RIA: Experimental Semiauto Springfield 1903 Primer-Actuated Rifle (Video)

During the 1920s, a lot of experimental rifle development work was being done in the US. The military was interested in finding a semiautomatic rifle, and plenty of inventors were eager to get that valuable military contract. One particular item of interest to the military was the possibility of being able to convert large existing stockpiles of bolt action 1903 Springfield rifles into semiautomatics, and that is what this particular example was an attempt at.

This rifle is built with a barrel and receiver made in 1921 (it was not uncommon for the government to provide parts to inventors working in this area), and uses an operating system which is pretty much unheard of today: primer actuation. In this system, the primer pushes back out of the cartridge case (intentionally) upon firing, acting as a small piston. This pushes the firing pin backwards (as well as the bolt face in this rifle), which begins the process of unlocking and cycling. It is a system that saw some popularity for a brief time in the 20s, as it allowed semiautomatic action without the need for a drilled gas port or a moving barrel – several of John Garand’s early prototypes operated this way. However, substandard performance and the need for special ammunition (most military ammunition had primers solidly crimped in place) led to its abandonment.


  1. That’s a really interesting rifle

    I wouldn’t want to fire it, but I’d love to have a good look at it.

    I’m guessing that the left/top lug seat is removed in order to allow the extractor to enter the receiver ring at the top, Krag & Jorgenson style?

    I didn’t catch the size of the firing pin hole – is the rifle more a dodgy headspace actuated, rather than primer set back actuated mechanism?

    and at last – a locked breech gun that has a recoil spring that is also the “main spring”

    incidentally, primers will back out quite happily during firing, if they’re not supported. I think crimping is more to prevent then from rattling out or from genuinely coming loose if tolerances are out

    in actual firing, a primer will back out due to the headspace clearence, and then be re seated as the pressure in the case expands the case. Al Haral has a good FE simulation of it happening:http://www.varmintal.com/a243z.htm

    • Thanks for emphasizing “Main spring/ Recoil spring” difference. Correct nameing should be important for clear description of parts for most of the readers.

  2. “Primer-Actuated”
    В.Е. Маркевич (Ручное огнестрельное оружие) states that F.V.Tokarev crafted in 1909 year primer-actuated rifle firing normal 7.62x54R model 1908 (designation of Spitzer bullet version of cartridge for Mosin rifle), but can’t make it work good enough. He also remark that in these time other primer-actuated self-loading rifle were tested [in Russia]: системы Нидгем, Хоккер, Решейн but they need special cartridges. (Apparently these rifle were designed outside rifle, but I don’t know how they names are in Latin alphabet)

    • http://commi.narod.ru/txt/markev/463.htm
      states that:
      В Англии оружейник Нидгем и инженер Хокер в 1884 году сконструировали гильзу с вогнутым дном с целью получения нового принципа автоматики. После того X.С.Максим сконструировал патрон с подвижным дном специально для автоматического оружия. Только через 10 лет Решейн в Швейцарии создал патрон с подвижным капсюлем и автоматическую винтовку, сконструированную по этому новому принципу автоматики.
      which mean (I preserve all names which I don’t know in Russia):
      In England armorer Нидгем and engineer Хокер in 1884 year constructed case with hollow base to get now principle of automatics. After that Maxim constructed cartridge with movable base specially for automatic weaponry.
      Only through 10 years Решейн in Switzerland created cartridge with moving primer and automatic rifle, using this new principle of automatics

      So I suggest to anyone interested in this search in: English patents around 1884 year or patents of Maxim’s to get more info.

      • “В Англии оружейник Нидгем и инженер Хокер в 1884 году сконструировали гильзу с вогнутым дном ….”

        Man, I like that; it surely sounds cute. I am not laughing at Russian long time by now, but still, it is real cute language. I am actually by part of your contribution re-learning it.

    • Daweo;

      There is no single standard for transliteration between Cyrillic and Latin alphabets. There are instead several systems and they overlap. This is stupid, but the other systems tested are of Nidgem, Khokker, and Reshein. It would also be suitable to render Хоккер as Hokker (Hocker?) and Решейн as Reshain, given the devoicing of the e character as a result of e-kratkoye.

    • Additionally, “DG” is commonly used as a replacement for the sibilant J, so “Nijem” or “Nijim” or something to this extent is also a possibility. Knowing that this is in connection with an English patent, then Hokker is almost certainly Hocker.

