lower spec observation. Any comments appreciated

[praythenspray]

I have two ARs. One is a "unique" RRA lower with U.S. Property stamped on it with a standard(not sure the brand)LPK. The other is a basic OT-15 lower(from On Target tactical supply) along with a Mil-Spec LPK from On Target as well. Now, according to the website the OT-15 is "CNC machined according to authentic military prints".

I have examined both lowers with the uppers removed and I have noticed that the RRA walls looks SLIGHTLY thicker when viewing the lower from above. Maybe its just me :confused:

Now, if the OT-15 is truly Mil-Spec, would the RRA be an example of when people say a lower is out of spec? I haven't had ANY issues with either lower. Hypothetical question: If you had the RRA lower and you put in a better mil-spec LPK, would you trust it like you would a lower from a more respectable company?

Thanks in advance for any insight guys.

[Hmac]

That whole "Mil-Spec" bullshit is a real can of worms. Crappy mfgrs always put that on their parts if it's black and looks even a little like a real army gun part, and both Rock River Arms and OnTarget (is it a DSG lower?) are not known to be the pinnacle of firearms manufacturing. As to "CNC machined according to authentic military prints", seems to me that at that time Colt owned the TDP, not the military, so that sounds like bullshit too.

In-spec?....do the guns shoot and cycle reliably? If so then I guess they're in-spec. If not.....

[26 Inf]

This might be a bit subjective - 'RRA walls looks SLIGHTLY thicker' - probably need to get the calipers out and do some comparison.

http://www.firearmfiles.com/files/AR15/AR15%20Lower%20Machine%20Drawing.pdf

Do various mags seat correctly and drop free? Does the rifle(s) reliably feed and lock back on an empty mag? Does the FCG work reliably? If so, why worry?

I trust anything that I have the technical knowledge to assemble more if I assemble it than buying a manufactured item - provided the parts I used in assembly are quality items.

As an example I have the technical ability to assemble carbureted gas engines, I do not have the technical knowledge to assemble a balanced and blueprinted carbureted gas engine that will turn 10,000 rpm for an hour. So I'd buy a higher level racing engine.

So I would say if you aren't having issues, put in the LPK of your choice if you desire and rock on.

Would you trust is largely subjective to you - I wouldn't trust any weapon for protection until I have assured it reliably functions, for me that mean a couple mags each of rounds I habitually use, for some guys they won't deem it reliable until they've fired enough rounds through it to nearly wear it out.

JMO YMMV

[praythenspray]

Thanks for the replies so far. HMAC, The OT lower is this exact one - http://www.ontargettacticalsupply.com/ON-TARGET-AR-15-LOWER-RECEIVER-OT-15-TEXAS-p/ot-15.htm .

26 INF, I understand that it would be considered a subjective statement. But for the life of me, side by side the RRA actually does look slightly thicker. Unfortunately, I do not have a set of calipers handy.

Yes, all mags tested droped free and the bolt locks back on both lowers every single time. I guess I was just slightly confused with the Mil-Spec claim on the ON target lower, I was thinking(perhaps wishfully since its on my SHTF gun) that it was on par with the better(Colt,BCM,etc) brands.

[Microadventure]

google AR-15 blueprints. if the size of the cavities are correct you are golden. if the overall width is thicker and the cavity is kosher, the outside walls will inherently be thicker

[Kain]

From personal experience with the two RRA lowers I own their lowers do vary from others. Most are only going to find that they are tighter then their girlfriend's asses when putting on a quality upper, but some of their external dimensions are rather different from other lowers I have built and worked on, enough so that depending on parts used I have seen issues. Though again, most will likely not see these since it was with RRA parts on non RRA lowers. That said, they function fine. But, it has killed the myth to me that a lower is a lower is a lower. They are not all the same.

[samuse]

But, it has killed the myth to me that a lower is a lower is a lower. They are not all the same.

Indeed.

I used to to own nothing but Colts and always read that 'lowers were lowers'. Bullshit. After assembling quite a few and owning a few so-called top tier lowers, I'm hesitant to buy anything but a Colt if I ever need another.

I picked up an Armalite lower from DSG awhile back and it's as good as any Colt, but I'm not pushin' my luck.

[praythenspray]

Samuse, you say you would be hesitant to buy anything but a Colt if you needed another lower. I would agree with that statement.

However, I actually didn't buy either one of these lowers. I tend to trade around quite a bit. That is how I got both of these Ar's. For the Uppers, one came with a Colt socom upper. I sold the RRA upper and some other parts and built a new one from a stripped Aero upper, MI free float rail, Daniel Defense 16" Middy barrel and A1.5 rear sight with the BCG and all the small upper parts coming from BCM.

