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Hey guys I have a complete FN15 tactical gen 1 rifle and I was wondering if anyone knew if the lowers on those rifles are mil spec? If so do you think it will work with a bcm upper? Reason I ask is because I have a bcm complete upper and it is just sitting and I would like to put it on my fn15. I sent a message to fn a while ago regarding it and still haven't heard back from them. Thanks.
Hey guys I have a complete FN15 tactical gen 1 rifle and I was wondering if anyone knew if the lowers on those rifles are mil spec? If so do you think it will work with a bcm upper? Reason I ask is because I have a bcm complete upper and it is just sitting and I would like to put it on my fn15. I sent a message to fn a while ago regarding it and still haven't heard back from them. Thanks.
No, they are not milspec, yes, they will work fine with your BCM upper.
What about them are not milspec? Also I thought that you could only use milspec lowers with milspec uppers?
everready73
11-06-17, 19:53
What about them are not milspec? Also I thought that you could only use milspec lowers with milspec uppers?
i believe he is referring they are not built off the TDP because Colt is the only manufacturer that can build to the exact TDP specs because they own it. FN can only use it for the rifles they provide to the military. All manufacturers other than colt have to reverse engineer the specs, so they are not truly milspec. The FN lower should work fine with any ar15 upper though. Hell, i dont recommend it, but a bcm lower would "work" on a $100 polymer lower.
Your FN lower should work fine with the BCM upper. I believe it would make a better overall rifle than with the FN upper especially if you have a BCM BCG
5.56 Bonded SP
11-06-17, 20:01
An FN lower with a BCM upper would be an awesome gun. I would personally consider it a ''tier1'' gun if it is loaded with proper parts, but that is just my opinion.
What about them are not milspec? Also I thought that you could only use milspec lowers with milspec uppers?
FCG, selector, and receiver are not "milspec". None of that matters for your intent, and it is GTG.
What part did you think was milspec?
5.56 Bonded SP
11-06-17, 20:18
Wouldn't a 6920 lower and fcg not be considered milspec either, since they can't use happy switches? Isn't the FN lower made of the same aluminum and anodizing as a 6920 lower?
I thought the only main difference from the FN lower and a 6920 lower was that the colt stakes their castle nut to TDP, which I wouldn't consider a deal breaker for the FN. (I also thought that new FN lowers do stake their castle nuts).
I also wouldn't be very concerned about the selector, but technically the 6920 selector isn't milspec either because it can't go to the third position?
Am I completely wrong here? I would like to learn as well, and am genuinely curious.
I asked similar things in a thread last month and all anyone really said was colt is better because they are built with TDP, but if that were the case then nobody would be buying danial defense or other ''high end'' AR's?
Wouldn't a 6920 lower and fcg not be considered milspec either, since they can't use happy switches? Isn't the FN lower made of the same aluminum and anodizing as a 6920 lower?
I thought the only main difference from the FN lower and a 6920 lower was that the colt stakes their castle nut to TDP, which I wouldn't consider a deal breaker for the FN. (I also thought that new FN lowers do stake their castle nuts).
I also wouldn't be very concerned about the selector, but technically the 6920 selector isn't milspec either because it can't go to the third position?
Am I completely wrong here? I would like to learn as well, and am genuinely curious.
I asked similar things in a thread last month and all anyone really said was colt is better because they are built with TDP, but if that were the case then nobody would be buying danial defense or other ''high end'' AR's?
Correct, the Colt 6920 isn't milspec either.
I'm sorry that all you got out of your previous questions was that Colt is built to the TDP. At some point you will understand the quality and standards which go into certain manufacturers components. A lower receiver is much more than simply a forging with holes. If you are ever in a factory and see all the rejected receivers, you will understand that standards are important. Good manufacturers aren't saying something is "close enough", they are keeping a standard or throwing it in the recycle pile.
I think some folks equate "mil-spec" with quality/durability/compatibility/etc.. Similar to "match grade" in that there is a heightened expectation of performance when labelled as such.
I think it's become a generic term in the commercial market.
