Twist rates

BHuij

Active Member
Hey everyone—

Got a noob question about twist rates. Conventional wisdom states that you need more spin to stabilize longer/heavier projectiles. From what I understand, a 1:9 barrel in .223 will usually do okay up to about a 69gr projectile, a 1:8 can do up to around 77gr, and a 1:7 can potentially stabilize even 90gr projectiles.

I realize that there are more factors in play here such as velocity, but as a rule of thumb, that's basically my understanding.

Reason I ask is because I'm hunting for a new mold for .223 and wanting to get something about as heavy as I can get away with. The barrel in question is a 1:9 twist. I'd like to be able to shoot both LV and HV, so I wanted a gas checked mold. I'm trying to decide between then NOE 225-67-FN-A5 and the NOE 228-74-RN-C2. Would the heavier one stabilize in a 1:9 without pushing it to max velocity? Seems like lead bullets behave a little different in terms of stabilization than jacketed.
 

Bass Ackward

Active Member
What’s your throat tell ya that ya need? That’ll determine bullet design & if ya need to get stupid to get weight.
 

JWFilips

Well-Known Member
I have shot the NOE 225-67 in my 1 in 9 sportsman 78 gas checked at about 1600 fps & they shot very well out to 100 yds ( farthest I have tried them)
 

462

California's Central Coast Amid The Insanity
Bass Ackward,
Good to see you, sir! You helped me with a revolver problem, about eight-years-ago, on that other site
 

Spindrift

Active Member
I can’t give you the excact answer, but I can offer my views, for what it’s worth.
The «rules of thumb» regarding stability limits, twist rates and bullet weight relate to lead core, jacketed, match-type bullets. Since the mean material density of lead bullets is higher than jacketed bullets (and even higher than monolithic copper bullets), a lead bullet of a given weight is much shorter than a jacketed bullet of the same weight. In addition, lead bullets typically have a much more compact form, with no boat tail and stubby noses. In short, the «rules of thumb» for jacketed bullets do not apply to lead bullets.
In the technical drawing of the 228-74, the overall length is .752. Measured a 69grs matchking, it was .900. Hornady 55grs fmj-bt was .738.
My guess is, you will stabilize the heavier bullet. Personally, I really like the look of the 225-67, though... But I have shot neither. Good luck!
 

Ian

Well-Known Member
Bass, you might as well add "It only matters if it does" to your signature line, we've quoted you on that one so many times here it's practically cliché.
 

BHuij

Active Member
The explanation on why I tend to be able to get away with heavier bullets and slower twist with lead makes lots of sense.

As always, first step needs to be a pound cast. I suspect the 67 is a better design than the 74 for high velocity shooting, but I’d like a better BC if I can swing it. Any heavier .225”ish bullet molds out there that lend themselves to HV shooting?

I do think I’ll work up a load with SMKs first to establish the accuracy potential of the rifle. Made the mistake of skipping that step with my AR and it resulted in a lot of wasted effort. The rifle is a TC Compass and is guaranteed 1MOA out of the box.
 

CZ93X62

Redlands, Kalifornistan
I have done a smattering of playtime with castings in 22 centerfires. My best success to date has been with 22 Hornet--Lyman #225438 (43 grains in 92/6/2, sized .225" and lubed w/Carnauba Red), 9.0 grains of Alliant 2400 in W-W cases and Rem #6-1/2 primers. 2375 FPS in 1-14" twist, groups at 100 yards ran 1.3" to 1.7"

I have a bolter 223 Rem (Ruger 77RC) that has superb accuracy with bullets it likes--Nosler BalTip 55s shoot 0.6 MOA to 200 meters/5 shots. Given its maker and the buggy-whip barrel profile, that borders on the miraculous--but there it is there. Its 1-9" twist runs the RCBS 22-55-SP with decent accuracy to about 1750-1800 FPS, but exceed that speed and accuracy goes to Sheol. Again, sizing is @ .225', alloy is 92/6/2, and lube is C/R. Powder coating or Linotype alloy might alter those outcomes, dunno. So might polytheism or Santaria, but the former is largely out-of-print and the latter is hard on the poultry.

