the other side half that. Perfect distance to test the 5mm on some ground squirrel sized quarry. I’ve mentioned this in past stories, but the ground squirrels we shoot on this ranch are big compared to those found in NE California and in the deserts, so much so they can sometimes reach 2 pounds depending on the food sources. Therefore, this wouldn’t be overkill. I found out later the 5mm would be just right!

The first stop found me staring at a ground squirrel not 60 yards away on a log. I slowly pulled the 592 out and dropped 5 rounds into the tubular magazine. As I eased over to the side of my vehicle, I spotted two more squirrels on another log about 100 yards back down the road. Perfect, I would shoot this one then go for the others. I took a good rest and lined the first squirrel up in the crosshairs. Because of the distance, I didn’t use any holdover. “Here we go”, I thought! I slowly squeezed the trigger and watched as the squirrel flew up into the air after the shot. I then heard it growl a little (they don’t call them ground grizzlies for nothing) and watched it go into a hole. I missed. I hit the log just below the squirrel. DAMN!! I then concentrated on the two squirrels a bit farther away. This time, I made sure to connect leaving the squirrel in a pile of guts. At 100 yards, the 5mm had ripped the squirrel in half!

I walked up the road some and shot another squirrel that was sitting on a stump. This one was only 40 yards and a lot smaller, but the damage was just as severe. It entered the squirrel’s chest and blew out the back. Literally, blew out the back (see picture below). I killed a couple of more on my way back to the vehicle, but did not collect them as they were piles of bloody guts.

Up the road some, I came across an open spot littered with deadfalls and stumps. As I parked, I saw lots of squirrels running for cover. It would be just a few minutes before they started working their way back out. I loaded up again and set up a shooting bag to shoot from. Suddenly, from a patch of grass 50 yards away, a squirrel started “chirping” very loudly. Anyone who has hunted ground squirrels with me knows I hate when they do that. In fact, I will spend quite a bit of time seeking these guys out just to shut them up!! This one was no different. I searched with my binoculars until I saw his head poking out from behind a tree within the grass patch. I slowly moved over so I could get a body shot. The chest shot splattered him all over the tree and grass. Seconds later, another squirrel took over where the dead one left off and started “chirping” his own song. GRRR!! He was easy to find and visibly exploded when I hit him in the side of the chest.

This went on most of the day. I ended up with about 30 ground squirrels killed with the Remington 592 and the 5mm Rimfire. The last one was a large squirrel on the side of a dirt mound, trying to cool off as the day waned. I estimated him to be 80 yards away, so I held a couple of inches high and shot. The shot hit home and tossed him back a few feet from where he was hit.

As I set the squirrel up for a picture, I thought about the kills made with this caliber. I had one squirrel make it to a hole after being hit. It was a half-hearted run with a pile of guts trailing behind it, so the result was surely the same as the others. It was a perfect end to a great day.

So, after shooting 50+ rounds of the Remington 5mm, I became a believer. I guess I had always been one, but that was based on articles and other folk’s experiences. Now that I have been able to shoot one and see how well it serves as a small varmint hunting caliber, I have become more than just a believer; I have become its champion. What the heck does that mean, you ask? Well, here it is. I believe that with the powders and bullets available today, the 5mm Rimfire Magnum (or 20 Caliber Rimfire) could be the next step in the rimfire revolution we have experienced in recent years. It could quite possibly match the early loads for the .218 Bee and .22 Hornet. The 5mm Craig conversion has shown us the potential, with velocities up to 3300 fps. This would be the first rimfire that could humanely take a coyote sized animal with consistency.

I can invision the new 5mm (or 20) Rimfire in a Ruger 77, or the Remington 504, as well as the wonderful Marlin and Savage rifles. The potential is there.

What do we need now? We need the gun industry to step-up and take a chance. We need a bullet manufacturer who is not afraid to take chances, to step-up to the plate and re-create a cartridge that can not only be used in new rifles, but in the old 591 and 592’s as well. If only half of the original 591 and 592 owners purchased 4 (50 round) boxes of ammunition for their guns, 5,000,000 rounds would be sold. This does not even include the 30,000 Thompson Contender barrels that are out there sitting in the back of a gun safe or closet.

Threads like this one at Rimfire Central, show the excitement behind such an idea.

By:  Eric Mayer

Editor’s Note: Part II on bringing back the 5mm Rimfire Magnum will be coming in the next few months. In the meantime, for more information on the history behind this caliber, please visit our Classic Calibers Articles Page and our new website dedicated to the 5mm Rimfire Magnum – The .

This article was originally published on 08/23/2005.

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