Any way to realistically predict "maximum" velocity for cast .223?

[BHuij]

I've done a few hours of reading on this forum about this topic, and seen mention of people pushing cast .223 boolits up to ridiculous velocities like 3000+ FPS.

I'm currently gearing up to build my first AR, chambered in 5.56, and want to standardize around 55gr boolits for plinking in the 100-200 yard range.

Elsewhere I've been told that if I use a 1:8 twist barrel, I'll be limited to about 1500 fps with a cast boolit (even gas checked and powder coated); if I go any faster, my boolit will vaporize a few feet past the end of the muzzle because it's spinning too fast. I don't want to go to a 1:9 or 1:12 barrel, but if this is true, it's kinda disheartening. I liked the 1:8 specifically because it's supposed to represent a good compromise between shooting 55gr projectiles and still having the option to go heavier for longer range applications if desired.

Anyone successfully pushing GC'd PC'd 55gr boolits faster than 1500 FPS in a 1:8 barrel? I'm leaning towards 16" right now.

[9.3X62AL]

No experience here with cast bullets in 223 gas guns (yet). 2 of my gas 223s are 1-9" twist, 1 is 1-8". I'll sum up what I've learned so far, which is not extensive. I should also add that I am not painting/coating/powdering my castings--I size and lube with LLS' Carnuaba Red.

My 223 work to date has been done in a Ruger 77RL with 16.5" barrel and 1-9" twist. Bullets tried so far have been a Lyman #225438 (42 grain RN)--RCBS 22-55-SP (57 grain spitzer-like) and NEI 72 grain RN. All used Hornady gas checks, and all were cast in 92/6/2 alloy.

#225438--accuracy held to 1700 FPS using Alliant 2400 powder, and a little past 1800 FPS using H-4198. Any faster, and they started blowing into patterns instead of groups. As an aside, this bullet has done STELLAR work for me to 2400 FPS in 22 Hornet cast in Linotype, 1.5"-class groups at 100 yards.

22-55-SP--similar "speed limits" with this bullet, maybe 50-75 FPS faster before things went sideways. This bullet from 1600-1700 FPS was VERY accurate in my rifle, using both fuels. LOTS of fun! I loaded and shot a bunch of these, and they tipped over some jackrabbits from time to time. I still have about 150 of these in the ammo locker.

NEI 72 RN--Fuggetaboutit. These would not shoot worth (insert serial cuss words {HERE}) 1200 to 1800 FPS, they tumbled at 25 yards. On quiet range days, their WHIRRING sound as they tumbled downrange was entertaining, in an aggravating sort of way.

Notes.......I have a bit of experience with 1-8" twist rates and cast bullets, in a 25/35 WCF. I used an NEI 114 grain flatnose gascheck design, that rifle was VERY accurate--until you exceeded 1600 FPS. Faster than that, and groups opened up dramatically. Bullets didn't tumble, but they did get "poetic" to say the least. There seems to be a cast bullet "speed limit" that kicks in with twist rates faster than the old 30 caliber "standard" of 1-10". I accept those limits, and accept that jacketed bullets may be a better/easier option for my gas guns. I really wanted that 72 grain bullet to stabilize in the 1-9", but it didn't happen. The coatings and sprayings being applied to cast bullets may enable castings to work better in fast twists than conventional "poured & greased" rounds. That is outside my experience, though. Dunno. HTH.

[BHuij]

Thanks for the info. If you're getting 1700 FPS out of a 47gr boolit in a 1:8, then it sounds like 1500 "hard cap" in a 1:8 barrel is a fairly conservative guesstimate for 55gr boolits. I'd be happy with 1700 FPS if it was accurate at 100-200 yards, I also suspect that powder coating would possibly help a boolit stay together at high RPMs (certainly couldn't make anything worse, right?)

[JonB_in_Glencoe]

BHuij,
welcome to the forum.

Since you didn't mention it? ...I'm gonna have to assume you are new to casting? or at least new to casting for rifle?
Loading cast boolits for Rifle is kind of advanced, in comparison to loading cast boolits for pistol.
There is lots more to it than the question you ask.

First a quick answer.
A boolit will not vaporize a few feet past the end of the muzzle because it's spinning too fast, if you are pushing it a little faster than 1500 fps (even gas checked and powder coated).

If you read a good manual, like the Lyman cast bullet handbook 4th ed. and you load some 223/556 with a 55 gr boolit to the recommended loads, in the range of 1800fps to 2100fps, which could be in the range of 18Kpsi to 24Kpsi, then you will have the best chance at achieving satisfactory accuracy. You can speed things up, but you probably have to do a few things differently, like using slower powder with longer pressure curves and a harder alloy, heat treating a softer alloy is one way to get there. another stumbling block to high velocity in a AR, is the required "jump".

[JonB_in_Glencoe]

Oh, and speaking of AR, you also need to have enough pressure to cycle the action. My lighter loads going less than 1800fps do not cycle the action of my AR reliably.


