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Discussion Starter · #1 ·
Once upon a time the Steyr-Aug hammers were a perfectly fitting replacement for the PS90 hammers. I was able to get a couple Aug hammers recently and decided to replace the Gen 3 hammers with these. Lo and behold, Steyr has modified their hammers to not fit the PS90 hammer pack. The differences;

1) The "axle" of the hammer is too long to fit in a PS90 pack. You have to take about 1/16" of each side for it to fit.

2) The diameter of the hole through the axle is too small for the pin to fit. Must drill out about 2mil's.

3) The cut in the hammer is at the right place but is too shallow for the sear to engage. Must use a triangular file or dremel to deepen.


Once the above steps are completed the hammer fits and works just as the Gen 1 or Gen 2 hammer.
 

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I'm still looking for the back story about why they would fit in the first place.

Even when one company rips off another's design, I've never seen a rip off so close that the parts will interchange. How did they get to be so close? Was AUG selling packs to FN for the early rifles? Was it an engineer who switched companies and stole the blueprints? Are they owned by the same partent company?

And the reason I wanted to do this was that I broke a part in my PS90 trigger pack. My only option was to order a new trigger pack, which were backordered by 6-8 weeks. However I found that there are a supply of AUG internals to be had, so you can replace an individual part, for a cost which is less than a complete new trigger pack, and which are available right away.

If FN had and sold internals (or even complete packs), this subject would be considerably less interesting.
 

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I'm still looking for the back story about why they would fit in the first place.

Even when one company rips off another's design, I've never seen a rip off so close that the parts will interchange. How did they get to be so close? Was AUG selling packs to FN for the early rifles? Was it an engineer who switched companies and stole the blueprints? Are they owned by the same partent company?

And the reason I wanted to do this was that I broke a part in my PS90 trigger pack. My only option was to order a new trigger pack, which were backordered by 6-8 weeks. However I found that there are a supply of AUG internals to be had, so you can replace an individual part, for a cost which is less than a complete new trigger pack, and which are available right away.

If FN had and sold internals (or even complete packs), this subject would be considerably less interesting.
I think it comes down to not re-eventing the wheel. Why does Barrett Firearms use an M-16 trigger group in the M107 .50?

Because it was an off the shelf design. What FN did makes a hell of a lot of sense, there was a proven Bullpup trigger design and just copy it.
 

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Once upon a time the Steyr-Aug hammers were a perfectly fitting replacement for the PS90 hammers. I was able to get a couple Aug hammers recently and decided to replace the Gen 3 hammers with these. Lo and behold, Steyr has modified their hammers to not fit the PS90 hammer pack. The differences;

1) The "axle" of the hammer is too long to fit in a PS90 pack. You have to take about 1/16" of each side for it to fit.

2) The diameter of the hole through the axle is too small for the pin to fit. Must drill out about 2mil's.

3) The cut in the hammer is at the right place but is too shallow for the sear to engage. Must use a triangular file or dremel to deepen.


Once the above steps are completed the hammer fits and works just as the Gen 1 or Gen 2 hammer.
Pictures???
 

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I think it comes down to not re-eventing the wheel. Why does Barrett Firearms use an M-16 trigger group in the M107 .50?

Because it was an off the shelf design. What FN did makes a hell of a lot of sense, there was a proven Bullpup trigger design and just copy it.
It's not exactly the same. M16 or AR trigger groups are made by lots of people, so it is easy for Barrett to buy an off the shelf system that is being sold on the market today, rather than build one.

However, for the PS90/Aug question, Styer was not selling components on the open market, so FN still had to go through the exercise of designing and building molds. Maybe it was pure lazyness that led to a direct copy versus a redesigned version, but I'm even thinking of small stuff - like how wide is the buttstock, and therefore how wide do the components need to be to fit in the pack that fits in the buttstock? It would have been easy for the two rifles to be sufficiently different that a 1-2mm difference in width causes the parts to not interchange.

Copying the base concept of the design makes sense, but making them so close that they interchange is something I have just never seen in industry.

It would be interesting to hear from someone on the inside about how this decision was made.
 

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Discussion Starter · #7 · (Edited)
Some pics. Color didn't turn out to well but the Aug hammer is an olive green color. The black Gen1 hammer actually came out of Gen 1 pack. You can see that it is warped and for some reason the tail angle is considerably larger than the FN Gen3 and the Aug hammers. This additional angle reduces the amount of travel towards the firing pin.