I guess I really dont understand what mil spec means. I know it has a mil spec buffer tube for stocks so I just assumed that it would be a mil spec lower but as long as the quality is good and it will work with the bcm upper no complaints from me. One more question then if fn lower isnt "mil spec" is the bcm lower considered "mil spec" or is it the same as the fn lower? I thought the reason fn couldn't use the tdp was because they make the rifles for the military. Can companies such as bcm, dd, noveskee, ect.. use the TDP?
Please correct me if I'm wrong.
My understanding was that the patents have expired and therefore reverse engineering the parts wouldn't get you in court trouble. This snippet seems to reinforce my thoughts:
1989: Jim Glazier and Karl Lewis of Lewis Machine and Tool Company (LMT), operating a new entity called Eagle Arms, begin producing complete AR-15 rifles for the consumer market. By this time, many of the earlier AR 15 Rifle related patents had expired, thereby opening up the market for complete AR-15 type rifles
Beyond that I don't know the exact date when the field opened up, Olympic Arms was making them in 1982.
I'd also be willing to bet that a lot of companies have a copy of the TDP, they just don't advertise that fact.
Other than the ar15 lower not being capable of full auto fire what constitues as mil spec? The fn15 lower is 7075 t6 mil spec buffer so is it the same as a bcm lower or a colt 6920 lower? If not how do they differ? I was under the impression that if it was 7075 t6 with the right buffer tube it was considered mil spec.
You might as well flush the words mil spec from your mind.
BCM lowers are good.
Colt 6920 lowers are good.
LMT lowers are good.
FN lowers are good.
Daniel Defense lowers are good.
etc
etc
etc
None of these can be considered truly mil spec, and it doesn't matter. Any differences between any of the above will be in areas that don't affect function, like the amount of mag well flare.
In the case of the receiver extention (buffer tube), milspec denotes the manufacturing process that produces a certain form factor (size/dimensions) that preclude which type of stock is compatible: commercial or milspec.
......and nobody here should be buying a commercial receiver extension. None of the above mfgs use them with their complete lower assemblies.
That doesn't mean that a home builder couldn't.
......and nobody here should be buying a commercial receiver extension. None of the above mfgs use them with their complete lower assemblies.
I am new to the platform and what I was told was that things labeled mil spec is more of a tolerance thing as to figure out what will work with what. So is there no difference between a commercial and so called mil spec lower other than the buffer? People on arfcom told me a mil spec type upper would not work on a commercial type lower. I came here to ask because I trust members of this board more and I tend to get the same ol' people answering questions over there.
For all intents and purposes, quality and price point aside, a lower is a lower. Purchase a known quality lower and the rest will fall into place.
Commercial and mil spec receiver extensions do have different outer dimensions and therefore must be paired with the appropriate sized butt stock.
For all real world use, quality uppers and lowers will all work together, and there's no such thing as a "commercial" lower, a "commercial" upper, or a mil spec lower that doesn't require NFA paperwork.
Let's clarify something. Forget buffers, unless you are confused on compatible carbine, rifle, or A5 recoil systems. Let's focus on uppers and lowers. If made to correct specifications, they should be universal. Meaning, you can swap uppers and lowers with other uppers and lowers. I can do this with all of my AR's no problem. Are the resultant configuration optimal? No. But, they will all go bang. So, I don't know what ARFCOM is trying to tell you. The only issue with "commercial" versus "mil-spec" is the compatible carbine stock choice based on what type of receiver extension you bought and installed. For my money, I always go with "mil-spec" type RE's and stocks. No brainer.
I am new to the platform and what I was told was that things labeled mil spec is more of a tolerance thing as to figure out what will work with what. So is there no difference between a commercial and so called mil spec lower other than the buffer? People on arfcom told me a mil spec type upper would not work on a commercial type lower. I came here to ask because I trust members of this board more and I tend to get the same ol' people answering questions over there.
5.56 Bonded SP
11-07-17, 15:28
I am new to the platform and what I was told was that things labeled mil spec is more of a tolerance thing as to figure out what will work with what. So is there no difference between a commercial and so called mil spec lower other than the buffer? People on arfcom told me a mil spec type upper would not work on a commercial type lower. I came here to ask because I trust members of this board more and I tend to get the same ol' people answering questions over there.
When you say buffer I think this is what you are misinformed on... commercial vs Milspec buffer Tube , the diameter of the commercial buffer tube is different than the outer diameter of a milspec buffer tube. Also many commercial buffer tubes are made of lower grade aluminum than true milspec buffer tubes. Do some google searches on what milspec means, I doubt many here want to go to the lengths to completely explain it when there are hundreds of threads about it on the internet.