      • Or for that matter “Hawker.”

        Apologies for the chained replies, I’m sick and “tripping mad balls” here and thoughts are not occurring in a sequence conducive to posting properly.

    • One would realy wonder if this kind of cartridge case would work. What retains the case in the chamber at instant of firing… There it seems no breech closure behind the case… No difference than simple blowback. What and which construction holds the front section of case as permitting its rear section to expand and extend rearwards and against which ressistance except breechbolt mass… Would it be any benefit building such kind of extending case than the one with thicker web at the rear. Pedersen might be accepted as a master of rather intriqued inventions but this one seems overintriqued.

          • Related my post… The patent seems describing a different blowback system in which, at instant of firing, the front section of cartridge case sticks in the chamber and the rear, accordioned part extends rearward as exposing the thick web section out of the supported chamber to push the seemingly unlocked breechbolt.

          • “more in detail”
            All cartridges have limited maximal pressure, if it will be excessed then поперечный разрыв гильзы happens, see drawing 95 (Рис. 95.) here:
            For normal cases this pressure was* 3500-4000 kG/cm^2, but there are method to go beyond that – one of it is that groove.
            *data from 1963 book Основания устройства и проектирования стрелкового оружия by Кириллов В.М.

          • is: “method”
            should be: “methods”

            6х49 мм was created to replace 7,62x54R, firstly (but not only) in sniper weapon – there was ТКБ-0145К bull-pup rifle created specially for it:
            6х49 мм cartridge fire 6,2-мм bullet (~0.244″) which mass is 5 g (~77.5 gr) with muzzle velocity (from 720mm barrel) of 1150m/s.* Objective was to have cartridge with effective range to 1000m. ТКБ-0145К was used in combat, it was judged as superior to 7.62x54R by users – weapon was more compact /because bull-pup/ than 7,62x54R weapons, better against moving faster /higher muzzle velocity/ and has smaller recoil.

            * – notice that these figures seems quite close to .244 Remington with 80 gr bullet. Does anyone have data or experience about accuracy of said .244 Remington 80 gr? Notice that with similar ballistic 6×49 has smaller case.

  3. As a compromise between converting existing guns and selecting a whole new design, would it have been theoretically practical to design a new gun using as many existing parts of the old guns as possible? I can see an advantage in regards to savings on having to invest in new tooling and less time need to train new production techniques and you can scavenge old guns for production or spare parts. Even with just a say 50% parts commonality I can see some advantages.

    • “using as many existing parts of the old guns as possible”
      I think barrel is (in most cases) most valuable piece, as it need to be precisely crafted and withstand high pressure.
      On the other hand sometime using as many part as possible is not sane – for example Mannlicher Yasnikov – http://www.hungariae.com/Mann95Ru.htm – is self-loading rifle with high % parts common with Mannlicher 1895, but it become failure. In theory it is very easy to convert straight-pull bolt-action into gas-operated weapon, but in practice it is not.

  4. Very unusual and almost got me stuck with my understanding of it, if it was not for mention of “primer actuated” system. If it does anything for understanding of process of conversion from repeaters to self-loaders it is clearly visible in parts commonality and controls. A ‘step between’ as observed with some previously featured rifles. It makes more sense now.

    What to say – I do not want to be judge of this thing; but it is real clever. Well, this is what Forgotten (and Unique) Weapons are about. Again, once more – super show!

  5. At 8:04 Ian demonstrates the spring loaded bolt face feature. The cam pin is just forward of the s-curve in the cam track. If the cam pin is moved forward from here along the long straight section, it would force the bolt face deep into the chamber. Since the bolt face drags the extractor along with it, I believe the modifications to the extractor are meant to allow it to slide along the bolt which at this point is locked and can’t move forward. For this to work the chamber would have to be deepened which is easier with the barrel off, hence the pipe wrench marks. Awfully weird.

  6. Here’s the patent for this experimental firearm:


    You’ll notice that this is as Keith (In England) suggested, “a dodgy headspace actuated, rather than primer set back actuated mechanism,” especially if fired with full power .30-06 ammunition.