Here is a thread that might help you out. My post #44 was the results of my first attempts to get the action to cycle.
http://castboolits.gunloads.com/showthread.php?302707-223-AR-load-data-help

[9.3X62AL]

Thanks for the info. If you're getting 1700 FPS out of a 47gr boolit in a 1:8, then it sounds like 1500 "hard cap" in a 1:8 barrel is a fairly conservative guesstimate for 55gr boolits. I'd be happy with 1700 FPS if it was accurate at 100-200 yards, I also suspect that powder coating would possibly help a boolit stay together at high RPMs (certainly couldn't make anything worse, right?)

1800 FPS/57 grain bullet/1:9" twist.

I have yet to see a cast bullet "fly apart" or "disintegrate" due to rotational or lateral speed--at some point, they just get inaccurate, and that isn't always a gradual progression--in fact, it is fairly abrupt. Now, jacketed bullets--I HAVE seen those "blue-streak" downrange, believed to be leakage of core-metal (lead alloy) through jacket fissures created by rifling impressions in less-than adequate jacket metal. Some varmint bullets have a "speed limit" listed by their makers (often 3400 FPS) because their light, frangible jackets will disintegrate at the high RPMs achieved by fast twists and uber-velocity. NO, I WILL NOT start another RPM thread here. Life is too short for that drag sequence.

One tendency I noted......slower-burning 4198 gave accuarcy up to a bit higher velocity than did the faster 2400. FWIW.

[sqlbullet]

Bhuij,

Glad you found your way here. I have been away too long myself, as is evidenced by what we are both learning on this thread.

For those catching up, I was the yahoo that indicated a gray poof may be the result if you pushed a 55 grain cast bullet to 2800+ fps, and that 1500 fps in a 1:8 twist would likely be a limit. Re-reading my post at reddit, I can see the two comments appear to be directly linked, though that is not how I intended them. Accuracy will decline sharply at some point, and if you start out shooting lead at a 10% reduction from your max j-word load, bullets can disintegrate. Gotta spend more time on post editing.[smilie=1:

Here is a good primer thread on RPM limits:

http://castboolits.gunloads.com/archive/index.php/t-25226.html

I am very interested to hear that alloys with copper in small amounts hold up well to faster velocities.

OP, I am also in Utah. If you wanna try out some heavier bullets, or look over some AR builds as you start out, let me know. I live in the Salt Lake Valley on the east side.

[BHuij]

Sure enough, username checks out ;)

Thanks all for your input, and my apologies for misreading your Reddit comment.

I should perhaps provide some context about both myself/my casting history and my goals with this future AR build.

I've been casting and reloading for only a few months, with lots of success in 9mm, but that's it. And that's currently the only gun I own. I'm planning on building this AR but would like to entirely avoid jacketed bullets and shoot 100% home cast, primarily for the cost savings. I can get used lead wheel weights for free from a contact in the auto industry, so if I make my own gas checks from ACE aluminum flashing, I'm sitting right in the neighborhood of $0.01 a bullet. Add in powder, primer, and brass costs and I'm shooting .223 for something like $0.12/trigger pull or so, which feels sustainable to me :D

So I'm actually fairly well-read in the theory behind selecting proper alloy for pressure/velocity, the importance of sizing correctly, lubrication options, etc. etc. I understand that rifle casting is a whole new ball game vs 9mm, which is why I'm here talking to the experts in the first place :D

My goal with this AR is more accuracy than velocity. As long as I'm getting a hefty enough load behind my 55gr boolit to reliably cycle the rifle, I don't really care how low my velocity is if it's accurate to 200 yards. It seems like this isn't terribly difficult to achieve with a 55gr boolit, gas check, and powder coat, and I can probably expect to land somewhere in the 1700-1800fps range when I dial in on my accuracy node, assuming a 1:8 barrel. Does this seem about right to anyone with real-world experience?

[Larry Gibson]

It would take 2800 + fps for a softer alloyed bullet to disintegrate in flight with a 9" or faster twist. This happens all the time in faster twist ARs with thin jacketed varmint bullets such as the Sierra Blitz (not the Blitz Kings), the Hornady SXs and Speer's 52 gr HP.

With an 8" twist using a 55 - 65 gr cast bullet that you cast extremely well, heat treat, PC and load correctly should function the action and provide useable accuracy to 200 yards.....probably not match winning accuracy though. Unless you are willing to dedicate funds for equipment, time to learn and develop the ability to cast quality bullets you might consider just buying bulk jacketed 55 gr FMJBTs for plinking and practice and match quality jacketed bullets for matches.

[popper]

Why do you want to shoot cast in 223? Why do you want a 223? It was designed for light fast jacketed (restricted for hunting in many places). Jacketed ammo is cheap and available. Yes you can but are the results what you want? Bater mould seems to be the best so far. You could go with 40WT or 300AAC and get good results easily. 30 cal and many mould options. Good fps with heavier boolits.

[sqlbullet]

You didn't mis-read my Reddit post. I wrote it poorly and definitely inferred something I didn't mean. I added a word at Reddit to clarify.

I think your goals are very reachable. The more care you take in prep steps, the better your results will be.