A commercial lower and milspec upper work fine together.
Let's clarify something. Forget buffers, unless you are confused on compatible carbine, rifle, or A5 recoil systems. Let's focus on uppers and lowers. If made to correct specifications, they should be universal. Meaning, you can swap uppers and lowers with other uppers and lowers. I can do this with all of my AR's no problem. Are the resultant configuration optimal? No. But, they will all go bang. So, I don't know what ARFCOM is trying to tell you. The only issue with "commercial" versus "mil-spec" is the compatible carbine stock choice based on what type of receiver extension you bought and installed. For my money, I always go with "mil-spec" type RE's and stocks. No brainer.
Every once in a while you will run into an upper that won't fit in a lower. If the lugs on the upper are to the maximum allowable tolerance, and the corresponding pockets in the lower are on the low side of the tolerance, you can have two pieces that meet the range of tolerances allowed but will not fit together. Tolerance stacking will get you sometimes.
5.56 Bonded SP
11-07-17, 15:29
Commercial and mil spec receiver extensions do have different outer dimensions and therefore must be paired with the appropriate sized butt stock.
For all real world use, quality uppers and lowers will all work together, and there's no such thing as a "commercial" lower or a "commercial" upper.
Sent from my iPhone using Tapatalk
This ^
Yep, no argument there. Thanks for pointing that out.
Every once in a while you will run into an upper that won't fit in a lower. If the lugs on the upper are to the maximum allowable tolerance, and the corresponding pockets in the lower are on the low side of the tolerance, you can have two pieces that meet the range of tolerances allowed but will not fit together. Tolerance stacking will get you sometimes.
5.56 Bonded SP
11-07-17, 15:31
Correct, the Colt 6920 isn't milspec either.
I'm sorry that all you got out of your previous questions was that Colt is built to the TDP. At some point you will understand the quality and standards which go into certain manufacturers components. A lower receiver is much more than simply a forging with holes. If you are ever in a factory and see all the rejected receivers, you will understand that standards are important. Good manufacturers aren't saying something is "close enough", they are keeping a standard or throwing it in the recycle pile.
So what you are implying is that FN has lower quality control standards?
I really have trouble believing they would make their commercial lowers to different specs than their lowers sent to .mil . Yes I understand the colt TDP situation, however it just doesn't make sense to make lowers to different standards, it would be a poor choice financially.
So what you are implying is that FN has lower quality control standards?
I really have trouble believing they would make their commercial lowers to different specs than their lowers sent to .mil . Yes I understand the colt TDP situation, however it just doesn't make sense to make lowers to different standards, it would be a poor choice financially.
Actually it wouldn't. You have lowers that have to meet U.S. Govt standards of tolerances between X and Y or you won't make spec. You know that lowers that miss these specs by .001" (hypothetical measurement) will still work just fine in the civilian market, so those are set aside for civilian use. You have a separate acceptable tolerance for the civilian versions. Ones that don't make either spec are recycled.
I'm not saying this is happening anywhere, but the scenario would still make sense if you had both .gov and .civ production.
So what you are implying is that FN has lower quality control standards?
I really have trouble believing they would make their commercial lowers to different specs than their lowers sent to .mil . Yes I understand the colt TDP situation, however it just doesn't make sense to make lowers to different standards, it would be a poor choice financially.
I have in no way, shape, or form implied that FN has lower QC than Colt. I've gone into way with FN weapons, and they have served me admirably. In my mind, FN is a very highly respected name in the weapon business, at least as much so as Colt, and more than just about anyone else.
5.56 Bonded SP
11-07-17, 15:49
Actually it wouldn't. You have lowers that have to meet U.S. Govt standards of tolerances between X and Y or you won't make spec. You know that lowers that miss these specs by .001" (hypothetical measurement) will still work just fine in the civilian market, so those are set aside for civilian use. You have a separate acceptable tolerance for the civilian versions. Ones that don't make either spec are recycled.
I'm not saying this is happening anywhere, but the scenario would still make sense if you had both .gov and .civ production.
Well, that is pure speculation, and by that same train of thought there is no reason that Colt isn't doing the same thing.