    The most interesting thing about it is the “assignor”: United Automatic Rifles Corporation

    This is the company that hired Melvin Maynard Johnson Jr. as a lawyer, then later tried to sue him for taking his ideas and running away with them. ^__^ While he was there he worked on a semi-automatic rifle design that was unsuccessful, but it inspired him to get it right with the development of “Betsy.” This may be the very rifle that Johnson worked on while at the company. This would be quite a find from a historical point of view and I’d quiz the consignor and re-examine anything else that was offered along with it to see if there could be a connection established.

    I’ve read that the inventor Young provided reduced load ammunition along with it, which would make sense. If this was fired with full power .30-06, the case would stick to the walls of the chamber at the front and the case head would set back, stretching the case and perhaps lead to a case head separation. If you down loaded it to the point where it would blow back, the mechanism might function.

    The designs that John Garand worked with were actually primer actuated and had a small movable portion in the center of the bolt face that would be set back by the primer backing out, but still provide support for the case head and keep the actual bolt head locked up to maintain proper headspace.

    • Thanks Brian, good to see that there actually WAS documentation available. I wish I’d learned that before embarking on idle speculation.

    • The gun is a rotating bolt implementation of the same principle used by Pedersen in what became the original Remington Model 51, and similarly the Benelli B76

      a short distance of initial blow back blows the unlocking piece back on its way.

      the long straight track on the locking and unlocking cam is to provide the necessary delay to opening.

      Unless loads were very far reduced, the gun will have needed to use greased or oiled cases to prevent the case heads from simply blowing off with the 2mm / 50 thou excess head space.

      The aims and claims in the patent (I’ve scanned through) are comical – one thing that can never be said of a 1903 receiver or bolt or trigger guard – is that it is in any way shape or form, cheap and simple to make!

      The Suomi style disconnecter shown in the patent drawings, coupled with the Springfield bolt release as its safety – would certainly make for an all too easy conversion to [about as pleasant as snorting Tabasco sauce].

    • Yeah, that is what I felt, just could not give it a name (“dodgy head-space”).
      The more conventional approach would be as you describe it later.

  7. Wow, that’s quite an interesting design. I wonder what the cartridge must have looked like — I’d guess the primer may have been like a long deep seated tube that acted like a one-way piston within the brass cartridge, in order to make sure the primer had considerable rearward travel but never pushed out of the case completely (and perhaps blasting hot combustion gas in the shooter’s face)

    Hat’s off to Ian for having the courage (or liability insurance) to dive in headfirst disassembling a unique, completely undocumented five-figure-value rifle design without fear of something going “THWOINGG” and flinging a bunch of tiny parts all across the room.

    BTW, I don’t understand why they didn’t just slap on a pistol grip of some kind to make up for the trigger (essentially) being pushed far forward.

    • ” pistol grip of some kind to make up for the trigger (essentially) being pushed far forward”
      This is obvious… from modern point-of-view. In inter-war period most military rifles don’t have [separate] pistol grip, so far I know.

    • The primer doesn’t have to travel far cause the action to work. So standard primer and cartridge case can have have been used.

      In Roy E. Rayle’s book ‘Random Shots’ in appendix 9 there is the analysis that was done by Dr. Karl Maier for primer setback actuation. Springfield Armory wanted it done as they were giving some consideration to using it for a GPMG.

      Dr. Maier allowed for the primer to travel 0.03 inches rearward. He also used the headspacing movement in his calculations.

      He did write that the problem with a crimped primer was only if it was crimped to point that there is a time delay between movement caused by headspacing and primer setback.

      FWIW Dr. Maier concluded that primer actuation might work for a rifle, but wouldn’t for a belt fed machine gun.

  8. I wonder what the cartridge must have looked like

    probably very well greased, or it would have separated with the 0.050″ excess headspace.

      • US Patent 1780566A:
        Pedersen coat is thin and uniform [same thickness in all places]. He states also that:
        It is smooth and glassy when hard and does not gather dirt or dust. However, when the ceresin on the cartridges is melted in the chamber of a gun, it becomes a lubricant.

        • It’s a wonder that Russian steel-cased revolver ammo (including .22) did not (apparently) come pre-waxed from the factory, as users have routinely complained about the fired steel cases getting stuck.

    • “probably very well greased, or it would have separated with the 0.050″ excess headspace.”

      Hmm … I’m going to guess that using lubricated full power .30-06 ammunition in this design would result in the complete destruction of the firearm. There is very little between the hot flaming gasses and the outside world in a standard 1903 Springfield. In this rather dubious blowback design, if you gave the case a free run at the bolt at max pressure you wouldn’t just get a case head separation, you’d get a full pressure case blowout with the usual destruction and flying metal parts.

