best .223/5.56 chamber specs and rifling?


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jason41987
April 5, 2013, 09:49 PM
i was wondering what are some of the better chamber specs available for .223/5.56mm that i should consider using on this rifle build of mine?.. its a semi automatic, so reliability in feeding is quite important, probably more so than accuracy but id like to get the best performance i can considering

so... .223 chamber specs probably wont be what im looking for, 5.56mm or the wylde chamber specs are what im looking at now.. does the wylde really offer better accuracy than the 5.56mm chamber without sacraficing reliability?

and i know there are various types of rifling, different land/groove counts, right/left hand rifling, rifling shapes, etc... in your opinion what sort of rifling do you prefer on your rifle?

i know its a pretty in depth question but im interesting in learning more about these options from the 5.56mm/.223 community

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NeuseRvrRat
April 5, 2013, 09:55 PM
you'll never know the difference

Welding Rod
April 5, 2013, 10:41 PM
There is no way to directly compare different chambers in two different barrels, but in my experience with approx 5 556 chambered barrels and 6 Wylde chambered barrels, of various profiles, the ones with wild chambers were definitely more accurate. How much of that can be credited to the chambers I can't guess.

Functionally, Neither has proven any benefit as both chamber types have been perfectly reliable. But I only shoot good quality brass cased ammo.

The brass out of the Wylde chambers has been less stretched which is nice for reloading.

jason41987
April 5, 2013, 11:57 PM
ok.. then as someone who wants better accuracy without sacrificing reliability, with the intent to reload, im probably better off with the wylde chamber

what about the number and type of grooves in the rifling?

Z-Michigan
April 6, 2013, 12:14 AM
What is the exact type of rifle and what is your main use going to be?

I'd go Wylde or NATO match (basically the same thing) for something that is accurate while having no concerns with 5.56 NATO spec ammo. I'd go a tight .223 Rem for maximum accuracy without that flexibility.

Twist rate is guided by what bullet you want to use and how far. That said, 1/8 seems to be the best all around compromise for modern use of heavier bullets, and 1/7 is also fine for most uses (not ideal for light bullets).

Almost everyone uses 6 groove rifling in this caliber. I don't know why. I have not seen any comparisons of accuracy with different numbers of grooves for 223/5.56. To me I would think fewer would be better, but I'm only guessing. Anyway, that's basically an issue of who you're buying the barrel from.

jason41987
April 6, 2013, 10:35 AM
the barrel is for an AK-74 conversion, ammo availability is the primary reason to convert this from 5.45 (i dont like having to rely on foregin imports as my only source of ammunition, and like the ability to hand-load)... also, im taking steps to make this rifle as accurate as possible but without sacrificing reliability

so obviously, the .223 chamber spec is simply out of the question, its too tight for such a rifle, and by the sounds of it the 5.56mm chamber spec might be too loose for better accuracy and reloading

wnycollector
April 6, 2013, 10:50 AM
The two most accurate AR uppers I own are Wylde chambered with 1:8 twist. They are ultra reliable with inexpensive Brown Bear 55 gr to Black Hills 77gr OTM.

Reloadron
April 6, 2013, 11:15 AM
This is a good link (http://www.google.com/url?sa=t&rct=j&q=5.56%20chamber%20specifications&source=web&cd=4&ved=0CEkQFjAD&url=http%3A%2F%2Far15barrels.com%2Fdata%2F223-556.pdf&ei=tzdgUfKSKoa60gGM2oDoAQ&usg=AFQjCNFG6ksa_Ywsmn0RwOH33C6v7qr3Ew&cad=rja) to the various chamber specifications for what they may or may not be worth to you.

Choosing a chamber and choosing the barrel twist rate becomes pretty much, as was covered, the intended use of the finished rifle and bullet weights and designs you plan to shoot the most of.

Ron

Ar180shooter
April 6, 2013, 12:49 PM
the barrel is for an AK-74 conversion, ammo availability is the primary reason to convert this from 5.45 (i dont like having to rely on foregin imports as my only source of ammunition, and like the ability to hand-load)... also, im taking steps to make this rifle as accurate as possible but without sacrificing reliability

so obviously, the .223 chamber spec is simply out of the question, its too tight for such a rifle, and by the sounds of it the 5.56mm chamber spec might be too loose for better accuracy and reloading

I wouldn't be too worried on the effect chambering and twist will have on accuracy with an AK pattern rifle. The inability to free float the barrel like an AR, combined with the long stroke piston, will have more of an effect on accuracy than the two things you're concerned with. If you want a super accurate .223, nothing beats a souped up AR (this coming from a fan of the Sig 550 rifles).

