Long range, HV cast - high BC designs vs better nose/throat fit

[BHuij]

I've been having a lot of fun with Hornady 68gr BTHPs in my TC Compass chambered in .223. Easily the most accurate rifle I've ever owned, it makes sub MOA easy.

Since I'm apparently a glutton for punishment, I really want to do a HV cast load for long range shooting. The Hornady bullets are about $0.20 each if I buy in bulk, and that adds up quickly. For shooting long range (which for .223 means upwards of 300 yards for me personally), obviously I would want to maximize ballistic coefficient to keep trajectory as flat as possible. Unfortunately, the normal bullet designs you use to increase BC with jacketed bullets (boat tails and spire points) don't work with HV cast, because boat tails preclude a gas check and spire points give you a lot of unsupported nose to slump or tilt upon launch.

Upon reading through Ian's Article #4 again, it seems like I'd be better off with a round nose design bullet, which represents a compromise between a non-aerodynamic flat nose, and a really skinny unsupported nose on a spire point/spitzer type bullet.

I realize that final bullet design is going to rely heavily on my individual chamber dimensions, but as a starting point, what do you guys think of the NOE 225-70-RN-B1? I like the 227-79-SP-B5 better (BC is like twice as high, and it's significantly heavier without being too long for my 1-9 twist to stabilize properly), but I worry that the nose would be completely unworkable at high velocity.

 

[Ian]

What makes you think spire point noses slump or bend?

I think you need to do more shooting and less pontificating because you make a lot of decisions based on suppositions which may or may not actually be true for you.

 

[BHuij]

If I could do more shooting and less researching, I would. Unfortunately I don't have as much time for shooting as I would like, but it's pretty easy to find 5-10 minute sections of time where I can read some articles on my phone. But I assure you given the choice between shooting or reading about shooting, I'd take the 1st option 99% of the time

To answer your question, what makes me think spire point noses slump or bend, it's this quote from your article #4. Let me know if I'm misinterpreting here.

If the bullet's nose doesn't match the throat, has large, unsupported steps between the bore-diameter portion and larger driving bands behind, the nose can "wad up", bend, slump, or get pointed crooked as the engraving process is taking place

 

[Ian]

Yeah, one or both of us doesn't understand the other. I specifically referenced the point the nose is at bore diameter and back, not the tip. I understood you to be referring to flat nose, round nose, and spire point designs as they are particularly shaped forward of the place that they would ever come into contact with the barrel.

Two-diameter bullets at high velocity in a barrel with a distinctly tapered throat is, for lack of better way to express it tactfully.... a really bad idea. I was very much trying to address bullet fit ( both static and dynamic) in my articles, you missed it some how. Also, if I remember right you bought Veral's book as well? If you did the answer is in there too, a little different but same concept of supporting the bullet.

 

[fiver]

my 2 fastest bullets.

 

[Brad]

Fast? Look to be standing still.

Idaho must have a weird idea of fast.

 

[waco]

Idaho must have a weird idea of fast.

It's the gravitational pull of the Pacific Northwest...

 

[Intheshop]

223 and 55g Lee @2800-2900fps with H4198 approaching mid way up JB load tables. It still has a touch of vertical on groups @100,150. Practically zero horizontal. IF,what Tony Boyer (hall of fame BR) serves up as a slight competitive "tip",in his book,is taken as a truth...... a bit of vertical helps in the wind. But this is from a competition viewpoint..... my rig is for <200 yd,cold bore X's in the hunting fields.

But wind is important to hunting X's just like BR. Obvious difference is no "formal" wind flags and certainly no "sighter" rounds. I won't even attempt to explain his supposition.... My loading is "clean" enough however that dialing in/out a bit of vertical is easy enough to do.

I will say though,swaging,with further....uniforming base to ogive is also,easy enough to do on the 224's that you can test bullet shapes almost,at will.

 

[462]

Fiver posted pictures!

 

[BHuij]

Well hey, glad I asked if I was misunderstanding.

