How reliable/accurate are published reloading manuals?

[Cassidy]

Last weekend when working up a reloading plan to tune my barrel for a new round, I had to determine the max powder load for 308 Win, 175 gr HPBT rounds using N550 powder. Two different reloading manuals gave me two different max powder loads - the difference between these max loads was between 2.5 and 3 grains. Can both manuals be correct? I sent an email this weekend to the company that produces one of the manuals and have not heard back from them yet. In your experience, how much can we rely on the accuracy of powder load data in published manuals? All comments are welcome.

Cassidy

 

[Immike]

If you look at all the data you will find differences in primers, barrel length and more. Older books have higher charges and the newer have lower as a rule. The reason is safety.

 

[Cassidy]

One manual is 2008 and the other came with the powder a few months ago.

 

[Immike]

Start with a load they both agree on and take the wheel. If it's too hot in your gun then back off until you are confident you are safe.

 

[Laurie]

Initial pressure testing is mostly done using a 'universal receiver' and a barrel which has been specified as matching SAAMI or CIP (European equivalent to SAAMI) specifications in terms of bore and groove diameters, twist rate etc. Chambering should likewise be with a chamber close to that specified by the regulatory body.

A range of charge weights with a powder / bullet will be test fired and the results graphed with a line drawn up the middle of a pressure / charge weight plot. This will be used to calculate what weight produces the SAAMI / CIP maximum allowed pressure. if the manual is laid out in 50 or 100 fps MV bands, the point on the central line that corresponds to the highest MV band where the load is estimated to still be within the allowed maximum pressure becomes the maximum charge weight in the table. I imagine this is all done on a PC now just feeding in charge weights and psi readings.

Many manuals then do a further test using a factory rifle to get MVs as SAAMI spec test barrels often gave higher MVs than slacker barrelled / longer throated production rifles and once shooters got chronographs, rather large discrepancies appeared and gave rise to a lot of criticism.

One reason for a large variation on Viht powders is that CIP specs which Vihtavuori use may be different from SAAMI. There can be other factors too. Viht .308 Win data is generally very severely understated and it may be that a CIP 308 barrel is very 'tight' / short-throated compared to SAAMI, or it may be that the company is concerned that the data will be used to load cartridges to be fired in 7.62X51mm rifles whose barrel and chamber specifications are NOT the same as .308 Win and have adopted the 'safer' option.

As noted too, companies have to protect themselves from the inexperienced, stupid, and litigious. They know that warnings that their data ONLY applies where all components are as per those listed on the data will be ignored. Their justifiable concern is that somebody loading 308 Win for instance will use the hottest primer on the market, fattest and thicket/heaviest jacket bullet of that weight available, the thickest lowest capacity ex-military case that barely complied with SAAMI / CIP specs with an oversize flash-hole, and fire all this in a tight-barrel 7.62mm 1st generation Enfield target rifle whose barrel is two or three thou' undersize to cope with poor quality 1960s and 1970s NATO 144gn milspec ball ..... and that the user may decide life is too short to waste it by working loads up from the recommended starting load.

The whole point about manuals is that you know the data is safe with the listed components in a standard specification barrel and chamber. It provides a starting point to getting an optimal load for the keen and knowledgeable handloader who has access to a chronograph and recognises the onset of over high pressure signs. Some of the most skilled people I know load initial test rounds singly purely as pressure test loads and will ever so carefully ease the bolt handle up on a fired case to see if there is that bit of extra resistance to the final lift, the bench-rester's 'click' that shows the case has expanded materially ahead of the web, while looking at what the chronograph says. Only when they're happy with those pressure signs, do they start loading threes for initial group size checks.

On the other hand, the average deerhunting Joe will be able to work up to the maximum in his manual and it may be a bit below what he might optimally get safely, but it's highly unlikely it'll cause him any problems.

