Help me please. JD ar-15 questions UPDATE!

[Pred]

So i went to a gun show to look for an ar-15 upper. I found one that was made by jd machine tech. The guy who sold it to me told me it was for 5.56/223 and so i got that upper. I have heard that if u shoot 5.56 out of a 223 upper bad things can happen. So i want to know how i can check to make sure my upper is for sure a 5.56 upper and not just a 223 upper. The only reason im worried about it is because i got it from a gun show and not from jd machine tech.

here is a photo of my upper

[PhantomII]

Look closely. The barrel should be stamped somewhere for the round it's chambered for.
There's no way to tell from the pictures you posted.

[rero360]

JD are a well known, good quality manufacturer, that upper has been built within the last 30 years, shoot all of it, .223 or 5.56, doesn't matter. Worst case scenario that is even remotely probable is that you'll have to rebarrel and change out all the small parts, springs, extractor, etc. etc. sooner by running the higher pressure ammo, but its no different than running hot reloads thru the gun, something people do all over the country on a daily basis. What I mean is that instead of rebarreling at 15K you'll be rebarreling at 12 or 13K.

And before everyone jumps on me about the differences in the leade and pressures of the two chambering, read what SAAMI has to say about it, their whole advisement against interchanging the two has nothing to do with real world noticable differences, its purely a CYA on their lawyers part as they would open themselves up legally if they said its ok even though military ammo is not under their control/ regulation.

[Mad Jax]

The exact same dillema I had. The barrel is unmarked, do not try to take the set screw out of the hand guard, it will strip & it isn't stamped under there either. I ran both .223 & 5.56 through it no difference in performance. It would be safe to assume its .223 1:9 and go with that. I lost a lot of sleep on the issue there is no true way that I know of from the advise I've been given to tell if the unmarked barrel is 5.56 or not. Matter of fact It looks like the exact same upper minus the EOTech clone I got AIMpoint clone with mine. Oriental guy for $550 right ( not a racial remark).

[damon1272]

You can shoot either round but if you must really know call them on Monday. They are very good to work with.

[Pred]

Thank guys for trying to help me out. I will give them a call on monday and see what that say. I kind of fine it to be odd that they dont have an email listed on there website but its all good.

[Mad Jax]

The uppers are multi cal. I do believe its the barrel that is in question. Please post what JD machine has to say for I could use this info also. Thank you

[FS00008]

I've never seen a JD upper that was not 5.56.

[PyroFox79]

Its nit the upper that is caliber specific its the barrel.

[hellraiser]

Hey i saw them at the gun show to but didint bite because I never heard of them. Please please please report back on how you like it. Im one good solid testimony away from picking one up at the next show!

[Cokebottle]

Hey i saw them at the gun show to but didint bite because I never heard of them. Please please please report back on how you like it. Im one good solid testimony away from picking one up at the next show!

JD as it exists today has been around for about a year.

The owner of JD was one of the partners in the old Kaiser Defense of San Diego.
That company stopped doing business as Kaiser, the partnership dissolved, and JD acquired the machinery and designs for the products.

The other partner has since continued operating as Kaiser Defense in Arizona with a completely new line of very nice products, focusing on the .308 platform.

The original Calguns state/bear lowers were Kaiser. The current Calguns state/bear lowers are JD. Other than the manufacturer name, they are identical in all respects.

JD is good stuff, and it's a California company.

[Mad Jax]

Hey i saw them at the gun show to but didint bite because I never heard of them. Please please please report back on how you like it. Im one good solid testimony away from picking one up at the next show!

I have a JD (upper & lower) VERY pleased with it. Its backed by a lifetime warranty regaurdless if you purchase it from him or a distributer. Mates together tight & mine works flawlessly. That and they are a very friendly group of people located in San Diego. I personally would recomend them to anyone. The only issues I've had were with the handguard which was not a JD product

[JDay]

Worst case scenario that is even remotely probable is that you'll have to rebarrel and change out all the small parts, springs, extractor, etc. etc. sooner by running the higher pressure ammo, but its no different than running hot reloads thru the gun, something people do all over the country on a daily basis.

The head spacing on 5.56 and .223 is not the same, this can cause a catastrophic failure. As long as the upper is stamped 5.56 you can shoot both 5.56 and .223 out of it.

http://en.wikipedia.org/wiki/5.56x45mm_NATO#5.56mm_NATO_versus_.223_Remington

The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military cases are generally made from thicker brass than commercial cases; this reduces the powder capacity (an important consideration for handloaders[11]), and the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56 mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 137.9 MPa (20,000 psi) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,366 psi) for 5.56 mm NATO, is reduced by SAAMI to 379.21 MPa (55,000 psi) for .223 Remington.[12] In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56 mm NATO.

The 5.56 mm NATO chambering, known as a NATO or mil-spec chamber, has a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 Remington chambering, known as SAAMI chamber, is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Rock River Arms)[13] or the ArmaLite chamber, which are designed to handle both 5.56 mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56 mm NATO chamber specification.

Using commercial .223 Remington cartridges in a 5.56 mm NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered gun due to the longer leade.[14] Using 5.56 mm NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and SAAMI recommends against the practice.[15][16] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14 (marked ".223 cal"), but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm NATO ammunition.[17]

It should also be noted that the upper receiver (to which the barrel with its chamber are attached) and the lower receiver are entirely separate parts in AR-15 style rifles. If the lower receiver has either .223 or 5.56 stamped on it, it does not guarantee the upper assembly is rated for the same caliber, because the upper and the lower receiver in same rifle can, and frequently do, come from different manufacturers - particularly with rifles sold to civilians or second-hand rifles.

In more practical terms, as of 2010 most AR-15 parts suppliers engineer their complete upper assemblies (not to be confused with stripped uppers where the barrel is not included) to support both calibers in order to protect their customers from injuries and to protect their businesses from litigation following the said injuries.

[JDay]

there is no true way that I know of from the advise I've been given to tell if the unmarked barrel is 5.56 or not.

You check the head spacing.

[Pred]

I just talked to one of the guys at JD and they told me that ALL uppers they sell are for 5.56.(they make 5.56 uppers and 308 uppers.)