I am a newbie to reloading. I was looking to duplicate a factory round that is no longer available. I have found that the max loads in two manuals suggest a muzzle velocity far less than claims on the box of loaded ammo. Began looking at multiple rounds and found this to be the case in every example, with discrepancies of up to 250 ft/sec.. can anyone shed some light on this? Exagurated claims?, proprietary powders?

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Exagurated claims?, proprietary powders

Welcome,

Your quick answer is "yes" exaggerated claims, proprietary powder, test barrel muzzle vs chrono 15' downstream The list will go on and on.

Sometimes you will find you can match factory and stay at a safe pressure. Often you can't. Just like the different load manual will show different powder max and velocity the factory ammo will as well.

Trying to DUP a factory load is often an expensive frustrating trip.

Find the bullet you want to shoot. Select a velocity you would like to achieved and simply work up a nice accurate load.

Possibly exagerated claims. Also could be that they have an unusually long barrel. The powders they use are usually about the same as what we get. From what I understand, the same people make their powders as ours ( viz , Winchester sells the same powders they use).

Yes, no, maybe all apply

Definitely maybe.
Don't worry about it. Load with loads that are safe and make your weapon function, and meet your accuracy requirements. I do check velocity, sometimes.
You will find that loading data varies as well. Don't fret about that either. It happens.

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Originally posted by stix1975:
I am a newbie to reloading. I was looking to duplicate a factory round that is no longer available.

pressure testing equipment was more rudimentary in times past. some of the wildcat and proprietary cartridges were likely overpressure, in addition to "optimistically" promoted.

as I recall, some of Ackley's data is now viewed with caution.

which cartridge is it?

LOTS of variables when reloading.
Some of my rifles shoot listed/published loads to posted velocities. Many of my rifles do not. Some get greater velocity.
Barrel maker, brass, powder lots, primers and bullets all act differently when put together.
Look at loads from multiple manuals, study and compare. Start w/ a load in the middle----averaged, from the multiple sources.
I did not use a chrono for years, then had to have one. It mostly tells me that the little factory ammo I shoot does NOT get the velocity listed on the ammo box. I did not buy it for the ammo anyway, just the brass usually.It also told me that (3) of my rifles will NOT reach the velocities of load data in manuals safely.
My full custom 35 Whelen will not get the velocity Nosler publishes in their manual or on their ammo box.
My 9.3x64 will not either.
My 7x57 #1 is 150+ fps slower.
My 260 Rem, nowhere close.
My 338 WM, yes, 30-06, yes and more

ALL shoot very well and kill great. So ?
I had the mag bug when I was younger. Even had a 6.5x300 Weath w/ 28 in tube built. It is impressive, but not needed----at all.
I would suggest you focus more on accuracy than speed, it's more fun and rewarding !
I'm still hung up on small groups w/ the ammo I load.

As a friend of mine in Germany has often said, "in the old days a lot of those velocities were fired across a typewriter".

First take everything with a huge block of salt.
What is printed on an ammo box is marketing.
In addition the data on an ammo box comes from a test barrel that may have a much tighter land diameter and it may be much longer.

You may treat marketing like the pole position speeds in a car race. The change the tuning and tires to get the top speed for a couple of laps. But the race is not ran with the car in the same condition.

Some times you see the 6.5 Jap producing very good velocities for the small case - even higher than the 6.5X55. However the full lenght Type 38 rifle has a 31" long barrel. The 6.5X55 data may have been shot with the 17.5" long barrel of the M94 carbine. Those are only rifle variables.

Pressure of the ammo may vary since there is only a max SAAMI value. I never have tried it but I know that if I load a 7.65 Mauser in a 1898/09 Mauser with a 29" barrel to nearly primer blowing pressure it will out run a 7.62 Nato in a 22" hunting rifle barrel.

Reloading just to duplicate 1 specific load is not a very good motivation. There are plenty of good loads existing. Just buy more ammo and test it. However you can develop your own best loads and quit gauging ammo against factory loads. In time you may own firearms that never fire factory loads. You will not know what factory loads with do and you will not care.

Published figures in ammo tables and reloading guides should be seen as guidelines and/or estimates. The only way to actually know what you're getting is chronograph the load. Most factory ammo falls short of published numbers when actually chronographed. Likewise most reloads don't achieve the published velocity. There are just too many variables to be able to predict results without chronograph testing.

I have had 5 factory rifle - Steyer Luxus, in 270 Winchester. All identical, at the same time.

I fired Norma 150 grain ammo in all of them.

The difference in velocity between the fastest and the slowest was about 150 fps!!

We have had rifles of the same caliber.

One will take several grains of powder than the other.

Each rifle is a law unto itself.

Many good points made. My first question to the OP is what caliber are you loading for? Certian calibers are notorious for being "loaded down" below their true capabilities. Especialy so of the older ones in deference to the antiquated actions they were originaly chambered in. More modern chamberings tend to be more consistant, but there are still going to be considerable variations among sources for various reasons.

Also which manuals are you using? There are HUGE variations among manuals. Generaly speaking I tend to prefer manuals put out by bullet manufacturers as opposed to powder manufacturers.

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Each rifle is a law unto itself.

I'll throw ACTUAL bore diameter into the fray.

My son borrowed a Remington rifle from a friend he worked with one time. The rifle looked like a Sendero SF but I don't remember what the name for it is, though it had the 26" tube. The owner of the rifle told Jake (my son) that it had a muzzle velocity of 3400+ ft/sec and when Jake related this to me I threw the BS flag. We ran the rifle with the ammo that the owner provided over my chronograph and it ran just slightly over 2700 ft/sec at muzzle plus 10 ft. Ammo manufacturers can make elaborate claims if they so desire but you they can't make it true by printing it on the box or on their web pages.

With smooth custom barrels and minimum chambers I'll usually get the manual speed and sometimes a couple hundred more. Other times I'll beat the advertised speed significantly with the starting loads.Factory ammo can very well produce the goods in these circumstances. What a short throat can do is significant.

With a typical factory barrel and sloppy chamber I'm lucky to get within a couple hundred fps of the book.

If you've read this far you have worked out that there be a couple or 400 fps difference between a fast barrel and a slow one with the same load.

Test barrels on pressure guns tend to be tight with tight chambers. They know that is its safe in it then a factory rifle will likely be lower.

One gets a flavor of what the truth is when he searches out ancient advertising of the (then new) .264 Winchester magnum. Incredibly few folks have ever reached the advertised performance and I seriously doubt that Winchester did either.

IMO the best indicator of potential velocity is found at the Hodgdon website for reloading.

I have now read my reloading manual through and through and sifted through many forums. My question is beginning to sound silly. I am shooting a Rem 700 xcr tlr .223, 26" bbl 1 in 9" twist. I am looking at a lee precision challenger kit to start out with. Any advice, tips, favorite loads? Coyote and target to 400 yds.