223 recommendation for 14.5" 1:7 barrel

[loose noose]

BunMan, Go ahead and try the heavier bullets in that little carbine, and let us know what kind of accuracy you're getting, I can't honestly say I've never shot one with that short of barrel. In Vietnam we had the M4 with a 16" or maybe a 20" barrel with I believe a 1:9 twist and we used, 55 grn bullets. Besides that bull barrel 20", I also have a M4 with a 16" Bushmaster AR-15 with a 1:9. Btw, I believe the Navy Snipers for long range use the 50's, as well as the 300 Win. Mag, a .338 Lapua. A good read is the American Sniper, by Chris Kyle, once you get past all the personal BS, as it is a autobiography. Any way have fun with that AR, and keep us posted as to your results, you've got my interest up. Loose Noose

 

[moxie]

loose noose,
You had the M4 in Vietnam? Really?

 

[helotaxi]

I just figured faster powders because I don't have the last few milliseconds of pressure behind the bullet before it clears my handy little carbine.

The powder that works best in the long barrel is going to be the same powder that you want to use in the shorter barrel. Your powder choices are limited on the fast side by peak pressure. That peak pressure occurs in the first 2" or less of the bullet leaving the case and then drops as the bullet moves down the barrel. Ideally, for maximum velocity, you want the slowest burning powder that will get you to maximum pressure within the constraints of the size of the case. If you go too slow, you'll fill the case before you get to maximum pressure and the powder won't burn all that well and you'll end up with low velocity. Go too fast and you end up with a small powder charge that reaches max pressure but then doesn't generate enough gas volume to maintain a good pressure and velocity is lost. Barrel length doesn't play into this at all. Barrel length merely determines how long the bullet is being accelerated by that pressure.

 

[loose noose]

We called them the M-16, but that was quite a few years ago, but I do remember the milspec ammo as being 55 grn. We had the A-2 stock none of that collapsible. In the States we used the M-14 until we went thru staging, and we were issued the M-16, really! yep really! Semper Fi.

 

[helotaxi]

His point was that the M16 and M4 are different even though they are based on the same original design and have parts that are interchangeable and the M4 didn't come on the scene until the '90s.

 

[BunnMan]

Helo,

Thanks for the explanation. If all that is true (not doubting it) then I was definitely off in my thought process. I was thinking that since you get flash out of the barrel then the charge was building through the full length so a faster powder would burn up the volume within the shorter barrel leaving less waste blown out the muzzle. I could stand a better education on the reaction time of the powder and barrel physics no doubt.

The local shop had 53, 55, 69gr HPBT SMKs . I picked up 100 each of the 55 and 69 and a pound of Varget. Aso picked up a Lyman manual as my Lee, Hornady, Speer don't support Varget in both those grain weights. I wanted a Sierra as well but they didn't have them. I figure I'll build 10 rounds in each step for two five shot groups...I anticipate best performance will be in the upper powder volumes but I'm still gonna work it up proper. Headed to the range tomorrow so I'll get back with a report.

I tried to attach a pic of my M4gery carbine, not sure if it worked from my mobile...

 

[loose noose]

Helotaxi, I know exactly what moxie was implying that's why I clarified the M-4 as being a M-16, I've graduated from Lassen JC in Susanville, Ca as a certified gunsmith back in 2006-2007, so I do know the difference, but thanks anyway, I'll have to proof read my entries a little closer in the future.

 

[helotaxi]

BunnMan- Nice stick. What scope is that?

 

[moxie]

Just a little course correction. Thanks for clarifying.

 

[BunnMan]

Range report

Alright...second time I'm typing this...got it almost done and hit a wrong key and lost my whole post!

Helo...scope is a Leatherwood CMR. Excellent mid price range scope at $320. Clear glass, excellent reticle zero lock, plenty on info online and the reviews were spot on, very high quality for the money but you gotta be looking center scope, no tolerance for off center and not much tolerance on the eye relief either. Promotes solid and religous cheek weld so I dig it.

Barrel is a Daniel Defense cold hammer forged 14.5" chrome Lined 1:7 twist, With Sabre Muzzle Brake WELDED ON to make 16". Barrel is fully free floated in a YHM Todd Jarrett handguard. Lower is milled/manufactured in house by Precision Firearms in Hagerstown, MD. Mil Spec trigger gently cleaned up and massaged by the skilled folks at Precision Firearms...I'd go on about her but I don't wanna brag .


OK here's the report...Groups were measured center to center of the furthest shots (except where noted) with a dial caliper. I goofed my math on powder steps and wound up with six steps instead of five...forgot you're starting at 1 instead of 0 AGAIN! All charges were individually hand trickled on an RCBS trickler2 and weighed on a Lyman 500 scale. I built 10 at each charge figuring I'd shoot two separate groups of five and take the best of the two for my comparison. Due to range traffic this got modified right away and became 10 shot groups fired in two stages of five each (same POA) at 100yds. I first zeroed the scope using 55gr "bulk" ammo purchased from the folks that built the rifle. The way the reticle works, an etched 1 MOA dot covers POA at 100yds. Of course, I never touched the turrets after the initial zero...bullseyes weren't as important as tight groups somewhere on the paper with a consistent POA on bullseye in each step. Fired at 4x sandbagged under the forearm and pistol grip with a 30rd Magpul Pmag.