 

[DRNewcomb]

Understand that the powders sold for reloading are actually blended from different powders to give fairly consistent performance batch-to-batch and year-to-year. This is why a, say, IMR 4895 sold in 1970 will load pretty much the same as a can of IMR 4895 sold in 2010. While the testing systems have been standardized, there are differences in the exact loadings tested. For instance, all 150 grain bullets don't have the same internal ballistics. All primers don't produce the same ignition. Different cases produce different pressures. All these factors can contribute to differences in published loading tables.

 

[its only light]

One other thing to take into consideration is what kind of brass was being used for the tests. I've noticed in my 308 that Winchester brass has quite a bit more capacity than say federal or lake city brass. I actually have to put more powder in the win cases to get the same velocity as I do with a fed case. Just a thought, it should be listed in the manuals what brass and other components were used. If they weren't using the same brass that could be at least part of the reason for the difference.

 

[Cassidy]

Common guys -my question is have you seen errors in loading manuals. I know there's some variation, but have you seen what you think is an error in a loading manual?

 

[oldroper]

One manual is 2008 and the other came with the powder a few months ago.

What's then name of the manuals your posting about?

 

[bozo699]

Common guys -my question is have you seen errors in loading manuals. I know there's some variation, but have you seen what you think is an error in a loading manual?

Hey Mr.18 posts,
posts like this really tick me off, you asked a question and several top notch shooters gave you there best answers, you never mentioned the manuals, was one a speer and one a barns? because there copper composition is totally different that is why they tell you never to substitute! what brass was a viable question, when was the powder made you were shooting, contrary to what you may have been told powder does vary in burn rate from lot to lot and especially from 1970 to 2010! No where in your post did you ask if we have ever found and error in a reloading manual,..this is what you asked,......[ In your experience, how much can we rely on the accuracy of powder load data in published manuals? All comments are welcome.] Now with all that being said YES I have found errors in reloading manuals, I have been loading for years and have most manuals made in the last 25 years and ONLY use them for reference I pretty much no where I want to start and with what but no matter if very experienced or not they should be for reference only and NEVER an absolute!!!
Wayne.

 

[LHSmith]

What Wayne said above echoes my thoughts exactly. There has been MAJOR burn rate changes in the same labeled powder by the same manufacturer through the years....H322 for one comes to mind. The OP got some very good responses....however EVERY reloading manual I have explains the "why" in variation between manuals. That's why they are called "manuals"....your supposed to READ them.
It seems Cassidy, you skipped Reloading 101.

 

[bigedp51]

Common guys -my question is have you seen errors in loading manuals. I know there's some variation, but have you seen what you think is an error in a loading manual?

Hey Mr.18 posts,
posts like this really tick me off, you asked a question and several top notch shooters gave you there best answers, you never mentioned the manuals, was one a speer and one a barns? because there copper composition is totally different that is why they tell you never to substitute! what brass was a viable question, when was the powder made you were shooting, contrary to what you may have been told powder does vary in burn rate from lot to lot and especially from 1970 to 2010! No where in your post did you ask if we have ever found and error in a reloading manual,..this is what you asked,......[ In your experience, how much can we rely on the accuracy of powder load data in published manuals? All comments are welcome.] Now with all that being said YES I have found errors in reloading manuals, I have been loading for years and have most manuals made in the last 25 years and ONLY use them for reference I pretty much no where I want to start and with what but no matter if very experienced or not they should be for reference only and NEVER an absolute!!!
Wayne.

Dear bozo699

I have never seen you this out of sorts and angry, I have this physic image of your wife washing your underwear in a tumbler with stainless steel pins and not rising the pins out of your underwear before you put them on.

I could be wrong its only a physic guess and a stab in the dark................

P.S. Let me know if anything I wrote here might be a misprint.

 

[bozo699]

Common guys -my question is have you seen errors in loading manuals. I know there's some variation, but have you seen what you think is an error in a loading manual?