      I believe that Hatcher’s Notebook mentions some mysterious case-head separation problems folks experienced at the national matches that could be traced to lubricant in the chamber. The case does a lot more work than a lot of people give it credit for. ^__^

      • The patent shows the rifle using the 1903’s cone at the breech end of the barrel,

        which was dubious from a case head protrusion and support point of view to begin with.

        Add to that that only the right (bottom) locking lug appears to be locking the breech (the Krag used a single bolt head locking lug, but with a lower pressure and smaller internal diameter case)

        and the safety lug at the rear of the ejection port, may or may not be seating on the bridge of the receiver

        safety lugs typically had a working clearance to avoid lifting the main front lugs off their seats.

        so yes, the gun would probably have had very marginal strength if it was used with full loads of .30-06.

  9. Primer actuated firearms always make me think of the 9mm spotting rifles with the turducken-like cartridges: a primer on a rimmed 22 blank pushed into a hole drilled in the base of a full size rifle case. The 22 pushes back into the action unlocking the breech – you get a very simple semi-automatic action from a complex cartridge. Some of the spotting rifles are thrown away after being used in anger no more than five times (eg. the spotting rifle for the LAW80 rocket), so they have to be simple/cheap.

  10. According to the related patent, the gun seems not primer actuated. It might be described as “Floating breech face” actuated in which, a locked breechface carrier would go unlocked by the force of an actuator block getting necessary power from very short distance blownback floating breech face, somewhat similar to Pedersen hesitating lock with a difference that of having the breechface carrier as locked at instant of firing and different foremost locations of both. The floating, forwardly springforced breechface would blowback very short distance and transmit gained momentum to an actuator block to go backward within the locked breechface carrier to unlock it from the receiver. IMHO.

  11. I agree with the thought that it’s not primer actuated but rather “excessive head space” actuated. It would be a case head separation waiting to happen unless the case was lubed or one might get away with using a fluted chamber. The amount of travel of the entire bolt face seems excessive if (as I recall from reading about Garand’s primer actuated rifle and as was mentioned above)a .030″ set back of just the area of the primer was sufficient to actuate the action.

    I do think that using the primer as the gas piston could be successfully developed, at least with non-crimped primers.

    • Sory but, would it be present in all straight blowback firearms this kind of excess head space… The term “Excess head space” should be referred to the distance for the back of related case dropping downward through gravity when the muzzle got 90 Dergees upward. IMHO.

      • “would it be present in all straight blowback firearms this kind of excess head space”

        Cartridges designed around the idea of a blowback action are constructed in the transition between the case head and the sidewalls to be strong enough to contain peak pressure even when extracting from the chamber. The .30-06 was not designed like that.

        Not to get into too long a discussion, the .30-06 cartridge does not blow back at peak pressure and is not designed to be strong enough at the transition between the case head and the side walls to contain peak pressure if it was lubricated so it would blow back. And the bolt head mass in this design is not significantly larger than the mass of the bullet and the powder charge, so if the cartridge were lubricated so it would blow back, it would do so at an excessive velocity.

        Now I suppose you could design a blowback firearm for the .30-06, but it would require lubricated ammunition, and the pressure containing chamber would have to be long enough, (the bolt face would have to extend inside the chamber), to keep the weak side walls of the cartridge supported until the pressure dropped to the point that the case could contain it unsupported.

        For a cartridge of this construction and pressure, a blowback design would only work in something in the heavy machine gun class, and for practical purposes even those are designed with a locked breech so they don’t require lubricated ammunition.

        • Thanks for detailed post. However, what I meant was, the embodiment of the breech face propping behind the cartridge case under spring tension and not a free travel clearance or an empty gap deserving the description ” excess head space”. As known, all straight blowback guns have breech faces propping behind the cartridge case under spring tension and if they properly built, none has excess head space.

          • Strongarm,

            Ah, I see where you are coming from.

            Yes, if I seat the case in the chamber and use a piece of paper for the bolt face, and that piece of paper is touching the base of the case, there is zero headspace. It’s not safe, but there is no headspace.

            A better term for the situation here might be “loose breech.” (Although this term is most used when talking about the fit between the barrel and the slide of a locked breech handgun.)