When I re-barreled my Rem 788 in 22-250, the barrel had a 1-12" twist. This sort of a compromise between the 1-9" 223 default twist present in 3 of my 223/5.56 rifles and the usual 1-14' twist given to the 22-250. I don't hurl javelins with my rat guns (77-90 grain bullets); the 1-8" twist in my varmint upper for my AR-15 is overkill for the usual 55-60 grain bullets I use in 223 and 22-250. The 1-9" supports the 69 grain Matchkings in my A2 upper and my Mini-14, and really makes that Mini-14 do good work. It runs those in 1.25"-1.50" groups at 100 yards with the aperture irons--must be a Wednesday rifle. The A2 upper shoots them just under 2", but dotes upon the Sierra 65 grain Game King. Go figure. The rat upper shoots the 65 GK, 69 MK, and just about everything else into 1" or less.

I haven't tried castings in the new 22-250 barrel yet, and won't be trying them in the gas guns. My principal objection to the javelin-hurling in the 223s is the price of the bullets, which is obscene. I will put up with 55 grain BalTip and 60 grain Sierra HP tariffs without much grousing, but even the 65 GK and 69 MK are pretty decadent. A lot of money to spend on whacking rats, but sometimes it is fun to see a Mini-14 shoot so well. My guilty pleasures.
 

Ian

Well-Known Member
A post ripped from one of my other threads here. Mossberg MVP varmint 5.56x45 with the factory throat cut halfway to the muzzle, suppressed, NOE MX3, powder coated and gas checked, no lube, 100 yards. I might note that this rifle averages 1.5-2 MOA with jacketed handloads.

More shooting today, this time with nose-sized, powder-coated, gas-checked, water-quenched WW, aged MX3 bullets seated to touch the throat. Won't go in the magazine but at the moment that doesn't concern me.

First go was with 21.6 IMR 3031, seated long (jam minus ~.015") the velocity dropped to 2676 fps.
Then I seated a little longer, to actually form a light jam in the throat. Lost another 16 fps and it didn't group any better.
Then I switched to H335 to push the velocity up a little and see what happened, still jamming the throat lightly. Started in at the mid 27s and pushed on up to 2845 @ 23.5 grains.

View attachment 7026

Seeing the little .100" cluster of four at the center of the group got me going, so I put in one click to the right and one click down, then added another half grain of powder (book max for a 68 grain bullet by the way) and got this 1-1/4" group, at 2908 fps:

View attachment 7027

It seems like the more pressure and velocity I add, the fewer the flyers. I'll keep shooting this load for a while and see if it holds up.

Closing in on MOA at over 232,000 rpm...with wheelweight alloy.
 

BHuij

Active Member
That looks great - 1.25 MOA at 2900+ FPS would make me extremely happy as an end goal. I remember spending a bunch of time reading this thread - is this your Mossberg that you had to disassemble and re-do all the bedding?

The MX3 looks like a terrific design. Are you using the 57gr or the 67gr version? Lots of bearing surface, sort squat nose, and just enough taper on the front couple of driving bands to allow for a pretty good seating depth without having to cram 85% of the bullet into the neck of the case, seems to be the ticket here.
 

Ian

Well-Known Member
67 grain version, comes out 68-ish grains fully dressed with check and coating. Rifle has a one turn in 9" ROT. I warn you that the mould I got was not cut to specification and suspect none of them are. The very front nose "band" and the second band are both .222" instead of the front one being .218". This will seat ridiculously deep in most rifles. My fix was to fashion a two-diameter reamer with transition angle to match the rifle's throat and then ream a nose-first sizing die for my Lyman 45 to correct the fit issue.
 

BHuij

Active Member
Good to know.

Well my original question here of how heavy I can get away with has been answered here. Once the rifle arrives, it will be working up a load with 68 Hornady HPBTs or 69 SMKs (whichever the rifle likes more), then working up a LV load with my existing Lee 55gr mold, and finally getting an NOE mold to see how far I can get out past 100 yards with HV lead.
 

Ian

Well-Known Member
Flat-base bullets need less twist and need less yardage past the muzzle to yaw-damp effectively. You may begin to have issues @ 69 grains with a BT, although plenty of people are doing fine with them at full power. Only way to know is to try them out.