Tight AR-15's - How to adjust the Rifle ?

[DoctorBill]

I have a RRA LAR-15 which I have not fired yet (too wimpy for Winter shooting).

Reading about some AR-15 rifles being tight and requiring the Small (Short) Base reloading
dies made me think about the rifle, not the bullets.

Discussing this problem with some acquaintances, I was wondering, if one has a finicky
rifle, could one not hone out (polish) the breech, where the fit is tight, just a bit to make it less tight ?
It must not take much to bring the rifle into Mil Spec.
Time consuming, but not difficult.....



If one were to take it to a Gun Smith, is that not what the Smith would do ?

DoctorBill

[Scharfschuetze]

I've loaded for several AR15 rifles for well over 40 years and while I have a small base (SB) sizing die, I've never found the need to use it. Of course it will depend on your particular chamber so one can only speculate, but if my experience is relevant to your rifle, a standard die should work fine.

Make up some dummy rounds with your standard die and see if they chamber from the magazine. If you don't get full bolt closure and lock up, then try dummies sized with the SB die.

[kencha]

The issue is feeding reliability. If it is 5.56 chambered, its likely already a little on the loose side as compared to a 223. You could theoretically enlarge the chamber diameter even more to improve feeding, at the expense of further stretching the brass beyond what it was designed for.

I don't think a good 'smith would do that for you though, unless the chamber actually measured undersize and wasn't chrome-lined. They'd probably tell you to check the adjustment of your regular dies, and then if still needed, go with the small-base dies.

I'm a fan of the small-base dies for 7.62 semi-autos. Don't know if they're necessary, as I don't even have a standard set. Never reloaded 5.56.

[BruceB]

DoctorBill, pard;

Well, let's see.... you are inquiring about a "problem" that probably doesn't exist in your rifle..... but you haven't even fired it yet?

Over many years, I've loaded ammo for probably at least a dozen different .223/5.56 rifles, of varying designs and manufacture.

ALL of them, every single one, functioned perfectly with rounds produced by STANDARD RCBS loading dies.

Like others on this thread, I too have a small-base die.... which languishes un-used in its box in some dusty corner. But, I'm READY if the need should ever arise, by gum! (I don't expect that to happen, given the history to date.)

Just go ahead and load your cases using the standard dies, and don't worry until you actually encounter the problems you asked about (which is unlikely).

I have just two .223s right now, a bolt-action and an AR15. Neither has ever seen a factory load, and neither has ever given any difficulty with rounds loaded in STANDARD dies.

I would expect your experience to duplicate that situation..... good luck!

[bdecker9]

My Lee dies make tight fitting 223 cartridges. They fire and function fine, but are a li'l hard to eject by hand. However, I prefer this as it should be good for accuracy and is definitely good for the brass. I've heard of some ppl taking steel wool to there chamber, but those were special circumstances, These companies selling us tools will come up with all kinds, of solutions for problems that may or may not exist. As mentioned TRY IT FIRST.

[DoctorBill]

Gentlemen ! Give me a break !

OF COURSE I am going to try it first.

Sitting here in mid-winter in Eastern Washington State, it is raining,
cloudy, foggy, snowing, blowing or - ALL of the above.

I am asking a "What IF" question. This Forum is not only for your
entertainment, it is for educating others. Discussions are read by
many people who learn from them. That is how I learned reloading.

People who are unfortunate enough to have a finicky AR-15 must
remedy the situation instead of putting up with it - I would hope !

Seems that a tight AR-15 chamber would be easy enough to remedy.

I will go shoot some reloads thru the RRA LAR-15 ASAP.
I don't have any Factory Loads - suppose I could buy a box of 20....

I am hoping I have a loosie goosie chamber that fires anything.

BUT - I did buy a used used Small-Based RCBS Die set "just in case."
If my AR has wide hips, I'll sell the Small Base Die Set.
I do not anticipate buying any more AR-15's.

I was (still am) ignorant.....but I'm learning.

DoctorBill

PS - a side issue......

I have read that one can zero one's scope at 60 yards with an AR-15
and then it will be zero'ed at 200 yards.
Have heard this before for different rifles.
What is that called ?
There must be some nomenclature for that kind of ballistics !

I would like to learn the jargon, so I know what to search for with Google.

[wlc]

Dr Bill, I have a very similar RRA AR. It eats anything I have fed it so far with no issues. Its always possible, but I would bet that you won't have any issues with chamber size, especially if it is a 5.56 chamber.

[Scharfschuetze]

I have read that one can zero one's scope at 60 yards with an AR-15
and then it will be zero'ed at 200 yards.
Have heard this before for different rifles.
What is that called ?
There must be some nomenclature for that kind of ballistics !

