New manual, favorite .308 load is listed as above max!


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madd0c
January 27, 2010, 09:38 PM
Ok, I received my Sierra 5th edition manual from midway today. I have worked up a load for my .308 rifle that is I have found is the most accurate in my rifle.

Sierra MK 168gr hpbt
43.8gr Rel 15
Lapua brass
CCI BR LR primers

I worked this load up over about 6 months of trying literally hundreds of rounds of various combinations. I can shoot 2.5" groups consistently at 300 yards with this, and I have several hundred rounds loaded with this load.

The alliant website shows a max charge of 45gr with a speer 168gr hpgt and this is what I based the max load on. I also am under max listed in the Lee manual and my Speer manual.

I bought the sierra manual because I find myself using mostly sierra bullets. I see zero pressure signs on the cases, no flattened primers, and these loads chrony right around 2600fps.

The Sierra manual list max DO NOT EXCEED loads at 43.6gr for my exact combination :p

I have tried the 43.6 max listed load and it is good, just not as good in my rifle as the .2 extra grains. For the record, it is a bolt action rifle and not a semi-auto gas rifle.

Should I be concerned? I am under the powder manufacturers listed max. Does the sierra vs speer brand of bullet make THAT much difference in a max load or is this a case of slightly lower max listed loads in a newer manual?

Thanks,
madd0c

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JimKirk
January 27, 2010, 09:55 PM
Each rifle is "individual" and your load appears to be safe in your rifle.

I have a 25/06 load that is 2 grs over max in most manuals, it is however safe in "my" rifle.

Jimmy K

ants
January 28, 2010, 12:42 AM
I'm always nervous that threads like this will encourage newbies to blow right past the manual and exceed max, because "It didn't show any pressure signs, so it must be safe. Besides, if the expert loaders on the internet surpass max load with impunity, everyone can do it. No worries."

A hundred years of metallic reloading and a million reloaders before you have determined that following the published data is generally safe, as long as your gun is safe and clean. Even then you need to start low and work up, never exceeding max load.

You choose the manual you wish to follow, then follow it. That's the value of buying two or more published manuals (eventually you build a whole library). You pick which load data you like for the load you're developing, then follow it.

madd0c
January 28, 2010, 01:25 AM
I still consider myself a beginner, but learning all the time. That is why I posted this finding. Basically, who should I believe? The powder company with a slightly different bullet, or the bullet company that has a max load listed that is below the other sources i have.

I definitely do not suggest that going above max load is advisable.
Thanks for the posts,
madd0c

Ridgerunner665
January 28, 2010, 01:33 AM
Sierra used a 26 inch barrel and only got velocities that are easily obtainable from a 22" barrel...that should tell you something (they stopped when they got to the 308's accepted performance level, without giving any consideration to the barrel length they were using)

twofifty
January 28, 2010, 02:47 AM
Thinking that tolerance variables might have something to do with your findings:

- You may not be using the same brass that Aliant and Sierra used for their tests.

- Your rifle's chamber, throat and barrel dimensions are different than those used by Aliant and Sierra to make their tests. It may well be that your chamber is slightly bigger, which effectively drops the pressure even though you have .2 grains extra powder. The powder & primers are not from the same batches.

- The bullets you are using may be ever so slightly smaller in diameter than the test bullets - certainly they did not come out of the same batch.

So there may be several tolerance variables that in this case stacked in your favor, because you were careful and paid attention. If your chamber had been cut with a worn reamer it would be smaller, so you might have found pressure signs earlier in your development process.

I read in another post that a reliable way to search for pressure sign (or was it to look for case fatigue and imminent case separation?) is to chart case diameter growth over several firings & reloading cycles of your favorite load. Measure the web area with a micrometer (not a caliper). Am not sure what numbers or rate of growth to look for though, maybe someone can pipe in.

dubbleA
January 28, 2010, 03:15 AM
Welcome to the world of inconsistancies in loading manuals. This is due to all the variables involved, ie make of barrel,chambers, bullets, brass, powder lots, temps, elevation and on and on.

Not one of them is absolutely correct and written in stone, they just list what they found safe in that particular rifle and combinations on thaticular part day(s). Look at the velocities they list for any given charge, it not very often that they agree with what I have found chronographing. Just to many variables.

