Bullet shape and its affect on reloading data

[NJSigfan 218]

Hey guys-

 

I'm still learning my way through the reloading world and have a question. How does bullet shape affect reloading date if the bullets are the same weight?

 

Example: I have 225 grain plated flat point bullets (sample pack of 100) and my Lyman book has a listing for 225 grain jacketed HPs . Can I use the load data for the HPs?

 

Thanks for the help

[T Bill 649]

Ballistic Coefficient has to do with a bullet's air resistance in flight.  Something like cars.  Pointy ones go better, farther.  Less wind resistance.

Sectional Density has to do with a bullet's weight in relation to its width.  Higher values means they go faster and hit harder.

 

In this case the makeup of the bullet, plated vs jacketed, is the issue here.

 

Plated are not as durable as jacketed.  Plated can be loaded using any lead loading data.  Jacketed data maybe to much for plated bullets.  Plated and lead are typically .001 larger in diameter over jacketed. 

 

Most jacketed bullets of the same weight can be loaded with the same data. Example, HP, FN, RN, SWC. 

Same is true for Lead.  But only within their construction categories (lead or jacketed).

 

Rainier states the following on their website concerning load data for plated bullets:

If you only have access to traditionally jacketed load data, we recommend a starting powder charge directly between the listed minimum and maximum load, and you may use published load data found in reputable reloading manuals.

http://www.rainierballistics.com/loaddata.php

[GRIZ 3,369]

There is one thing to add to what T Bill said. The bearing surface of the bullet and how deep its seated are also factors. You can use the same data for a RN, FN, HP, or SWC but I wouldn't for a full wadcutter seated so the bullet is entirely contained within the case. This reduces space in the case and gives more pressure for a given powder charge. If you look at max charges for full wadcutter they are lower than other bullets. Hollowbase bullets are limited to lower velocities as higher pressures can blow out the base and leave a ring of lead in the forcing cone or barrel.

 

However I think you're safe using data for any 225gr bullet other than a wadcutter.

[T Bill 649]

Thanks Griz............

 

Yes, the COL of the loaded round would be different with each type of bullet even though the powder charge maybe the same.

[NJKen 23]

If you are loading with any type of hodgdon, imr, or winchester powder go to hodgdon.com and look up some load data.  There are a LOT of bullet choices for any given load you can think of. 

Ken

[GRIZ 3,369]

There is one thing to add to what T Bill said. The bearing surface of the bullet and how deep its seated are also factors. You can use the same data for a RN, FN, HP, or SWC but I wouldn't for a full wadcutter seated so the bullet is entirely contained within the case. This reduces space in the case and gives more pressure for a given powder charge. If you look at max charges for full wadcutter they are lower than other bullets. Hollowbase bullets are limited to lower velocities as higher pressures can blow out the base and leave a ring of lead in the forcing cone or barrel.

However I think you're safe using data for any 225gr bullet other than a wadcutter.

No problem. If I wrote an answer as comprehensive as yours I might leave more out:)

[noylj 5]

If you start at the lowest starting load you can find in at least two manuals and adjust COL. Many manuals lump all their bullets of a given weight and caliber under the same data, so that should tell you something right there.

Any time you change bullet, you need to work up the load again.

COL is dependent on the bullet's ogive, the magazine (if using one)--particilarly the feed lips and when they release the cartridge, and the barrel's feed ramp and chamber. Thus, as you change gun or bullet, COL can change.

[raz-0 1,259]

Bullet shape matters more in rifle than in pistol. In pistol, bullet shape CAN affect the case volume you are left with when seated to a given OAL. This has the most effect, but I tend to jsut look up the powder data, never start at the max end, and as a sanity check look at the lead and HP data for the given powder/cartridge/bullet weight. If the HP vs. FMJ has a much narrower range for the HP than FMJ, the powder is probably very volume sensitive so work up accordingly. If you want to start someplace higher than start, I look at the max load of lead for the same weight/powder/caliber and start there. 

 

For rifle, profile affects bearing surface, can do so dramatically, and affects max charge more. For example, take the 60gr nosler partition bullet vs. the 60 nosler varmint bullet and the 64gr nosler bonded core. If you go look at the nosler data, you will see that the 2 60 grainers have a lower max charge than the 64 grain head. THe reality is that is because the partition 60gr head is FAT with a huge bearing surface that generates higher pressures. I load the partition to 24.5gr of TAC, which is nosler's max load. You can do more for 5.56 pressures, but you are actually entering the realm of where the cartridge is having to work. the 60gr varmint round, even reaming the military brass and thus leaving a bit more space to flatten, doesn't look like you fired anything other than the firing pin dent in the primer. Even using nosler's data the 64gr has a higher max charge than the 60 grain bullets as the 64gr has a less fat and stubby profile. Heck even in ramshot's data for tac, the partition has a lower max charge with a higher pressure than 62gr m855 bullets and 62gr barnes TSX copper bullets (which protrude farther into the case. For ramshots data for accurate 2520, the partition maxes out at 25.6, and the hornady 68gr maxes out at 25.8 with less than 200 more psi at max charge (granted the hronady is loaded a couple hundredths longer as well). 

 

With pistol rounds, you only see really dramatic changed in bearing surface length when you get into some really weird projectiles. 

[NJSigfan 218]

Thanks guys...

 

So in short, as long as I stay in the same construction family (plated or jacketed) I can use the load data for the bullet weight regardless of bullet shape. Ie load data for 225 grain RN can be used for 225gr FP, HP or SWC.

 

Thanks!

[Tunaman 562]

Thanks guys...

 

So in short, as long as I stay in the same construction family (plated or jacketed) I can use the load data for the bullet weight regardless of bullet shape. Ie load data for 225 grain RN can be used for 225gr FP, HP or SWC.

 

Thanks!

I wouldn't say for sure that you are ok.  There are a lot of variables to consider as some mentioned,  the most important being bullet seating depth and powder compression.  This issue arises when using flat point bullets such as the Berry's HBFP.  You will need to seat these much deeper,  and using certain powders that fill the case you could get higher pressures.  I use Winchester 231 and that seems to be the ticket for staying away from trouble.  Always work the load up slowly.