A session at the range with the chrono this morning, partly spent working up loads from scratch for the recently acquired .308 has got me thinking about what I'm aiming for.

For any given weight of bullet in any given calibre, is there such a thing as an optimum velocity?

Reloading for the .303 Brit is easy in the sense that one's trying to recreate a service load velocity of around 2440 fps.

Is optimum velocity anything more than the velocity at which group size is optimised?

I guess what I'm getting at is whether there's something you might call a design velocity, so that the designer of bullet X in calibre Y intends it to be driven at velocity Z?

This comes out of starting from scratch with 4 different bullets in one calibre - 147gn fmj (I think this is basically a service spec bullet), 168 and 180gn Lapua bthp and now 150gn fn. [I should add that the latter is intended as a deer load, the first three are for range activity with the intention of pushing something back to 1000 yards.]

Previous development with the .22/250 and 55gn V-Max was entirely driven by optimising group size and in that respect, velocity was secondary to accuracy.

Too much thinking and not enough shooting quite possibly but is there such a thing as a design velocity?

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tikka 3 barrels

Pete,

Their is a design velocity for military rifles so the graduations on the rifle sights deliver as indicated with the service ammunition.

For we hobbyists and hunters there really is no design velocity per se. Usually optimum for a hunter means highest with good accuracy. What is good you decide for your individual application.

For target work you generally want the bullet to remain supersonic over the trajectory to the target. That corresponds to more accurate shooting.

I think gun writers like to talk about optimums, but it us usually an artifice for getting more words on the paper it seems. A true optimum is a little mountain top wherein perfromance falls off if you move in any direction away from that optimum. Most of our ballistic parameters don't operate that way, but accuracy as measured by group size generally does as you noted with your varmint example.

I use 150 gr, 165 gr and 180 gr hunting bullets in my .308 depending on the animal hunted, and I don't worry overmuch about velocity -- as long as it is "enough". I am almost always within 200 yards of the animal.

jim dodd

"If you can get closer, get closer; if you can get steadier, get steadier."

[This message has been edited by HunterJim (edited 02-20-2002).]

Optimum velocity?

I believe some rifles are velocity sensitive and some others are not. I don't think there is an optimal velocity for a cartridge. I always thought there was an optimal WEIGHT for each cartridge though. However, after discussing this with Gerard I'm beginning to think there is an optimal LENGTH.

I have an old Rem 700 ADL that will shoot ANY bullet of ANY weight into one hole if I load it to that guns optimum velocity which is 2,850 fps. Took me twenty years to figure that gun out. I won't live long enough to figure out the twenty-five or so others I have.

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The older I get the better I was.

As a hunter/handloader, I take a look at the factory published velocity and try to get as close as I safely can to matching it. If I'm not getting at or near the velocity I need, the load means nothing to me, other than bragging rights.

I've found over the years that its more a matter of the degree in which the rifle is tuned as to how much steam you can put behind your loads. (Proper bedding, and a crisp, light trigger.) Load development is the third step after doing the other two.

One of my .308s, a M70 FW Classic, shot HV loads poorly until I tuned it. Now, it shoots near max. loads into nice little groups. The load I'll be trying in this rifle this next season is a Hornady SST 150 gr. over 46.0 grs. IMR 4895 @ 2830 fps m.v. chrono. I get 3 shot groups under an inch with it. Another favorite load that has worked well in my .308s with a variety of 150 gr. bullets is 46.0 grs. IMR 4064. Averages around 2800 to 2820 in my 22" barrels.

There are several factors that figure into what might be called optimum velocity for a particular and they are, as you might imagine, quite closely related.

(1) Rate-of-twist of the barrel.
(2) A combination of length of bullet and how
much of the bullet is in contact with the barrel.
(3) The construction of the bullet. Drive a
fragile bullet at to fast a velocity and
you will see streaks in the air where it
vaporizes....likewise when hunting if you
have a non-premium bullet and you drive
to fast it will blow up in the game and
not penetrate (this is range dependent).

Not a simple question!

Way too many reloaders get hung up on the velocity trap. I sue my chrono to clock my start load to see if it's in the ballpark listed in the manual. If it is, I let the paper do the talking. When I have a load that works, I clock the load. My best loads are usually a grain and a half to 2 grains below the max listed in the manuel. That helps me sight in for elevation. None of the deer and elk I've killed have complained becasue my load was a 100 FPS slower than max.

Hi Pete,
I would have thought that the design velocity would have been (with any calibre)a point at which the powder is burn't the most efficiently, and at which powder = fps is at its peak.

Griff

I am no expert and have asked about load development before and not found an answer to satisfy my curiosity, or else I don't understand.
It seems to me that the end use of the cartridge should determine where to start.
I read in an earlier post to load for velocity and then work on the accuracy.
I have a 22-250 that I want to shoot 55 grain bullets out to 200 yards and maintain a trajectory of 1 inch above and below line of sight. A look at ballistic tables indicates that I would need a velocity of 3400 fps and above. I have loaded several rounds and test fired for accuracy across my chrono. Three powders have shown reasonable accuracy at 100 yards. I will try to fine tune these loads to tighten up the groups and increase consistancy.
Just my thoughts, or am I way out in left field?
burt

The barrel is like a string of a harp. Vibration depends on how and how much you irritate the string.
As your gun system will only shoot well when it vibrates in its specific and individual way, and as each type of bullet causes a different irritation, you need to develop individual loads for each type of bullet.

Pete, In a past issue of a rifle magazine I read an article about hunting bullets. In that article Randy Brooks of Barnes Bullets indicated that for hunting the optimum velocity would around 2700 fps for his bullets and those he competes against. He indicated that in testing of hunting bullets both his and others that Barnes had done, it appears that most bullets suffer somewhat when impacting game at higher velocities. He used an analogy of a diver on a platform of say 25' hiting the water and penetrating deeply into it, versus a person diving and hitting the water from an airplane, would be akin to hitting concrete. I wish I could find that article again, but cannot locate it. It was the best article I have read about hunting bullet performance. I saved it somewhere, but cannot remember where --------Chainsaw

Consider the Ladder Test for load development. http://home.snafu.de/l.moeller/Laddertest.htm

The Viht book had a particularly good statement that max velocity rarely meant max accuracy and that a small decrease in charge made a larger decrease in pressure than velocity.

In my rifles I have allways tried to achieve an accurate load about at 5% (ie a grain or two) below max that burned cleanly and did not have muzzle flash in the day.

A lot of people think that the most accurate loads are a couple of grains below maximum. Unfortunately this is not always true, often the most accurate load is at or even above safe maximum. In such cases, you have to use a load that is less than the most accurate. However, this may be OK, as long as the load you end up with gives enough accuracy for your intended use. Optimum velocity is something else again, and as mentioned by previous responses, bullet construction has a big influence on this. Muzzle velocity needs to be high enough to let your bullet do its intended work at the maximum range at which it will be used. This may mean that you will have to impose an arbitrary maximum range that you will limit yourself to, while hunting.