I will say this, always start with the reccomended starting charges and work your way up until you get signs of high pressure such as hard extractions, flattening of primers, carefully measure case head exspansion and the back off 1/2 grain. Keep good records and if you are using max loads make sure you back of the charge and work up if anything is changed, even powder lots.
Over all, the manuals do a pretty good job with the data they acquire and spend alot of money doing so but with that said they cant all posibly be right. Personal experinces tell me that some of my loads reach a max before what a book says while others will take a bit more powder than a manual states.


your milage will vary

qajaq59
January 28, 2010, 09:19 AM
Just so some of the newer guys don't get the wrong idea, you'll notice that every one of the experienced guys have said the same thing. "Begin at the starter load and work up." It's advice that is worth remembering!

loadedround
January 28, 2010, 10:03 AM
Just checked my current #14 Speer Manual and the loading data shows 41.0 gr of RL15 as a starting load and 45.0 gr as a max load for that bullet/powder combo. As others have said, each rifle is different and if it works in your's without pressure signs, then you're good to go.

RainDodger
January 28, 2010, 11:43 AM
Good advice here.

I've been loading for over 40 years (42 to be exact) and I've found the same thing. A load I've been using for 20 years in my .45ACP is now listed as over max in some manuals. I continue to use it with no problems.

Reloading manuals are guides. You work up a safe load in your firearm and it should be fine. I would say though, if you buy a new batch of powder, you should back off the load to something below the newly stated max and work it up again. Powders do change from lot to lot, but it shouldn't take more than a few rounds to verify you're still good to go.

dagger dog
January 28, 2010, 12:25 PM
madd0c

The rule of thumb concerning the miking of the fired case just above the extractor groove or rim, with a blade mike is 0.0005" over a non fired loaded case, measured in the same spot. This info was from Hornady Handbook of cartridge Reloading 5th Edition page 23.

I have several loadings in different calibers that have the same discrepancy in several of my loading manuals . I seldom use the max loads, and I practise "working up" as you do. It is a concern to me also.

You may want to buy or borrow a blade mike and check that case head expansion, and also form a small hook on some thin wire and insert that into the case and see if you can feel any streching at the base (it will form a groove inside). But usually this will also show up as a ring visible on the outside.

twofifty
January 28, 2010, 01:38 PM
Just so some of the newer guys don't get the wrong idea, you'll notice that every one of the experienced guys have said the same thing. "Begin at the starter load and work up." It's advice that is worth remembering!
Yes. And just as importantly the most accurate loading will not necessarily be found at or above the manual's maximum.

The basic outcomes of loading are accuracy and a bullet that performs on game. It should not be about telling our buddies "well, mine go x gazillon feet/sec" (knowing theirs is 250fps slower).

Bottom line is that you don't necessarily need to work up to the max.

dagger, thanks for the base miking reference.

madd0c
January 28, 2010, 01:47 PM
Good information in the posts. Thanks.

Twofifty, My goal was not to have a MAX load, as I said I worked up from the listed starting load and after a bunch of rounds found "the load" that works extremely well in my rifle. As far as I knew I was 1.2gr under max by several diffferent manuals, that is why it was a shock to see the Sierra manual have a max that was so much lower than the others.
I am not trying to get some power factor, or the highest velocity I can, I was developing the load for the best accuracy I could obtain, and did. It just happens that the load is over max in one of the 4 sources I checked.

Dagger, I do know about the paperclip trick, but have not checked any of my fired cases with this load. As a matter of fact, I have reloaded this exact load in the same cases 3 to 4 times with no evidence of case damage, so I just didn't even think I needed to do the paperclip test. After I fire the rounds I have loaded, I will check the cases this time.

Thanks again,
madd0c

qajaq59
January 28, 2010, 02:31 PM
Yes. And just as importantly the most accurate loading will not necessarily be found at or above the manual's maximum. You have that right. I've been loading since the 60s and only once has the best accuracy been at the max load. Usually I find it somewhere above the half way mark. My theory is that velocity only counts IF you hit what you aimed at. :D

snuffy
January 28, 2010, 02:39 PM
Twofifty, the technique you're referring to is called PRE and CHE. Pressure Ring Expansion, and Case Head Expansion.

Pressure ring expansion is measurable with a normal micrometer, BUT one with capability of measuring .0001. It is taken in front of the extractor groove. Case head expansion is measured at the bottom of the extractor groove. There you need that blade micrometer that also has to have .0001 resolution. Both methods are looking for CHE or PRE of as little as .0002-.0003 expansion ABOVE max pressure.

Now you ask; so what is max pressure? Hard to say, but the accepted method is to fire a factory round in your rifle,(actually a minimum of five), then measure the CHE or PRE of those cases. Then, after that, you measure your reloads to see if they exceed that much expansion. At around .0003 expansion, primer pockets start to loosen up.

I certainly wouldn't be worried about a .2 grain over charge as listed in one manual.

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