Maximum velocity with lead boolits?

[archangel2003]

The basic question?

1: What is the maximum velocity a lead boolit of reasonable hardness can take before it starts stripping the rifling off the boolit or begins leading the barrel?
I have read somewhere that 1800 fps is supposed to be the maximum no matter what, however a harder boolit will be stronger so there is that.

2: How much difference does adding a gas check make to preventing leading the barrel at increasing velocities?
Or I should say, can we get copper jacket velocities with harder lead and gas checks?

3: Does Powder Coating the boolits make a difference to prevent leading?
I have read where those who powder coat seem to get Full Metal Jacket velocities and similar performance out of powder coating hard lead projectiles.

[Winger Ed.]

Powder coating does let you get more speed before Leading gets to be a problem.

With the right alloys, barrel lengths, lube/powder coat, powders, gas check, etc. you can get cast on up into the lower 2,000s.

Plain base, soft alloy stuff seems to do well for me in the lower teens for speed.
Without a decent lube, proper boolit to barrel fit, nice smooth bore, you can get heavy Leading even below 1,000 fps.

[Bigslug]

I do not paint my bullets, so I can't give you any guidance there.

One of the functions of a gas check is that it serves as a "driving key" to lock the bullet into the lands and prevent what you might call "torque-widening" itself out of a tight fit. That's prrrrrrobably where a lot of gas blowby comes from.

Thus far for me, the low 2,000's is where it typically seems to come apart, and that's with checks, harder alloys, and good lubes. That threshold lets you duplicate the pre-spitzer, jacketed round nose ballistics of the early smokeless era - - roughly 200 grains around 2,000-2,100 fps. Beyond there is where I leave the map and only find dragons. I look forward to seeing replies of the folks who's Kung Fu is stronger.

The velocity game with bullets was a little like it was with airplanes; the copper jacket was effectively what traded in the propeller for the jet engine and got us to where we can reliably fly through Mach 1.

[Silvercreek Farmer]

https://castboolits.gunloads.com/sho...-XCB-600-yards

[Larry Gibson]

archangel

1: What is the maximum velocity a lead boolit of reasonable hardness can take before it starts stripping the rifling off the boolit or begins leading the barrel?
I have read somewhere that 1800 fps is supposed to be the maximum no matter what, however a harder boolit will be stronger so there is that.

Cast bullets, for the most part, do not "strip in the rifling" at higher velocity. That is a myth from days of yester yore when the "experts" didn't understand what was really happening. There is an RPM threshold for lubed cast bullets falling in the range of 120 to 140,000 RPM. Above that and accuracy is lost not to the bullets stripping in the rifling but due to the adverse effects of centrifugal force. With 10" twist rifles barrels that threshold falls between around 1580 fps to 1940 fps. The best accuracy will almost always fall within that range of velocity given a 10" twist.

Also what is "accuracy"? many find usable or what is thought to be good accuracy at 50 yards with loads that are above the RPM threshold. Some even find usable accuracy at 100 yards with such higher velocity loads. However, if they shoot those loads at longer range they will find the group expansion to not be linear in nature and may be down right discouraging. Thus how much velocity depends.

Keep in mind the RPM threshold is not a "limit", given a specific barrel twist, as it can be moved a bit up in velocity as it can be moved down in velocity. All depends on the care in casting, the right alloys and other componants and the powders used.

In shallow grooved barrels, usually less than .003" deep grooves, the bullet can slip over the rifling. We have found through thorough testing that a lubed cast bullet will not come out of a .308 (for example) groove diameter barrel at .308". As it must ride on a layer of lube it will come out .003 or more less in diameter. Thus if the bullet is sized down more than bore diameter it will slide over the rifling and probably not stabilized. However, it does not "strip" on the rifling.

FYI; I shoot a 30 cal bullet (the NOE XCB) at 2900 fps with moa accuracy out to 600 yards. The velocity is 2900 fps with the #2 alloyed cast bullet. The rifle barrel is 31" long with a 16" twist.


2: How much difference does adding a gas check make to preventing leading the barrel at increasing velocities?

All the difference in the world.

Or I should say, can we get copper jacket velocities with harder lead and copper jackets?

With some cartridges cast bullets can equal jacketed bullets in velocities. The 30 carbine, 30-30 and 45-70 are excellent examples. However, in cartridges such as the 223, 308W, 30-06, etc. the answer is no, not if you want any accuracy at any reasonable range.

3: Does Powder Coating the boolits make a difference to prevent leading?

Yes it does if it the PC is done right with the right alloy.

I have read where those who powder coat seem to get Full Metal Jacket velocities and similar performance out of powder coating hard lead projectiles.

Some do indeed say that.

[Bird]

Using bens red lube and gas checks and 0.0005'' to 0.002'' over size water dropped ww boolits, I get 2300fps in a 10'' twist 30-30, and 2150fps in a 22'' twist 45-70. No leading, and accuracy in the 45-70 is as good as factory ammo, and close in the 30-30.

