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Old February 17, 2020, 18:43   #1
BarnOwlLover
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Mechanical question regarding ejectors/ejection angle

This is a question regarding ejection port location and ejector function/location.

Most AR-18 based rifles have the ejection port at basically a right angled compared to the bolt. Most AK-type rifles have it so the ejection port is above the bolt.

Before this gets too far out of hand, I'm well aware of how AKs are constructed with a main receiver body and a dust cover over the bolt. Most AR-18 rifles have the bolt in an actual upper receiver and the trigger mechanism/mag well in the lower.

I'm mostly wondering if it's possible to have right angle (or near right angle ejection) with a rifle that has a two lug rotating bolt and a fixed ejector (similar to the set up on a FN FNC or a FN Minimi/M249 LMG)? What would the hurdles be?
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Old February 23, 2020, 23:13   #2
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I'm also asking based on this patent registration image submitted by HK for the Mk 4 version of the HK433. Look at the head on image of the bolt. Based on video illustrations, I've seen the rounds being ejected at like between a 2:00-3:00 angle, but the bolt actually sits down where half of the head can be seen though the ejection port. And thehead on image shows the ejector at an angle below 90 degrees from the vertical.

Just wondering what governs ejection angles of common self loading rifle actions.
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Old February 24, 2020, 08:53   #3
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Well, the AR15 port is pretty close to 90 degrees from the bolt but it still has angled ejection. Some of its geometry related since the bolt head has to be in line with the bore axis which is towards the bottom of the receiver on most modern SLRs (which have their gas systems above the bolt head). I suspect some of it has to do with the upward pressure that cartridges in the magazine might be putting on the extracted round and this might cause problems with truly horizontal ejection. Note that most autoloading shotguns have the gas system under the action, are fed from tubes and thus many do have near 90 degree ejection.
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Old February 24, 2020, 09:53   #4
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I'm mostly wondering how this relates to ejection port placement. AKs tend to have them fairly high above the bolt/barrel, while most AR-18 based actions have them at nearly 90 degrees to the bolt and barrel.

For example, here's a couple of photos of the HK433, one with ejection:



And one with the bolt locked back (not the postition of the bolt compared to the ejection port):



Is such a bolt/ejection port placement possible with a fixed ejector?
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Old February 25, 2020, 19:47   #5
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It has been said that you can change the angle of ejection on a fixed ejector by altering the angle of contact with the extracted case. Do a search for the ggiilllliiee mods to see the discussion about this subject.

With the AR and other types of spring loaded ejectors, the angle is pretty much controlled by the ejector location.
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Old February 25, 2020, 21:48   #6
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I've been exposed to guns my whole life (father and uncle are collectors and target shooters), but I'm trying to understand the finer points of more modern weaponry. I really got interested in guns when in Junior High we started studying World War II and got exposed to the first Medal of Honor PS1 game.

However, I've gotten more interested in recent years by more modern stuff when I started to expand my horizons (was actually interested back then, but didn't start studying a lot of the newer stuff on the internet until about 10 years ago).

I've also seen mentions (not sure how accurate though) that various versions of FALs had fixed ejectors, and others had spring loaded bolt mounted ejectors.

That out of the way, just based on Tac-40's comments and what else I've read, fixed ejectors have the theoretical advantage of a few fewer parts to make or possibly wear out or break. However, ejection pattern is dictated by manufacturing tolerances and ammo loading, which is why some AKs for example have erratic ejection and why sometimes ejection pattern from rifle to rifle may be different

However, bolt mounted ejectors don't involve that many parts, seem to work fine in most instances, and you can tune ejection better and more predictably.

It's like how most AK bolts use fixed ejectors mounted to the receiver. I'm betting that Kalashnikov thought that by reducing parts it could improve durability somewhat and reduce one or two machining operations on the bolt.

However, the M1 Garand, which Kalashnikov drew a lot of inspiration from as far as the bolt/gas system (in modified form) and the trigger mechanism, has a bolt mounted ejector like say and AR-15 or AR-18/180 type bolt.

Other than what I've pointed out, is there any advantage or disadvantage either way, or in reality does it all cancel out in the end?
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Old February 28, 2020, 12:54   #7
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The extractor and the ejector are usually on opposite sides of the bolt face. This allows for maximum extractor claw tension aginst a spring loaded ejector. On an AR the ejector is at 9 o'clock, so the round kicks out at the 3 o'clock position. If the elector is at 7 o'clock, the ejection should occour at the 1 o'clock position.

It is possible to change the angle of ejection of a fixed, i.e. non spring loaded ejector by altering the angle of the ejector face or even the length of the ejector. For a spring laoded ejector I think you're pretty much stuck with what you have.

