Need some help from "Bullet Math" guys

[JWFilips]

Hi Folks,
I'm shooting a .223 Rem in a Remington Sportsman 78. It is a super shooting rifle with cast but I found a bullet that perplexes me: It is a plain base NOE FN 55 grain which drops at 61.5 grains Plain base.
The 78 has a twist of 1 in 12....by doing the math does anyone know how slow I can shoot this bullet?
I can shoot the 62.5 Gas Checked version pretty well at 1900-2000 fps with 10 gr of 2400. Just can't seem to figure out were to start loading for a plain base version. Any loads I have tried in the 1600 to 1800 range turn into shotgun patterns with leading of the bore on a BHN 22 alloy
Jim

 

[quicksylver]

Hey Jim why can you get it down to 1100 or 1200 feet per second I don't understand

 

[Rick]

Any loads I have tried in the 1600 to 1800 range turn into shotgun patterns with leading of the bore on a BHN 22 alloy Jim

Could well be too hard of an alloy. Too hard can definitely cause both leading and accuracy issues. I shoot air cooled CWW with 2% Sn at 12 BHN to 1900+ fps with zero leading. No need to be shooting diamonds.
.

 

[JWFilips]

Dan,
Not sure it is stabilizing that low. That is why I asked the question about the weight vs my twist rate.
Sure is easy for me to shoot light loads in 30 cal & up but there is something about the sub 25 cals that always hangs me up.
I have a .243 that is a super cast shooter also but only at 1900 + loads have not been able to shoot anything lighter accurately
Jim

 

[Ian]

Because he's using diamonds for alloy.

Jim, try air-cooled range scrap for the slower loads. Also, if you're planning to shoot out to 100 yards you might consider doing the math on speed of sound and the estimated BC of your bullet because they will likely destabilize at the sound barrier, particularly if marginally or understabilized. Look for about 1050 fps or less or 1350 or more.

On the twist vs. weight thing, put down the calculator and just go shoot some. 2.3-2.5 grains of Titegroup worked great for me with plain-based 60 grainers at under 1K fps, and I have a feeling had plenty of room for more without bumping the pressure too much for the alloy.

 

[JWFilips]

Could well be too hard of an alloy. Too hard can definitely cause both leading and accuracy issues. I shoot air cooled CWW with 2% Sn at 12 BHN to 1900+ fps with zero leading. No need to be shooting diamonds.
.

Ah I remember Paco Kelly mention that very thing..... if you want to shoot light load softer is better.
Maybe I could anneal

 

[Ian]

Wow, I'm too slow on the draw there. Rick and I both thought "diamonds".

 

[catskinner]

Wow, I'm too slow on the draw there. Rick and I both thought "diamonds".

 

[Ian]

Alloy and powder. Alloy and powder. Alloy and powder. The whole key to everything with cast. What does that mean? Different alloy blends do different things for or against you. Same with the hardness you make them. Powder selection and charge weight make the pressure curve that acts on the alloy. These things go hand in hand and if they aren't balanced for the job you're trying to achieve, you won't get good results.

If you try to duplicate the same bullet reaction that your 2400 fps load has with your 1000 fps load, you'll have to use an alloy that's about 1/3 the strength...unless you kick it with a fast pistol powder and stress the bullet similar to your 2400 fps load....however that pressure with the fast powder drops way off after the first inch of bullet travel and the bullet is left hanging in with a whole lot more barrel to traverse and not adequate pressure to keep it happy and sealed. Fiver calls this the "relax point" and will show you all sorts of problems with lube and metal fouling in your bore, and usually very poor accuracy. Ever hear of "running out of lube" due to leading in the last few inches of the bore? That is nothing more than too little pressure for the barrel length (pressure curve drops off too fast) and too hard and alloy for the job.

 

[catskinner]

Use the Greenhil formala

 

[Ian]

The sooner you throw Greenhill out the window and just go see what your rifle does, the happier you will be. Once I did that, I learned a few things about what really works in the real world and what doesn't.

Like I mentioned previously, taking note of your BC and velocity to insure the sound barrier doesn't screw you up is important, and one more thing that's way more important than Greenhill when crowding the margins is the center of gravity/center of pressure relationship of your bullet.

