Home Forums Reloading Big Game Rifles Chronograph - the great truth serum

SJ,

I get your point and have seen other instances where a manual seemed to have poor data because of using powders -- I think Lyman and Sierra both show instances of choosing a faster spectrum of burn rates than I would have.

But I would suggest there are probably reasons for Nosler's lack of higher-velocity data, reasons other than incompetence or cowardice. (Some of their velocities for cartridges I've loaded have come in much higher than I've ever been able to manage.)

For instance, I recall reading in one of the manuals that whichever company it was did shoot other powders but didn't list all the results, only those that gave acceptable levels of accuracy. Maybe in Nosler's particular test barrel they got poor results with RL-25.

Another thought -- was RL-25 available in 1996 when the Nosler 4th ed. was published? (And remember the shooting had to occur even earlier.) I honestly don't know, but seem to recall that it's a relatively recent addition.

You could always call them and ask, I know several people who've gotten unpublished data from various companies that way.

John

John Fraser-What do you make of the situation with the data for the 7mmremmag,7mmwbymag and 7mmstw in the nosler reloading manual number 4 that myself and Steve NO discussed in the previous posts?While you are at it compare the loads for the 165gr nosler bullets in both the 300winmag and 300weatherbymag.Nosler actually is producing 48fps more from the 300winmag than the maximum velocity from the 300weatherby mag even though the 300 weatherby has much more case capacity and has a barrel 2" longer. Check it out and see if it makes sense to you.

Ringman,

I guess on the low side, based on chamberings with simliar bore to capacity ratios and similar volumes.

Since I load at the range, I throw a low side powder charge and shoot it through the Chrono. I then increase a couple clicks (approx 1.2 grains) at a time until I get good accuracy, run out of case capacity, see the velocity spike, or in rare cases, get a conventional sign of pressure. I then change powders and start again. I then take the most promising powder and mess with bullet seating depth, going in .005" increments.

I usually take 50 or so prepped and primed cases to the range along with bullets, powder, my Harrel Powder Measure, my little RCBS partner press, and other misc reloading tools.

Blaine

Well, I'm not quite sure what you want me to look at; but what I see with the 7mms is that the bigger cases show increases in velocity -- not necessarily an increase in the highest velocity ever reached with a load, but increases in general.

For instance, with the 160-gr. bullets, they got to 3112 with one load in the 7 RM but only got over 3000 with 4 other loads. (And, the most accurate load was only 2904). With the 7 WBY they didn't quite reach 3112 (3110 max.) but 6 other powders got over 3000, several close to 3100 (including the most accurate), and only one powder tested did not make 3000. And in the 7 STW they got over 3100 with 5 powders, and over 3000 with every powder tested.

I don't know what to make of the .300 data, I guess if I owned a .300 of either variety I'd cross-check with other data for the same bullets.

John

Ringman-Since you are the owner of a 7mmstw you might want to have a look at the nosler data that I have been discussing in the previous few posts.It may have a bearing on which data you want to use for a reference when loading for the 7mmstw.The larger cases of the 7mmweatherby should have provided a higher attainable velocity than the 7mmremmag but in the nosler manual this was not the case.The extra 2" of barrel in the case of the 7mmstw should have added more than 50fps over the 7mmremmag on it's own let alone the huge increase in case capacity that the 7mmstw offers.As well r-22 is well known as one of the best powders for producing top velocity with 140gr bullets in the 7mmstw so the fact that nosler produced more velocity with this powder and the 140gr bullets in the 7mmremmag than with the 7mmstw really shows a problem with the data.If you add in the data for the 165gr loads in the 300winmag and 300wby it is obvious that nosler does have some serious problems with their reloading data and if you own one of the cartridges discussed you may want to look elsewhere for your reloading data when reloading these cartridges.

stubblejumper,

When I loaded for the 7STW, it was called a 7MMCoyleWildcat. That is what is on the barrel. It predates the STW. I knew it was an 8MM Rem. Mag necked to 7mm. That' why I called it an STW when I mentioned it earlier.