Last edited by Sgt_Gold; February 29, 2020 at 23:26. Reason: Cause I can't tell time.
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Old February 29, 2020, 07:56   #8
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I'm still wondering which is better from a mechanical standpoint. Normally I'd favor fixed ejectors just because of fewer parts, but it seems that with an AR-18 type bolt carrier (like what the SCAR and HK433 and such have) the bolt mounted spring operated ejector seems to be what you're stuck with.

I'm mostly wondering if a fixed ejector is compatible with a 3:00 ejection port to the barrel and if there's a practical reliability difference between fixed vs spring loaded.
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Old February 29, 2020, 10:13   #9
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IMHO, the fixed ejectors are problematic with most select fire weapons. The fixed ejectors are subjected to huge stresses caused from the repeated violent impacts by the brass case during extractions. And due to the design necessities, the ejector is required to be behind the magazine, thus allowing full stoke of the bolt before ejection starts. And more often or not, fixed ejectors are depot level repairs or not repairable at all.

On the other hand, the internal, spring loaded ejector is only subjected to the impact of the bolt closing on the round in the chamber. This is much less violent due to the chambering and bolt locking process. Additionally, the ejection process begins as soon as the brass clears the chamber and is often enhanced by the impact of the brass on the rear edge of the ejection port. This would ensure positive ejection during the full auto firing sequence. The added benefit of these types of ejectors is a low level maintenance and repair ability instead of requiring the weapon to be sent back to the depot.
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Old February 29, 2020, 10:58   #10
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99% of my full auto shooting has been with subguns.. After years of shooting many makes and models it seems to me that the reliability of the design has a lot of factors but how hard it treats the ammo really shows up.

UZI bolt is so big and heavy it flattens the rim on firing. The rim is then subject to more abuse on ejection and brass is shaved off and deposited in the action. When the bolt moves back for ejection the damaged case hits the fixed ejector and either flips the spent case out or flips the spent case around behind the fixed ejector and the gun jams. A serious jam.

A better design wouldn't leave space to allow a empty case to get behind the fixed ejector. Yet the guns run good in most cases if they are cleaned and only factory ammo is used.

My impression of fixed ejector varies from gun design to gun design. The 1911 is fixed and runs really well even with reloads but the 1911 doesn't beat up the cases.

My H&K clone of the 91 beats the brass up like all H&K guns do, it just hammers the crap out of the brass. Yet the gun doesn't fail to operate but then I only use fresh factory ammo in it. The design is tight in the sense there isn't room for many different types of jams and not much room for dirt and debris to get in it. Old design like the FAL and the 91 were ahead in their day and worthy guns today.
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Old February 29, 2020, 14:11   #11
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In regards to the FAL, I've read (though quite a while ago) that there were versions with spring loaded ejectors and fixed ejectors. But it seems in either case they were designed to be serviceable components because of the expected wear and tear they tend take. I'm not sure if they're user serviceable, but DSA and other companies that make parts for FALs do sell ejector block modules as repair/replacement parts.

The AK-47 family and FN FNC use fixed ejectors, but are noted for sure as being harsh on ammo. A lot of Valmet rifles and later FNCs even have a spent case deflector to try and keep the shell casings from getting flung back into the dust cover or upper during ejection and to keep ejection to a convenient angle for the firer.

I also wonder this about machine guns. The FN M249/Minimi has a fixed ejector (like an AK), and has pretty nasty/fierce ejection. But the Minimi is rated as very reliable when properly built and maintained. The M240/MAG, which has regularly been described as one of the most reliable automatic weapons ever made, does use a bolt mounted spring loaded ejector, just like the BAR it's locking mechanism is based off of.

Based on what you guys are saying, even in machine guns, spring loaded, probably bolt mounted, ejectors are probably the way to go, especially nowadays.

That being said, most automatic pistols still use fixed ejectors, but they're designed to be usually user serviceable if they wear out and not be overly harsh on ammo on ejection.
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Old March 21, 2020, 14:02   #12
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Sorry to resurrect this post, but I was just looking up some stuff on the FN Universal Carbine (intermediate caliber immediate predecessor to the FAL), and on Forgotten Weapons I found one of the manuals in PDF format for the UC. It's actually fairly well illustrated with schematic drawings of stuff like the tilting bolt and trigger mechanism and gas system, all of which were based on a semi-auto rifle that would become the FN 49 semi auto full power rifle.

But on page 12 of this document, it actually shows the ejector (which is fixed in place just behind the magwell as on the production FALs), but it shows a head on view of the bolt and ejector relative to each other as the end of the bolt's rearward stroke. Note the position of the extractor relative to the ejector.

As to the relevance to the topic, looking at the drawing, I'm wondering if ejection pattern (angle of ejection) is down mostly to an interaction between the angle of where the extractor is mounted vs ejector vs how the ejector is powered (fixed vs spring loaded, receiver vs bolt mounted).

Document is here, go to page 12 to see bolt/ejector schematic (and read the whole document if you want more info on this early FAL variant, as well as a bullpup version):

https://www.forgottenweapons.com/wp-...L%20report.PDF
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