            So, in a locked breech firearm, (which this one is), where you need that locking to safely contain the pressure in the chamber, if you take all the springs out of the mechanism and push all the parts as far as they can go before they hit their locking surfaces, you need to still maintain the maximum headspace dimension in order to safely contain the pressure in the chamber.

            So, yes technically we should be talking about “loose breech” here rather than “headspace.”

        • 0.030″ is between five and ten times the allowable headspace for a rifle firing full power bottlenecked cases.

          a straight blowback in .30-06 requires (IIRC) a bolt weighing about 56 pounds to keep the case safely in the chamber for long enough.

          Delayed blowback guns achieve that by accelerating a smaller mass, the appropriate number of times faster

          It may actually be that the bolt face only gives a couple of thou of an inch if it is chambering a loaded round.

          any more than 0.006″ movement of the head of a fired case (assuming that it is of conventional construction, rather than specially made with an extra thick head) would be un acceptable.

          Springs do not play a significant part in keeping a fired case from ejecting its head from the chamber (at potentially around 2000 fps or more for an unconstraibed case head!) in a blowback gun.

          the inertia of the bolt does that job.

          the job of a recoil spring is to decelerate the bolt, and once the bolt has stopped travelling back (which might be due to impact on a solid part of the receiver or on a buffer of some sort), to return the bolt to battery.

          In the gun that Ian is showing, the ounce or so of bolt head is something like 1/900 times less than the weight needed to work safely in straight blowback.

          so, three posibilities present themselves

          maybe the movement of the bolt face is only in a few thousandths of an inch

          perhaps conventional cases were loaded to much lower pressure

          or, perhaps it was intended to fire with cases with extra thick brass in the case head, and lubed so they could slide back without separating and without leaving the front portion of the case stuck firmly in the chamber.

          • Another factor is the bottle necked cartridge in a true blow back system. Not only is chamber pressure working to rip the case head off while the case wall is being retained by wall friction, pressure is also acting against the area of the shoulder to retain the front of the case in the chamber. It’s done with mildly bottle necked pistol cartridges like the 7.63 Tokarev in sub-guns but would be a bigger problem in something like .30-06. I’ve never examined spent cases from a PPSH-41 but I suspect the shoulder has fire formed forward a bit during ejection. Some years ago, at the behest of a friend who thought it would be a fun experiment, I made a .30 Luger chambered barrel for an Astra 600 (straight blow back 9mm Para).
            I only fired it a few times. It worked pretty well to turn bottle necked .30 Luger cases into something closely resembling straight 9mm Para. An interesting but ultimately useless experiment 😉

          • Brian and Keith,

            Thanks for your very detailed and informative posts. I would only want to point out the difference of the terms, “Head Space” and “Excess Head Space”. If The term “Head Space” refers the needed clearance from bolt face to the locations where the cartridge case stops, The term “Excess Head Space” should refer the additional clearance from the needed lenght value and should not contain any limitations about the force or power to hold the bolt face behind the cartridge case. There might be the mass of bolt or compressed push of a spring or another but the bolt face stands behind the case with zero tolerance and techinacaly with “Zero excess head Space”. Any kind of straight blowback gun has a bolt keeping its foremost position under spring tension and if is correctly crafted, with zero excess head space, But its mass might be unsufficient and its possible function would not be what ought to be. What I would want to say, in short, describing this rifle’s working system through the term “Excess Head Space Actuated” should not be correct. There it would need to find another term embracing it. IMHO.


          • By the way, when I introduced the term “excess head space actuated” it was only intended as a short hand name to distinguish from true “primer actuated” or “primer set-back actuated” since the actual process had been adequately explained by previous commenters. Probably a poor choice of terms.

            I would argue that the floating/spring loaded bolt face in this design however does not provide correct head space even though it closes the gap behind the case head since it does not support the case in that position during the stresses of firing. If that qualifies as proper head space, most rifles with excess head space due to deformed or worn locking faces could be remedied by pointing them muzzle down and allowing the natural “spring” of gravity to correct the head space. Semantically correct perhaps but not functional.

          • Thanks Ownerus. There it seems we found out a gap in description of the term “Head Space” which should be corrected as; ” Supported in the due course Breech Face” at the beginning.

          • Strongarm,

            I’m glad you’re happy with ”Supported in the due course Breech Face”.