Fiver, that picture on the left looks suspiciously like the Lee 55gr FN, or whatever bullet it was based off of (can't remember if that design was originally an RCBS or Lyman or something).

Looking at the 227-79-SP-B5, only the driving bands are .227" the area of the bullet forward of that is specced at .219. Would that make it difficult or impossible to achieve good fit? I realize the exact answer to that depends on my specific chamber, but since .223 bore diameter is supposed to be .219, this appears to be a bore rider design, aka not a good idea for HV.

Is there a heavier cast .22 cal mold (somewhere in the 70-80gr range) that both avoids design weaknesses rendering it unsuitable for HV, and has a reasonably high ballistic coefficient (above 3.0?) Or is long range cast .22 just doomed to deal with rainbow trajectories? The 68gr Hornady bullet gives me about 14 inches of drop at 300 yards and 31 inches at 400. The NOE 225-67-FN-A5 (the M3X that Ian has used in some threads here) gives 19 inches of drop at 300 and 46 inches at 400.

 

[Ian]

19" of drop at 300 yards is 6 MOA. You're gonna be spinning the dial anyway.....what's a few more clicks?

Intheshop might find if he recovered a bullet that it is no longer a bore- ride shape after kicking it in the pants with 4198. Transforming the bullet shape as it engraves is a little trick that can work really well or really poorly depending on how well you pull it off, and he is pulling it off. The Lee 55 also has a very short bore ride section so it is less of a disadvantage than a silhouette design.

 

[BHuij]

Ah, is this the trick you mentioned in the article but didn't elaborate on? Seems like black magic indeed. So... are we talking loading a faster powder that ratchets the pressure up at just the right moment that the bullet obturates to permanently fill the grooves instead of attempting to ride the bore? 4198 falls between 4227 and 4895 in burn speed, and it's closer to 4227 than it is to 4895 unless I'm mistaken.

 

[Intheshop]

Well now,that is NOT the pic I posted above.... so,either a moderator changed it or something?The pic was a shot of an "engraved",zero runout,ready to shoot,loaded round.I will leave the text....

Done with this thread.

Good luck with your project.

 

[Rick]

Hhmmm . . . No one changed your picture, I do see a picture of a loaded round. We have in the past had a software issue where others photos gets swapped around including avatars. Hope that's not happening again. Quite frustrating but refreshing the page usually straightens it out. I shall ask Kevin to look into it.

 

[Spindrift]

@fiver, would you care to elaborate which bullet it is, the one with the blue lube?

@BHuij, nice to hear your rifle is working out for you!
I am by no means an expert, having just started load development with PC bullets in the. 223. But I think your primary concern should be about accuracy. The benefit of high Bc would be meningless without accuracy. The heavier of the NOE bullets has a good BC, but also limited bearing surface, and I guess not the best candidate for accuracy at high velocities. I would just start with whatever mold I had (in my case, a Lee 2-cavity)

 

[Ian]

On the photo swap, it's happened quite a few times and caused a great deal of confusion, particularly due to which photos get mis-displayed when it happens. It happened to me yesterday on another thread but refreshing the page fixed it.

 

[fiver]

I have seen the photo change before too but it generally fixed itself with a refresh.

the one on the left is the RCBS 22-055s and the big one is the XCB bullet from NOE.

as far as dimensions go on the other bullet BHUIJ mentions the 219 on the nose and 227 diameter is exactly the diameters I specified for the HM-2 hybrid of the rcbs and the saeco 60 bullet.
you need that 219 to take the rifling head on [almost just like Elmer described how his 429241 bullet works in a revolver] it's a guide.
227 is just about maximum for scuffing up the ball seat area in a 22 cal rifle, sizing down to 226 just gives you some latitude [powder coating up to @229 gives you more] moving forward where that nose can start taking up the rifling and your not going sideways too terribly bad on the back end yet.

check that thread that points out what happens when the primer pops off, I think you'll see why I run a pretty light neck tension in my 22[err 5.56] rifles.
and why I run mostly a jam fit on my 308 type rifles.

start putting some of these steps together and you'll also see why these types of designs work best with a harder alloy [one that's usually a bit slicker] and a pattern will emerge.
a pattern of movement and stress and one of when in time a bullet is.

