Manual Discrepancy

[eleaf]

I'm looking to load the 175 SMK in my .308 Win.

In 3 manuals, the discrepancy in max charge for IMR 4064 is large enough to make me pause and want to inquire further.

I tend to generally go with bullet manufacturer data, but it seems awfully conservative in comparison to both the Lyman manual and Hodgdon's database.

<span style="font-weight: bold">IMR 4064</span>
Sierra: 42.8
Lyman: 44
Hodgdon: 45.6C

Nearly 3 fully grains of difference makes me pause.

What number would you go with as the max when trying to work up a load? I've looked through the thread on .308 data and every load I saw when coupling the 175 SMK and IMR 4064 is above 42.8, and a few were approaching the Hodgdon number of 45.6.

I only ask because although I'm certainly going to drop my number by 10% and work my way up, 10% from the Hodgdon max charge is only about 1.8 grains less than Sierra's max.

I'm also under the assumption that I won't go from "lookin' good" (from a pressure standpoint) to "holy shit" when working up in small increments. In other words, I should see definite signs of pressure (anything from the bolt handle being a little sticky on extraction to primer craters to extractor marks or any other sign) before I see a bad accident.

EDIT:
I've also noticed similar discrepancies between the same 3 manuals and Varget and IMR 4895.

 

[Greg Langelius *]

Re: Manual Discrepancy

Hodgdon sells IMR powders, etc.; so loads will favor using more, and proclaim stratospheric performance. I have <span style="font-style: italic">ALWAYS</span> taken their maxes with a grain of sand.

Sierra sells bullets, and cannot predict the ruggedness of the rifles that shoot them. So for liability's sake, they will favor a lighter max; since they may be prejudiced against providing data which might conceivably cause problems that involved their bullets and their data.

Lyman has no horse in a race involving Sierra bullets and Hodgdon/IMR powders. I would therefore use their data with slightly more credence.

As an experienced handloader and shooter, I have learned over the years that load incrementation follows a pattern of diminishing returns, both in safety and bore life, and have long since learned to moderate my loads.

My experience tells me that while quite often an accuracy node will occur high on the charge weight curve, there is also usually another, lower, node which delivers comparable accuracy. Given the choice, I favor the latter.

As long as a load will accurately reach my desired range, a bit more drop is simply a matter of sight adjustment, and a bit more drift is just another factor that needs to be learned and estimated using the same customary judgements.

Greg

 

[vman]

Re: Manual Discrepancy

I dont use that projectile so i cant help you, but you may want to see what others who do use it have to say... just in case

Last thing you would want is underpressure, as that can be dangerous as well.

Someone please correct me if im wrong, but i recall hearing that the Sierra manual is usually conservative

 

[ZLBubba]

Re: Manual Discrepancy

I'm fairly new to rifle reloading myself, but I will say this: there are many discrepancies THROUGHOUT all the various manuals. Hell, even a pistol round will have 3 different max charges depending on where you're looking. I tend to favor the powder maker because it's their job to know how much of their product consumers should use, much more than the bulletmakers. I'm not sure how liability claims work in this case, but I doubt people ever blame Sierra for when they have a blowout. They look at the powder company. And in my experience, Sierra has pretty tame loads for most of their product line.

But if you want to be safe, what I'd do is load 90% of the lowest, then 95, then 100%. If those loads are fine, then do the same with the "middle" max charge of the manuals you're looking at. And if you make it to 100% without pressure signs, then you can work from the middle groundtoward Hodgon's max load. Just my 2 cents.

 

[Top Cat]

Re: Manual Discrepancy

The short answer is that you are good to go with your plan using Hodgdon's data, but pay close attention to the other components they are using as well, primer, brass, and O.A.L. If you analyze all of that together, the apparent discrepancies may not be as great.

Reloading data is a recipe that when all of the specified components are put together exactly as stated, the results should be similar to the lab data. Of course, the rifle is always different, so that is why they give some thought to the "max" load.

Generally, it is not necessary or advisable to run max loads to give good performance from a 308. Factory Match loads are loaded to less than max and perform well, because accurate loads are found at less than max pressures.

The only way to know for sure how your loads perform in your rifle is to run them over a chronograph, and find your accuracy node around the velocity goal you wish to achieve.

A chrono is a more important piece of equipment to a reloader than a digital scale and is less expensive.

