I have a new rifle that is 100 fps slower than book max loads but at the book max powder volume. Has anyone else ever had this issue. I am assuming pressure = velocity. If that is so, then it seems safe to go slightly above "book max" in this rifle to reach top end velocity?? What say you?
And what is the reason that book loads are as much as 150 fps slower in this rifle? I have double checked my pro Chrono and this is consistent across a number of different powders. I know some manuals use a 24" barrel vs my 22" but the discrepancy still seems way off. Looking for everybody else's "2 cents". Thanks, John.

Because the book wasn't made with your rifle. Throat, chamber, internal barrel dia. choice of powder primer and bullets can all affect your pressure and velocity.

I have some loads that are maxed out 1-2 grains below "book", and others that are maxed out a few grains above. I can swing my velocities 200 fps just by changing primers and brass, and in some instances adjusted my powder charges accordingly.

I have a Sako 22-250 that doesn't even get going until I'm a couple of grains above typical listed maximums.

My 7mm-08 with 140 Accubonds over 44 grains of RL-15 is at 2780 fps, with absolutely no pressure signs. This is way low of the web-site data shown below and I felt I should be able to exceed 2780.

So, after viewing this site...
http://sed88.tripod.com/rem7/peth.html, which maxes out at 44.5 grains of Varget with 140 Nosler BTs for 2950 fps, I slowly went up and stopped at 46 grains for about 2850 fps and still no pressure signs. I wasn't trying to get to 2950 fps.

I haven't measured, but I attribute this to an oversize bore diameter.

If you look at several different "books", you will see different results posted.
I interpolate from multiple books data and move forward carefully watching the chrony and looking for signs.
See antelope sniper's response above.
Add that you have a different measuring device and distance from the barrel also, and EVERY barrel is different.
jmho
Tim

PS- Yes there are slow and fast barrels. Each must be treated as the individual that it is.

Pressure does equal velocity, with a few exceptions (secondary ignitions, etc).
There are RARELY any fast barrels...

Pick-up your powder bottle, or your manual. They have this printed warning saying "Drop loads 10% when switching lots". So, there is your swing amount.

Book data also gets shoot in SAAMI minimum spec equipment, you have a production rifle; not the Same thing.

I had a Freedom Arms .454 that ran about 100 feet per second slower than any I read about. Being a wildcatter, I just increased the powder to get the velocity I wanted. My favorite load was a 240 grain Freedom Arms bullet at 2,014 feet per second. Killed lots of jack rabbis with it.

No, pressure over time equals velocity; peak pressure, which is what the manuals list, does not.

The difference is that some barrel or load conditions can cause high peak pressure without meeting published velocity.

You guys that think you can just load to match published book velocity are going to get bit sooner or later.

If we want to get picky, it's pressure over change in volume.

Not trying to be picky, just reasonably accurate for safe loading practices.

High peak pressure might blow up your gun, but does not necessarily translate to increased velocity. Estimating pressure based on velocity, especially velocity measured in a different barrel, is not a safe loading practice.

Wouldn't that principle be more applicable if you are comparing velocity between different powders with different burning rates?? If you are consistently recording -100fps velocities for progressively increased powder volumes, up to book max loads, then wouldn't it stand to reason that your particular firearm just needs a slight increase to reach near published velocities???

Ridiculous.

What exactly do you think is causing the barrels to be slow?

David

How many powders have you tried? 1 powder isn't enough to just state that you have a slow barrel. More than likely, it's the powder itself that isn't delivering the speed your after.

I have tried primarily one powder but have played a bit with a couple others. It seems to be a consistent observation.

The reason I ask is because I have a .243 that happens to be the same exact type of rifle used in the testing of my Hornady manual, and with IMR4350, H4831, and IMR7828, it gets exactly the velocity that the book says it should get. Between 2900-2950fps. However, RL22 goes over 3100, and the brass is expanded no more than the other 3 powders, so I will take an extra 150fps

Some lots of powder are just different from others, and that can be a big factor.

Within the same powder, would it be permissible and safe to expect the same velocity as published with a modest adjustment of powder, not over compression?

