Hi all,

what's the general feeling when it comes to comparing published (as in loading manuals) with actual velocities using a chronograph? Are they significantly different?

TIA

quote:

Originally posted by rugeruser:
Hi all,

what's the general feeling when it comes to comparing published (as in loading manuals) with actual velocities using a chronograph? Are they significantly different?

TIA

Define "significantly". In general the numbers you see in the manuals (or posted on factory ammo) are only ballpark figures for your rifle/load. It is not untypical to find differences of up to 100-300 fps. Does that qualify as significant to you?
- mike

I don't shoot much factory ammo and thus haven't chrono'd much of it. The two that come to mind are the white box Winchester 223 that was supposed to go 3600fps. Must have been 40 grainers. That chrono'd over 200 fps low. Remington 260 140 grain corelock's clocked just a hair under 2700 fps out of a 22" barrel which I was pleased with.

mho, by 'significant' I mean a difference that will be noticed in the field... not 'significant' in the statistical sense, 100fps either way doesn't strike me as significant in real world applicatons. With the 270, a 200fps difference in MV makes a whopping .4" difference at 300yards. I don't regard that as significant.

I realise that any published load is going to be 'ballpark' (I've been shooting/handloading for 40+ years) - I'd just like to know how big that 'ballpark' is.

I agree with you about the 'significant' factors when it come to published versus actual velocities. Probably all us folks that handload would like everything exact. That's all good at the range shooting paper. I really think what is significant is the shooter being able to control the adrenalin rush at the moment of truth during a hunt. That has caused more missed game by me than any of my less than perfect reloading calculations.

quote:

Originally posted by rugeruser:
mho, by 'significant' I mean a difference that will be noticed in the field... not 'significant' in the statistical sense, 100fps either way doesn't strike me as significant in real world applicatons. With the 270, a 200fps difference in MV makes a whopping .4" difference at 300yards. I don't regard that as significant.

That sounds like a sensible definition. At what point (additional drop in inches, or inches further winddrift) does difference in the field start??

Naturally, it will depend a lot on what taget size you are shooting at. For big game hunting at 300 yds, say, 5-6 inches, perhaps?? Much less than that, and it will be within field (in)accuracy levels. (I'm not asking because I believe I know the answer. Rather, your definition seems to make sense, but what are the practical boundaries we are looking for??).

Once you have a number in inches of drop, say, then it is back to the ballistics table and figure out what drop in muzzle velocity will produce that drop.
- mike

P.S. just did a quick simulation in a ballistics program. I used a .300 Win Mag with a 168 grs TSX at 3200 MV as an example - simply because that was what happened to be loaded in the program when I started it up. At 300 yds, you have to get WAY down low in velocity (maybe 2400 fps), before the kind of "significant" additional drop we talked about above materialises. So that was obviously no good, published velocities won't be THAT far off real velocities.

At 400 yds, you'd be looking at maybe 4-6" additional drop if you reduced MV from 3200 to 27-2800 fps. That is also outside the discrepancy range I would expect between published and actual velocities - but we are beginning to approach something that might be realistic.

One last thought, we should not forget that actual ballistics differ from calculated ballistics. So BY FAR the best way of gauging where you'll be in the field, is to have shot your rifle/load at distances you figure on encountering in the field.

Published loads are developed in "test barrels" that are cut to minimum dimensions. This produces higher pressure and higher MV. This is good, safe practice, because typical chambers vary in size, and, if you're publishing data, you want your loads to be safe wherever they are used.

So, most of the time, your own results will be a little slower than what's published.

Good point Denton, puts things into perspective.
- mike

quote:

Originally posted by FVA:
to mind are the white box Winchester 223 that was supposed to go 3600fps. Must have been 40 grainers. That chrono'd over 200 fps low. .

Might have been 45gr. I still have some but too
lazy to look. They would have been 200 fps slow
in my 20" barrel, but they continually shoot
5/8" groups. If I wanted a varmint load that's
all I'd use.
John L.

Thanks guys, by asking me th equestions you have, and with your input, you have made me take a different line of enquiry, which has helped me to answer my own question.

In other words, in 'real world' situations, even if there is a couple of hundred fps difference in velocity, it ain't going to matter all that much downrange... gee, if I could shoot a group
in the field where anyone would notice a .4" difference at 300m, I'd be a happy camper!!

I've taken the occasional shot at that range, but I can usually get a lot closer.

Just one of those questions that kinda gets into the mind... I'm sure you know the feeling...

If you go to http://stevespages.com/table1.html there is a list of several of my favorite loads. In each listing I have what the published reloading manuals state the velocity "is", what QuickLoad states the velocity "should be", and what I actually chronied.

Steve's numbers remind me of something that always makes me wonder. You want a new load, so you check multiple data sources (read: manuals). And you find.... one manual's max load is below another's min load. Now go figure how you correlate that information
- mike

Generaly published data is very close to TC Encore velocities,but not revolvers,obviously because the TC is closed breech .The only revolver that was close to published data is my FA 83 475 Linebaugh,I assume because the cylinder gap was minimal .002 .


Sean

The data published in most reloading manuals is EXACTLY the velocity yielded FROM THE GUN IN WHICH THE LOAD WAS FIRED. Your particular gun not only may, but WILL be different in the way it behaves and performs with any given load.

"Factory" published velocities are almost always optimistic by several percent because factories almost always use a faster-than-optimum powder for a given load since a faster powder requires less powder, thus less cost to the factory. I have ocassionally run across factory loads that actually yielded higher velocities than speced, but they are the exception than proves the rule.

I believe there is a lot of differene between what the manuals say these days and what the actual performan e is. I say this based on using the manual for starting loads, and chronographing the results. I believe this phenomenon is rather recent, as the figures in older manuals, such as those published in the 50's, 60's and 70's, are more like the real performance I get when chronographing. In particular, I have found Nosler velocities to frequently be as much as 200 FPS above what my rifles produce using Nosler's bullets and powder charges.

This may be due in part to the manufacturers' use of tighter chamber dimensions, which develop higher pressures and velocities at lower powder charge levels than do our "average" sporting rifle barrels.

The ADI reloader's handbook has loads that are significantly slower than what is chronographed. One load in 45/70, I reduced by 8% to start and managed 50fps over the maximum claim. I think that some of the original data was "computer simulated" which may explain why.
Cheers...
Con

quote:

by 'significant' I mean a difference that will be noticed in the field... not 'significant' in the statistical sense, 100fps either way doesn't strike me as significant in real world applicatons. With the 270, a 200fps difference in MV makes a whopping .4" difference at 300yards. I don't regard that as significant.

Thank goodness there's someone out there that knows the difference!

In that light I say there's no difference.

vapodog,



To me, a rifle is a tool... I use rifles to hunt, and if they do what I want them to do, ie, drop game, I'm happy.

I'm not one for extracting the last .001" group, however I would be the last person on earth to demean those who do. If it wasn't for them 'raising the bar', perhaps we wouldn't have achieved the accuracy in factory rifles many of us take for granted.