Due to the "in-line" stock design of the AR15/M16/M4 rifles, the sights sit necessarily high above the bore. The first catch (where the bullet first crosses the line of sight) has the bullet climbing at a fairly steep angle up to the line of sight. Given that, the second catch can be pretty far down range. So the ballistic ability and velocity of your bullet, the sight's height above the bore and the distance to your first catch will all have some impact on where your second catch or zero will be.

The M16A2 was zeroed at 25 meters and enjoyed a grazing fire range of about 350 meters. In other words, it would hold a 39" high E-Type Silhouette from the muzzle to 350 meters without any adjustment to the sights while holding center mass in large part due not only to the green tip ball round, but also because of the height of the sights above the bore.

All rifles can be zeroed as you suggest and in fact an initial 25 yard zero usually works out pretty well for scoped rifles of the 30/06 class to get them close to zero at 200 yards. Of course some refinement will be required to perfectly zero it at the longer range.

A couple of the computer ballistics programs can predict all the above when fed the data outlined above.

[bdecker9]

You can zero a 223 at 1" high at 100 yards and be on at 2 1" low at 300. Or somewhere real close to that.
And we aren't being mean, we've all just been there done that, and wish we still had our $ from misled purchases. I'm sure you're at is fine.

[kweidner]

I have the RRA and mine does require small base dies particularly if the brass was once fired from unknown origin. If it was shot in mine it's not an issue. I just use em now cause that is what seems to give me zero problems.

[Screwbolts]

I to have a set of Small base dies for both 223/5.56 and 30-06, they both set unused in the drawer. My standard LEE dies actually size the 223/5.56 case egual or more than the SB dies. IMHO, I believe SB dies are a good marketing ploy of RCBS.

There is no correct answer for a Hypothetical question. Every time you multiply zero by zero, you will always get zero. Or zero by any number (hypothetical question) you still get Zero.

RRA is known for QUALITY work, I believe their rendition of a 5.56 chamber will be right on Mil. spec.

Here is a link to a thread with accurate drawings of an AR chamber/lock up system, they are totally different than you show.

http://www.ar15.com/archive/topic.ht...&f=12&t=308716



Ken

[GabbyM]

I own a DPMS bull barrel in 223 Rem (SAMI) chamber. It's even a very tight to SAMI spec chamber. I like it. Also have a Wylde chambered barrel and a NATO. There lies the conundrum. Shoulder diameter on my fired NATO brass is .359". 5.56mm NATO chamber drawings show this dimension to be .3560”. SAMI is .2553”. My new 223 brass measures .350”. My FL resized brass measures the same as new. I am not using a small base die. Head space on the NATO chambered rifle is huge. From a new or piece of brass sized to the bottom grove in a Wilson gage. Case gets stretched .013” when fired. That’s measuring a case in the gage after the brass has sprung back. Not a desirable dimension IMHO. I used to just minimum FL size the brass to fit chamber so it wouldn’t get stretched that much every shot. Still had to trim to length every reload. This barrel is about at the end of it’s service life. Having thousands of rounds down it. Bore is even wavy now. Chart below shows NATO headspace to be .004” longer than SAMI headspace. See under L Base to Shoulder. Under C base diameter. You can see the NATO chamber has an extra .0020” in diameter to the SAMI chamber. Size dies are cut to give plenty of clearance fit with a SAMI chamber. My resized brass measures .376” just above the web which measures .373” on new or fired cases. I suppose the small base dies are supposed to remove this little bulge step from a fired case. Been sitting here with a pile of cases measuring them. I note my fired cases from my Wylde chamber are only a few tenths larger at the base as my resized cases. However brass springs back a little so that’s where the clearance is. I’ve never had issues even with the SAMI chambered AR-15. Here in Illinois where we deal in mud but very little dust. With all these numbers in mind. If I were in some twilight zone scenario, ask to load ammo to send to Iraq with some young soldier. I’d use a small base die to get it back to new brass spec. My NATO chambered rifle has a .002” clearance at the base with a sized case. When spring back is figured in. Stories I hear from men returning from the “sand box” are pretty gritty. They say you have dust in your mouth all the time. So it’s going to be in your rifle and on your ammo. Little of that dust is the dried up material from there open sewer ditches. So yes I’d use a small base die for that work. Texas can get dusty too. Last time I drove through the oil patch I hit zero visibility dust storms. I actually own a small base die but never ran a case into it. Bought it, An AR series RCBS, to get the taper crimp die and the set on sale was about the same price as the crimp die alone. What I have now for AR-15’s. Is the RCBS X die that extends case life. Reduces or eliminates trimming requirements after initial trimming. They are made in standard or small base in the 223 chambering. Mine are the standard die.
I have new ball ammo here and loads built with new brass. So I think it’s covered.