Hey Mr.18 posts,
posts like this really tick me off, you asked a question and several top notch shooters gave you there best answers, you never mentioned the manuals, was one a speer and one a barns? because there copper composition is totally different that is why they tell you never to substitute! what brass was a viable question, when was the powder made you were shooting, contrary to what you may have been told powder does vary in burn rate from lot to lot and especially from 1970 to 2010! No where in your post did you ask if we have ever found and error in a reloading manual,..this is what you asked,......[ In your experience, how much can we rely on the accuracy of powder load data in published manuals? All comments are welcome.] Now with all that being said YES I have found errors in reloading manuals, I have been loading for years and have most manuals made in the last 25 years and ONLY use them for reference I pretty much no where I want to start and with what but no matter if very experienced or not they should be for reference only and NEVER an absolute!!!
Wayne.

Dear bozo699

I have never seen you this out of sorts and angry, I have this physic image of your wife washing your underwear in a tumbler with stainless steel pins and not rising the pins out of your underwear before you put them on.

I could be wrong its only a physic guess and a stab in the dark................

P.S. Let me know if anything I wrote here might be a misprint.

Nope your pretty well spot on as per usual Ed,
Wayne.

 

[Cassidy]

You guys are pretty sensitive. A simple yes would have worked.

 

[LHSmith]

You guys are pretty sensitive. A simple yes would have worked.

A simple tactful re-phrasing of your question would have worked also.....and yes.....some of us "common" guys are pretty sensitive,but most are just sensitive and not all that pretty ???.....Come-on ...that's funny right there.

 

[mac86951]

Sensitivity aside, I can say another reason for checking multiple references is to avoid the copy-editing error or typo. I've found a few places in the Lyman 49th, where the Max load is listed correctly, but velocity has a typo. EG 3954fps instead of 2954fps. Easy to find these by researching various loads in the same manual.

If you only have one manual, I find that there are plenty of online resources to use like Hodgdon website, or other powder manufacturers. Even the bullet manufacturers have some information too. Like others have already mentioned, make sure you compare apples to apples by looking at powder, bullet, primer and understand variances can occur by changing any of those.

-Mac

 

[bozo699]

You guys are pretty sensitive. A simple yes would have worked.

No sir your original question was a how can you rely,...it was not a yes or no question or answer, then you said all answers welcome, now if you had of want to know has anyone ever seen a mistake in a loading manual you would of had 12 replies of yes but that is in fact not what you asked then you came back with COMMON GUY'S! anyway then you started another thread on how to safely kill a live round, several super knowledgeable shooters told you how to do it and you told them you read somewhere that that was unsafe and you wanted another alternative???? Anyway I hope you safely are able to disarm your loaded rounds and I hope you find a loading manual with a safe max load in it for your rifle,...best of luck.
Wayne,

 

[BoydAllen]

After years of reloading experience, the only thing that I use book data for is to come up with a safe charge weight to start a workup with. I would never use the maximum manual load as a starting point, for a couple of reasons. One is that I like to do my own mini ladder/pressure test, starting well below where I think that I will end up for a selected load. The other is that I have never loaded to a standard OAL, because I have usually found my best accuracy with bullets loaded longer than touching, and since I know that this increases pressure, I usually drop back to a middle value in the book loads to start my investigation. I would also add that I do my workups at the range, shooting over flags, and a chronograph, on days when the wind is not too tricky. How do you work up your loads?

 

[280shooter]

This is better than TV. It is easy to tell who has been loading for a while verses the newbe. BOZO an you other guys that give out the info I really like to read your posts. An I have been reloading for40 Years you still can learn something new.

Johnnie

 

[jonbearman]

I trust these guys as well as they have more experience and probably forgot more than I will ever know.That being said,I think anyone should have as many reloading books to extrapulate all the imfo they can before making a loading plan.I start at near the bottom always looking for a node at lower pressures to be on the safe side.If it is match ammo then I look for a higher node for wind bucking ability(time of flight) to be sure I have max velocity safely.