 

[Rick]

Ah I remember Paco Kelly mention that very thing..... if you want to shoot light load softer is better.
Maybe I could anneal

Jim it all depends on what your alloy is. Annealing will only draw hardness out of heat treated alloy, either oven quenched or quenched from the mold. If your using a high Sb alloy that is 22 BHN with no quenching no amount of annealing will make it softer than 22.
.

 

[JWFilips]

I believe these were water dropped ( range lead & some mono type) ...so annealing should help soften ( I hope)

 

[Brad]

I find it far easier to start with a lower Sb alloy up front. I can easily make it harder when required but it is damn hard to make a higher Sb alloy soft!
This is why I love my range scrap. With 1.5% Sb I can hear treat it when I need harder but air cooled it is about perfect for lower pressure loads.

Jim, want to learn what leading is? Try a hard, slightly undersized bullet. When you don't get obturation gas cutting and leading occur. Think of a commercial cast bullet sized .356 ( not sure why that small) in a light 38 special load. I needed a backhoe to help remove the lead from my GP100 after 50 rounds. By that point keyholes were the norm.

 

[JWFilips]

Brad: you take me back to my early years of pistol shooting when the guys were telling me on the pistol range my alloy wasn't hard enough!and was "over" bore!
I don't shoot pistol with them anymore!

 

[JWFilips]

Guys,
I just want to say : putting out a thread like this is a great learning experience from you all! This place is so great in the fact that I see no arguments among you: you guys all agree on the answer!
Truly a place to discuss the Art & Science of cast bullets!
Such a refined community ...I'm so grateful to belong to!
Thank you all
Jim

 

[RBHarter]

I can't help on the 225-55 PB mine is the GC and I've only run it wide open in 223 and 222 .
I did try 4 gr of Unique in the 222 with the 50 gr Bator naked . It was still running as memory serves 1500 fps . These little bitty cases are very efficient . I tried to get subsonic in a 6.8 Rem , I had to get under 4.0 Unique with a 150 gr to do it.

I had a 32 Rem and cast some lino like bullets for it lordy the lead that piled up . I bought some commercial 30cal cast. They would have been fine but the rifle needed a 311 to get the leade full enough to be passable 10 shots of the fabled 10 gr Unique and the lead started in the neck .....
It was horrible and took me to Steel wool and a brush .

 

[Josh]

Hi Folks,
I'm shooting a .223 Rem in a Remington Sportsman 78. It is a super shooting rifle with cast but I found a bullet that perplexes me: It is a plain base NOE FN 55 grain which drops at 61.5 grains Plain base.
The 78 has a twist of 1 in 12....by doing the math does anyone know how slow I can shoot this bullet?
I can shoot the 62.5 Gas Checked version pretty well at 1900-2000 fps with 10 gr of 2400. Just can't seem to figure out were to start loading for a plain base version. Any loads I have tried in the 1600 to 1800 range turn into shotgun patterns with leading of the bore on a BHN 22 alloy
Jim

Jim,

I am shooting a 55 gr Lyman from my 1-12 twist 222, here is a group shot with the CZ, it is only 2.5 gr of Titegroup but it surely works!

 

[Ian]

There ya go, Jim, Josh is doing it with that long, RN Lyman in a 12 twist at under 1100 fps.

I got away with using air-cooled 50/50 clippy weight/sticky weight metal with my Lee 55-grain/2.5 grain Titegroup loads, but sorta had to because anything softer (mine were ~12.5 bhn) would deform too badly on their way into the AR-15 chamber. Also, my sticky weights have a lot of tin in them which makes the alloy very squishy.

Interesting thing, when I started putting gas checks on my Lee bullets, I had to cut back two tenths of a grain to stay reliably subsonic, so there was blowby somewhere but no leading at all, ever. Accuracy improved some with checks, but not enough to warrant using them all the time. 50 yard groups were consistent at 1.25" for ten all day or night without checks. I used one light coat of BLL as lube before I started powder-coating all my AR bullets.

 

[Josh]

That is a Lyman 225646, I know it is kinda long for a lead 55 gr bullet but out to 50 yards it was hitting square and grouping well. That was with a batch of 464's that was quenched WW and allowed to cure for 6 months, lubed with Car Red. (Before I made the switch to LSL) they were not weight sorted, so I would guess that would account for the left and right flyers.

It is a great load, I wanted to try making a really quiet load to plink around the house with, I didn't achieve that but did find an excellent use for those cast bullets.