I have some alloy around here that has some copper and makes really hard bullets. Glad to spot you some to try out if you want. I can also spot you some 80 grain bullets to try out if you want. This mold:

http://noebulletmolds.com/NV/images/N.O.E._Bullet_Moulds_227-80-SP_(GC)_Sketch.Jpg

Let me know if you wanna meet up and grab 10 lbs or so of copper enriched alloy.

[BHuij]

That's super generous of you. I may take you up on that. Did you alloy it yourself by adding some copper source into lead, or source it somewhere? Because if it works really well, I'm going to want to reproduce it haha. TBH this AR plan is a ways down the road, but when I finally do build it I'll be sure to come talk to you when developing the right boolit and load for myself. Thanks all!

[9.3X62AL]

The 9mm success you have had bodes well for your transition to rifle-oriented cast bullet shooting. The 9mm shares a lot of the rifle's tricky attributes as far as cast bullets are concerned--high pressures and fast twist rates being chief among those. You are more than half-way there, if you can make a 9mm behave itself with castings.

That NOE bullet wants 1-7.9" twist for stability @ 1700 FPS; 1-8.4" @1900 FPS. Google "Barrel Twist Calculator" for a handy online Greenhill Formula short-cut.

[runfiverun]

Allen why didn't you just ask Dawn what she was shooting in her AR at the NVCBS.
you chased enough of her brass.

[sqlbullet]

I made the alloy myself and it was a huge pain in the....neck!

I started by grinding down some copper wire into a dust that I hope would dissolve in the melt. Some minuscule amount may have, but no where near the measurable fraction of a percent I wanted.

So, I went a different route. I used my big cast iron 4# ladle and melted down four ounces of copper with a MAPP torch. I then added a pound of tin, and to that a pound of isotope lead. The whole mass was then added to a 750° pot of about 75-80 lbs of isotope lead.

This should result in something around 3% antimony, 2.25% tin and 0.3% copper, with the balance being lead. The alloy is quite hard when air cooled, but a good bit more malleable than the antimony number and it's hardness would indicated.

Shortly after I made up this batch several years ago a remodel project started on my home. This fall the detached garage/last phase of that project will complete. I will then have a shop again and I plan to make a small DIY foundry, which I would make this process a good bit easier. At that point I will probably alloy up a number of 1% copper one lb ingots that I can add to isotope at a 7:3 ratio for a .3% mix.

Definitely PM me when you are ready to tackle this.

[KrakenFan69]

That NOE bullet wants 1-7.9" twist for stability @ 1700 FPS; 1-8.4" @1900 FPS. Google "Barrel Twist Calculator" for a handy online Greenhill Formula short-cut.

Any ideas for what to do for the Twist calculation when you have no idea of the BC? I'm trying to shoot Hi-Tek Coated in a 1 in 7 twist 225-61 Elvis form Arsenal and they don't list a BC. I'm getting decent accuracy form them (good enough for a 3 gun match 2 weeks ago but we only went out to around 75 yards) Wanting to push them a bit harder than the 19.4gn of CFE223 I'm currently using.


Kraken Fan #69

[sqlbullet]

http://kwk.us/twist.html

This just needs bullet length, diameter and velocity.

More information means a more accurate prediction, but if you don't have the more information this gives you a pretty good idea.

[9.3X62AL]

Allen why didn't you just ask Dawn what she was shooting in her AR at the NVCBS.
you chased enough of her brass.

Ack!! I didn't know those were castings. I'll be darned.

Castings in gas guns really aren't on my radar. They definitely weren't at NCBS. If I can get them to behave in bolt guns, maybe I will advance to self-loaders.

[Boolseye]

Early in my trials with cast bullets and the AR platform, I was achieving 2700 ft./s with respectable accuracy and no leading. This was using the NOE 225–55 RCBS clone. I saw no need to shoot them that fast and now shoot around 1800 ft./s, but higher velocity is easily attainable. These were not ridiculously hard bullets, coww, water quenched. This was, however, 1/9 twist. I’m confident I’m within Larry’s RPM threshold with my current loads, probably not so much with the early attempts.

[Larry Gibson]

"Any way to realistically predict "maximum" velocity for cast .223? "

If you're talking using a ternary alloyed regular lubed cast bullet and you want "useable accuracy" (3 - 4 moa) beyond 100 yards then don't exceed 140,000 - 150,000 RPM.

[9.3X62AL]

"Any way to realistically predict "maximum" velocity for cast .223? "

If you're talking using a ternary alloyed regular lubed cast bullet and you want "useable accuracy" (3 - 4 moa) beyond 100 yards then don't exceed 140,000 - 150,000 RPM.

You "went there". Ruh roh, Reorge.

[Larry Gibson]

Just the facts mam.....just the facts........

[sqlbullet]

Technically, I think I went there when I told the OP that on another forum, sent him here and referred him to Mr. Gibson's excelllent writings on the subject.

Larry lives there.:grin:

[Bama]

You can usually run faster without coming apart by adding copper. There are a number of threads on the subject on this site.