Twist rates for ar 223

[Snuby642]

I will apologize right off the bat for these 2 questions.
Evadently I suck at searches , amongst other things.

I have a new 5.56 sbr 10.5in barrel m16 profile (medium contur ?) That is button rifled and target crowned with 1/7 twist.
During break in I noticed what to me seemed excessive group size at 50 yards, 3-4 moa.
Shooting what is leftover of a case of PMC bronze 55gr fmj.
That same ammo will hold 1 moa in my 16in barrel for me, some days better some worse it's an average.

I'm thinking 55gr is a problem? and would like your input on ammo grains for that setup.

My 16 inch barrel has a 1/8 twist would a 62 or 75gr likely do better than the 55gr?
For now it's mag length factory loads, just like some experience before trying everything out there.

 

[longshot2000]

Let me start with the obvious. You are shooting an extremely short barreled rifle. The 10.5" is a "close quarter battle" rifle. It is not known for accuracy. Next, you are shooting 55 grain, which is known to be a scatter-blaster. Finally, your ammo is PMC...

What barrel are you using with your 10.5," and do you know the gas port size? I am assuming Carbine gas system?

Amongst my many endeavors, I build both sniper rifles and CQB rifles. For the CQB, or Mk18 style, you can do better than 3-4 MOA, but not much. Keep in-mind the purpose of this rifle is to kick down doors and shoot targets that are 25 to 75 yards. At 50 yards, 4 MOA can hit just about anything. If you were to improve on your accuracy, this is what I would look for:

• Either shoot suppressed or not, but don't mix.
• Make sure you have a Carbine length gas system, not Pistol.
• Use a Colt or LMT chrome-lined barrel. Heavy SOCOM is even better.
• If you cannot find or cannot afford a Colt or LMT, then Daniel Defense.
• Make sure your gas port is at 0.070"
• Use 77gr Black Hills OTM ammo.

 

[Snuby642]

I have a similar sbr in 300 blk and get groups less than 2 inches running subs suppressed or not at 50yd. Off bags.
I'm running buis and eoteck on that rig and was hoping to get similar results with the 5.56.
I put a 1.5x4 Leopold on it just to see what it could hold for a group , not impressed but was day one.
I will run some 75-77gr and see what happens.
Both my sbr's have carbine length gas systems and crome lined barrels and after checking the 5.56 is a heavy profile also.
Not sure of the gas port size but is working well with a carbine spring and buffer .
Got the upper from DSG.

Getting to old to kick doors but not to old to defend mine.

 

[longshot2000]

If the gas port size were an issue, you would likely have problems with cycling, gas block-back. If you have to put a heavy buffer in, that is a sign the gas port is too big.

50 yrds is hard to measure MOA, but a 300 BO is a pig at 100 yrds, so a tuned 5.56 should win over a 300 BO all day long. If you are running carbine gas, then it is the barrel or the ammo, or both, but on a good day, a 10.5" SBR is a 2.0 MOA gun.

Start with the ammo, since that is the cheapest option. Common wisdom has been that you can use lighter grain ammo with lower twist barrels (10 to 12) and shorter distances, and that longer distances (300 yrds +) need higher grain ammo and higher twist barrels (7-9). Think of a football. You want to really put the spin on a long throw, but can lob a shorter throw. This would lead to picking 55 grain for short distances, and a 1:12 twist in an SBR. The truth is two things: 1) faster twist seems to not do any harm to shorter distances, so you start seeing 1:7 and 1:8 barrels at all lengths, and 2) the 77 grain ammo just works great at the extremes: shorter barrels and longer barrels. I would save the 55 grain for a 16" gun. The Army moved away from M193 55 gr. some years back in favor of an equally shitting round, the M855 6s gr. The snipers went for the 77 gr, and were amazed at the accuracy, so the door-kickers tried it, as it had a less pointed tip on their fast cycling Mk18s, and found it helped with both throat erosion and accuracy. The Obama administration, in their quest to rid the battlefield of lead, stumbled into a new round that is showing amazing results: The lead-free 62 gr steel-tipped M855A1. This round is a great flyer. It turns out that the added length (since armourers had to add more metal, as copper and steel are less dense than lead) helps stabilize this round for very long distances. The steel tip, however, would not be kind to an SBR. If you can find M855A1, use it in your 16" to 18" rifles, then ratchet up to 77 grain for 20" rilfes.