IMO a 5.56 chamber and 1 in 9 twist would be the best option for that sort of rifle. It will have no trouble with 55-69gr bullets, and you should still be able to achieve MOA (or close to it) with handloads, but without compromising reliability or the ability to shoot cheap bulk M193 accurately (for instance, my SL8 with 1 in 7 twist cannot shoot 55gr ammo very well... it patterns at 100 yards... not groups).

jason41987
April 6, 2013, 01:09 PM
hmm... so a hypothetical... imagine an AK, standard contour barrel, but a higher quality, new barrel, 5.56mm chamber specs, 16"... what sort of accuracy do you think it would be able to achieve?.. also, ive seen free floating forearms for the AK, downside is that rear sight block needing to be pressed onto the barrel

Ar180shooter
April 6, 2013, 03:01 PM
hmm... so a hypothetical... imagine an AK, standard contour barrel, but a higher quality, new barrel, 5.56mm chamber specs, 16"... what sort of accuracy do you think it would be able to achieve?.. also, ive seen free floating forearms for the AK, downside is that rear sight block needing to be pressed onto the barrel
2 MOA, maybe closer to 1 if you can work up some decent handloads and opt for a slightly heavier barrel profile. But really, as long as you're under 2MOA, you're doing fine. A rifle of this sort is not a precision instrument, and 2MOA allows you to effectively engage a man sized target out to 600 yards.

One thing I would be looking for in a barrel is making sure it is chrome lined or has gone through some sort of nitrocarburization process. This will greatly decrease wear and increase barrel life. IMO versatility and longevity are factors that I would place above accuracy in an AK action. This isn't to say that you should be satisfied with something that will only do 3-4MOA, but it is very difficult making an AK in to a sub MOA shooter, and you have to compromise on things such as weight and reliability to do this.

It does sound like a neat project though. I'd love to see pics when you're done.

jason41987
April 6, 2013, 03:57 PM
i was looking to stay under 2moa.. id be happy with 1.5moa with quality ammo if at all possible, and i do intend to get a nitrocarburized finish inside the barrel

Ar180shooter
April 6, 2013, 04:12 PM
i was looking to stay under 2moa.. id be happy with 1.5moa with quality ammo if at all possible, and i do intend to get a nitrocarburized finish inside the barrel
Sounds like you've got it figured out. I would opt for a slightly heavier profile than a standard AK barrel though, maybe closer to RPK weight.

jason41987
April 6, 2013, 04:17 PM
ar180, i was wanting to get an RPK contour... problem im running into is i would need an RPK rear sight base, front sight block, forearm retainer, and gas block... i wonder what a de-milled front end would cost me?

jason41987
April 7, 2013, 02:17 AM
basically.. relating to twist rate for example, what im looking to do is design my own .223 hand loads based on the 75 grain hornady a-max bullet which has a very high ballistic cofficiency and will do significantly more damage at any range giving a well-tuned 75 grain load a HUGE boost in performance over the 55 grains... BUT, i still want the option to cycle military ammunition, even if its not optimized, i just want the option of being able to load general, run-of-the-mill military 5.56mm ammo of lower weights

this is why i was considering a 1-7 or 1-8, it seems better for this idea of using 75 grain handloads... i took some data from a load data chart for 75 grain bullets, using the a-max (bullet of my choice) i came up with a load that would do over 800ft/lbs at 300 yards and 500ft/lbs at 600 yards.. 55 grain loads do barely 600ft/lbs at 300 yards, and barely 250ft/lbs at 600... so the 75-grainers are a HUGE boost in performance... plus run at about 2800fps which is about the velocites i get in .308 and similar caliber rifle, so the flight path would be almost identicle to what im already used to

so.. best twist rate for 75 grains as the targeted load with the ability to reliably chamber and fire 55-62 grain military ammo, even if at lesser accuracy?

hentown
April 7, 2013, 08:04 AM
You're going to take a loosely-made, generaly non-match-quality commie rifle, change the barrel, and start shooting benchrest? I doubt it. ;) Whether you pick 5.56 or a Wylde chamber won't make any difference for your purposes.

My chrome-lined, 1/9 16" Bushy Shorty has shot some 1/2", five-shot groups @ 100 yds, using match bullets. I set up a friend's Bushy Shorty just like mine, and I witnessed the friend shoot a 1/2" group with the first five shots out of the barrel, using Hornady 53gr Custom ammo. I've free-floated the barrel and installed a JP match trigger/hammer. Ya gonna get better accuracy than that out of that AK? Nah, ain't gonna happen.

Reloadron
April 7, 2013, 09:07 AM
You're going to take a loosely-made, generaly non-match-quality commie rifle, change the barrel, and start shooting benchrest? I doubt it. ;) Whether you pick 5.56 or a Wylde chamber won't make any difference for your purposes.