I was just hoping there was some empirical data points that prove Colt lowers truly are better than FN lowers, so far I have yet to see that.
The only real difference I have been informed of is that Gen 1 FN lowers did not stake their castle nuts, which I really don't consider a big deal. From what I understand Gen 2 FN lowers do stake their castle nuts.
I was just hoping there was some empirical data points that prove Colt lowers truly are better than FN lowers
Why...?
5.56 Bonded SP
11-07-17, 18:58
Why...?
Just for my personal knowledge so I can make informed choices for firearms purchases, and share the knowledge with others.
Maybe I should have worded it better, something along the lines of the actual differences of FN vs Colt lowers.
I'm still trying to decide if I should buy an FN Tactical II or a Colt Combat Unit, I can buy them both for about 1,200$.
( the FN link price only applies to LE/Mil )
https://www.midwestgunworks.com/page/mgwi/prod/35-36312
https://www.budsgunshop.com/catalog/product_info.php/products_id/719014177/Firearms/Rifles/Colt/Colt+Combat+Unit+M4+5.56+16in+30%2B1
I would be more interested in the gas port sizing of the Colt vs. the FN.
5.56 Bonded SP
11-07-17, 19:41
I would be more interested in the gas port sizing of the Colt vs. the FN.
FN has answered emails pretty fast for me in the past. I don't know the answer to that question, and also I don't even know what the appropriate size for a mid length gas port would be? Somewhere between carbine .063 and rifle .0935 ?
everready73
11-07-17, 20:38
IMO for a 16 inch midlength you would want around .076-.078. many manufacture will go .08 plus so the guns will run under powered ammo
I was just hoping there was some empirical data points that prove Colt lowers truly are better than FN lowers.
I don't think you are going to find enough data to categorically say one way or the other.
Perhaps if one were to get a look inside the warranty repair records for each company you could spot trends.
Other than that most of the evidence you will hear/see is anecdotal and often tempered by bias. We are prone to remember and over-emphasize flaws in products we believe are of less value and discount the discrepancies in brands we value.
This is not to say that some brands do not deserve their reputations for shoddy QC, etc., just that in some cases it is overstated.
FN buffer tubes (even though they are mil-spec diameter) are likely made from 6061 aluminum since they have never advertised which aluminum they are made from.
I believe that FN does use 6061 on the buffer tube at least with the gen 1. I tried to ask them but they wouldn't confirm. I have seen another form where someone said that it is in fact 6061 apposed to 7075. Does that make a big difference?
Yes. The receiver extension material is critical (7075T6). I'd buy the Colt CCU, without hesitation, over the FN offering. Just me.
FN's use of 6061 makes no sense to me, and I'd be surprised if it is correct.
Sent from my iPhone using Tapatalk
I feel the same way and it is by no means confirmed. They emailed me back about their lowers being 7075 so I just emailed them back asking what they use for their buffer tubes. I will update when I hear back from them.
IME, if they don't specifically say "7075-T6", or are reluctant to say, then it's most likely 6061.
6061 will work, but 7075 is superior.
Say they said their lowers are 7075 t6 and made to mil spec. Still waiting on reply about buffer tube material.
I got a call from someone at FN and they said they believe that the buffer is 7075.
I got a call from someone at FN and they said they believe that the buffer is 7075.
The buffer? Ask what the Receiver Extension is.... and the receivers aren't milspec. If you are told that a receiver is milspec, ask them what part. Milspec anodizing? Milspec forging? Milspec what??
I asked them what the buffer tube is. Should I follow up and call it an receiver extension?
I asked them what the buffer tube is. Should I follow up and call it an receiver extension?
No, I wouldn't keep calling them. The particular item you were asking about is the RE, though it is often called buffer tube by people who use that as slang.
In much the same way, you will see me correct people when they say they have a jam, when they really had a malfunction.
Just for my personal knowledge so I can make informed choices for firearms purchases, and share the knowledge with others.
Maybe I should have worded it better, something along the lines of the actual differences of FN vs Colt lowers.
I'm still trying to decide if I should buy an FN Tactical II or a Colt Combat Unit, I can buy them both for about 1,200$.
