Avoid Semi Auto .17’s

We just read on WTA that there has been another KB with a Semi-Auto .17HMR rifle.  Most of the time the result of a KB is only stings and scares… but this time the shooter was hurt badly.

A blow back semi auto .17HMR (and even the .17 Mach 2 but to a lesser extent) is a bad idea.  No matter who makes the gun or how custom the gun is…. it’s going to, at some point, have a KB.  This is the same problem with EVERY semi auto .17.   Which is why all of them have been recalled and dropped from production by everyone that has ever made them.  Except for Alexander Arms, who is making a 1200 dollar AR type – that will still do the same thing everyone else’s did.   Even in one of the Gun Rags, during the review process the writer mentioned this happening but kept shooting it.
There are a couple causes of the .17 Rimfire KB’s.
1.  The bolt, rebounding off of firing the last round, slams forward into the cartridge rim hard enough to set it off while the round is in the magazine.
2.  A few rounds fires slightly out of battery puts enough carbon fouling in the chamber to builds up until a case is completely unsupported and firing pressure blows it.

A successful .17HMR Semi Auto design needs a locked breach – which is why most .17HMR brass from a Semi show the case head to be mushroomed out.    The bolt isn’t holding it in and it’s opening too soon.  The bolt will have to close on the round and lock it into the chamber, just like a bolt action rifle.  It also needs a speed controlled bolt so the bolt doesn’t hit the case head too hard.   To accomplish this, the rifle will need a Linear Electric Drive to cycle the action via electric power instead of by Blow Back.  The technology to build an electric linear drive is out there.  We’ve been using them for years in other applications.  We just need to make it smaller and put it into a rifle.

Until that time… Do not fire any – ANY – Semi Automatic .17 caliber Rimfire guns.  Because at some point, the thing will KB and someone will get hurt.

I remember when Magnum Research first started dealing with this problem… and still to this day… blame the Ammo Makers for making .17HMR ammo that was “too hot”.   But this is intellectually dishonest because if you are going to build a gun for any caliber, it needs to be able to handle that caliber.    Hornady, Winchester, Remington, CCI… out of a bolt action rifle, when fired over a Chrony, we find very consistent velocities.  Which is one of the reasons the .17HMR is such an accurate round.  The ammo isn’t the problem, I don’t care what Magnum Research says.   When I talked to the guy there on the phone with Magnum Research, he went on about pressure spikes and that it’s all the Ammo Maker’s problem.  Well, everyone else had already started dropping and recalling their .17 Semi’s… and these guys were still blaming Hornady.  Then they blamed CCI, and Winchester.   Finally they issued a recall.  You send your gun back to them and they rebarrel it to .22 Magnum, like it or not.  This isnt cool in my book.  You didn’t buy a .22 Mag, that’s not what you wanted.  They should issue Refunds.  This is one of the reasons I really dislike Magnum Research.  They have impressed me as being really shady over this SNAFU.

15 thoughts on “Avoid Semi Auto .17’s”

  1. I don’t think you need an electric action to handle the 17 HMR; a scaled down M1 carbine action should be able to handle it just fine. Locked bolt firing and with a short piston stroke gas operated action that doesn’t take much gas to function, just high pressure, it would be exactly what is needed for the 17 HMR. As far as the bolt closing velocity, that is controlled by the bolt stroke and the bolt spring; both of which could be easily matched to the requirements of the 17 HMR since the bolt spring no longer has to be stiff enough to help hold the bolt closed against firing.
    I guess we need to start sending emails to Kahr/Auto-Ordinance to get them to suitably modify their M1 Carbine.

  2. An electric system isn’t the best idea for a firearm for a few reasons (durability, number of small moving/intricate parts, the need for batteries, etc.) so I would suggest the use of magnets. They will do the same job except won’t require a power source and won’t have small moving parts. Part of the blame for. 17 semi rimfires actually goes to the consumer who practically begs for a product that isn’t ready for market. I would also vote for a minature M1Carbine action for a locked breach action. IMO it would do the job very well.

    1. A linear electric motor is solid state… Magnets. Very solid and reliable. Also they are very energy efficient. Besides this is a plinking gun… Not a military type weapon. Even though military guns have been running on electric for a long time with outstandingreliability.

      1. AFAIK there hasn’t been any shoulder fire rifle-type electric military weapons. Yes, we are talking about a plinking gun but that doesn’t mean durability has to be comprimised. This is a rifle who is possibly going to be living in a dirty trunk or behind a truck bench seat among the McDonald’s bags and empty beverage cans…not the cleanest place. Get some dirt/grit/debris in a small electric motor or see what happens to electrical contacts when they get wet or corroded. Magnets have no moving parts and are pretty tough and can do the job just as good…and for a much cheaper price.

  3. The .22 rimfire magnum rounds seem to be reliable in rifles for the most part. Is this because the straight wall case seals and sticks more in the chamber?

    1. That, and the .22 Mag is less over bore so it uses a faster powder and thus has a shorter pressure curve.

      The longer pressure curve of the .17 means that it’s got more pressure remaining when the bolt starts to open. Combine that with the thin brass necessitated by being a rimfire round and that’s a bad thing.

      1. That’s exactly right. So any Semi would basically have to be just like and autoloading bolt action. Controlled bolt speed forward, pressing in and turning a locking bolt, and then upon firing a specific delay time before opening.

        1. In theory you could make it a gas operated autoloader, but with such a small volume of gas it would be like building a gun with parts from a Swiss watch.

          Putting the bolt on an electrically driven lead screw would be interesting. You wouldn’t need any extra locking mechanism and it would be super easy to control.

  4. I was looking at the indexing bar on my Lee turret press. It is just a piece of cold roll that has been twisted on part of it’s lower half to form a lead screw. A rotary motor is cheaper than a linear motor so it might not be to awfully expensive to build. I can’t make up my mind on rather to use a bolt carrier or not though. You need the delay more than you need strength of lock up. If you used the bolt carrier you could have mechanical delay built in. When the trigger completed a circuit for the motor you could have enough of a mechanical delay for everything to get moving to eliminate the need for sensor or timer to start the extraction sequence for after the pressure drop. The motor speed would take care of all the rest?

    1. Not so much. One review published a glowing report about how fine that rifle was… But detailed how the gun was blowing cases in the receiver and bending the ejector and that they had to use pliers to get it functional again. I believe the article mentioned this happened more than once. So that means a broken ejector shortly following in a 1200 dollar rifle.
      Why bother?
      And that article linked of yours…
      “I found that out my first day at the range with the Alexander .17, as I was scattering shots all over the place.”
      Really? I’ve never seen that before. And then he got it back shooting “MOA”? Feh. A good bolt action is shooting .17HMR .25 MOA. Quarter MOA is what the .17 is all about. Blowing that group out for the sake of shooting faster? No thanks.

      For that much for just the rifle you can get a reliable bolt action and some great glass for it – and not have to worry about bullshit.

  5. Has anyone had any experience with the Volquartsen 17hmr semi auto? They seem to be selling quite a few of them and from what I’ve found in my research not too many complaints on them, in fact I haven’t read about anyone complaining about them. I have a Savage 17hmr bolt bull barrel that shoots great, I also have an Alexander Arms 17hmr that shoots just as good accuracy wise. However, it’s not 100% reliable like the Savage of course. I’m trying to find a semi auto .17 that is as reliable as a bolt action but beginning to wonder if it’s possible? From my experience with the AA 17 as long as the ammo is fresh and you clean it after every 100rds or so your good to go.

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