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WARNING !! 17 HMR blow up

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  • WARNING !! 17 HMR blow up

    Lucky for me the 17 HMR doesn't develop the case pressure of its center fire brethren, otherwise I could be looking at a lot more destruction and potential injury.. And in getting near 40 years of shooting, this was my first blow up (darn sure hope I don't have another one for at least another 40<grin>).. But I wanted to post this in case anyone else is shooting an AR set up for this powerful little rim fire round..

    Having been recently upgraded by the factory with all of the latest modifications, I was shooting a factory AR upper, chambered in 17 HMR.. It was sitting on a billet lower with a Timney trigger, and the factory recoil spring assembly..

    (The original owner put the muzzle brake on this little thing.. As if a 17 really needs a MB<LOL>.. Anyway, I like the way it looks so, perhaps the guy wasn’t so silly after all <grin>.. And yes, the scope base has also been swapped around)..

    Anyway, I had been having intermittent failures to feed problems with the bolt not stripping the top round of the magazine, but rather moving it slightly forward, and then crushing the heck out of it.. The jam could happen as you let go of the charge handle to load the first round, or on any round then auto loaded..

    In fairness to the manufacturer of the upper, they recommend stock trigger for best results, and since I was not using a “stock” trigger, I was not getting “best results”.. I was trying different brands and bullet weights to see if any would work better.. And I was finding Hornady ammo worked the best of what I had tested thus far.. And then I noticed if I held the magazine forward slightly.. It would have less of a tendency to crush the top round.. I went back to the ammo which seemed to jam the worst (about 5% failure rate), and I fed 2 magazine without any failures (note my tests are 5 rounds into the 10 round mag’s)..

    I feeling pretty good that I had been able to work out the jams.. But then what happened next I was not expecting.. I pulled the trigger on the 2nd round from the magazine, and the sound of the report was significantly subdued.. Also I could see traces of smoke coming from area around the receiver you normally don’t see smoke.. Seeing smoke where you don’t expect to see it is normally the first indication of something “not good”..

    I remove the magazine, and notice it had be split apart, and the front of it appeared to have been cut.. I look into the action, and notice the bolt was not all of the way forward, and there appeared to be something in front of it.. I drew the bolt back and the ruptures on the case were obvious.. When I first looked at the case, it appeared the neck had been blown off

    But looking more closely, the neck all there, it was just blown out.. Basically, the gun went off without the case being completely in the chamber..

    It was clear the case failure was caused by the firing pin being able to strike the rim without bolt being into battery.. For some reason, the case got stuck going into the chamber, leaving the case head unsupported..

    I think this is kind of unsafe and intend to discuss it with the manufacturer.. But I did want to warn anyone who has a 17HMR to be careful with it and please always wear eye protection..

    Checking for grins and giggles, sure enough the bullet was in the barrel.. With a cleaning rod, I drifted it out.. The upper now sits on a lower with A2 stock and stock AR15 trigger group.. I have put 10 rounds through it since moving the upper, and have not seen any further jams.. I also check to make sure the bolt is fully into battery before I pull the trigger.. I will probably do this for a long time..

    Flk k

  • #2
    The 17hmr has issues with semis. Thsi is old news the kits for converting Ruger 22mag to hmr where pulled for this reason along with several semis by other makers. I have one 17hmr a Savage bolt that has had several cases of ammo through it with no problems. There are reports all over about semis having this issue and most ammo says not to use it with a semi.

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    • #3
      Since this thread deals with a safety issue, who was the manufacturer of the 17 HMR upper?

      Comment


      • #4
        Alexander Arms made the upper I am using.. Also again in fairness to them, I was not using a stock trigger as they recommend when the blow up occured..

        But I would guess the failure could occur with any of the blow back AR designs.. In fact since I understand the failure mechanism, I am going to see if I can duplicate it in my 9mm.. Of course no powder in the case..

        As a follow up.. I put 20 rounds through it today without any failures of any kind.. And I was using the ammo which had the highest failure rate.. That was 4 mag's, each with 5 rounds..

        I have never been able to fire 4 mag's without at least one of the failures to feed.. Of course after each round was fired, I checked the bolt to make sure it was fully closed.. Still it was a lot of fun to fire.. I really like this little AR, cheap to shoot, yet still packs a nice little punch out to 100 yards..

        flk k

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        • #5
          I am glad you didn't get injured. I guess you could duplicate it in 9mm but it doesn't inherently happen.


          Sent from my iPhone using Tapatalk

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          • #6
            I would pose another question- what does the stock/standard trigger have to do with wether or not it will or won't blow up?

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            • #7
              Originally posted by Beef_Supreme View Post
              I would pose another question- what does the stock/standard trigger have to do with wether or not it will or won't blow up?
              To be honest, I don't know.. But then tuning is everything.. I believe it has more to do with the hammer spring tension, which must impact bolt speed..