( the FN link price only applies to LE/Mil )
https://www.midwestgunworks.com/page/mgwi/prod/35-36312
https://www.budsgunshop.com/catalog/product_info.php/products_id/719014177/Firearms/Rifles/Colt/Colt+Combat+Unit+M4+5.56+16in+30%2B1
If you are trying to decide which to purchase based on that info, you are barking up the wrong tree. They are both fine.
I got an email from FN and they said their receiver extensions are made out of 7075 t6 aluminium as are their lower receivers per "mil spec". I don't know why that guy was trying to say they were 6061. Now that its solved what is the everyone's opinion on replacing the FN upper that came with it, with a bcm upper I already have? For the most part they are the same as far as specs go only differences being the fn upper came with the lower as a complete rifle and the bcm has a 4150 cmv CHF barrels opposed to the FNs 4140 CHF barrel.
5.56 Bonded SP
11-08-17, 16:47
I got a call from someone at FN and they said they believe that the buffer is 7075.
The buffer, and buffer tube are two different things FYI.
Right, I meant to say buffer tube.
5.56 Bonded SP
11-08-17, 16:49
For the most part they are the same as far as specs go only differences being the fn upper came with the lower as a complete rifle and the bcm has a 4150 cmv CHF barrels opposed to the FNs 4140 CHF barrel.
This doesn't make sense to me.
What about it doesn't make sense?
5.56 Bonded SP
11-08-17, 16:59
What about it doesn't make sense?
What upper is it exactly? From what I have seen, on FN's commercial line they do not specify the type of barrel steel they use, I usually read they state it is ''16-inch cold hammer-forged, chrome-lined free floating barrel'' Or ''machine gun steel''.
I have personally never seen them state they sell a 4140 CHF barrel... Which is why I ask, what upper is it, and what gun exactly is it?
I have the fn15 tacitcal gen 1. The barrel steel is in the manual I will find a link to it. https://fnamerica.com/wp-content/uploads/2016/10/FN15_Tactical_Carbine_OM_Addendum_36169-05_160729.pdf I believe all their ar style rifles are 4140 from what I seen looking through the other manuals as well.
5.56 Bonded SP
11-08-17, 17:05
I have the fn15 tacitcal gen 1. The barrel steel is in the manual I will find a link to it. https://fnamerica.com/wp-content/uploads/2016/10/FN15_Tactical_Carbine_OM_Addendum_36169-05_160729.pdf I believe all their ar style rifles are 4140 from what I seen looking through the other manuals as well.
Thanks for the link. That is news to me, first time I have seen a document provided by FN which actually gives the specifics of the barrel.
Thank you.
In my humble opinion, I doubt you would notice any significant difference between the two barrels, but I am sure others more experienced than myself can answer that better.
If it was my gun, I would leave the FN as it is, and just buy a Colt lower for that BCM upper so you can have two guns instead of parts. I also would fancy having a complete factory FN gun rather than an FN lower with a BCM upper.
What evidence do we have that Gen 1 barrel material is the same as Gen 2 barrel material?
5.56 Bonded SP
11-08-17, 18:03
What evidence do we have that Gen 1 barrel material is the same as Gen 2 barrel material?
We don't.
And to complicate things further, FN also uses button broached barrels on a bunch of their rifles.
https://fnamerica.com/products/rifles/fn-15-military-collector-m4/ and there are other AR type rifles they sell that use button broached as well.
I assume the button broached barrels are 4150cmv, but I have no evidence to support that theory other than speculation.
My speculation is that their CHF barrels are 4150cmv and their button rifled barrels are 4140.....just to be different.
It'd sure be nice for their website to provide the specs that we, hopefully their desired customers, require.
I also think it would be cool to own an FN AR, but I wouldn't choose one over a Colt or BCM (for equal prices).
FN uses the same barrel steel in their gen 2 rifles as their gen 1 rifles https://fnamerica.com/wp-content/uploads/2017/05/FN15-Tactical-Carbine-II-OM-Addendum_36312-01_36313-01LE-161129.pdf Its hard to get complete specs but if you go to this link thats as close to specs you will find https://fnamerica.com/customer-support/owners-manuals/
My speculation is that their CHF barrels are 4150cmv and their button rifled barrels are 4140.....just to be different.
Response to bold: Brownell's FN button broached rifle barrels are 4150.
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