Different Starting Loads?


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Joshua M. Smith
September 14, 2011, 02:31 AM
Hello,

I start my handloads using, of course, the minimum load.

I'm aware that below minimum can cause pressure spikes.

My question is this: Different sources list different starting loads. For example, I like Varget. When loading for the 7,9x57J, I go first to Hodgdon Powders' data. They list, for a Hornady 150grn soft point bullet, a starting load of 45.5grns for a velocity of 2561fps and a pressure of 37.5K CUP.

Now, I flip over to Sierra and their load data says 45.1grns to start. Granted, different bullet with different bearing surface, but it also has a longer COL. Same weight bullet though.

Now, I go to Hornady's load data and they list a starting load of 43.5grns for a 2400ish feet-per-second. I like that -- but why the 2 grain discrepancy between the powder and bullet manufacturer?

I tend to think the powder people know their pressures and such the best so I go with their data before the bullet peoples' data, but it still leads to some confusion.

On top of everything else, my bullet is this:

http://www.buffaloarms.com/ItemMedia/10024/10024_40849.jpg
http://www.buffaloarms.com/Detail.aspx?PROD=158303&CAT=4178

It's made by Buffalo Arms Corporation and appears to have about the same bearing surface as the Hornady, so I load and watch for pressure sign.

Is this the correct procedure?

Should I be doing anything differently? How does one go about getting data for bullets not listed?

Any other advice?

Thanks,

Josh

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noylj
September 14, 2011, 03:30 AM
The only problem you will have with starting loads (and believe, you ARE NOT going to have any problems with starting loads) is if you were using a very slow powder for a very reduced load. None of the starting loads are any where near that reduced.
Also, I do not believe the myth of pressure waves coming together and causing some huge spike in pressure from powder igniting at the back and the front. All primers have more than enough brissance to light up the whole case. No test lab has ever been able to produce such a spike and they have tried. What does happen is the pressure is too low due to VERY slow powder being used at VERY low charge weights and the powder just sputters out. You end up with a bullet in the barrel and often a gunky mess of partially burned/melted powder forming an obstruction.
This is NOT happening with your loads.
Several of my manuals say to "ALWAYS start with the LOWEST starting load." They don't say to start with their starting load, but the LOWEST starting load. I take this to mean check several sources and use the LOWEST starting load.
What does your manual say about starting loads?
What many people think they know, 'cause someone told them so, is often not correct. I think that there are simply too many people who can't admit they made a mistake and think up some hobgoblin to explain their disaster.
If you ever want to make reduced loads, you would go to a faster powder and not just drop your starting load by 70%

56hawk
September 14, 2011, 03:50 AM
One big question is what rifle is this being loaded for? I just ask because I load 8mm for a couple different rifles. With my G43 I just use the starting load because it's semi auto and I don't want to break any parts on such a rare rifle.

In a modern bolt action, or even a WWII K98 I would suggest starting somewhat above the minimum load. 8mm has traditionally always been very downloaded because of the whole .318 vs .323 bore size. I have found that even two grains above the starting load it is still backing out primers and blackening the case necks.

Either way, I seriously doubt you are going to have any problems with any of the listed starting or maximum loads. Also wouldn't worry about the bullet, as long as the data is for the same weight you will be fine.

SlamFire1
September 14, 2011, 10:44 AM
Also, I do not believe the myth of pressure waves coming together and causing some huge spike in pressure from powder igniting at the back and the front.

So, does powder burn like a candle? That is nice, even, linearly?

Are there pressure waves when smokeless propellants burn?

Do waves interact?

I believe the differences in starting loads and maximum loads not only can be explained due to differences in test equipment, but also in terms of the difference between powder lots.

As we now know, W231 and HP38 are the same powder, same thing with H110/W296. Yet look in older manuals, the min and maximum loads and pressures are different. And yet they are the same powders fired in the same test equipment. The difference must be due to the differences in powder lots.

Robert101
September 14, 2011, 11:10 AM
I tend to believe exactly what Noylj wrote. I've been trying loads that are slightly lower than the starting data (and yes the various resources do not agree). My initial load of a Sierra 150 grain soft point is 41.6 for Winchester brass and 39.2 for NATO brass of H4895 [.308]. My AR functions just fine with these reduced loads. I will go slightly lower just for fun.

My general rule for reduced loads are as follows:
1. I don't go below 25% of the starting load.
2. I make certain the case is at least 75% full.
3. I use a powder that has good burn characteriatics for that caliber.

ranger335v
September 14, 2011, 11:27 AM
No one's start load will be dangerous and there is no line below which we will detonate anything. Even those who believe in the low charge detonation and pressure wave theories have been unable to duplicate it. Bottom line, it doesn't matter, start charges are not critical and no more precisely repeatable than max charges are.

The major issue for extremely low charges, to me, is that they are basically worthless. Powers burn most consistantly in the pressure range for which they are intended. Very high pressures become erratic and so do very low pressures; the low end won't kill you but it will make accuracy virtually impossible while accomplishing nothing good.

rcmodel
September 14, 2011, 12:21 PM
Even those who believe in the low charge detonation and pressure wave theories have been unable to duplicate it.Smokeless powder simply cannot detonate in quantities sold & used by reloaders. There isn't enough powder mass in a cartridge, 1# can, or 8# drum to support a detonation wave.
If there were, we could not buy it, because we could make very effective bombs out of it.

All documented cases of powder detonation I am aware of have been in rail car & factory storage magazine fires.
In other words, it takes mass quantities of smokeless powder to support a detonation wave.

I believe what really happens with reduced load blow-ups in over-bore calibers is this.
Primer lights the slow burning magnum type powder.
That limited amount of pressure from the primer and start of the reduced charge powder burn blows the bullet out of the case, where it promptly sticks in the rifling.
Then the powder continues it's burn, pressure builds up behind the stuck bullet faster then it can get out of the way.
Then the case lets go, and the rifle blows up.

To answer the OP's question?
Different manuals show different starting and max loads because the pressure testing was done in different barrels, with different test equipment, on different days, with a host of other variables thrown in.

Rest assured that any published starting load is safe.
Just don't reduce it more, "just to be safe".

rc

gamestalker
September 14, 2011, 02:15 PM
I've been dealing with that same issue for many years and honestly, I don't give it a second thoght and haven't any pertinent reason to. And in adition to that and undertand this isn't someting I advocate, I don't normally start at the minimum charge but more to the middle. But that confidence comes with years of loading and observation. I simply hate wasting powder and bullets getting to where I already know I want to be in terms of performance.
An example of this, is I just put together some 7mm RM loads early this morning and I started my load with a bullet weight I've never used, but with a powder I've been using for decades and I started mid way between middle and max. Once you've been doing it for a very long time, you'll know what to expect, and also learn to trust the data. Most often I'll use the data provided for the bullet I'm working with, and if all goes well, my next sesson will get bumped up in powder charge to what the powder manufacturer indicates if I feel the need for more speed, which is more often than not a higher charge than that provided by the bullet manufacturer. But I'm also very maticulous about how I load in that I aways trim, weight every charge on my RCBS beam scale, and run my OAL's to just barely off the lands. I also carefully inspect every single piece of brass for any signs of expiration. I haven't ever punched a primer or had a first stage case failure I wasn't expecting due to that particular brass edging on expiration. By the way, what I consider a first stage case failure, is actually the first indication of a case separation in the works, in other words it all comes out in one piece without any pressure leaks.

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