              I do know since putting the upper on a lower with stock trigger, it has functioned without any failures.. flk k

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              • #8
                Lighting trigger pulls frequently involvs lowering the pressure of the hammer spring.
                This can and does, affect the ammount of inertia to ingague and hold the hammer in place.
                Many blow back weapons, and some locked breach weapons are dependent on this pressure to slow lock time, and slow recoil of the breach.
                As a funny aside, the venerable 1911 also uses hammer pressure to slow the slide! I'v replaced a number of slides that have been battered because someone clipped a couple of coils off the hammer spring to try to get a lighter trigger pull.

                Respectfully
                Terry
                Last edited by Tripledeuce; 10-04-2012, 18:21. Reason: spelling

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                • #9
                  I can comment that the CMMG dedicated 22LR Rifle does not at all like any triggers such as CMC or Timney. I have had customer who have tried to run these triggers and many failures happened.

                  I would bet tomorrows lunch that even with a mil-spec trigger that you would likely still have failure in every magazine, it would be interesting if you could test this and see how many failures happen.

                  I would also like it if anyone could link any positive reviews on this product, i couldn't find any posted on any of the likely places.

                  Comment


                  • #10
                    I would give Alexander Arms upper, an overall thumbs up.. On balance, I would rate it 7 on a scale of 1 to 10..

                    In fairness to the manufacturer, I did purchase the upper used from an individual, and not directly from Alexander Arms or their dealers.. I knew I had just bought someone else's problem when I started talking to the Alexander Arms tech, and he knew the guy from whom I bought it.. I was quite happy when the rep offered to upgrade the upper to have all of the latest modification.. Apparently both the bolt and upper receiver were replaced..

                    I fully believe had I purchased the upper as part of a complete rifle I would have not have had the problem I have experienced..

                    However besides the problems of which I have already covered in this thread, the design has a shortcoming, at least as I see it.. The bolt does not stay open after the last round.. It is just the way the action was designed..

                    One may argue, the AK47 bolt doesn't stay back after the last round either, so what is the big deal.. In most cases I would agree with this position..

                    But the 17HMR is a rim fire cartridge.. If you don't count your shots you will eventually drop the hammer on a empty chamber, there is nothing to cushion the firing pin and it can get flattened.. I know for myself, I am going to buy a spare firing pin or two just to have "in case"..

                    Since moving the upper to a lower with stock GI trigger group, the rifle has functioned without failure for 20 rounds so far.. That is 4, 5 round mag's have been fired through it.. Before making the move I could expect at least 2 to 3 failure to feed in 4 mag's.. I have 4 more mag's also loaded each with 5 rounds, and if they also feed without a problem, I think I have the major problem resolved.. So I would say things are looking up..

                    The Alexander Arms 17 HMR is a great little varmint and pest rifle.. It is fun and relatively low cost to shoot.. In spite of the learning curve when adapting a complete upper with an existing lower, I would not give mine up.. And I guess, when it comes down to it, that says more than anything else of which I can think..

                    Flk

                    This review is freely given by me.. I receive no consideration of any sort from anyone for the testimonial..

                    Flk k

                    Comment


                    • #11
                      I am glad you got it worked. out. I would still be weary of the 17hmr used in a semi auto..

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                      • #12
                        Alexander Arms AR-15 17HMR, no one answers the phone...

                        I just ordered one today. They do have a WARNING Statement about the correct trigger spring. Either you made them put this out there or you didn't read and understand it. I read it 10 times but figured out what they ment when I ordered it today. Still no answer on the phone, too busy to anwer calls I guess, and e-mails too. Sent 10 over the weeks and no answers.

                        Comment


                        • #13
                          Originally posted by Maine04657 View Post
                          I am glad you got it worked. out. I would still be weary of the 17hmr used in a semi auto..

                          Did you even order a 17hmr or just giving input? Thanks for the advise.

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                          • #14
                            Originally posted by Tedward View Post
                            Did you even order a 17hmr or just giving input? Thanks for the advise.
                            No I do not have a semi 17HMR nor would buy one. The reasons are very easy to glean from information already out there. In a couple more years when I hear of a platform that has NOT had problems I may buy one in SEMI. For now the BOLT one I got works 100 percent and I have yet to read a problem with 17HMR and bolt guns.


                            Comment


                            • #15
                              Originally posted by Maine04657 View Post
                              No I do not have a semi 17HMR nor would buy one. The reasons are very easy to glean from information already out there. In a couple more years when I hear of a platform that has NOT had problems I may buy one in SEMI. For now the BOLT one I got works 100 percent and I have yet to read a problem with 17HMR and bolt guns.


                              I too have one just like that but not the 4" addition on the end of the barrel. What is that? I also like mine too but when I have a field of rabbits instead of pulling back on a bolt and trying to take a second shot, I want to pop a few rounds off so thats one more reason for me wanting a semi-auto. One shot and every varmint is gone where I come from. These little rascals are faster than me moving my hand from the trigger to the bolt and back to the trigger so I'll be the guinipig and see how well I can get more rounds off than one or 2 before the field is bare till the next day.

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