Left to Right - FN Gen 3, Steyr-Aug, FN Gen 1 (warped) The "axle" of the Aug spans 22.9mm end to end; FN - 19.7mm


Hole diameter of Aug hammer is 3.9mm compared to the FN diameter of 4.0mm






Notice the sear cuts on the hammers. The Aug and the Gen1 have the cuts as the same location. See how shallow the cut is on the Aug hammer. It appears that some of the material on the face where the cut is has been removed.


On a side note, has anyone ever seen a warped hammer and/or an FN PS90 hammer that has different geometry such as seen in the Gen 1 pic?
 

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Thanks for posting the pics!

Though they are not conclusive of dimensional likeness (which can only be measured anyway), but they do speak thousands of words and is support for the claims that have circulated the web.
 

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Discussion Starter · #9 ·
What is interesting is that the "old" Aug hammers were a perfect fit in the PS90 and FS2000 packs. The new releases are as I said, must do three mods to make them fit and function. Someone "advised" them to do so. Yes, I have my tin foil hat on.
 

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What is interesting is that the "old" Aug hammers were a perfect fit in the PS90 and FS2000 packs. The new releases are as I said, must do three mods to make them fit and function. Someone "advised" them to do so. Yes, I have my tin foil hat on.
I wonder what that makes my 20 year old spare AUG pack worth?
 

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Discussion Starter · #11 ·
Worth what someone will pay for it. The components (hammer, disconnector and auto sear) will fit into a PS90 pack but the pack itself will not fit into the PS90. Someone with an AUG may pay a premium though.
 

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Thanks for posting those pictures.
 
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Interesting, FN seems to have done a nicer job of the mold design, plus added strength as an afterthought.

The first thing that struck me was the Aug hammer has a visible mold parting line running down its face, which the FN does not.

Also, the hole in the hammer sear. This is classig injection molding technology. If you get a big fat section on an otherwise flat part, the plastic won't cool evenly, leaving sink marks. By adding the hole, the sears cool same as the rest. I also saw this in the disconnector - the FN part has a channel to help mold cooling.

In the crook of the hammer, there is a slight concave, where you can see FN made it that way, then later modified the mold to allow more plastic.
 

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Based on Data found in the wild

To adjust AUG hammer for the PS90 hammer,

You will need to take out an equal amount of materials from each side of the pin shaft:
from 0.912" to 0.780".

This will ensure appropriate engagement of the hammer/disconnector **Caugh** I mean the front sear

The pin hole will need an adjustment from 0.154" to 0.60".

Disclaimer: Please do not attempt this at home using a toothpick, ice pick, nail clipper etc etc etc

Use common sense


uploadfromtaptalk1427088712962.jpeg uploadfromtaptalk1427088765996.jpeg uploadfromtaptalk1427088782136.jpeg
 
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Some pics. Color didn't turn out to well but the Aug hammer is an olive green color. The black Gen1 hammer actually came out of Gen 1 pack. You can see that it is warped and for some reason the tail angle is considerably larger than the FN Gen3 and the Aug hammers. This additional angle reduces the amount of travel towards the firing pin.

Left to Right - FN Gen 3, Steyr-Aug, FN Gen 1 (warped) The "axle" of the Aug spans 22.9mm end to end; FN - 19.7mm


Hole diameter of Aug hammer is 3.9mm compared to the FN diameter of 4.0mm






Notice the sear cuts on the hammers. The Aug and the Gen1 have the cuts as the same location. See how shallow the cut is on the Aug hammer. It appears that some of the material on the face where the cut is has been removed.


On a side note, has anyone ever seen a warped hammer and/or an FN PS90 hammer that has different geometry such as seen in the Gen 1 pic?
Thanks for the pictures!

The Gen1 hammer looks a little off to me?! two things we can see from the first glance: (you pointed out one)

First, the warping of the tail on the Black Gen1 hammer.
Second, the Gen1 hammer doesn't have the Calender wheel on the side of the it. You can see it in the Gen3 but not the Gen1 you have in there.
 
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What software did you use to generate these measurements? I presume you are measuring right off the picture?

Also note, you say to enlarge from 0.154 to 0.60. I think you meant 0.160.... the picture is also wrong, it lists 1.154 instead of 0.154.
 

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Correct on the numbers
Not sure about the software, I'll get back to you in that.
 

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Your "warped" hammer, did that come from a P90 parts kit???

I bet that's for the original P90.
 
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