I can tell you that my SWAT clients swear by Colt barrels at under 16." I mean, they are throwing name brands under the bus all day long that I thought would be better. Chrome lining itself adds to barrel inaccuracy, but what it does at such high pressures of an SBR gas system is protects the throat from metal jacketed bullets slamming into it with increased velocity. Some barrel makers are better than others at chrome-lining and maintaining some accuracy. I am not sure from where DSG sources their barrels. In the short barrels, there is a reason Colt and LMT cost $350 to $500, and DD $250 to $350, and other guys are selling for $69.

https://charliescustomclones.com/blogs/news/how-to-improve-accuracy-of-a-short-barreled-rifle

 

[Snuby642]

Thanks for the help.
The dsg barrel is mid price range and ? Proprietary (house brand). Many local le agencies source them.
At 50 yards a 2 inch group is only shooting 4 moa, i thought that to be a resonable goal at that price point.
My army son took all my m855a1 he was a dm in his deployment unit and his gun likes it, he said they used it a lot.
Some of the local ranges won't let me shoot it anyway.
Sounds like you are rite on with the short range 55gr twist rate in my 16inch barrel it calms down at 100 yards, 1/8.

I will start testing the heavy stuff in both barrels.
Would be way cool to find one round acceptable by both.
Just got a scope for the 16in that is 6x24 so I should get out a ways with the 75gr stuff
The 300 bo subs are a pig in a sbr and bolt gun, but a fun pig, can hear the paper rip at 100yd. Lol

 

[padom]

Ok, lets step back here and say no, a 10.5" is not a 2moa all day barrel. This is the most ridiculous thing Ive ever heard. Barrel length has jack shit to do with accuracy, it has to do with velocity. I have built 100's of 5.56 AR's and many 10-10.5" ones. The barrel maker is the biggest factor in its accuracy, not the length. Ammo is also a big part. My 10.5 1:7 5.56"s with PMX X-Tac M855 shoot between 1-1.25moa at 100yds. Quality match grade ammo or handloads, 1/2moa or better from a good barrel.

Take for example this Daniel Defense Govt Profile 10.3" CHF 1:7 Carbine barrel

PMX Xtac M855 shoots 1-1.25moa

55Vmax in 1xLC brass and H4895 - Seating Depth Test 5 Shot Groups 100yds

Here's a Rainier Ultramatch 300blk 10.5" Barrel 7x5 accuracy test at 100yds wtih 125TMK/H110

I own and have shot and built many WOA 10.5" 1:7 5.56 barrels that shoot just like the above DD barrel. I have tested extensively the whole short barrels arent accurate myths. They are exactly that, myths.

 

[padom]

Its not the 7 twist barrel as you can see with my above target shot from a 7twist and 55g projectiles. Its most likely the barrel and/or ammo. Just because PMC shoots good in your 16" doesnt mean it should or would shoot the same in your 10.5". If you dont handload pick up a box each of 5 or 6 different types of ammo and test them in your 10.5". Find what shoots best.

 

[longshot2000]

Ok, lets step back here and say no, a 10.5" is not a 2moa all day barrel. This is the most ridiculous thing Ive ever heard. Barrel length has jack shit to do with accuracy, it has to do with velocity.

Yes, Pandom, and you and I agree, all other things being equal. But, all the other factors that go into making a 10.5" gun also make it typically less accurate. The velocity makes it fall off early and not shot well at a distance -- which is really the point I was trying to make. Also, many guns have barrels that are not made for accuracy, they are made for durability, they have chromed lining, and not all chrome lining is the same, and can affect accuracy in a big way, and then there is the cycling issue with over-gassed barrels, which is common, etc. So, not all other factors are usually held constant in comparing a 10.5" barreled gun to a 18" gun.

 

[padom]

Yes, Pandom, and you and I agree, all other things being equal. But, all the other factors that go into making a 10.5" gun also make it typically less accurate. The velocity makes it fall off early and not shot well at a distance -- which is really the point I was trying to make. Also, many guns have barrels that are not made for accuracy, they are made for durability, they have chromed lining, and not all chrome lining is the same, and can affect accuracy in a big way, and then there is the cycling issue with over-gassed barrels, which is common, etc. So, not all other factors are usually held constant in comparing a 10.5" barreled gun to a 18" gun.

