Stupid Newbie .308 question

[enichols]

Hey all,
This is gonna seem like a stupid newbie .308 reloading question (hence the title), but so far for reloading my .308 I've only used 168gr Sierra Matchking HPBTs. If I wanted to use, say Nosler 168gr HPBTs or Hornady A-Max 168grs, is it safe to use the same powder charges for these bullets as for the SMKs as listed in my Sierra reloading manual? Sorry again about the stupid question, but like I said, I'm new to reloading and don't want to leave anything to chance. Thanks,
Nic

 

[jimb124]

Not a stupid question. Better safe than sorry when you are touching off an explosive just inches from your face!
As far as my experience goes, the powder charge doesn't know if the bullet is a Sierra, Hornaday, Nosler, or whatever - just that it is 168gr. When you start changing components (like primers or cases), it's best to back off of your favorite load 10% (or so) and work your way back up to your rifle's favorite loading.
Hope this helps...maybe some others on this forum will jump in here and help out a little.

Jim

 

[Dave R]

OTOH, the Speer No 13 manual warns against using the same same powder charges for different bullets of the same weight. One of the variables that affects pressure is "bearing surface"--the are of the bullet that contacts the bore and rifling. If two bullets have the same weight, but one has more area in contact with the bore and rifling, the one with more bearing surface will have more friction, and therefore can cause higher pressure.

So the safe thing is to either use a manual with load data for that particular bullet, or back down and work up.

 

[larryw]

Also, the sweet load for your rifle with the 168SMK may not be the sweet load using a 168SPBT from another vendor. Change any one component and you're better off starting from square one.

 

[Master Blaster]

Start at the minnimum in the Sierra manual, and then work your way up until you get an accurate load in YOUR rifle. Watch for pressure signs, if you see any stop and back off a 1/10 gr. Dont exceed the maximum in the manual.

 

[GooseGestapo]

What has been said is right on point, however there's an additional consideration;
The ogive

Sierra, Nosler and Hornady shape their bullets differently and it can make a difference in a very tightly (read MATCH) chambered gun.
However, mostly it dosen't really matter as the accuracy loads for the .308 are generally mild. A recently deceased friend used essentially starting loads for his 40-XB bench rifle. Floating between H4895, IMR-4064, and whatever else was the "Rage" that month. (Ie; VV powders, RL-15, ect). His observations were that the only real difference was in the OAL he had to seat the bullets to, for the desired accuracy level. He did have a slight preference for the Nosler bullets after they came out, as he believed that the lot to lot variation on them was slightly less due to the consistency of the J-4 jackets. He also liked the fact that they came in boxes of 250 and cost a little less.

He said it was like a free 6-pack of beer once a month !!!!!

 

[Black Snowman]

It's not so much an issue in rifles but in pistols you also have to watch for changes in case volume due to differant bullet designs. For the same weight a hollowpoint will seat deaper for the same OAL. A lead bullet will be more shallow due to less volume caused by the denser metal. FMJ rounds can have differant thinkness jackets effecting strength, pressure as the bullet hits the lands, and bullet volume.

Lots of variables that are almost impossible to predict. In the 2003 Hodgdon Annual reloading manual has a ballistic pressure test involving OAL where the pressure went up until the bullet hit the lands then dropped, which is the opposite of the conventional wisdom as far as I know.

You just don't really know until you try so it can't hurt to start low and work up. There's a good chance you'll find the most accurate load on the way.

 

[Clark]

Reduce your old load, and work up to the old load in increments looking for pressure signs shown in your load book.

The difference in appropriate loads between the bullets you mention would be very small. You should wind up with the same load for the new bullets.


CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

I just did an overload incremental experimental work up this week on 168 gr. HPBT in the .308 with a Hodgdon Powder.

It only takes a few extra grains to make the primers cratered [CCI200 and 98Mauser], but the amount of overload powder was large required to reach:
1) Short brass life
2) The primer falls out from the first shot

--
A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian.

 

[Grump]

Yeah, using Nosler J4 168s, I'm almost 100 fps lower than what the "classic" load of 4064 is supposed to get using a Sierra MatchKing, using military match brass. Anyone notice evidence of softer jackets/more powder required with the J4s?

 

[goon]

That is an excellent question.
Using the same charge with the same bullet weight is often a NO-NO.
Eventhough bullets may be the same weight, they may be different lengths.
So if they were loaded to the same OAL, one load would have significantly higher pressure than the other.
So in general, the answer is don't do it unless the manual says it is OK.
If you have a good load, reduce it by 10% and work back up toward your load, watching for signs of excess pressure as you go.
I have done this before and it does work.

 

[enichols]

Re: Signs of excess pressure

When you guys say "watch for signs of excess pressure", what specifically should I be looking for? Case bulging/deformations and such?
Thanks for all the great info, you guys! I really appreciate it.
Take care,
Nic

 

[GooseGestapo]

The best way short of having pressure equipment is to use the case head measurement system. Measure the head above the rim but behind the "pressure buldge" where the case expands to fit the chamber.
When a single loading causes this to exceed .001", measured at exact same location on case, you've exceeded max.

There are number of descriptions of this if you're planning on using this method.
FWIW; I've found not exceeding the manuals to be easier, more productive. How fast do you really need to push a 168gr BTHP match bullet. I've found the starting loads in most manuals to be more than sufficient (~2,500fps) and adjust up or down to fit rifle's accuracy "sweet spot".

If you need more speed, get a bigger chamber (ie: .30/06, .300 WinMag, .30/.378W-M).

 

[Clark]

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

I load at the range so I can make changes quickly.


1) The pressure sign I look for in .308 is the primer falling out or the bolt jamming. I work up to find this in 1 gr. increments.
2) Then I reduce the load until the extractor cut only grows .0005". I work down to find this in .1 gr increments.
3) Then I reduce the load until I get accuracy. I work down in .1 gr increments and play with the over all length.

I like the accuracy load to be at least 6% less than the primer falls out load, to account for the tolerances in my technique, my components, the air temperature, and the chamber steel temperature. That way I know I will not have an ammo caused gun jam when I am taking an important follow up shot.