[lar45]

I have a 14 twist 30-06XCB, I get great accuracy around 2500fps with either Carnauba Blue or 2500+, but have pushed it to 2800. I'll need a slower twist to go faster. My lubes have been pushed past 3000fps and left a clean barrel.

Mauser 98 with 14 twist Krieger barrel built by MBT Custom.

[Larry Gibson]

lar45

[P Flados]

I have read where those who powder coat seem to get Full Metal Jacket velocities and similar performance out of powder coating hard lead projectiles.

Getting full power FMJ performance from powder coated 9mm or 45acp is no big deal.

I have never heard of folks getting this level of performance from most of the other rounds normally associated with FMJ (223/5.56, 308/7.62x51, 30-06).

The 7.62x39 can probably achieve "full power" but it may require special techniques.

Look up Larry Gibson's XCB efforts to get a clue on what this may involve.

[dverna]

Note:

The guys who have pushed over 2300 fps are not using factory barrels. Some people poo-poo the effect of twist rate....I am not one of them.

[waksupi]

Note:

The guys who have pushed over 2300 fps are not using factory barrels. Some people poo-poo the effect of twist rate....I am not one of them.

I've ran an average of 2450 fps with a Schmidt Rubin, 2650 fps with a factory Remington .223. Both in the inch and a half range for groups size.

[ShooterAZ]

There are many variables, such as barrel twist rate, type of lube used, and on and on. When I want maximum velocity with usable hunting accuracy, I have gone to smokeless paper patching. It's still a cast boolit right? Or is it cheating?

[Winger Ed.]

It's still a cast boolit right? Or is it cheating?

Good question.

We need to apply for a big govt. grant to study this further.

[imashooter2]

How fast will a bicycle go?

Depends who’s riding it.

[Bad Ass Wallace]

I have my "cast boolit rifles" set aside from my normal hunting ones for one prime reason, having shot many thousands of cast rounds the barrels are pristine and highly polished. I started with powder coat about 3 years ago and tested many different combinations.

These rifles are never used with "J" boolits. Each rifle is a rule unto itself, my Browning 223 (1 in 12" twist) will shoot 55gn PC to 2700fps then accuracy dissapears. My 270 Savage thrives on PC bullets, the smaller case will push 130gn PC to 2,700 without leading and that is after approx 800 rounds.




My 30.06 s not a HV bench gun but has fired over 3000 cast rounds, shoots exceptonally well but only to 1800fps wth the Lyman 311284 boolit.

[Wolfdog91]

Been talking to some bench rest guys and some of them are pushing cast out to 2700fps regularly but their pure lino and the guns are scustom built for the purpose. Think it all depends on the gun and bullet though. For instance Ive been running PC'ed Lee .225's with a gas check out of my 5.56 are and my .223 H&R and either way they just plain Don't go well past 2180fps. I've mapped my shots of target in relation with my Chrono anything in 2180 fps they group decent. The minute they get out side of that their flying out

[charlie b]

I also had the urge to push velocity in my 10" twist .308. Both lubed and powder coated.

Using 180gn Lee bullets with conventional lube I found accuracy started to suffer at around 2100fps. Best was in the 1700-1800fps range.

I powder coat all of them now. The most accurate loads I have found in it have been between 1900 and 2000fps. That is good for just over MOA on a regular basis with many groups being below MOA. When I have gone up to 2300 and 2400fps the groups begin to open up to 2MOA. For many hunters that is satisfactory. FWIW, my favorite bullet is a 210gn. ~2400fps is considered to be max vel for 210gn jacketed.

I do believe powder coating helps on the upper end. I am also a believer in the 'rpm limit' that Larry refers to. We did some research back in the 1980's and found that there was an RPM where the bullets would start to go 'unstable'. It varied between bullet and rifle, ie, one bullet might do ok in one rifle but not another (same twist). It was explored a lot by the bench rest guys back in those days.

There were a lot of theories about why it happens, from strength of the lead alloy, to inclusions in the casts, to aerodynamic issues. I do not know of anyone who has proved what it is.

PS even with PC a gas check is necessary for good accuracy at these velocities, at least in my experiences.

[centershot]

There are many variables, such as barrel twist rate, type of lube used, and on and on. When I want maximum velocity with usable hunting accuracy, I have gone to smokeless paper patching. It's still a cast boolit right? Or is it cheating?

It's still a cast boolit in the same sense that a PC'd boolit is.

[ShooterAZ]

It's still a cast boolit in the same sense that a PC'd boolit is.

That's my way of thinking too, except that I can approach factory velocities with good accuracy. Not only that, it's fun to do. It took me a while to get things dialed in, but once I did it was off to the races. It gives a resounding thump when it hits a deer.

[Larry Gibson]

Been talking to some bench rest guys and some of them are pushing cast out to 2700fps regularly but their pure lino and the guns are scustom built for the purpose. Think it all depends on the gun and bullet though. .........

Probably 30 BR guns with 16 to 18" twists in them. The gun (meaning the twist rate of the barrel) and the bullet [because some cast bullet designs are more conducive to accuracy at HV] definitely have something to do with it.......