            I think I’ll just call it “A Bad Idea” and leave it at that. ^__^

          • Ownerus: interesting story about the 7.65mm Parabellum converted Astra. It would be interesting to know if the 8mm Nambu chambered Hamada pistol suffered from the same problem. As for the 7.62×25mm Tokarev chambered open bolt SMGs, I have not heard about such a case deformation. Probably the “quasi-API” system helps keeping the case forward and minimize when the pressure is greatest.

    • Dr. Maier calculated that a 30/06 the power of the setback of the entire case was 16 times that of setback of the primer.

      So the setback of the whole case wouldn’t need to be even 0.03 for the gun to function.

  12. http://www.talpo.it/files/64084385-armi-portatili-gucci-1915-i.pdf Interesting manual (in Italian, sorry) on the portable weapons edited in Italy in 1915. It already covered the problems posed by the self-loading infantry rifle (the Mondragon had been already adopted by the Mexican Army) and the preference between converted rifles and new designs.
    Aknowledging that the self loader was surely the future of the individual armament of the soldier, and correctly recognizing all of its advantages (ironically, almost all the armies still used bolt actions 30 years later), it concluded however that “every conversion of the actual bolt-actions weapons is not convenient. The same qualities of the automatic weapon (over all, the rate of fire) would render illusory in short time every economy provided by the conversion”.
    Infact the main cost of the new weapon would not be the rifle, but the cartridges (L.60 for every new rifle and L.100 for 1000 rounds were calculated).
    Talking about a Carcano self-loading conversion that had been experimented (and I would really know of what conversion he was talking, since the Cei-Rigotti was not a conversion, and I don’t know other Carcano self-loaders first than the ’20s). He tells that, “altough the experimented rifle had proved to be simple, easy to handle, durable and reliable, and the conversion is relatively cheap”, the barrel needed to be replaced anyway (existing barrels reached 450C° internally after 80 rapidly fired shots, so, to take full advantage of the increased ROF, better alloys or much more barrels were needed). “Therefore, in all respects, there can’t be any convenience in doing a conversion that, for how much simple and well designed, does not cease to be a compromise, and, as such, can not meet all the requirements that are demanded for an optimal automatic rifle for infantry”.

  13. The 9mm spotter cartridge that is for the recoiless anti-tank gun has a 0.22 hornet blank in the base that moves back
    on firing to push to the rear the roller locking wedge and then residual pressure operates the action.
    I believe that it is the only successful “primer actuated” firearm

    • The SMAW is not a recoilles gun but a rocket launcher. The difference is somewhat subtle but still quite real, despite the fact that the SMAW rockets burn out in the launch tube unlike for example RPG-7 rockets, where the main motor is ignited only after the rocket has been launched by the launching charge and has traveled to a safe distance from the operator. (The RPG-7 is in fact a hybrid system.)

  14. I may be wrong, and please let me know if I’m way off here, but wouldn’t there be an issue with hot gasses being able to escape back at the shooter with a system like this? It seems like with an angled cartridge wall you really wouldn’t have anything to make a seal against the chamber other than the neck as the bolt started moving back.

    If I haven’t managed to quite explain what I’m thinking, I’m sorry, it’s 6 am and I haven’t gotten a cup of coffee yet….

  15. I found this video to be quite fascinating.

    Clearly, primer actuated operation was a dead end, but the spring loaded bolt face reminded me slightly of a Benelli shotgun inertia piece. Perhaps if this bolt head was given a very strong spring, and the cartridges were hard waxed, it might have worked as a sort of delayed blowback gun. Obviously, it would need a pistol grip too.

    Now all we need is for somebody to build one and give it a try.

    • suggestions that people who come to this site “love guns” are incorrect

      we only say that we do, to get them into bed…

  16. It’s a “natty” sort of prototype, design. Lot’s of good, little designs within a… Interesting operating, principle.

    I think you could use this design in a purpose built weapon, extend the front of the bolt, and enlarge it as appropriate for- The current bolt face, to fit inside the bolt via the extension aforesaid. Then have the bolt have it’s own face, which is surrounded by a series of radial ports that sit above the rim of the cartridge. Fluted the chamber- Gas from this enters the ports, hits the old bolt face, compressing it’s spring against a section to facilitate this within the bolt. Tweak the springs resistance to gain more a sufficient delay, before the “bolt face” acts on the other components as now.

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