Clipped this chart below from a pdf on http://www.ar15barrels.com/tech.shtml

　
　
223 Rem 5.56 Nato Difference
A Shank 0.4370 0.4370 0.0000
C Base Diameter 0.3760 0.3780 0.0020
D Shoulder Diameter 0.3553 0.3560 0.0007
E Neck-2 0.2550 0.2550 0.0000
F Neck-2/Case Mouth 0.2540 0.2550 0.0010
G Freebore Diameter 0.2245 0.2270 0.0025
H Pilot Diameter 0.2180 0.2180 0.0000
K Base-to-Case Mouth 1.7720 1.7750 0.0030
L Base-to-Shoulder 1.2340 1.2380 0.0040
M Neck Length 0.2200 0.2180 -0.0020
N Freebore Length 0.0250 0.0500 0.0250
O Rim/Belt Thickness 0.2000 0.2000 0.0000
Q Shoulder Angle (Degrees) 23.0 23.0 0.0
R Throat Angle (Degrees) 3.1 2.5 -0.6
The throat in the nato reamer is not good for accuracy, so we do not chamber it.
223 Rem vs 5.56 Nato
The dimensions above are from Clymer. Dimensions in inches unless noted.
The main difference between the two is in the headspace length and throat.
The throat in the nato reamer is not good for accuracy, so we do not chamber it.

[tomme boy]

RRA's uses a chrome lines barrel on all but the SS ones. You would have to have a really sharp reamer to cut through the hard chrome they use. If the rounds you make are ejecting a little hard by hand, screw the FL die in more. Just about all FL dies will size the brass to about the same size as a SB does. The actual problem is you have no leverage trying to eject the round on the AR platform.

[DR Owl Creek]

I don't have a Rock River AR, but I believe all the Rock Rivers use the "Wylde" chamber design, which is somewhere between .223 Remington and 5.56 NATO specs.

All of my AR's and Galil use the 5.56 NATO chamber. I generally haven't needed to use the small base dies for these, unless I'm using once-fired 5.56mm military brass that's been fired through full-auto weapons, and stretched out badly.

Dave

[GabbyM]

Big Difference between Wylde chamber and NATO chamber is the free bore diameter. Can't recall about lead angles and neck taper. If they are any different. Several of the builders "match" chambers are just Wylde chamber with throats to precisely fit a certain match bullet. Like Sierra 80 grain loaded to specified length. Hence with every new bullet that comes along. Another batch of chambers gets designed.

Did you all notice Sierra has come out with SMK's with plastic tips? Amazing B.C. The new tipped 69's are almost as high a B.C. as the HP 77's. 4 cents per bullet more money too. Believe they will still fit the same chambers.

[Screwbolts]

RRA does offer SOME of their Chrome Moly barreled rifles with Chrome lining, but certainly does sell many NON chrome lined rifles.

Yes RRA does offer a few rifles with the Wylde chamber but most are listed as 5.56 NATO Chrome Moly, that is not the same as Chrome lined.

Just take a few moments and browse there fine website. NATO chamber is the most common and plain Chrome Moly barrels, Chromed barrels are higher priced

[dkf]

There are sizing dies sold that are small base dies and just don't list it.(Like Dillon) For ARs I use a small base die. Besides you are only talking .001" less at the very base of the brass which is not a lot.

[dragon813gt]

I believe SB dies are a good marketing ploy of RCBS.

W/out going to far off topic, they aren't a marketing ploy. I need a SB 300 Savage die so converted LC brass will chamber in my 99s. Every piece of brass and firearm are individual entities and can require different loading techniques.

[wlc]

RRA does offer SOME of their Chrome Moly barreled rifles with Chrome lining, but certainly does sell many NON chrome lined rifles.

Yes RRA does offer a few rifles with the Wylde chamber but most are listed as 5.56 NATO Chrome Moly, that is not the same as Chrome lined.

Just take a few moments and browse there fine website. NATO chamber is the most common and plain Chrome Moly barrels, Chromed barrels are higher priced

You beat me to it. I have a factory RRA AR and it certainly does not have a chrome lined barrel and it is chambered for 5.56. RRA does both chrome and non chrome and 5.56 and wylde chambers.

[DoctorBill]

Looks like it is time to state that the Serial Number on my Rock River Arms AR is
CM 24####.

Chrome Molibidiunumbium !

Is that Plated into the barrel or is it a sleeve or what ?

How thick is the "Chrome Molibidiunumbium" ?

My spell checker just freaked out !

The weather is improving here....maybe...... !

DoctorBill