I will not own an STW until the Brown Precission arrives in the spring (I hope by then.). Each day I tell me and others, "I'm one day closer." Of course the others don't know what I am talking about. They erroneously think I'm crazy.

Hondo64d -- As you have noted, a chronograph is one of the most useful tools that a handloader can have. I have done a lot of test firings in different rifles outfitted a with strain gage and plugged into my M43 and am convinced that a chronograph is a useful instrument for estimating pressure ranges if one is using reliable data.

While on the subject of reliable data, I will say that I do not consider the Sierra 4th edition (50th Anniversary Edition) to be a reliable source of data and find much that is suspicious in the Hornady manuals. Nosler #4 is variable. The only rifle reloading manuals I trust pretty well are the current Hodgdon (#27) and Speer (#13) manuals. Even some of the data in the Hodgdon freebe 2003 Basic Reloaders Manual (and on line) is highly suspect. An example of this is on page 30 where they show 18 grs. of Li'l Gun behind Hornady's 158 gr. XTP as producing 1577 fps @ 25,800 CUP in a 357 magnum with a 10" barrel. I have run more than one test duplicating this load as closely as possible and obtained an average pressure of 42,700 psi. The SAAMI maximum average peak pressure for the 357 magnum is 35,000 psi.

Another consideration when looking at data in the manuals is the SAAMI average peak pressure for the cartridge. Generally speaking, the loading manuls will show maximum loads at or just below the SAAMI peak, but how they determine this is problematical since most do not actually provide pressure data and don't explain the procedures used to determine "maximum" pressure. For example, Sierra states they used a Winchester M70 with a 26" barrel in their '06 tests. So, how did they determine the maximum loads listed? Case head expansion? Velocity? Selected loads fired in a pressure gun? The same questions can be asked about any number of other data manuals.

As for sophisticated laboratories, I will say now without equivocation that when you see pressures given in CUP or LUP units, the data is not from a sophisticated ballistics lab.

Okay, now that I have said all this, let the disagreements begin. By the way, I am a professional ballistician who consults with the Army's Field Artillery as those of you who have surfed out to my web site might surmise.

OKShooter
Give me a call at 1-936-258-4984 sometime during the day Saturday or Sunday if you get a chance......I've got some info that will just blow your skirt up.. <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" /> <img src="/ubbthreads/images/graemlins/shocked.gif" alt="" /> <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
Charlie

OKShooter-So you are saying that from your own testing with specialized pressure testing equipment the data supplied by at least 3 of the bullet manufacturers and most of the powder manufacturers is not reliable.It sounds like reliable data is either very rare or a chronograph is really not an accurate way to estimate pressure.I guess that is why a company such as ohler that makes some of the best chronographs available also makes specialized pressure testing gear such as the m43.

A chronograph is a reasonably reliable way to qualify pressure range if one has other independent, reasonably reliable data. (Note that I specifically said here and in my previous post 'qualify' and not 'quantify.') Obviously I haven't tested every load combination in any of the manuals, but I have tested more than a few from each major manual spread across several different cartriges. As I said in my previous post, I consider Hodgdon and Speer data from their current manuals sufficiently reliable for most purposes.

To use a chronograph effectively to qualify a pressure range, though, one must pretty well know their stuff and apply judicious logic to the situation. For example, that 26" barrel M70 that Sierra used for their '06 data is not what one is likely to find on the gun rack today or for many years past. The general rule of thumb is a velocity change of 35 fps per inch of barrel for cartridges in the '06 velocity range. Taking, for example, their IMR-4831 data for their 200 gr. SBT (55.4 grs. for 2600 fps), one could expect that a chronograph reading of around 2530 fps with a 22" barrel and around 2570 fps with a 24" barrel would be approaching a maximum pressure range for the '06 cartridge (60,000 psi/50,000 CUP). That did prove to be so when fired in my M700 (22" barrel) since I recorded 2538 fps @ 57,900 psi using 56 grs. of IMR-4831.