If you said that first, or said a 10.5" sbr isnt the best suited long distance gun I would agree with that... But you said "but on a good day, a 10.5" SBR is a 2.0 MOA gun. "

If ANY of my SBR's were a 2moa gun on a bad day they would be gone. The 300blk will go 5 for 5 on steel at 200, 300, 400 and 500meters all day long too. So while its not a 800-1000 rifle, thats pretty damn good 100-500yd accuracy... The 10.3" DD 5.56 with 55Vmax can bang steel with boring consistency with a T1 out to 300yds no problem. That was the limitations of the red dot at that point..

 

[Snuby642]

That's nice groups with the 300blk.
I shoot 1000fps 200gr class subs and the wind plays hell with them, never got a group that small.
I got both my 300blk guns to shoot subs for fun and quiet no recoil, great new shooter's teaching tool at 50-100 yds.
Newbies get bored with rimfire and the 300blk is a fun next step for them without distraction of noise and recoil.
Maybe some day i will get out some of the super stuff i have for them, stashed in the bottom of the safe for a rainy day.

300blk 0.020 off the lands. Are we single feeding rounds in our door kicking rig?
Will that fit in a mag?

 

[padom]

300blk 0.020 off the lands. Are we single feeding rounds in our door kicking rig?
Will that fit in a mag?

Single feeding? lolol not even close. 2.235" COAL in Lancer mags. I dont single feed anything in any AR

 

[Snuby642]

Got my ass on that I do see daylight.
Was not sure of max mag length. coal, I use mostly pmags I'm guessing same max maybe not?
Will be reloading asap, as space in the house allows, family constraints at the moment.
At the moment I have to wait for grandkids to go to sleep before even cleaning guns.
First pmag i grabbed had 2.25 max clearance so I think I can go that far.
Got a dillon and and rcbs sitting in storage and want to get a Forster for the bolt guns.
I read a different post and see you like Forster press, I consider that a solid recommendation, thanks!

After a lot of review my 223 barrel may be a durability hose pipe as designed after all, and what I paid for.
Dissapointing but correctable, my bad! The barrel may be a pos, unless you need a dependable hose.
By now I should have known the difference before the purchase, absolutely no bad on DSG!
Will probably just bang close plates with irons and get over it for now.
I will keep the 1x4 scope on it till settling on ammo, then transition to eotec / buis.


I am here to learn, and apreciate your time spent !

 

[padom]

I run ASC SS mags normally or BCM metal megas..Allow coal in the 2.29-2.32 range...unless plinking 55gr I don't run PMAGS.

 

[Snuby642]

An extra 0.07 available coal, I'm in on that when I start reloading. Thanks
Completely forgot about wall thickness on the mags
Never ran past factory length on an ar, actually have one barrel it may be worth the effort on and a good scope for it.
I had quit using cheap steel mags because I kept bending the lips as I dumped them onto concrete and rock base.
The cheap and reasonably. durable pmags made drills run faster for me, just let them fly.
Those ss mags would probably hold up to that but will be used for the extra cole and to segregate ammo as well.
I lable a pile of mags on the bottom as what they have but sometimes they fall off.
I will be able to feel the difference and know it's a handload without looking..
Probably won't make a difference to what i have to shoot at short range in a hurry.

 

[bfoosh006]

I'm with Padom... try a variety of 55gr FMJ prior to deciding the barrel is a hose.

I suggest, GECO 223 and 5.56, MEN 56gr, Wolf Gold, and PMC XTAC 55gr.... if all else fails... Fed. 50gr Tipped Varmint ( that one has never let me down.

Also how are you shooting your test groups ? Benched , Prone ?

benched wise , try resting the handguard at different positions... against the mag, mid way, and towards the front.

 

[Snuby642]

I'll try that as best i can.
Shooting bench this time of year, will lay in the fire ants soon enough.
My bag is 3-4 inches wide, my handgaurd is 9 so differance may not be dramatic at the short ranges?

Have waited to go back to the range, have been trying to find some 62 or 75gr bulk ammo, non steel and maybe expanding.
I don't have to have match ammo to be better than the PMC 55gr but for the price it is reliable pretty much no primer strikes.
Once i get that sbr running good it wont see much bench, and the scope will come off, and my can will go on.