View Full Version : Disparity in Muzzle Velocities

345 DeSoto
12-31-2007, 06:08 PM
I'm getting ready to start reloading for my 22-250, and no two powder or bullet loading manuals seem to give the same muzzle velocities for the same bullet/powder/grain weight. As an example H380, 55 grain jacketed bullet loads. The MV spreads are all the way from 3.400-3,700 fps. WHAT am I to missing?! Unless I'm perceiving something wrong, muzzle velocity is measured at the muzzle (more or less), and a 55 grain jacketed bullet is a 55 grain jacketed bullet. I understand that DOWN RANGE velocities will vary between all the different variations of 55 grain bullets, but at the MUZZLE shouldn't they be pretty close to each other...using the same powder/weights?...:confused:

Larry Elliott
12-31-2007, 06:58 PM
The best way to determine muzzle velocities from YOUR rifle is to invest in a chronograph and use it when developing loads. Many years ago when I first started handloading chronographs were neither readily available nor very convenient to use, but now they're both and relatively inexpensive too.

I'd suggest that you don't do what I did when I first started either, try to use every possible combination of bullet and powder trying to find the "best one". Most of the bullets from the major bullet makers are good enough now that an accurate load can be developed with any of them. Pick a bullet then look in the manuals to see what powders are recommended. Most likely a good powder will give good velocity and good accuracy together, but remember that the fastest load that's not accurate isn't any good. The bullet whizzing by 2 ft away will not impress any critter.

Oh, yes, the answer to the question. Velocities differ because of the different methods used by the various manual publishers to determine what a maximum load is. Some use pressure guns, others may or may not since they don't say. The barrels can vary in tightness and length, powders vary lot to lot, and the same with primers, and to a lesser extent bullets. If a load is developed using a pressure gun then fired in a production gun that may have a longer throat and/or larger bore velocity will be reduced. Although the use of pressure barrels with minimum spec bores and chamber is denied, anyone developing loads in a max spec bore with a max spec chamber would only be inviting lawsuits IMHO.

12-31-2007, 08:19 PM
When I first started reloading I wondered the same thing. A lot of things can effect the velocity as stated before, the atmospheric conditions, the bullet construction, and the method used to measure are a few more. If you do chose to invest in a chrono you may be supprised to find that using the publishers data, bullet, and the same length barrel you get supprisingly different velocities. Thats the fun.

01-01-2008, 12:15 PM
I understand that DOWN RANGE velocities will vary between all the different variations of 55 grain bullets, but at the MUZZLE shouldn't they be pretty close to each other...using the same powder/weights?...:confused:

--All firearms are individuals, and will produce varying velocities and pressures with the same load.

--Loading manuals use different pressure barrels and/or firearms to develop their pressure/load data.

--Different barrel lengths can produce different velocities--sometimes significantly different velocities, sometimes not.

--Different seating depths can produce different pressures/velocities.

--Not all bullets are the same--different brands or styles of bullets can produce different velocities.

--Then there are things like ammunition temperature (which can produce significantly different velocities), atmospheric pressure, humidity, and the algnment of the moon and Venus..............:)

--Buy a chronograph as soon as you can afford it. The CED Millineum is currently the best on the market--I don't care for the other popular ones. If you run across a used Oehler Model 35, it's an excellent chrono.


01-01-2008, 03:46 PM
345 desoto, are you confused yet???

What you're hearing is for the most part true, BUT perhaps not completely comforting nor helpful eh? Take heart, handloading's not quite as hit-or-miss as it's been made to sound :) If it was, you may be sure that I wouldn't handload! (and I do, always) For your own comfort and safety you need to KNOW how to establish your maximum loads, IMO this is the first thing to learn well when handloading, ALL ELSE is peripheral to safety. You may wonder about true velocity but you need to KNOW whether or not you're operating in the safe pressure range.

First re the chronograph........ I use them, in fact I have several of them, but they're NOT required for safety. IMO a chronograph is an important tool but one which can wait until you've defined some parameters/goals. Knowing your exact velocity isn't really important nor even really useful until you've achieved a certain proficiency with your loading/shooting. Many very successful professional shooters have never owned a chronograph. If you get one and learn to use it you can develop certain loads more quickly and incorporate some routines to make you "more safe" but I've also watched folks with chrono's get themselves into trouble trying to achieve the unachievable...........safety and proficiency are the result of good THINKING not gooder toys :)

You're doing the right thing here by asking the meaningful question.

Regarding your specific question, there are many reasons why seemingly similar loads vary in velocity, some good ones have been listed here. But what you NEED to know is when to stop in your particular rifle............and of course you want to stop just before things fly apart.