Another example is their 52.8 gr. RE-19 load for 2600 fps. I started my testing using only the Oehler M35P and increased the propellant charge in 1 gr. increments until I reached approximately the idealized 2530 fps level. (Actual average velocity recorded with the M35P was 2620 fps.) I stopped at 56 grs. since I was a solid 3+ grs. over the data point and then plugged the M700 into the M43 and recorded an average velocity of 2517 fps @ 56,800 psi.

The other thing that bothers me about some of these manuals is exactly what does the listed maximum charge really mean. Referring again to the '06 200 gr. load data in the Sierra manual, they show a maximum load of 58.7 grs. H-1000. I think that most of us know that one is going to be hard pressed to get enough H-1000 in an '06 case to cause pressure problems and still seat a 200 gr. bullet. I tested a load of 62 grs. H-1000, again in the M700, behind the Sierra 200 gr. SBT and recorded 2441 fps @ 51,600 psi. What I found matches fairly well with the Hodgdon data, although they did use the Speer 200 gr. bullet instead of Sierra's. Anyway, Hodgdon listed 61 grs. as producing 2510 fps @ 44,400 CUP out of their 24" pressure barrel. If the 10,000 unit difference between CUP and psi holds at these lower pressures in this cartridge, that indicates a pressure of around 54,400 psi.

The point of this long-winded dissertation is that when the publisher of a data manual does not explicitly explain and define their technical procedures and publishing policies we handloaders are really left to guess what at least some of their data really means. I could go on and on with other examples from other manuals, but I doubt if there is any point in it.

OKShooter,did you get much difference in pressures between different brands of standard bullets,say 180gr flat base PSP in 30.06.

I have heard that the partition-style generate higher pressures than standard ones.

Stubblejumper,

Give it up already! Maybe if I hook the back part of what Stan said to my chipped DMax I can stretch Stan's comments to get to what you posted.......... <img src="/ubbthreads/images/graemlins/blush.gif" alt="" /> <img src="/ubbthreads/images/graemlins/grin.gif" alt="" /> <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" /> <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

Now what you could say is that my technique of considering bullet maker data the most reliable data is out to lunch, based on Stan's comments. Of ocurse, I would just repeat that my primary method is to look for accuracy first the the velocity spike next, which I almost always reach before seeing any conventional pressure signs or reach the max manual velocities.

All this makes me wonder what you'd think if you know that I only consult manuals for the first load with the first powder for a new bullet, and that I do not weigh any powder charge until after I find a good load. <img src="/ubbthreads/images/graemlins/blush.gif" alt="" />

Have a good one. BTW, you are welcome--for me inviting Stan to the thread, that is!

Downwindtracker2 -- No, not so very much. In one set of my testing, I used the 30 caliber Remington 180 gr. Pointed Core-Lokt, new W-W brass, and Winchester's standard WLR primer. All of the brass was run through a neck sizing die to true up the necks and trimmed to 2.482". The primer pockets were uniformed, and the flash holes were deburred. The propellant was 58 grs. H-4350, and my Winchester M70 Classic '06 was the test bed. This index load produced an average instrumental velocity (10' from the muzzle) of 2700 fps @ 53,600 psi with a velocity standard deviation of 12 fps and a pressure standard deviation of 1,100 psi.

All of the conventional bullets I substituted, both flat base and boattail, kept the pressures in the 54,000 to 56,000 psi range. The Swift A-Frame, the Nosler Spitzer Partition, the coated Barnes XLC, and all of the Combined Technology bullets did so as well. The Nosler Ballistic Tip pushed pressures into the 58,000 psi range, and the uncoated Barnes XFB pushed pressure to almost 60,000 psi. The Swift Scirocco pushed the pressure to 60,900 psi, which is, of course, slightly over the SAAMI maximum for the '06. In summary, the only bullets that I can say increased pressures significantly were the Nosler Ballistic Tip, the Barnes XFB, and the Scirocco.