This will redefine making a silk purse out of a sow's ear.

On a serious note I tend to agree. The AK type platform was never designed to be or intended to be a match quality rifle. It does what it was intended to do very well but that is as good as it gets.

The fact that I and others may see this as a waste of time and money is really here nor there. The OP can do whatever he wants. We do have a forum member who knows just about all there is to know about the AK types including quite a bit about rebarreling them. I just can't recall who that is? Reading everything they have had to say on the subject is good materiel.

Ron

meanmrmustard
April 7, 2013, 10:22 AM
2 MOA, maybe closer to 1 if you can work up some decent handloads and opt for a slightly heavier barrel profile. But really, as long as you're under 2MOA, you're doing fine. A rifle of this sort is not a precision instrument, and 2MOA allows you to effectively engage a man sized target out to 600 yards.

One thing I would be looking for in a barrel is making sure it is chrome lined or has gone through some sort of nitrocarburization process. This will greatly decrease wear and increase barrel life. IMO versatility and longevity are factors that I would place above accuracy in an AK action. This isn't to say that you should be satisfied with something that will only do 3-4MOA, but it is very difficult making an AK in to a sub MOA shooter, and you have to compromise on things such as weight and reliability to do this.

It does sound like a neat project though. I'd love to see pics when you're done.
Lengthen the sight radius with a Tech sight, too, and it'll be even better at range.

jason41987
April 7, 2013, 12:54 PM
FFS, i mentioned changing a barrel because im converting it to a different cartridge, and if im spending the money to rebarrel something im going to be sure i get the barrel i specifically want, the barrel thats absolutely best for what i intend to do.. and you accuse me of trying to make a benchrest or something out of a sows ear because i intend to go with 75-grain loads?... i shouldnt even dignify those comments with a comment of my own

for a more serious comment, i dont see any need to change to a different type of sight, theyre just for backup, i intend to use either

Reloadron
April 7, 2013, 01:41 PM
My reference to a silk purse out of a sows er was in humor. I thought I made that clear, sorry if I didn't.

As to AK barrels I suggest you give these guys a call and look. (http://www.k-var.com/shop/Barrels)

You mention 75 grain bullets? Personally I suggest a 1:7 twist like those in the link. My experience with the heavier 75 grain and 80 grain bullets in .223 or 5.56 chamberings is the faster twist works best. However, that same twist can suck for the lighter than 55 grain bullets. Yes, you can compromise with a 1:8 or 1:9 but the more you compromise trying for one twist rate fits all something will suffer.

You wanted chamber specifications and I provided what I thought was a pretty good link as to actual dimensions.

Manufacturers like Sierra are pretty straight forward when it comes to barrel twist rates and their match grade bullets:

http://www.bearblain.com/images/Twist%20Rate1.png

http://www.bearblain.com/images/Twist%20Rate2.png

Finally as I mentioned swapping a barrel on an AK type rifle is not for the faint of heart. I wish I could remember the name of the forum member who is really knowledgeable on this. He covers it quite well in several threads on the subject. Possibly I missed it but do you plan to do the work or have it done? If you plan to have it done I suggest a very competent gunsmith.

The fact that I wouldn't bother with such a conversion is here nor there as it is your decision and your money. I would call the guys in the link and get their take on doing it.

Ron

jason41987
April 7, 2013, 03:25 PM
you know, i just cant think of another bullet size in 5.56mm id actually like, i mean, doing a ballistics calculation using real load data of different bullet weights, and then finding the best bullets for those weights the 75 grain loads absolutely dominate the 55 grain loads, especially beyong 200 yards... may not be necessary in an AK, or similar military style rifle, but at any given range theres more power, punch, and penetration... suprised the military wont use it?

so i think what im going to do is get the green mountain 1-7 barrel, chamber this with the wylde chamber specs, and have it contoured to match the standard ak-74 contour because the added cost if i went with an rpk contour would be quite high and im not sure it would even be worth it

NeuseRvrRat
April 7, 2013, 03:43 PM
but at any given range theres more power, punch, and penetration

what's your intended use for the rifle?

jason41987
April 7, 2013, 04:24 PM
no main use.. general purpose, all-around 5.56mm rifle

NeuseRvrRat
April 7, 2013, 04:24 PM
what are you going to shoot it at?

jason41987
April 7, 2013, 04:34 PM
targets, might take it hunting once in a while too.. when i mean target shooting, i mean practicing improving my range and accuracy, not just plinking for fun, but im sure ill be doing that too

NeuseRvrRat
April 7, 2013, 04:39 PM
what are you going to hunt?

jason41987
April 7, 2013, 07:00 PM
occasionally deer, why?.. 5.56 is legal in the state im moving to, and the 75 grain loads are quite suitable

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