Most guys get into reloading with the intent to "just stay within the reloading manual and not push it........just work on consistency and stuff".....

HOGwash!!! :D:D

We mean well, but we're hotrodders at heart. And in support of this notion, WHY would you not want everything you can get out of your rifle??? Anything LESS than maximum velocity/accuracy/efficiency is stupid if you have the ability to better it................this is why we hand load.

Sooooooo, you need to KNOW how to stay out of trouble. Something BETTER than some charts in some books...........charts which show very little agreement as you've found!

Presuming now that you're shooting a solidly built modern BOLT-ACTION rifle..............not something like a TC Contender or and NEF Handi-rifle or a lever action or somesuch ............... you can gauge safe pressure via something called "case head expansion". The reloading manuals talk a lot about "reading primers" and such, I say fah'GIDDABOUT reading primers because they can LIE ;)

But back to casehead expansion. The head of the cartridge case is the end which holds the primer, the end with the "headstamp".......it's on the opposite end from the "shoulder", "mouth" and "neck" ........ go figure.

Now you're gonna' read about all sorts of methods for measuring casehead expansion, most of them referencing mic's and calipers and "measuring in the extractor groove" and similar bunk. Life's too precious and money's too short and can be better spent elsewhere. We need to borrow a method from days of yore, gauging. Gauging ( or as my stupid spell-checker seems to prefer, "gaging") is the time honored and proven method of setting a standard and gauging against it. Shotgun bores were set up this way, 20ga, 16ga, 12ga etc..........Gauging offers the advantage of being simple and repeatable while using the minimum amount of tooling. In this case your gauge is the primer and your tool the primer seating tool. You'll find once you start reloading that primers seat with a certain "feel" or resistance. PAY CLOSE ATTENTION to this "feel"............it is your "gauge", perhaps the single most important gauge you've got at your disposal. Seat your primers carefully, learn to be attuned to them. Your primer seating will talk to you, it'll tell you when you're getting too hot. As you approach the MAX limits for your particular setup the casehead will begin to expand from gas pressure within the primer cavity. As pressure expands the primer cavity or "primer pocket" you'll feel your seating pressure lessen, your primers will begin to "seat loose". When this happens, STOP!!!

The perfect high-end or MAX load will be as hot as you can go WITHOUT making your primers loose. A load which loosens the primer in one shot is very much over max and will probably show other signs of high pressure like "bolt opens hard" or "ejector marks on the casehead". A more subtle "max" load is that one which is just hot enough to slowly loosen the pockets over a series of shots. THIS one will r'ar up and BITE'cherass. A load which gently loosens pockets today may well go 'WAYYYY over max another possibly warmer day.

IMO the perfect SAFE MAX load is that load which will allow you to reload a case 10 or more times while maintaining a nice tight pocket. You may find this load to be well under where you expect to be when loading for the 22-250 but TOUGH :) life ain't fair. What you'll find is that the 22-250 is NOT a handloaders dream case. They're well worth reloading for but you must live with the fact that they've got a little more capacity than they can effectively use and they don't handle high pressure well. An alternative is to run up a little hotter and only use your cases once or twice but :confused:?????:confused: then why handload?

Soooo, here's how you do...... and it's a whole lot easier if toy set'cherself up to load at the range :cool: You start with 5 cases and slowly work UP on the powder charges until they loosen, then you THROW THOSE CASES AWAY!!!!! They were part of your gauging/load workup process, they were sacrificed for your knowledge, THEY ARE RUINED!!!

I'm yelling because it's just sooooooo tempting to shoot them again. STUPID but tempting. :o To this day I have a hard time throwing them away. I'm good enough at it that I can catch them early, while they still DO have another shot or two in them so I have a tendency to load them up as "throwaway varmint rounds" for that ONE last shot......

Here's what happens.

When you load too hot or let them get too loose they "leak" or let hot gases escape around them. This leakage of high-pressure gas will cut your boltface (or your eyeball) and is not recommended.

Some absolutely indisputable signs of too high pressure are:
--leaking primers.
--popped or "pierced" primers. Properly termed "blanked" primers.
--loose primer pockets.
--leaking primer pockets......you'll smell an acrid whiff just like when you pierce a primer, and see a small curl of smoke. EXCEPT for those once in a lifetime situations where you'll see NOTHING because the gas chose to leak BACK instead of sideways and it's permanently seared your retina.....wear those safety glasses folks!!!

I hope this all helps and is relevant to your question :)

Happy New Year!