I also think if you look at the picture Ian put up in the case cleaning thread and compare it to the picture I never posted of my 223 cases you'll see they look pretty much the same.
thee is a reason why they are so dirty, yep it's cause they ain't sealing the gas off.
think about why they ain't so efficient and put it in relationship with that whole when the bullet is thing.

 

[BHuij]

So the part of the bullet that is .219" serves as a pilot as the bullet begins moving into the rifling, helping it stay straight and concentric with the bore as engraving takes place on the bearing surface? That make sense, it just seems like you would want to use a slow powder to delay peak pressure until after most or all of the .227" part of the bullet was into the rifling, or you'd have a high likelihood of ruining the base and something going sideways.

The question now I guess becomes what @Spindrift brought up, which is whether that design has enough bearing surface to support the bullet and keep it straight as it travels down the bore.

Fiver, do you have a link to the thread you're referencing? Correct me if I'm wrong, here, but the light neck tension you run in your .22s would help the bullet get out of the case and into the rifling sooner and at lower pressures, correct? Meaning pressure doesn't peak, expanding the case against the chamber, until after plenty of gas has gotten back around and made for some dirty cases.

Unless I'm way off the mark (entirely possible), it sounds like the name of the game is getting as good of a fit as possible in the throat, and piloting the bullet into the rifling at the lowest pressure you can get away with. In other words, you still need a good pressure peak for a uniform burn, but a slower powder will delay that peak until the bullet base is engraved and relatively "safe" from harmful deformations? That all makes sense to me conceptually, but I still couldn't confidently tell you if that NOE 79gr bullet would do the job haha.

 

[Ian]

Land tops piloting the nose to center sounds great but it don't really work that way with narrow lands.

It takes whatever pressure it takes to get a bullet of given shape and alloy shoved fully into the rifled part of the barrel. You can manipulate things to change the when and how much of that pressure is required, but the powder must exert that much pressure plus some of the bullet is to move. Even a primer in a case 3/4 full of corn meal will move a bullet at least mostly into the throat, but any combined system of powder/cartridge/bullet/bullet alloy/rifle has powder choices which exceed the necessary engraving pressure RATE and rivet the bullet base, and those that do not. It's all a matter of timing and what you want (or need) to do to get that bullet launched straight. My analogy is hitting a thrown baseball with a bat, a 3" ball bearing, or a tomato. Which will respond better?

 

[BHuij]

Conceptually I understand that spiking the pressure too soon (with using too fast a powder being the easiest way to commit this error) will rivet the base and ruin accuracy. Having too much neck tension would also contribute to an early pressure spike, which explains Fiver's practice of using light neck tension.

The obvious answer here is to use a slower burning powder, yes? The only pitfall I'm aware of with using slower powder is getting an inconsistent burn from too light a load or too short a barrel, leading to vertical stringing. I have 22" of barrel to work with, so I would think I have room to use a slow enough powder. Other than these limitations, what disadvantages are there to just going with the slowest burning powder I can get my hands on? Something in the RL22 range, for example.

Where I'm struggling to apply general theory to my own situation is still fit. Fiver is telling me he helped design a bullet with a .227" base and a .219" nose section, as the bore-diameter nose was intended to guide the bullet into the rifling while the base fills the throat. At the same time, everything else I've ever read about bore riding bullets and HV tells me that it doesn't work that way. Is a bore diameter section of bullet only a problem if it is dangling in the throat? Seems like having anything at or below bore diameter would not matter, as long as the throat is filled and the >=.219" section is only protruding into the rifled part of the barrel.

I'm all for learning the fundamentals here, but I also just want to know if the 79gr NOE bullet in question is likely to be a good candidate for HV shooting so I can either buy it or not