Watch your pressure signs, work up carefully, and see where your rifle groups the best.

Pressure does NOT equal velocity. Some powders produce higher pressure to achieve the same velocity as others.

There are a lot of things that can affect pressure.
Temperature, altitude, chambers, bores, and i'm sure there are others also.

Example of temp: Friend of mine had a near book max load he developed for a rifle in early spring, no pressure signs. In July he went out with same load to do some penetration testing, primers blew out and it was all he could do to open the bolt.


And yes there are slow and fast barrels.
2 of the Reminton 700 30-06's in my house shoot the same load of IMR 4350 in R-P cases, with the same primer, with a 165 gr Hornady. One of them gets 2720 fps the other right at 2900 fps, and they both have 22" barrels. The load shoots accurately out of both rifles.

Pressure = Velocity

There's no way around it. No one is talking about comparing different powders - this is about book powder charges not reaching book velocity. Loads that shoot fast in high heat do so because of high pressure (caused by the xs heat).

There's no such thing as a "fast barrel" or a "slow barrel". There are barrels with tight cut chambers and precison bores that make max velocity (and pressure) w/ a minimal powder charge and there are sloppy cut chambers and sloppy bores that make less pressure and less velocity with the same powder charge. The powder charge to reach the same velocity can vary significantly, the pressure will be close to the same.

David

Pressure creates velocity but pressure does not equal velocity.

And if this is about " book powder charges not reaching book velocity", that is because different pressures in different rifles create different velocities.

" No one is talking about comparing different powders"- This is relevant when comparing pressures and velocities. Because if "X" powder takes 60,000 psi to reach "Y" velocity in a certain cartridge, and "Z" powder takes 62,000 psi to reach that same "Y" velocity then pressure does not equal velocity.

Pressure X Burn Rate= Velocity

If you are working up a book load and are 200 fps below book Velocity you can safely add more powder to get to book Velocity.

Yes different powder lots may have a slightly different Burn Rate however the difference effects Velocity far more than pressure. If one stops at the given Velocity for a book load given any lot of powder your pressures will be very close to book pressures.

Shod

That makes no physical sense.

So in my .338 I can load to the same velocity with Bullseye as I can with H4831?

Don't think I would want to be next to you if that was tried.

Interestingly I have a pair of rifles that when loaded to book max with 335 I don't get published velocity, but have gotten stiff bolt lift under high temp conditions.

Where as a very similar burn rate of powder Benchmark gives me published velocities at 1 grain under max with the same components, same conditions and have not reached the point of stiff bolt lift.

Go figure

Another epic thread.

Yep, another doozy.

David

I'll offer a few thoughts, for your consideration, but there are so many things unknown so I'll first state we just don't, and wouldn't, have enough information to determine which way to turn, and what the next step "should" be.

1. How does your barrel feel when running a tight patch through it, or brush if you run a brush in your barrel. If there is not consistent tension from start to finish, it's very possible that specific barrel will not duplicate a published book data points.

2. Brass - can make a pretty big difference if you don't sort brass. A large variance in case volume can result in a wide range of velocities. And neck tension, and...

3. Type of powder - I learned this one through field tests and later it was confirmed by research/reading. I had a 22-250 loaded with H380 - and large rifle primer. All my loads were about 200 fps less than book data - that was also with LR primers. I switched primers to LRM primers, started load work up again, and my loads matched the book data. Through reading later I found several sources that stated ball powders, in general, like hotter Magnum primers to burn clean. Which was 100% consistent with what I experienced. That being said, I matched powder charge-weight and velocity to the book, but did not match published primer. Suffice it to say, since then, I've become much more sensitive to trying different primers when building a load.

4. I encourage you to try this. Take a known load, that is very consistent of known velocity. Set your chrono up, and be very specific to shoot directly over the sensors. Then intentionally shoot over to one side or the other from the sensors. Another way would be to line up 2 separate chrono's - just offset them an inch or two. Not shooting DIRECTLY over the sensors will yield a very LARGE difference in velocity. My point is, it may be as simple as you THINK you are not getting the expected velocity, when in fact you ACTUALLY ARE - due to something as simple as not shooting directly over the chrono sensors. It's a huge difference, and very educational.