TC

 

[Hunt]

Re: Manual Discrepancy

I have found Lyman's manual closer to reality than other manuals. Sierra and Hornady are hopefully optimistic.

 

[Guest]

Re: Manual Discrepancy

The issue everyone in print has, is they have no control over the stacking of compounts, chambers, barrels, and even you powder scales.

Lets say you have a 30" barreled bolt action, short throat, tight match chamber, and tight bore (.298), they don't know that, nor do their lawyers.
Now take a 18" barreled gas gun, loose bore (.301 or better) large chamber, long throat, they don't know that either.

Any time you start stacking on the tight or loose side things change, quick. Also remember compounts are "Supposed" to be the same, but are not most of the time. Load books, are there as a guide.

I've been playing with reloading for awhile, I've shot my own single powder loads, duplex, an triplex powder loads with buffers, within the same cases, and will tell you this. Just when you think you have the game down pat, it will jump up an bite you.
Who cares how fast it leaves the barrel,(unless your punching threw) how does that load look on target, at the range your shooting?

 

[Fuzzball]

Re: Manual Discrepancy

"What number would you go with as the max when trying to work up a load?"

If it's a new rifle that I have no idea what it will take, I'd start at the minimum and only work up to any max IF no excess pressure signs indicated the need to stop and back down a bit.

The manual data you quote isn't foolish, it simply proves that rifles are individuals. They are giving you the info as they tested it in THEIR rifle. Your's is different and you have no idea in which direction it's different until you test it on the range.

In the final analysis, WE are and <span style="text-decoration: underline">must</span> be our own final authority because no manual can tell us exactly what is or isn't safe in our rifle. Nor can any of us on the web!

 

[Rob01]

Re: Manual Discrepancy

Hodgdon makes the powder. Use their data. I always use Hodgdon's data but obviously don't start at max. Use the starting load. You will notice that the data is different from sourse to source. Sierra's max load with Varget isn't even the starting load from Hodgdon. Sierra is well known for being very conservative. You can use Sierra's if you want to be able to watch the round go down range

 

[Explorer]

Re: Manual Discrepancy

All are ONLY guides which document the results of their testing. The bore diameter of your gun's bore, brass, temperatures, etc. all influence the results; take none as gospil, take care in your reloading, and you should remain safe if you use common sense.

 

[desertHK]

Re: Manual Discrepancy

I use 44.2 grains of IMR4064. I think Greg said it well "take it with a grain of salt.." Work up properly. In all honesty, with all the lawyers walking around looking for money, they have to be a bit on the conservative side to make sure that nothing catastrophic happens.

 

[Powder_Burns]

Re: Manual Discrepancy

Compare the seating depths and bullets used in the different manuals and see how they came up with diff. max charges. Sometimes its err on the side of caution, other times there are significant differences in seating depths..gives you a good picture of how seating can affect your pressure.

 

[eleaf]

Re: Manual Discrepancy

Thanks for the replies.

I planned on working up all along using the OCW method, I was just wondering where I should start (OCW basically states to start with 90% of the max load), as opposed to trying to make a load that intentionally hovers around the max load just for velocity's sake. I'm not interested in approaching a max charge unless my rifle demands it (or asks for it nicely - "Please sir, can I have some more").

I know that these manuals are but guides, as opposed to gospel, but one would expect them to be reasonably close (especially when all of them warn to NOT go above the max pressure), and 3 grains of difference doesn't seem all that close (unless I'm overjudging what 3 grains of powder actually is (about 60% of a pistol load). If the Sierra manual were all I have, it seems that their data, being ultra-conservative could lead to some pretty "uninteresting" loads if there is, in reality, another 3 grains of loads to safely test.

 

[eleaf]

Re: Manual Discrepancy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Powder Burns</div><div class="ubbcode-body">Compare the seating depths and bullets used in the different manuals and see how they came up with diff. max charges. Sometimes its err on the side of caution, other times there are significant differences in seating depths..gives you a good picture of how seating can affect your pressure. </div></div>

All 3 list 2.800" as their COAL. Lyman and Sierra list the other info, but Hodgdon doesn't.

I always start with the COAL listed in the manual. If I feel like I need to tweak seating depth (not generally for my applications), I start at the manual COAL and move it out by .005"-.010" at a time until I find the sweet spot.

I have a number of primer brands on hand, but am using my CCI LR primers right now as I have a metric shit ton of those as opposed to the other brands I have (Winchester - which burns pretty hot IIRC; CCI LR BR).