Case: Lake City
Powder: Varget 23.4 Start/26.0 MAX Never Exceed
Bullet: SMK 69gr BTHP
Primer: CCI 450 Small Rifle Magnum

Load1 23.4gr
10 shot group 1.94" very consistent dispersion centered windage but about 3.5 - 4" low compared to initial zero

Load2 23.9gr
10 shot group 2" very consistent dispersion centered windage climbed about 3/4" up closer to bullseye. Not perceivable different than Load1 other than 3/4" higher up

Load3 24.4gr
10 shot group 2.255" dispersion not quite so consistent with a little "clumping". Group center continues to creep up toward Bullseye. Starting to get discouraged here as I think I see a trend developing in that the groups are openning up.

Load4 25.0gr
First 5 shot group WOW!!! 0.80" Sub MOA!!! 3 rounds in damn near the same hole!! This is why I came here today!! I would like to thank all my sponsors, and remember all the little people that got me here . Next five shots...I think I got my rifle mixed up with some other very unique AR at the range. All shots in the second 5 were either low or right of the first and openned the 10 shot group to 4.05" with both holes making the extreme spread being punched in the second 5. Broke the rifle in half over my knee and left!!! Just kidding...I'm pretty sure the cause was my excitement at the first five and rushing the second half of the 10 shot group through a "hot" barrel. Not counting the second 5 because it's MY DAY at the range and I can do that if I want to...lol

Load5 25.5gr
10 shot group 2.72" with 3 shots outside a fairly tight 7 shot group of 1.14" I think I'm noticing a trend...I get impatient when things go well. Last two groups are still inching up toward bullseye but also starting a slight 3/4" at a time creep to the right.

Load6 26.0gr MAX
3 shots were couple inch off flyers with the 7 tightest shots measuring 2.15". Were are obviously past our prime at this charge. This one was at elevation with bullseye, with two holes touching at the leftmost portion of the spread both cutting the bull. Even though the proximity of the majority of the group to POA is RDC (Reeeally Damn Close) This is obviously the least consistent group yet.

Summary...Best two groups were the 25.0 and the 25.5. At the range I marked the 25.5gr as the load of choice for consistency and accuracy and because I felt like some of the second 5 of the 25.0 group may have been honest and I was giving myself too much of an excuse. Ahhh...those first 5 were OFS (Out...standing) though. Upon arrival home I noticed a split neck while dumping the cases I collected into the tumbler. It was definitely one of the reloads as the production stuff uses gold primers and my CCI's are silver. The obvious assumption is that is was one of the MAX loads, but not really sure. I will check the others when I pull them out of the tumbler. Of course I don't have a way to track them back to which step in the powder charge they came from but this find was enough to kick me back to the 25.0gr charge of Varget. I'm gonna load the last 40 69's I got at 25.0gr. and order some more. I did build 5 steps of Sierra Game King 55gr BTHP with Varget as well but after 60 rounds of benchrest shooting bullseye stress I dismissed myself to the pistol and sporting clay ranges for a spell. Aint nothing like a scattergun to cure that, "I gotta lopsided eyeball cuz I'm trying to punch a 1/4" group through the scope" feeling. Though when I got to the pistol range I tortured myself through a 5 step work up of 124gr XTP's using Power Pistol in my Glock 34 9mm. that went very well and much faster than the rifle. Sooo much faster to change paper 25yds away than it is 100yds away. I've decided I like my 9mm because I only need 5.3gr to produce a 10 shot group at 4.71" standing off hand. But then again I like my 44 because I don't have to wait for a cease fire to see how big that group is .

Oh, and I ordered a chrono that should be here this week so hopefully either next weekend or the one after I can get a read on velocities.

Thanks for the help...I'll post back on further developments.

 

[MtnCreek]

Sounds like fun. The split neck was likely from old, worn out brass. If you start w/ new or confirmed once fired brass, you can keep them in a batch and toss them when you start to see some of that batch splitting necks.

On your next workup, you could mark the cases with a sharpy with either a charge weight or a batch number (#1 = 23.4gr...). That is very helpful to me when working up loads; I'll take the fired brass and inspect for pressure signs.

Edit: And don't rule out some of your loads as being not accurate. The load that is repeatable the best shooter is your load.

 

[loose noose]

Very impressive I stand corrected, must be those young eyes, beat the dickens out mine every time.

 

[helotaxi]

Personally I use 0.3gn charge increments when working up loads. 0.5 is fully 2% of your charge weight and is just too big of a step IMO. I also don't shoot more than 5 shot groups until I have a promising load that I want to prove. Waste too many components otherwise and don't necessarily learn anything, but I also mostly ignore group size when doing initial load work.

 

[dprice3844444]

http://www.giraudtool.com/