hi everyone
my question is, with my 300 rum i get 3175 fps with 94.5 gr of rl-25 using a 168 gr. bullet
and in a few book they say i should be around 3350 with such a load.
does it mean that if i use 200 grainers i will get around 2875 instead of the books 3050 fps?

i also chronographed a 180 nosler partition factory load at 3150 instead of the advertised 3250 fps.

is it just a slow barrel for whatever reason?

Check your chrono against a "known" one. That said, barrels are unto themselves, their own world. Some are fast, some slow, accurate, you get the picture. Advertisement is exactly that. Advertising.

I agree with checking the chrono to be sure. You could also run some .22 RF ammo of known velocity , or someone's tested loads over it. If the numbers are not making sense, something needs to be verified, and the chrono's accuracy would be the easiest, I expect. I often find that factory ammo does not live up to its advertising, so I don't thing that measurement is reliable.

If the Chronograph checks out, you should not be too shocked at the individual differences of your barrel. They are all unique.

I have seen side by side chrono's differ by as much as 200fps on bullets that are going(~)3000fps. These were the more expensive chrono's also.

I'm no "guru" on the subject but IMO it all depends on the light and the shadows.

Bottom line.......everyone's gotta believe in something,or,"does anybody really know what time it is ??" I probably would believe a reloading manual(if you stick to the "formula" precisely)over my own chrono. -----pruhdlr

300rum,

You didn't say what your barrel length is? The load velocities will all be given at one standard barrel length. 30 fps or so velocity difference per inch of barrel isn't uncommon n rifles. It gets lower as the barrel gets shorter.

Bad chronograph readings are all too common, too.

In addition to the above suggestions, the composition of your loads can influence the outcome, i.e., type and brand of primer, brand of casings, type and brand of bullet, depth of bullet seating, lot number of powder, etc.

I have seen side by side chrono's differ by as much as 200fps on bullets that are going(~)3000fps. These were the more expensive chrono's also.

I'm no "guru" on the subject but IMO it all depends on the light and the shadows.

Bottom line.......everyone's gotta believe in something,or,"does anybody really know what time it is ??" I probably would believe a reloading manual(if you stick to the "formula" precisely)over my own chrono. -----pruhdlr

I agree to a point. It is quite possible to get bad readings from a chronograph, and it is usually easy to spot them. But if I run 10 over the screens and get an extreme spread of say 125 fps, and a standard deviation in the 20 fps range, I would believe the very consistent results of the chronograph over any manual's listing.

In addition, if I set up the machine 3 times and get results that average within 35 fps of each time for a specific load, I think the results are valid.

Statistical analysis is not intuitive sometimes, but there are ways of differentiating bad data from good data. I think that I have lots of personal load data from chronographs that varies from published data by significant amounts. It's still good data.

One more point, I have seen very consistent results from more than one chronograph tell me that I was getting very different results than the testers got from a specific recipe from a manual. I have also seen reliable results from a chronograph that proved two rifles shooting the same load gave very different results. So I think the manuals are a very rough guide, and a chronograph, properly used and understood, is a very important tool.

Several good points and maybe some element of wishful thinking in all that. Unfortunately, proving consistency of performance is not the same as calibration. If you separated the sky screen sensors by an extra inch and kept them that way, your consistency and resolution could still be good, even under different light conditions, but the accuracy would be poor. In other words, the tool can't really self-calibrate.

Using more than one machine for comparison is another matter. Now you can look for some level of consensus, which adds weight to a conclusion of accuracy. As long as the original design is basically sound, you can expect errors to tend to be randomly distributed on a bell curve that has its peak position (the mean, or average) pretty close to absolute accuracy. If there is an error in the design, though, then the result may be biased. The best way to avoid that is to compare the results off a number of different designs, which is most likely to happen if you randomly try different brands at the range.

Good point on manuals, though. If you get QuickLOAD and just adjust the brass volume a little, you quickly come to appreciate what a modest difference in chamber tolerance can do to velocity. And that doesn't take into account things like stronger/weaker firing pin strikes or properly/improperly seated primers, difference in start pressure due to COL, etc. The manuals have the plus side of being fired in real guns, for a reality check, but the downside that they aren't fired in your particular gun. The computer model has the downside of not being a real gun, but the plus side that you can match it to your particular gun pretty exactly.

By the way, when you look through manuals with pressure numbers, unless it states otherwise, the loads were developed in a SAAMI pressure test barrel. These barrels are specified at the same time other SAAMI specs for the cartridge are created, and include a minimum chamber and a typical bore and rifling pitch and the length of the barrel. The chamber tends to create worst case pressure peaks by being small, so unless you have a tight bore (slug it to see), you will find your gun most often has a little leeway for more powder with these loads if you are using the the same case and primer.

