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Old December 02, 2018, 17:46   #251
grimjim
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The main reason a forging was used by FN was for cost. I can't say this for a fact, but in the industry I work in, the manufacturing cost pecking order for cost-to-produce, the hierarchy from most expensive to least expensive is; billet, forging, casting. Forgings are significantly cheaper to manufacture than billet and only slightly more than a casting. A properly designed forging blank will be just slightly larger than the finished part. And if the engineers are really on their game, a well designed forging blank will have some surfaces that need no machining, similar to a casting (think AR-15/M-16/M4). Forgings do present some challenges as far as manufacturing processes used to machine the receiver. Forgings will have higher residual internal stresses from the forging process and this will sometimes cause distortion issues as material is being removed. A good manufacturing process for forging 'hogout jobs' will incorporate stress relief steps to control distortion.

One misconception about forging is the phenomena of 'grain structure' in a forging improves the strength properties. While this is true in the 'as forged' condition, this changes once the forged item is subjected to a 'quench and temper' heat treating process. The receiver is heated to the critical temperature (solution heat treating) and then quenched in an oil bath or a blast of cold nitrogen gas. Once the receiver is heated to the critical temperature, the grain structure reverts to a more randomized pattern. This could be a benefit of induction hardening where the heating is localized, but it introduces other issues with uneven residual stress distribution within the part.

The reason no one has seen cast uppers and lowers for AR platform weapons is because there really isn't much cost savings in doing a casting on these versus a forging. Not to mention that you run into material problems trying to finding a suitable aluminum casting alloy to replace the 7075 used for forgings.

At the time the FAL was designed (early 1950's), casting technology was nowhere near what it is today. It was not possible to cast a receiver even close to the quality of what is available today.

Before I get myself in trouble badmouthing OE FN Type III cast receivers, I'll confess that there isn't much verifiable information. The little information I have found suggests that original FN cast receivers were only for commercial market weapons starting around 1977 (or 1973?) until the mid 1980's. And these weapons were never sold or intended for military service. The FN cast Type III receivers were allegedly hoped to have a service life of 40,000 rounds versus an 80,000 round service life for forged receivers. If there are some verifiable source of when/where FN made cast receivers and the market they were sold in, please do tell.

https://forums.somethingawful.com/sh...readid=3512923
https://www.remtek.com/arms/fn/fal/index.htm

I have no issues with investment cast steel IF the design was originally intended to be manufactured as a casting.

IF the FAL receiver is redesigned to accommodate design requirements to make it suitable for a casting process, i.e. changing the sectional thickness to make up for the different material properties of a casting, then I see no problems with a casting. But this would mean that you can kiss any notion of a dimensionally accurate FAL receiver goodbye if you want a casting.

I think the jury is still out on cast FAL receivers that are dimensionally identical to the original design (Type I, Type II). There just isn't enough of them out there to do any kind of meaningful statistical analysis. And to my knowledge, no government or military has duplicated the acceptance testing procedures that the original FAL was subjected to with a cast receiver (FN or aftermarket). However, the original FAL is a robust design and it just may be dumb luck that cast receivers (from the right material) that are dimensionally identical to forged/billet receivers still fulfill the necessary strength requirements.

Last edited by grimjim; December 02, 2018 at 23:18.
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Old March 06, 2019, 18:04   #252
gwgn02
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I've never seen a FAL receiver that has kaboomed because of being cast. I'd like to see pics or video of that, seems to me it would be all over the place on the net. Maybe I need to get out more and shoot my cast receivers well past the 15k rounds I have through them. Not really concerned.
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Old March 07, 2019, 19:00   #253
C1 Chinook
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The cost of the 40,000 rounds and 3 to 4 rebarrels can buy a dozen fal's. Who cares!!!
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Old March 07, 2019, 19:07   #254
lockjaw
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Quote:
Originally Posted by C1 Chinook View Post
The cost of the 40,000 rounds and 3 to 4 rebarrels can buy a dozen fal's. Who cares!!!
... obviously you don’t know the FALfiles community! That thought process holds little water here.
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Old March 08, 2019, 11:49   #255
C1 Chinook
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Like all old military rifles or clones ,wear it out save the parts that are good . FAL's are a dime a dozen. Throw away rifles like all battle rifles. Its just a bullet launcher a tool.
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Old March 08, 2019, 11:54   #256
S.B.
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What would all contributors here suggest to the few who still manufacture these receivers? These receivers are getting hard to come by. As far as I found out while trying to build my Chilean kit into a shooting rifle.
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