RDB chambering

audet548

audet548

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Alright, so first of all, I am not telling or suggesting anyone to do anything, we are all grown ups (or should be) and each and everyone of us can make their own decisions. The idea is to discuss the subject and gather some information.

So...got my RDB last week and like most people found out that it was "chambered" or marked as .223 REM and 20" instead of the advertised 18.6".

With the whole don't shoot 5.56 in a .223 barrel or you will blow your face off thing, I decided to make some research. And of course surprise, some say it would be the apocalyspe shooting 556 in a 223 and others saying that it is not that big of a deal, that yes pressure would be slightly higher but not considerably.

I then decided to try 556, starting slow and checking for overpressure signs, nothing on the cases, no popped or deformed primers, no case splitting, no hard extraction. Ended up shooting 100 rounds without issues.

Today I have contacted Kel-Tec to further investigate because the manual says it is chambered in 556 and they make their 17" and 20" barrel in house, so why would they go and chamber a very small number in 223 just for Canada? The reply I have received from Kel-Tec is that the 223 stamped on the barrel is for export purposes and that they are in fact chambered in 556.

I know that Vault said they are chambered in 223 but if it is in fact an export "loophole", they will for sure stick to the "official" version...

Now, there must be someone on this forum with the proper knowledge and tools that would be able to check if it is in fact chambered in 223 or 556?

Flak jacket in now ON, go ahead lol
 
The .556 export thing seems to be just another poorly thought out regulation, hopefully that will get cleared up by the Americans.... till then let's just enjoy what comes north without fanfare.
Everyone should read up on the differences and proceed as you did with a bit of caution and look for pressure signs.
 
You have approached the issue very sensibly, firing 5.56mm ammunition in your rifle and carefully observing the results. You now know your rifle will handle at least some 5.56mm ammunition without problem. Why worry further about it?
 
Went through this with the su16. Despite marketing lit stating differently there were no 5.56 markings on the barrels of Canadian product.. A few discussions with the factory indicated the removal of 5.56 markings from the barrel was purely an export to Canada "Military caliber" marking issue and was assured the Canadian barrels were the spec'd the exact same as the American 5.56/.223 barrel so not to worry.

Are things different now, I doubt it.
 
👆 What he said...
American laws call 556 and military round as so they export 556 as 223...
That's about it...

The 223 and 556 issue in "life" is independent of these rifles per say.

That's my understanding.
 
I thought the US dept. of state export 'ban' died in 2012??? why are they still doing it when Daniel Defense and tons others aren't?

In any case, the only actual difference between 5.56 and .223 in the chambering (not even the chamber, the actual chamber dimensions are identical, as per the SAAMI spec) is the actual lead in to the rifling. It's a bit longer on 5.56, but with a semi-auto rifle it's not going to be an issue because you have looser chambers and longer lead ins anyways. They probably use the exact same chamber reamer for everything they cut.


In a bolt action rifle with a tight chamber and the rifling sitting only a hair away from the bullet depending on how you seat it, an overpressure issue MAY occur if you're shooting really hot ammo.... But likely it won't ever be any kind of serious issue.
 
I have shot an extra 45 rounds of 5.56 yesterday, still no issue and no sign of overpressure.

I have also dialed down the gas setting considerably compared to how it was from the factory, big difference, way softer recoil and smoother operation.

One more point, I had to locktight the screws on the top rail, the were coming out... Other than that, no issues, no malfunction and I was able to do approx 1.5" groups at 100m
 
Spartan46 said:
From kel-tec after I sent a ticket : "They're chambered in 5.56, but must be stamped .223 legally I'm told. "
Click to expand...

That's consistent with explanation of their other Canadian ".223" offerings and, imo, the only thing that makes any sense at all from an ease of production "cost benefit" point of view.
 
Bringing this dead thread back to life. With the help of a borescope and and piece of wire I attempted to crudely measure the freebore of the RDB. The spec'd freebore of a Nato 5.556 chambering vs the .223 is .0566"" and .025" respectively. Freebore is the distance from the end of the casing neck to the point where the barrel rifling commences. Freebore diameter,throat angle and throat length being the same, a longer freebore reduces max chamber pressure and these adjustments in freebore length also affect accuracy.

I'm no expert on this stuff and just really started looking at it today but that's my quick coles notes take away on what I've read so far. Anyways here's a photo that depicts my crude measurement setup. Using a borescope with a 45 degree mirror and a piece of wire notched at .090" and .160" for reference I estimate the freebore of my unfired RDB to be about .120". Four times the .223 spec and twice the length of the 5.56 Nato spec.

Part of the plan to keep pressures down or just really poor quality control who knows but if if this is the norm (without knowing the throat angel) I'm thinking this is evidence this barrel is engineered for 5.56 Nato ammo.

Would enjoy reading remarks from the gunsmiths and other experts here.

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This whole debate is stupid. .223 Remington and 5.56 NATO are completely and 100% interchangeable without consequence. Just shoot it. Nobody has ever injured themselves firing .223 in a 5.56 or vise versa.
 
Blastattack said:
This whole debate is stupid. .223 Remington and 5.56 NATO are completely and 100% interchangeable without consequence. Just shoot it. Nobody has ever injured themselves firing .223 in a 5.56 or vise versa.
Click to expand...

Haven't fired the RDB yet (has nothing to do with worrying about the interchangeability of rounds. I agree this is likely splitting pedantic hairs but there has been an ongoing debate as to whether the Keltec USA 5.56/.223 offerings are the exact same as the "stamped" .223 Canadian barrels. After discussing this matter twice with Keltec management and one of their engineers in Florida they assured they are the same barrels. However the Canadian distributor is singing a different "legal" tune which is causing some confusion among owners. I invite others to interpret my crude findings.
 
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Jaylegger said:
Haven't fired the RDB yet (has nothing to do with worrying about the interchangeability of rounds. I agree this is likely splitting pedantic hairs but there has been an ongoing debate as to whether the Keltec USA 5.56/.223 offerings are the exact same as the "stamped" .223 Canadian barrels. After discussing this matter twice with Keltec management and one of their engineers in Florida they assured they are the same barrels. However the Canadian distributor is singing a different "legal" tune which is causing some confusion among owners. I invite others to interpret my crude findings.
Click to expand...

Seems like there exists some kind of go/no-go gauge for 223 vs 556. Maybe some local gunsmith have this so people can settle it for sure.

http://www.m-guns.com/tool_new.php?product=gage
 
From discussions I've had with the gunsmith at Vault Distribution (the official Canadian importer), all of the Canadian market .223 rifles (RDB and SU-16) are marked and chambered for .223 Remington. It's a US Export thing, and the gunsmith told me that the customer service reps at Kel-Tec unfortunately pass on incorrect information that they are 'the same barrels with different markings'. He was very clear that the Canadian market barrels have .223 chambers.
 
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