Subsequent to the '06 tests, I have run bullet substitution tests for the 6mm Remington (Remington M700 Classic), 280 Remington (Browning Medallion with 22" barrel), 7mm RemMag (Remington M700 with 24" barrel), and the 375 H&H (Winchester M70 Classic with 24" barrel) with very similar results. (The Scirocco, of course, wasn't available for 6mm or 375 tests.)

Stan - I'm assuming (which I know can be a bad thing <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />) that the rifles you used in your tests are standard production units. Is that correct?



Have you ever done tests using a SAAMI spec chamber/barrel and, if so, how do they compare with OEM rifles? I'm guessing SAAMI's specs are pretty much a worst case, ie, minimum chamber, etc.., so, pressures obtained in them would probably be higher than the same load would generate in a production rifle?



Man, this pressure thing has really got my curiousity piqued. Especially after reading Barsness' article; and, now Charlie keeps dropping crumbs, but won't let us see the whole loaf. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />



R-WEST

RWest -- Yes, I purposely decided to use standard production rifles in order to get some handle on what one could expect from off-the-shelf rifles. I have, though, done some comparison firings using SAAMI spec barrels for two different cartridges. On the average, a SAAMI-spec lab barrel will cause around 2,500 to 3,000 psi increase with respect to most production barrels. This does, of course, establish sort of a safety cushion for published data that has been developed using a lab setup.

The gotcha with this is that many of the custom rifle barrels being produced will develop pressures pretty much in line with what one would expect from a SAAMI-spec lab barrel. In fact, that Remington M700 I mentioned in my previous posts does so as well. The Remington consistently produced results that were around 2,500 psi higher than the same load in the Winchester M70.

While on this subject, let me add one more observation. I am convinced that there is no such thing as "fast barrels" and "slow" barrels but only barrels that produce more or less pressure. For example, many of the loads I tested in the '06 in both the M700 and M70 produced virtually the same velocity even though the M700's barrel was 2" shorter than the M70. It did it, of course, because it produced higher pressures.

This observation also gives one more reason why a chronograph is a useful tool for handloaders. The rules of thumb about velocity variations correlated to barrel length is valid only if the different rifles produce about the same pressure levels. In no case, however, have I ever seen a load combination produce excessive pressures when the results of chronographing are judiciously analyzed.

If a person has an ohler M43 and access to several rifles chambered for the same cartridge and with the same barrel lengths it would be relatively easy to prove whether or not there are in fact fast and slow barrels.All that you would need to do is set up and test fire the rifles while adjusting the loads slightly until the pressures were the same in all of the rifles.The chronograph would then prove one way or the other whether or not there really are slow and fast barrels.Several rifles would be required to make the sample large enough to be valid and it would be even better if both production and custom barrels were used possibly even barrels of different construction such as button rifled and cut rifling or hammer forging.If anyone with access to the M43 and the rifles was to undertake this adventure it would certainly make an interesting experiment that would answer this question once and for all.Unfortunately there are few people with the resources and time to take on this project so until such a test is conducted no one will know the true answer to this mystery.

OKS:

Thanks for your learned and very professional input on this subject. The points that you expand upon are the ones that AFP and I (among others) occasionally put forth to some of the velocity fans. IE: #1 "there ain't no free lunch" and #2 "she ain't blowed up...YET" is not a reliable indicator of wise loading practices.

It is strange to me that some of the folks that push the envelope the hardest are already using the biggest case, fastest cartridge within a given bore size. Then they proceed to push 150-200 fps beyond the (consensus) norm for their cartridge.

SJ, don't get riled up here, this is not intended as a personal affront to you. Merely an observation and an illustration of a practice that most if not all (professional) ballisticians would consider unwise.