5. My final point is probably the biggest. WHO CARES??!! The first couple of years I reloaded cartridges, about 45 years ago, I was pretty tuned in to velocity in my reloading practices. Then I stumbled on an incredibly consistent and accurate load at significantly less than book velocity, or charge. Upon considering what to do about having such a good load at reduced charge and velocity, it came to me that reloading is NOT about velocity as an end all. If your loads are consistent, but slower than published data - why wouldn't you want to stick with that load? Wouldn't you rather shoot a slower load and know exactly where it will hit time after time than chase velocity? If your recipe is tight, accurate, and POI is predicable, velocity is so far down the list of goals. Add to this that excessive pressure is SO dangerous that there is very good reason to be very careful with anything that exceeds published data. It's honestly not worth chasing velocity. Were any of your slow loads extremely accurate? If so - WHO CARES if your velocity is slow in comparison. That type of thinking allows you to reload for the next 45 years, safely.

There is no free lunch when it comes to velocity and pressure. You most likely will not find a magical recipe that is so much better than all the other published data sources and friend experience. Load to accomplish tight grouping, and drop velocity as a measure of performance when reloading - it's dangerous.

In a nut shell, these are just a few things, and there are many more, that may explain the discrepancy you believe to be faced with. YMMV.

True.

Although it would not be uncommon language to call the sloppy barrel "slow". The owner is going to be perplexed....looking for explanations as to "why",which is also pretty normal.

Although I frequently wonder about so many people making absolute statements about the pressures generated when so few have the means to accurately measure it unless they own the right equipment....which few do.

Most run to QuickLoad these days and make assumptions based on that.Most of the rest of us just "guess" and watch velocity,and case life.

I have seen more variation of this type due to differences in bore/groove diameter, throat length,barrel length etc. I say this having had quite a few barrels cut with over-sized groove diameter and/or longer throats. Friends have done the same. The results usually are pretty predictable. These conditions will even exist from one barrel to another,whether factory or custom.

Generally I think it relates back to the amount of resistance the bullet encounters traveling down the bore.

Anyway what I've come to learn after messing around with too much of this stuff is....if you want to hit a certain velocity level with a certain bullet, make sure you buy a big enough cartridge.Much tidier solution.

Tibbe by any other name is still Tibbe.

But Tibbe is not a word.

Now THERE is some truth!

And put a long enough barrel on it.

No, No, No!!!

You cannot simply keep adding powder to get book pressure and be guaranteed safe!!!

There are a host of reasons your rifle is slower than the one used to work up the loads in a manual, but to blindly keep adding powder is just asking for trouble. Just because your velocities are lower does not mean your gun is operating at less pressure than the test gun!!!

If you a calibrated means to measure the peak pressure in your gun, then you may find that your gun operates at less pressure than the test gun and you many find that your gun can take a few grains more powder. But there are no absolutes.

I own a 1991 vintage Win. M70 in 7mm Rem. Mag. To reach book velocity with 175 grain bullets I have to load something like 4.5 grains over book maximum. Have been shooting the load in question over the years and case life is good. Can't explain the anomaly but my feeling was that I didn't buy a 7mm Rem Mag in order to get 7x57 velocities. It is kind of a moot point now since I haven't hunted with the rifle in years.

Jim

Post 64 M70's in 7 Rem Mag have/had longish throats and blocked magazines restricting OAL to the "gold standard" 30/06 level. Bullets are seated deeper than necessary and jump to the lands.Often, this affects velocities.

I've seen more than one not even start to percolate properly until charges were at or over max.

Same/same with 300 Win Mags. Seen it a bunch of times.

Among the many reasons results vary so much rifle to rifle and guys scratch their heads.

Why is it like that? I think it's so the rifle will function with a wide range of factory ammo under many temps and conditions. Cuts pressure. We won't notice 100 fps difference on an animal at 300 yards but will notice if the bolt freezes up from a too-hot load.