Several good points and maybe some element of wishful thinking in all that. Unfortunately, proving consistency of performance is not the same as calibration. If you separated the sky screen sensors by an extra inch and kept them that way, your consistency and resolution could still be good, even under different light conditions, but the accuracy would be poor. In other words, the tool can't really self-calibrate.

Using more than one machine for comparison is another matter. Now you can look for some level of consensus, which adds weight to a conclusion of accuracy. As long as the original design is basically sound, you can expect errors to tend to be randomly distributed on a bell curve that has its peak position (the mean, or average) pretty close to absolute accuracy. If there is an error in the design, though, then the result may be biased. The best way to avoid that is to compare the results off a number of different designs, which is most likely to happen if you randomly try different brands at the range.

Good point on manuals, though. If you get QuickLOAD and just adjust the brass volume a little, you quickly come to appreciate what a modest difference in chamber tolerance can do to velocity. And that doesn't take into account things like stronger/weaker firing pin strikes or properly/improperly seated primers, difference in start pressure due to COL, etc. The manuals have the plus side of being fired in real guns, for a reality check, but the downside that they aren't fired in your particular gun. The computer model has the downside of not being a real gun, but the plus side that you can match it to your particular gun pretty exactly.

By the way, when you look through manuals with pressure numbers, unless it states otherwise, the loads were developed in a SAAMI pressure test barrel. These barrels are specified at the same time other SAAMI specs for the cartridge are created, and include a minimum chamber and a typical bore and rifling pitch and the length of the barrel. The chamber tends to create worst case pressure peaks by being small, so unless you have a tight bore (slug it to see), you will find your gun most often has a little leeway for more powder with these loads if you are using the the same case and primer.

Maybe a little wishful thinking, but I have tried to be conscious of the difference between consistency and accuracy. I have run competition level .22RF over screens as a sort of "test" because that ammo is astonishingly consistent. Of course, that is relatively low speed stuff, but an estimate of the error can be made. It is true, though, that the possible inaccuracy of the machines is hard to pin down for us guys with limited technology.

I like to think also that, even if there is some inaccuracy, good consistency can tell you a lot of useful stuff, especially if you keep good records (and I like to think I do - maybe more wishful thinking?).

Agree on your last point. Keep an eye on ratios of change as opposed to absolute numbers. You can use that perfectly well for comparing old loads to new and looking for velocity dead spots that might indicate pressure, and so on. Most game doesn't care, give or take a couple hundred fps, as long as shot placement is good. The instructions that come with chronographs warn you against trying to work loads up to match manual load or commercial load performance, anyway. That is both because of gun and chamber and component tolerance introducing velocity difference, but also the uncertainty of absolute accuracy of the velocity readings.

The only places it can be an issue to be off 200 fps would be in working up loads for 1000 yard shooting, where even an extra 50 fps can keep you out of transonic drag problems near the target, and in figuring exact ballistic coefficients. I like to work on both those, and use an old Oehler 35P and a CED Millennium, both set up with 4 foot screen spacing. I just feel more comfortable knowing the longer spacing allows more time for screen triggering errors to lose their significance.

I've heard it claimed .22 match ammo can get you within 50 fps of absolute, but I don't know with what barrel lengths or other conditions? The .22 runs out of steam before it exits most rifle barrels, so it may be that there is relatively little of the kind of change in velocity with barrel length that you see among high power rifles, where it is usually in the range of 20-40 fps per inch, depending on the load and starting length. I'll have to check that with the .22 rifles I have? I've still got half a brick of Federal GM Ultimate Match set aside for testing this kind of thing.

One thing I've found over the years using 3 different brands of chronographs is atmospheric conditions (especially lighting) has an effect on readings.

As mentioned above, there are so many variables that attempting to duplicate exact manual listings is virtually impossible consistently. I'm happy if loads come within 100 fps of manual listings and in nice, tight groupings. I go for grouping first and tweak up or down to find the best combination, then go for location of groups at various ranges.

300rum wrote : "my question is, with my 300 rum i get 3175 fps with 94.5 gr of rl-25 using a 168 gr. bullet
and in a few book they say i should be around 3350 with such a load."