An example would be the 7mm STW. It's already the fastest production 7mm around, no question there. But why would one take the risk associated with pushing it so hard that there could be serious long term (maybe even fairly short term) consequences. (Note Ken Howell's comments on the Wby powders thread)

It seems to me that if one "wants" more than what a 7mm STW can deliver at 62K or so, the sensible thing to do is just get a bigger case and load (it) to 62K or so. For some reason, that never seems to get much traction among the hotrodders. They would apparently rather risk the consequences of loads that might be in the 70K (plus) range.

I guess the biggest problem I have is that despite some perfunctory statements such as "work up from below watching for pressure signs" an inexperienced or new reloader with the hots for velocity will read these threads and think "Well it worked for him, why not for me"? This all fails to account for the increasingly obvious fact that conventional pressure signs often don't show up below 65K PSI or higher. This pressure level is CLEARLY not wise for long term use. Again reference Ken Howells recent comments on the Wby powder thread.

Last aside to SJ:

No axe to grind with you. PLEASE don't take this negatively. If you think your loads are safe in your rifle, cool...so be it. I only question the means with which you quantify safety, especially in light of the most recent findings Re: pressure signs. Most especially, I question the wisdom of posting those ballistics to others, outside of a private post.

While you vehemently defend your loads and your methodology, I think you are savvy enough to know you are near the ragged edge. Maybe over it, maybe not, who knows......but you (ABSOLUTELY DO) know you are close. If you choose to tread that line....again, that fine, it's probably not wise to encourage others (even indirectly) to do the same.


JimF

Stan,

If you corrected pressure for the difference in barrel lengths, do you think you'd generally find that it takes a certain pressue to acclerate a given bullet to a given velocity from a given chambering in a given barrel length?

I understand there will be slight variances between barrels, but with barrels of the same length barrels, won't a given pressure/time scenario yeild similar velocities?

I think of this more in terms of a conservative factor. if the SAAMI standard for a 165 grain 30-06 bullet from a 24" barrel is 2850 fps at 60,000 PSI, then I say when I get 2950 fps I am doing so at a higher pressure.

Blaine

This is a very good set of posts. As already stated, I've also come to the conclusion that the Hodgdon data set is the most reliable indicator of potential velocity. I've had alot of problems attaining the velocities posted in the Nosler manual for the given powder charges and have had mixed results with the Barnes data.

As a result of using my chronograph, I use the Hodgdon data as a starting point and work up to the bullet manufacturers recomendations. Sometimes I can't get there without excessive pressure.

I do have a question, why does SAAMI use several different pressure standards for 06 based cases? The 06, 280 stop at 50,000CUP/60,000 PSI, 270, 338-06 and 35 whelen go to 52,000 CUP and the 270 goes to 53,000 CUP. Why?

Additionally, I think alot of the difference in pressure readings/velocity differences comes from the differences in equipment used to determine pressure/velocity. I would think pressure barrels use uniform, standardized dimensions while most of the data given by bullet and powder companies use real life firearms, leading to slight differences in bore diameter, finish, twist, throating, chambering, etc.

When all is said and done, does it really matter if you're 7mm Loudenboomer is pushing 140 gr bullets at 32, 33 or 3400 ft/sec? The difference in trajectory at 400 yards is 1.4 inches (assuming a BC = 0.471). The difference in energy is 269 ft/lbs. Can anyone really hold 1.4" at 400 yards in actual hunting conditions AND do we really think the animal cares about the extra 269 ft/lbs ?................

You can speculate all you want but the" only way to POSITIVELY PROVE or POSITIVELY DISPROVE the fast or slow barrel theory is with a test such as the one I suggested".The rest is just theory that can't be POSITIVELY PROVEN one way or the other.I do not have access to the resources to conduct such a test myself though ,and only posted this in the hope of putting the idea in the head of someone that may have the resources.If such a test is ever performed it would not only answer the questions debated here but would benefit all reloaders as well as ammunition companies