Hardness vs velocity ?

[Motor]

The boolit: 160gr 2R TL Lee powder coated and gas checked. Sized to .311"

Caliber: 7.5x54Mas For comparison you could just "think" .308 Win.

The load: 18.5gr of 2400. Velocity should be high teens.

The alloy: Lead mixed with Linotype

The question: What is the minimum hardness for this load?

Background: 16bhn shot great. I'm thinking about using 12bhn. Do you guys think it can handle it?

Motor

[Scottyh]

As long as .311 fills the throat on your rifle. With a gas check and powder coating, it should be fine.

[OnHoPr]

Hey, I like this type of thread. When a lot of threads are referring to a start grains of powder and then work your way up @ .5 or 1 grain at a time. This one is going from how hard the boolit is and dropping the BHN down one increment at a time. Now that would be an idea, to cast 50 to 100 boolits from 16 to 10 or 11 and check for the difference. Though you are opening up a whole new can of what ifs when it comes to the actual powder. Unless you are just sticking to the 2400.

[Mk42gunner]

A plain old air cooled wheel weight boolit (Lee 312185) sized .311" lubed with FWFL works fine in my .308 with 16 grains of 2400 @ right around 1600 fps. The last time I checked that batch of WW was about 12.5 bhn.

From what I understand, powder coating should allow you to use almost pure lead; but I still believe that fit is going to be more important than hardness.

Robert

[Yodogsandman]

Yes, 12 BHN should get you up to about 2000 FPS with proper fit and lube.

[Scharfschuetze]

Yep, I've shot thousands of 30 and 31 calibre boolits made from straight air cooled COWW alloy up to 1,850 fps or so without any issues. I'm sure that they were no harder than 12 or 13 BHN. I could have probably shot them faster, but that velocity level seems to be a sweet spot for all my military rifles.

Good fit, good lube, proper powder and a well seated gas check is all it takes.

I might note that older WWs seemed to have a higher tin content and needed no additional tin. My latest WWs now seem to take a percent or so of tin to fill out a mold properly, but they are still a long way from lino type hardness.

[stu1ritter]

Figure approx 1440 psi chamber pressure per unit BHN will give good obturation of the bullet base. In other words, 15,000 psi requires BHN 10 approx and 40,000 psi requires BHN 27. I believe the formula comes from Phil Sharpe's book.
Stu

[Wolfer]

I run my 10 bhn boolits to around 1800fps with 2400 before accuracy starts falling off. In 30-30, 30-40 Krag, 30-06
The faster twist stuff like my 7x57 and 8x57 start losing accuracy at or below 1700 fps with 2400. With a slower powder like 4759 or 5744 I can push these into the upper teens

[Litl Red 3991]

Considering the use of gas checks, the hardness wouldn't have as much to do with possible leading as with the maintenance of the bullet shape. Softer alloys would allow slumping which could basically turn that 2R nose into a wadcutter. And the uniformity of the resulting noses wouldn't be consistent.

Black powder lead bullets seem to shoot best for me @ 1100-1250 fps velocities when the BHN is around 9-11. Harder or softer and the accuracy goes away. Those cartridges are used for Silhouette and Buffalo target competitions and they don't allow gas checks. And they're not of value at those velocities and hardness as getting the right hardness solves any leading problems. The right hardness also solves the accuracy requirements.

You alloy description really isn't enough to guess what hardness you're working with. But with those two parts, you'll be able to produce whatever you'll need.

[Litl Red 3991]

BTW, the Lee reloaders guide just out has an excellent section on hardness versus pressure, and it's easy to work out hardness from your fps. Look at the guide's data showing velocity and pressure with each recipe.

[Motor]

I have a hardness tester so I absolutely know what hardness I'm working with. As far as the pointed boolits go they have been modified to have a .180" diameter flat point. Powder coated and gas checked they still weigh 168grs.
The goal is to have a boolit that has good velocity but will still be accurate and expand on whitetail deer.

Thanks for all the feedback.

Motor

[Harry O]

I have worked up from light loads to heavy loads with lead bullets many times over the years. My experience has always been that the accuracy starts going bad in the neighborhood of 200 to 400fps below where leading starts. Never once did it start leading before the accuracy started going bad. Your load may or may not lead. However, if you are getting poor accuracy from it, the bullet is starting to fail.

[Litl Red 3991]

What you're after is an alloy (hardness) and a pressure (velocity) that is soft enough to provide a good seal and just hard enough that it doesn't slump or lead. The Lee manual explains how to use your velocity and hardness to accomplish that.

[dudel]

What you're after is an alloy (hardness) and a pressure (velocity) that is soft enough to provide a good seal and just hard enough that it doesn't slump or lead. The Lee manual explains how to use your velocity and hardness to accomplish that.

Sounds like a case for duplex boolits. Handloader magazine did a story a few years ago, where the base was harder lead; but the nose was pure lead. Supposed to keep leading down, velocity up, while still having good expansion. They sound a bit painful to make; but the author seemed to have streamlined the process.

[Mk42gunner]

Sounds like a case for duplex boolits. Handloader magazine did a story a few years ago, where the base was harder lead; but the nose was pure lead. Supposed to keep leading down, velocity up, while still having good expansion. They sound a bit painful to make; but the author seemed to have streamlined the process.
Our very own BruceB (RIP) developed a method that works well and isn't too hard to do: http://castboolits.gunloads.com/showthread.php?11749-Casting-Softnose-Bullets-From-ANY-Conventional-Moulds

Now that I think about it, it should work okay with powder coating also.

Robert