I wouldn't change a thing about either upper, I feel I got some of the best parts I can get(I know I could get better/different rails though). Just after looking at the differences in the lowers and really reading up, I know that the fact is all lowers are not created equal. That has kinda made me question the quality of my lowers.

But on the other hand, if both of my lowers are 7075t6, drop all mags, lock the bolt back, and just function 100% percent like they should. Why would I bother changing them out?

If any of you have any other thoughts or comments, don't hesitate to respond. I have just started diving into(about 4 or so months) the AR world and I am trying to read and soak up as much knowledge as I possibly can.

[samuse]

If they funcrion and do everything you want 'em to, don't change a thing.

There are probably thousands of good ARs built on RRA lowers...

[Wayne Dobbs]

It ain't mil-spec unless it was built to the TDP standards and verified as such. That causes lots of butt hurt, but it's like saying some chick is "beautiful" or somebody is "intelligent". Those terms lend themselves to lots of subjectivity! And as stated, lots of mfgrs will say their product is "mil-spec" just as a sales/marketing move.

[C4IGrant]

I have two ARs. One is a "unique" RRA lower with U.S. Property stamped on it with a standard(not sure the brand)LPK. The other is a basic OT-15 lower(from On Target tactical supply) along with a Mil-Spec LPK from On Target as well. Now, according to the website the OT-15 is "CNC machined according to authentic military prints".

I have examined both lowers with the uppers removed and I have noticed that the RRA walls looks SLIGHTLY thicker when viewing the lower from above. Maybe its just me :confused:

Now, if the OT-15 is truly Mil-Spec, would the RRA be an example of when people say a lower is out of spec? I haven't had ANY issues with either lower. Hypothetical question: If you had the RRA lower and you put in a better mil-spec LPK, would you trust it like you would a lower from a more respectable company?

Thanks in advance for any insight guys.

Neither of your lowers or LPK's would be considered as quality or GTG by serious AR guys. With that said, if they work for you, drive on!


C4

[praythenspray]

Neither of your lowers or LPK's would be considered as quality or GTG by serious AR guys. With that said, if they work for you, drive on!


C4


I kinda figured as much. With that said, in your own personal opinion, if you were piecemealing parts, what stripped lowers would you suggest?

[C4IGrant]

I kinda figured as much. With that said, in your own personal opinion, if you were piecemealing parts, what stripped lowers would you suggest?

That really depends on your budget. The S&W stripped lowers are a pretty good quality, name brand recognition and cost. With that said, the BCM blem lowers (complete) are the best value to quality going IMHO.


C4

[wahoo95]

RRA does have tighter dimensions around the rear take down lug recess which provides a tighter upper to lower receiver fit.....no wobble. Not mecessary but a nice feature as long as you're using their parts.

Sent from my SM-N910V using Tapatalk

[lysander]

I have two ARs. One is a "unique" RRA lower with U.S. Property stamped on it with a standard(not sure the brand)LPK. The other is a basic OT-15 lower(from On Target tactical supply) along with a Mil-Spec LPK from On Target as well. Now, according to the website the OT-15 is "CNC machined according to authentic military prints".

I have examined both lowers with the uppers removed and I have noticed that the RRA walls looks SLIGHTLY thicker when viewing the lower from above. Maybe its just me :confused:

Now, if the OT-15 is truly Mil-Spec, would the RRA be an example of when people say a lower is out of spec? I haven't had ANY issues with either lower. Hypothetical question: If you had the RRA lower and you put in a better mil-spec LPK, would you trust it like you would a lower from a more respectable company?

Thanks in advance for any insight guys.
The width of the forging is +/- 0.10", per print.

The width of the pockets is +/- .005", per print.

If you have one at the maximum material condition, the walls can be .015" thicker than one at minimum material condition.

Yes, you can see difference....

[Iraqgunz]

I have several different lowers (3xBCM, SIONICS, Colt, Sons of Liberty Gun Works, Mega Machine) and a few more I can't remember. I must be exceptionally luck as all of the parts work and they all work with all types of mags) Magpul Gen2/3, Lancer/Lancer AWM, Surefire and USGI.

[praythenspray]

Well, it looks like this thread is kinda winding down. By the post views, if anybody else was gonna comment they would have done so. Again, both of these lower have ran 100% and I have had no kinda malfunctions at all. Still, it looks like I will be saving up for a BCM lower. If I have two decked out uppers, I am gonna strive for a at least one of them to be a head to toe complete "GTG SHFT gun" just for a piece of mind. Thanks again for all the replies

[Texas_Mike]

google AR-15 blueprints. if the size of the cavities are correct you are golden. if the overall width is thicker and the cavity is kosher, the outside walls will inherently be thicker

From an engineering standpoint, this is the correct answer. It is not unusual to have varying receiver wall thicknesses, even in forgings from the same batch. The set values are generous in tolerances for repeatability in the machining process.