Announcement

Collapse
No announcement yet.

22lr national match vs. standard chamber

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 22lr national match vs. standard chamber

    I am in the process of building a gb22 pistol. For those not familiar, it is a dead simple open bolt single shot 22. Drawings say to use a national match chamber, after some explanation it calls for that so when you chamber a round it holds it slightly in place. If not, being open bolt it you went much past horizontal with the muzzle the round would fall out.

    I am using a chambered and rifled barrel blank for this with no idea of what the chamber specs are but put a round in and it will fall right back out if tipped upside down.

    Am I able at this point to start taking small face cuts on the chamber end until the round goes far enough to start making contact and will stay in place? Is that what the difference in a national match and standard chamber is?

  • #2
    Originally posted by oxford View Post
    I am in the process of building a gb22 pistol. For those not familiar, it is a dead simple open bolt single shot 22. Drawings say to use a national match chamber, after some explanation it calls for that so when you chamber a round it holds it slightly in place. If not, being open bolt it you went much past horizontal with the muzzle the round would fall out.

    I am using a chambered and rifled barrel blank for this with no idea of what the chamber specs are but put a round in and it will fall right back out if tipped upside down.

    Am I able at this point to start taking small face cuts on the chamber end until the round goes far enough to start making contact and will stay in place? Is that what the difference in a national match and standard chamber is?
    Goggle "saami specs", go to the rimfire section, and you will learn the difference!

    Comment


    • #3
      The chambers are described in the SAAMI website. You want to look at pages 9 to 11 of https://saami.org/wp-content/uploads...2018-06-13.pdf page 14 (or the 21st page of the PDF file.)

      That PDF file and others are available from https://saami.org/technical-informat...mber-drawings/

      Dan
      At the end of the project, there is a profound difference between spare parts and extra parts.

      Comment


      • #4
        Corbett types faster than I do.
        At the end of the project, there is a profound difference between spare parts and extra parts.

        Comment


        • #5
          Thanks for the link. If I a reading the chart correctly it looks like the sporting chamber could be shortened .175”. It won’t exactly give you the match chamber since the length in the 5 degree taper is a different length between the 2.

          It this sounding correct?

          Comment


          • #6
            The match is tighter in all dimensions. Among other things, the chamber is slightly shorter to push the bullet further into the rifled part of the barrel.

            https://www.rimfirecentral.com/forum...ad.php?t=92365 has a chart with the comparative dimensions.

            From that source:
            Type______Length__Mouth Dia._Throat Dia._Taper @ Throat
            Sporting____0.7751"____0.2307"____0.2270"
            Bentz______0.6900"____0.2270"____0.2255"_____1.5° Taper
            Match _____0.6876"____0.2267"____0.2248"
            Win 52-D___0.5800"____0.2278"____0.2248"_____2.0° Taper

            The "Ruger" 10/22 factory chamber is the "Sporting" chamber above.
            The "Bentz" chamber is the 'match' chamber for semi-autos.
            The "Match" chamber is for bolt actions.
            The "Win M52-D" is a bolt action target rifle.

            .22 Long Rifle Headspace: .0425" GO // .045" NO-GO
            At the end of the project, there is a profound difference between spare parts and extra parts.

            Comment


            • #7
              Thanks, I missed the mouth and throat diameter differences. There is a big discrepancy between the info on rimfire and saami. Rimfire has sporting length at .775” while saami has it at .875”. I am going to assume the saami pdf is correct?

              Is there going to be a problem taking the sporting chamber to the match chamber length?

              Comment


              • #8
                Biggest problem with taking the sporting chamber to the match chamber length (off the top of my head) is that the mouth and throat diameters are directly coupled to the length and angle. They also match the dimensions of the specified 22LR round.

                The match specs give you a more accurate placing of the round in the chamber. The sportster spec is more forgiving and less likely to jam on loading or ejecting. If the match chamber is properly cut and the bullet is properly cast, the lead bullet will be .221 to .225 diameter and the throat will be a maximum of .219. That gives you an interference fit.

                So use the match dimensions.
                At the end of the project, there is a profound difference between spare parts and extra parts.

                Comment


                • #9
                  I would caution you that ATF regards ALL open bolt guns are machine guns, even single shots!

                  Comment


                  • #10
                    Originally posted by deltaenterprizes View Post
                    I would caution you that ATF regards ALL open bolt guns are machine guns, even single shots!
                    Please link a source to this, I believe you are wrong.

                    Comment


                    • #11
                      Originally posted by deltaenterprizes View Post
                      I would caution you that ATF regards ALL open bolt guns are machine guns, even single shots!
                      Back in the late '50's, buddy had a Winchester .22 single shot "automatic". Yep. Fired from the open bolt position. After you fired a round, the bolt would lock in the open position, and on top of the action was a drop down gate with a groove in it. Put a round in the groove, push down and forward and the round would chamber. He was able to cycle that rifle real fast. Just checked,it was a model 55.
                      Last edited by Corbettprime; 09-13-2019, 08:14 PM. Reason: Adding

                      Comment


                      • #12
                        Originally posted by oxford View Post
                        Please link a source to this, I believe you are wrong.

                        Just google it. I believe that the rational goes back to the definition of a machine gun.

                        The National Firearms Act, 26 U.S.C. 5845(b), defines a machine gun to include any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.
                        I don't know if it applies to the single shot, but that would rely on whether it could be easily converted to semi auto or auto fire in the eyes of the ATF.
                        At the end of the project, there is a profound difference between spare parts and extra parts.

                        Comment


                        • #13
                          Originally posted by danlb View Post
                          Just google it. I believe that the rational goes back to the definition of a machine gun.



                          I don't know if it applies to the single shot, but that would rely on whether it could be easily converted to semi auto or auto fire in the eyes of the ATF.
                          Google what? By atf definition that you posted there is no way a single shot pistol with no provision for a magazine or place to hold multiple rounds can fall into the definition of a “machine gun” or easily converted to one.

                          That is why I am asking for a link to where they say any open bolt gun is considered a machine gun.

                          Comment


                          • #14
                            Originally posted by oxford View Post
                            Google what? By atf definition that you posted there is no way a single shot pistol with no provision for a magazine or place to hold multiple rounds can fall into the definition of a “machine gun” or easily converted to one.

                            That is why I am asking for a link to where they say any open bolt gun is considered a machine gun.
                            You are correct. Unfortunately, the ATF is notorious for issuing decisions based on ever changing rules and definitions. There are several rulings online that brand certain weapons as machine guns because, in their opinion, it's "easily modified" by file, saw or removing parts to make it autofire.

                            Can you change the design to add a feed mechanism? That seems to be the key.
                            At the end of the project, there is a profound difference between spare parts and extra parts.

                            Comment


                            • #15
                              There is no feed mechanism, you load a round in by hand, extract by hand. You can look up the specs it is a GB-22. Here is a picture of it.

                              Comment

                              Working...
                              X