Brass is all Lapua virgin.

 

[Fuzzball]

Re: Manual Discrepancy

"If the Sierra manual were all I have, it seems that their data, being ultra-conservative could lead to some pretty "uninteresting" loads if there is, in reality, another 3 grains of loads to safely test."

There <span style="text-decoration: underline">isn't</span> any presumed and automatic safety in another 3 grains to test, no matter what your books say. Point is, Sierra, et al, aren't being overly conservative, they are quite likely telling us what really was max <span style="text-decoration: underline">in their rifle</span>. They also know full well that SOME rifles will need more powder to achieve the same pressure levels but it would be very foolish to say that in a manual for people who don't have the knowledge and/or experience to deal with it safely. Every dummy out here would automatically think (?) his rifle was one of the exceptions, blow his eyes out and sue the book maker for not holding his hands as he reloaded his bombs. Thus, they ALL say to never exceed their maximums, and rightly so.

I doubt you will find any max load deviation range of 3 grains in any fast powder pistol loads.

 

[oneshot onekill]

Re: Manual Discrepancy

Not sure if this has been addressed because I didn't read all of the posts... Sorry. But keep in mind what kind of brass you are using. If you use Lake City Brass you need to back your load down by at least 10% because the brass is thicker and therefore has less internal volume! I tried to put 44gr of Varget in one and practically filled it to the top! There is other "Military" brass out there that will also be thicker. I have other brass with the headstamp "CAVIM". I haven't checked it fully yet but it appears to be thick also... FWIW

John

 

[Kinsman]

Re: Manual Discrepancy

If you have the LATEST book, regardless of source, you are probably safe to start at the listed maximum and work up.
All the loads listed are below SAAMI requirements to be safe to shoot in the oldest guns in that caliber. IE, the loads in 30-06 will be safe to shoot in Granddads old 03A3. Or in the 45-70, it will be safe in the falling block guns of the 1800's. Unless otherwise specified for a more modern gun.
I, personally, do not start at maximum. I will, however, start at
mid range, and work up. Starting at minimum is a waste of powder.

 

[Fuzzball]

Re: Manual Discrepancy

"If you have the LATEST book, regardless of source, you are probably safe to start at the listed maximum and work up.
All the loads listed are below SAAMI requirements to be safe to shoot in the oldest guns in that caliber"

My friend with a near new M70 in 22-250 would challenge your suggestion to start at a max load and work up. He gets blown primer pockets with mid-range loads of Varget and no "old" loading books cover that powder. IF he had started at max loads he would probably still be picking bits of wood and steel out of his hide, IF he still had the eyes to do it with. Perhaps the book makers know something when they ALL suggest atarting at the low end and working up from there, including for cartridges of modern design so there can't be any stock of (supposed) old, weaker guns for them.

I really doubt any of the book makers would agree with your accessment that "all" of their loads are well under SAMMI. In fact those books which list their pressures confirm they bump right up to the SAMMI limits so I wonder how you justify that observation. ??

 

[dmgreene]

Re: Manual Discrepancy

Run a ladder test. I don't use it so much as to find accuracy as I do to find the max for a particular load. Powder charges above 50 grains I load in half grain increments and below 50 I load in .3 grain increments. I start with a load near minimum and load 1 round each until I get 1 to 3 grains over max. I shoot all loads over a chrono and if I start show pressure signs before I get to max I stop. I want to know where the maximum limit is for the simple reason that I want to stay away from it.
I have worked up loads that I thought were perfect only to find out that they were on the edge and any little change would put the load over safe operating pressure.

 

[Sig685]

Re: Manual Discrepancy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">Hodgdon makes the powder. Use their data. I always use Hodgdon's data but obviously don't start at max. Use the starting load. You will notice that the data is different from sourse to source. Sierra's max load with Varget isn't even the starting load from Hodgdon. Sierra is well known for being very conservative. You can use Sierra's if you want to be able to watch the round go down range

</div></div>

Rob01 said it best. If I want to know how to use a product, I get the information from the manufacturer not from a third party. Powder manufacturers know how to use their product and they have the equipment to develop safe loads. Of course, their data will be for their own products.

 

[Kinsman]

Re: Manual Discrepancy



The caveat:

I, personally, do not start at maximum. I will, however, start at
mid range, and work up. Starting at minimum is a waste of powder.