I'm in the process of having my preban Oly lower remanufactured and hand matched to a Oly flat top upper. After I receive the set back I'm wanting to add a Bushy M4 14.5 barrel and phantom FS.  The question is has anyone else done this and will it work.  I know both Oly and Bushy are claimed to be mil-spec, thus interchangable, but I'd like input from owners before I order the Bushy barrel.

Supposedly Oly and Bushmaster get their uppers from the same place.  Bushmaster then treats the inside of the upper with another protectant.  Otherwise they are the same upper.  You should have no problems.

Vinnie, thanks for the info.  Any idea where I could get the inside of the Oly upper treated with the same dry lube that Bushy applies to their uppers?

That I couldn't tell you.  I also couldn't tell you if it were absolutely necessary.  I say just build the rifle.  Uppers can't be that hard to come by.

I'm gonna go ahead and order the Bushy bbl and build it.  If something doesn't fit I can always sell it and buy new.  Thanks Vinnie.

Yes, they are interchangable.

i have a bushmaster lower and a oly 24in flattop upper that work great together

Quoted: Supposedly Oly and Bushmaster get their uppers from the same place.

Let me clarify this. Oly and Bushmaster DO NOT get their uppers ( or lowers or barrels etc.) from the same place. You see, this is not true because we make our own parts, and Bushmaster does not. We make our uppers in house, we make our lowers in house, we make our bolts in house, we make our bolt carriers in house, we make our barrels from bar stock here in house, we own our own casting house and therefore make our own hammers, triggers, selectors, bolt catches etc are made by us from molten steel to finished product. We machine our own trigger guards and charging handle latches from extruded aluminum (not plastic) made on tooling we own. No other manufacturer of AR15 products in the US can make such claims. No one but Olympic.

It may be true that some raw forgings are purchased from the same manufacturer of forgings, but they are certainly not the same finished product. There are only a small handful of manufacturers making the raw forgings for AR15 style receivers (only 3 or 4 come to mind, and Alcoa Aluminum has not made any for some time), so we do all purchase the raw forgings from the few foundries out there.

Bushmaster then treats the inside of the upper with another protectant.  Otherwise they are the same upper.  You should have no problems.

I cannot comment on the internal coating (that other Bushmaster® might use, other than it is certainly not required for proper operation, nor is it on or required by any of the military prints that I have seen for contracts we have filled.

All in all though, Bushmaster® sells a fine product, and I am certain that our barrels and uppers are fully interchangeable.

Hope this helps.

Tom S.
Oly Arms

Thanks Tom, nothing against Oly bbls (I own a few) I'm just don't want a SS M4 bbl.  Thanks to you and the guys at Oly for building an excellent weapon.

OK just call me Mr Misinformation...here's the skinny.

Last time I'm writing the answer to this question, I have replied to this topic several times. Their are only a few companies in this country who actually make the forging for these rifles. All manufacturers buy raw forging from the same companies. The raised letters on the side of the receiver at the rear sight are forging markings, not manufacturer markings. These raises letters tell us(the manufacturers) which forging mold was used in case of any defects. The difference comes when the manufacturer actually machines the raw forging to their tolerances & applies their finish. We are stamping the letter "L" or "V" on the front or rear lugs on the upper receivers to show it is of our manufacture. We are also the only company to use the dry film lube coating inside the receiver to ensure long wear & smooth operation. This will show on the inside of the receiver as a light grey coating, this is what you really need to look for to make sure you have a Bushmaster receiver. Jarrod Bushmaster Firearms

Link to Jarrod's quote

Sorry about the mistake.