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Posted: 8/29/2017 11:08:33 PM EDT
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Besides a scope, a factory bipod is the accessory sought by most Portuguese
AR10 owners. The bipods require a special handguard set and there seems to be more handguards out there than bipods. 
A friend and fellow Porto owner offered to make a short run of reproduction bipods. This gent is also a crack machinist and has already made a variety of small parts for Dutch AR10s, including sling holders, various detents and pins, hardware for leather slings, bolt stop keepers, and other small parts. The greatest challenge is that the original bipod yoke and feet were precision castings while those reproduction parts are best done in small quantities by CNC. Having original drawings was a great help and a bipod was loaned to the machinist to assist him in the reproduction. 
The photo below shows the yokes in a semi completed state. These pieces were water jet cut and then subjected to a series of operations on a mill. 
The reproduction hinge parts are shown below, next to originals. The oriignal bipod on loan was somewhat distressed so there was no sin in disassembling it. 
After all of the parts were created they were mag phosphated coated and assembled. The repro and original can not be distinguished at a distance. However, some edges on the originals have a slightly more gentle curvature. So, an educated party will be able to tell if his bipod was made in 1961 or 2017. Below the one with the nice finish is the reproduction. 
The bipods function and fit as intended, folding up into the handguards. In particular, the spring action the hinges is exactly like the factory bipods because the hing assembly was faithfully copied down to the number of windings on the springs. 
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A few years ago I was lucky enough to find a NOS bipod and handguard set. (see pic)
Otherwise, the most direct route to a complete bipod assembly is just to buy it attached to a rifle. Since A.I. made spares there seem to be way more handguard sets out there than bipods. So if one looks hard enough,,, 
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The Portuguese contract AR10 handguards(shown previously) were made from some thermoset
composite that might be called Bakelite. Its not really Bakelite but just some sort of composite. Anyway, before the Dutch perfected the composite recipe they made handguards out of wood, then later from polycarbonate, and finally the Bakelite type material was developed. Transitional AR10s used these prototype materials while the Portuguese AR10 variant, by definition, used the production Bakelite. The polycarbonate handguards are rare and the bipod version of the polycarbonate handguards is uber-rare. Below is a photo of the uber-rare polycarbonate bipod handguards. If a new mold was to be made these would be the ideal models, since they have a very smooth and regular surface. The original Portuguese AR10 buttstocks appear to be made fom a very similar polycarbonate, which is prone to cracking. 
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The scanning is complete. The polycarbonate HGs had some hidden areas so it was easier (cheaper) to scan the composite HGs. Sometimes scanning is assisted by spraying a nonrefective coating on the object. I had given very detailed instructions that no solvents or anything other than talcum powder or cornstarch be applied to the HGs. To my horror the worker performing the job admitted that assorted junk like harspray was used on my precious HGs. No apparent damage done this time but beware for any of you wanting to have some precious items scanned. Hairspray might have ruined the shine on my polycarbonate HGs.
Now to get a couple of quotes for replication. 
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They HGs are being made because:
1) two friends each need a set to use with reproduction bipods 2) its also a reason to go through and learn the whole replication process I expect that the costs will put these items beyond the reach of most people. It is not intended that any/many extra HGs would be made and I have no idea what they would cost since I am a noob at this. CORRECTION: I have been told that printing using polyester (PET) or polycarbonate material would cost less than about $50 per HG half. So I guess the costs per piece are reasonable, even after adding a bit to recoup the scanning costs. |
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Quoted:
Why the horizontal vents and not the rounds on the back? It all came down to chosing the HGs with fewer "shady" areas.
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Update showing 3d printed pieces. They still need to be fitted together.
I will probably do some sanding on the outside to smooth them a bit. They are made out of a polyester material that should stand 180 degrees C, which should do for non wartime usage. 
Also, the guy ran out of material and ruined a piece. you can notice that some extra junk is printed, like in the holes. This comes off easilty since it is only weekly connected. There is a bit of hand labor involved and the company doing the printing charges me about $50 a side. 
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The 3d printed HGs have been installed. All that needed to be done was to flatten the mating surface
using a belt sander. No attempt was made to smooth the outside or make it more regular. The HGs fit the rifle and the bipod legs fold into the HGs as designed. The HGs were installed along with one of the reproduction bipods, using some NOS heat shields that were lying around. The rifle was an average condition Portuguese AR10, built on a nicer Hahn reweld lower. The rifle has an aluminum buttstock that came from a forum member (Lionel?). All the furniture is black. Here is what it looks like from a distance. 
Shows how the bipod legs fit nicely into the HG recesses. 
The lower has minor cosmetic issues but is straight and strong. 
Except for the virgin heat shields, this is a rifle that can be beat to hell and back with no worry. The stock is indestructible and the HGs are replaceable. But if she ever leaves the shop I will install some worn heat shields. |
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