I had precisely the same experience, trying to work up a load for the 300RUM. I had killed my bull elk with my old trusty 30-06, at 306 yds. After that hunt, I decided that I needed a cartridge/rifle combination producing enough MV to get consistant hits on game at 400 yards AND I did not want to go to a smaller caliber. I bought a new Browning A-Bolt in 300RUM and began judiciously working up loads. Within the same velocity range as my 30-06, the RUM shot excellent groups. I did all the correct break-in cleaning. When I reached velocities higher than what I had been able to safely attain with 30-06, my groups opened up AND max loads were roughly 200 fps lower than the advertised MV. I tried various propellents, cases, primers and bullets, with no marked improvement. I loaded the bullets closer to the lands and then backed them off, to no avail, in terms of getting what I expected. In the final analisys, I decided to sell the RUM and continue hunting with the 30-06. Accuracy is much more important to me, than is higher MV. What good is flatter shooting, if I cannot score the hit in the vitals?
I received mixed reviews from other 300RUM shooters. I deduced that performance, using that caliber, varies on a wide scale. By time I gave up, I had logged 800 rounds. I had been told that the RUM barrel would begin to show a down turn in accuracy, due to wear, after 1200 rounds. I figured that before I worked up a good load for that rifle, the bore would be shot out!

You also say "in a few book (sic) they say I should be around 3350." So if not all the books agree, are you simply believing that the highest one is right? Why? Is your chrono result close to the lower reported book speeds? Is it close to the results shown by the bullet maker? (Brand of bullet DOES make a difference, not just weight.)

You also say "in a few book (sic) they say I should be around 3350." So if not all the books agree, are you simply believing that the highest one is right? Why? Is your chrono result close to the lower reported book speeds? Is it close to the results shown by the bullet maker? (Brand of bullet DOES make a difference, not just weight.)

no all max loads for 165 g in the ultra mag are over 3300 fps even 3485 for nosler
no matter the powder used
as for barnes they list 3327 with 94.5 g rl-25
they list 3150 as a start load with 86.5 g. rl25
that's what i get with 93.6 g.
somebody was kind enough to run this in quickload for me and it was right at 3150.
so why is so many people getting 3300 with 180 grainers? they load way over max
or they have custom barrels that make a difference?

hi everyone
my question is, with my 300 rum i get 3175 fps with 94.5 gr of rl-25 using a 168 gr. bullet
and in a few book they say i should be around 3350 with such a load.
does it mean that if i use 200 grainers i will get around 2875 instead of the books 3050 fps?

i also chronographed a 180 nosler partition factory load at 3150 instead of the advertised 3250 fps.

is it just a slow barrel for whatever reason?


Same result I got today. My factory ammo went 3180 out of a 26" Sendero.

"with my 300 rum i get 3175 fps with 94.5 gr of rl-25 using a 168 gr. bullet and in a few book they say i should be around 3350 with such a load. does it mean that if i use 200 grainers i will get around 2875 instead of the books 3050 fps?"

All it really means is that you are getting 3175 with that 168 gr. load.

Try laying a white sheet on the ground out in front of your muzzle. After you shoot, use some tweezers to pick up all the unburned powder kernels. They will show up nice against the white sheet! Weigh them, subtract that from your 94.5 gr load to determine how much of that slow powder actually burns down the barrel. That will give you your max load for the RL-25 and that bullet! :D

Maybe you're rifle is spitting unburned kernels out the end of the muzzle! :eek:

All joking aside, you might try a little faster powder with that lighter bullet like H4831 or RL-22 to get your speed up. I'm shooting a 165 boat tail at 3215 fps with 85 grains of H4831 in a plain old 26" bdl, and its got plenty of room to go faster.

E

Try laying a white sheet on the ground out in front of your muzzle. After you shoot, use some tweezers to pick up all the unburned powder kernels. They will show up nice against the white sheet! Weigh them, subtract that from your 94.5 gr load to determine how much of that slow powder actually burns down the barrel. That will give you your max load for the RL-25 and that bullet! :D

Maybe you're rifle is spitting unburned kernels out the end of the muzzle! :eek:

All joking aside, you might try a little faster powder with that lighter bullet like H4831 or RL-22 to get your speed up. I'm shooting a 165 boat tail at 3215 fps with 85 grains of H4831 in a plain old 26" bdl, and its got plenty of room to go faster.

E

you might be right.
i didn't try your white sheet trick yet but i found while cleaning my rifle that there is a LOT more powder residue with this load than factory loads i used before reloading.

can you recommand a powder i could try that would also fit for my wife's 260 with 120 grainers.
i know RL22 and imr 7828 would do for 140 grains, but for 120?
maybe h4831 would do both.

BL(C)-2 or Varget.