Discrepency between bullets of same type and weight

[njcioffi]

Hey guys,

I'm fairly new to reloading, but have been studying the tables, etc. for quite awhile. My question for the more experienced reloaders here is: Given a bullet design of similary type/weight/sectional density/ballistic coefficient, can they be treated interchangeably, and if not, why?

For example, if I have a 165 gr SPBT from Sierra, and 165 gr SPBT from Hornady, both .308 dia., what is the potential danger from using one in a recipe published for the other?

 

[rg1]

Different manufacturers jacket thickness,jacket hardness, bearing surface, recommended seating depth, bullet base difference, CAN effect pressure. It's always recommended to drop down your powder charge and work back up whenever changing bullet brands. Not always but you could run into pressure problems when switching bullet brands or types. A good safety practice to always drop down your powder charge and shoot a few rounds to double check that your new bullet is safe.

 

[njcioffi]

Thanks, RG. I would want to work up the load from the bottom(ish) anyway to find the sweetspot. I've just been getting frustrated by the holes in the data when cross referencing the published loads from different manufacturers.

Thanks again.

 

[Funshooter45]

You're good to go especially since you already know about starting out low. As far as that goes, it doesn't matter if it's a BT or a flat base, and it doesn't matter what the tip is. In your case that you mentioned, I treat those 2 bullets absolutely the same. In fact, I include the popular 168 gr bullets as the same bullet for loading purposes.

The one exception I make is if I see loads specifically using the Barnes bullets, which are all-copper, no lead. In that case, the bullets are quite a bit longer for the same weight, so some things change. Maybe not a lot, but enough to make a difference.

 

[mc223]

Different manufacturers jacket thickness,jacket hardness, bearing surface, recommended seating depth, bullet base difference, CAN effect pressure. It's always recommended to drop down your powder charge and work back up whenever changing bullet brands. Not always but you could run into pressure problems when switching bullet brands or types. A good safety practice to always drop down your powder charge and shoot a few rounds to double check that your new bullet is safe.

This post is one of the best I've seen.

 

[noylj]

What I do is check at least two different manuals for loads and take the LOWEST starting load for similar bullets. There is too much variation is barrels and chambers to only use one source.
Granted, they try to make the starting load safe for any properly chambered gun, but I still prefer to know that I am starting at known low starting load.
I NEVER simply take a load and try it. Even if God himself gave me a load, I would reduce it at least 10% and work up.

 

[ranger335v]

"Given a bullet design of similary type/weight/sectional density/ballistic coefficient, can they be treated interchangeably, and if not, why?"

Generally, yes, but.... In application, all loading data is generic by bullet weight and powder type. No change we can make has more impact on a book load than a different firearm, and that's true even if you use the same components and rifle the book makers used. That's why ALL manuals tell us to "start low, only work up...." etc. Do proper load work up and any differenences in guns or components will be taken care of automatically, don't do it that way and nothing else can make you safe. Caution requres that any change we make in an established load should start with a charge reduction and working up again.

I've been doing this since '65, never been close to an accident and have never found any need to check multipule books for lowest starting charges, nor averaging book loads, etc. Starting loads are by definition low enough to prevent a KABOOM so worring over such things in mulitpule books is trivial, IMHO. Now, from all that I can say that checking and averaging multipule book "max" loads has never been shown to be needed either. If I see excess pressure signs I will drop back no matter what any book says.

 

[gamestalker]

Unless you've already worked with that bullet and established it's loading characteristics, you start at the lower end of the data and work up while watching for pressure variations. This is also the time to look for the sweet spot, for both pressure and accuracy. It is during this stage of hand loading I get my jollies and satisfaction knowing that, it is my personal touch that is having a noticable impact. Fun! Fun! and more Fun!