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Firearms of note and ridicule


rmgill
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Plus Maximi beats itself to death in about 1/2-2/3 time PKM does, while costing about 4 times more. Original 5.56 Negevs were also pretty fragile, don't know if that was fixed.'

There is absolutely no problem in making 7.62x51 PKM with pull-push, even using M13 links* working well, but that means you have to play with the "black art" of the gun design, bolt/carrier mass ratio and it's relation to a spring. Plus all that affects reliability of feed system. Hence you have to do some very serious mathematics before making it. But it is perfectly possible.

*PKM works with disintegrating  ShKAS belts quite well (especially considering state of it...), non-desitntegrating ones are a consequence of Soviets being cheap. 

 

Edited by bojan
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our Negevs had  problems because we used and reused old belts in training till they just stretched out, hence stoppages, other than  that quick google on local mil. board did not bring up anything specific. oh and barrels broke when 18-year old kids shot them glowing and then stuck in water.....

if Maximi´s problem was that receiver was too short, cannot  this be corrected by just a relatively little redesign? like AR-15 that  took 2 redesigns and 20 (30?) years to get it the current standard....

 

of course the simpler solution would be for nato to standardise on .303 rand PKM with rails  

😁

anyway, still the same question - would it be have been better to have  a separate squad level  belt fed 7,62LMG  and  on upper level units/vehicles different (GP)MG  ?

Edited by bd1
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If you lengthen receiver weight will go up. That is a genius of the good old "pull-push" - use free energy from a recoil for pulling rounds out of the belt and since you are dumping that energy you can have shorter receiver, weaker main spring (which translates into less recoil), etc. In contrast push through has to have longer receiver and stiffer spring, first to allow recoil energy to disipate, second for both that and to ensure reliable feed of the rounds on the return stroke.

Major example of "simpler is not always better".

As for separate "squad" MG, Israelis do have it that way. Negev in both calibers for squads and MAGs as tripod mounted. Russians also (PKP/PKMS), through those are more unified. Common receiver, different barrels is probably a best solution.

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thanks bojan, have you ever thought of doing a ´´firearms for dummies´´ book? 🙂

btw, one more squad-LMG question -  what were the hk-21e problems? i know the closed bolt makes it more likely to overheat and cook off, but do they really shoot that much in squad level? 

not that much info out there besides ´delta uses it, so it´s the best out there´ level stuff and Forgotten weapons video. ..

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I am thinking about more serious firearms book, about development of Yugoslav small arms 1945-1992, but covid shitshow put indefinite hold to it. :(

HK21 had so many problems, from reliability unless in perfect condition, overheating etc. You can not make LMG from AR just by slapping some things on it.

SFs use a lot of things that are borderline crap or at least very dubious mechanically. Prime example is Stoner 63 that fell apart after ~3000 rounds, had gazillion problems with parts breaking (especially bolt lugs that were not well radiused to a bolt body, so too much stress concentrated there, or extractors that were not well heat threated) etc..., but because they had a lot of support and could afford to have a huge weapons turnover they liked those. SEALS were basically using Stoner 63 for 1-2 missions, then changing entire guts of gun, or even whole gun. IOW, they can afford to throw away iffy guns after first signs of problems, regular army can not (or does not want to).

Also mission profile for SF favors certain type of weapons that are if not unsuitable, than at least iffy for a regular army.

 

Edited by bojan
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Some how I missed that Karl and Ian were doing the WWSD and with the upgraded 2020 model. 

I note how they go with the pencil barrel that I remember that Simon prefers over the other profile barrels, especially the ones profiled for Grenade launchers/etc. 

Edited by rmgill
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Time to dumb this topic down.

Count on Alexander Arms to bring in fresh gun porn. http://www.alexanderarms.com/products/ulfberht

— I suggest the title
Fat bolt between two flaps and DP with a twist

 

Edited by Blunt Eversmoke
Because phone keyboard hates me. Also, because porn is video.
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More on that gun using plastic-cased ammo. I like how they arranged the extraction, avoiding longitudinal tension stresses in the spent case, but that chamber separated from the barrel could be tricky in the long run.

 

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On 10/16/2021 at 7:04 PM, bojan said:

If you lengthen receiver weight will go up. That is a genius of the good old "pull-push" - use free energy from a recoil for pulling rounds out of the belt and since you are dumping that energy you can have shorter receiver, weaker main spring (which translates into less recoil), etc. In contrast push through has to have longer receiver and stiffer spring, first to allow recoil energy to disipate, second for both that and to ensure reliable feed of the rounds on the return stroke.

Major example of "simpler is not always better".

 

So the idea was to replace " pull out, drop down, push in on the return stroke" with push through and in in one motion. 

I wondered why they abandoned the former when I re watched the M1917 episode. 

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Seems that rimmed cartridges (.303 British, 7.62x54R) have to pull the rounds out of the belt, while rimmerless (grooved) cases could use push-through.

Probably Bojan would come in to point to an earlier example, but it seems the MG34 could be one of the first mass-adopted, belt-feed MGs with push-through feed. Perhaps the advantage was that system it enabled a shallow, thin receiver.

Edit to add:

Just remembered the Hotchkiss MG, model 1914 for instance, that had a kind of push-through, more likely push-and-raise because of the shape of the 8mm Lebel cartridges.

 

Edited by sunday
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Czechoslovakian UK59 is push through (as with Hotchkiss "push and move down", but enough to qualify) in 7.62x54R and so was Nikitin's prototype which has competed with PK.

Both Maxim and Browning played with push through and have abandoned it as "energy ineffective". For the Hotchkiss push-through was a way to avoid Maxim's patents.

MG34 ended with push-through as it was adoption of the previous mag fed gun with a minimal changes, so pull-push would not have been possible to adopt easily. Rest of the west cargo culted on this in the name of NATO standardization.

If you look at Ian's comparison videos of PKM and UK59 you will note way more serious recoil and shaking of the UK59, despite it being heavier. Result of push through. You can not make gun as light and as controlable as PKM with push through unless using "exotic" tech (as FN is trying with Evolys with titanium parts...).

Edited by bojan
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As long as done by someone even remotely competent to calculate bolt/carrier/belt feed/gas bleed ratios correctly.

Edited by bojan
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20 hours ago, Markus Becker said:

Ding Dong, the Palestinian is not dead. But if I where the other guy I'd be worried. 

Possibility of getting Galilized, for sure.

 

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A question for you belt-feed fanatics...

All I know of feed belts is the old USian canvas thing and the bog-standard disintegrating link belt. Surely there must be something newer than that.

If a western arms maker wanted to do a clean-sheet, best-of-breed evolution of the PKM, what would be the main design elements, including belt?

 

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