Home Forums Hunting & Shooting Ask The Gunwriters When is it too much of a good thing?

Without some form of strain gauge on a rifle and relying on the practice of reading pressure signs such as brass flow, badly flattened primers, sticky bolt lift, etc - how do you really know when you've exceeded the realm of sensible pressures? Case in point - Barnes loading data for CFE-223 is quite energetic in 308 Winchester. Their current published data on the site shows 2877 fps from a 24" tube which is fast for a 168g bullet in a 308 Winchester. My rifle has a 20" Rock Creek 1-11.25" tube. After doing some tinkering with seating depth, 1g under the max charge I'm getting an average of 2712 fps with standard deviations in the 7 fps range and groups in the 0.5" to 0.6" range.

I've been tinkering with 308s for years and this load is quite a bit more energetic my actual speeds I've obtained with IMR 4895, Varget, IMR 4064 and RL15 in several other shorter barreled 308 before pressure signs started to appear. Extraction is just as easy as opening on on unfired case, no ejector marks, or flattened primers. Is this just a case of that particular powder just generates impressive velocities in the 308 win with heavier bullets? I'm just trying to understand if something seems too good to be true - is the truth that I'm running significantly higher pressures than I think I'm running?

I look at velocity to give me an indication of pressure, velocity = pressure. Accounting for some velocity loss due to your shorter barrel you seem to be OK. Looks like Barnes doesn't publish pressures with their loading data but you could always call and ask. I'm sure they're within SAAMI specs. Newer powders do sometimes generate higher velocities at the same pressures. Reloader 26 comes to mind. I believe it's the area under the pressure curve that determines velocity, not the amplitude of the curve (max pressure).

Hodgdon shows 45.0grC max for the TTSX, WW brass, F210M, for 2664 at 49,800 psi. The top load for the Sierra is 49.0, not compressed, but at over 60k. I suppose the long mono-metal bullet is to "blame" for the reduced capacity with the bullet seated to 2.800.

Why not contact Barnes and see if their data was pressure tested, or done the old fashioned way? Sounds like you have a winner there, but 200fps over the Hodgdon data is interesting. What is the charge weight?

I got almost the same kind of results from a 22" .308 using 2000MR and the Swift 165AF. No "sign" from the brass, easy extraction, etc and 2750fps! I used a BR2 primer, Win case. I always "hedged my bet" with any load that I knew was "up there. I always hunt with new or once fired cases. I set aside about 30 rounds to rotate through for practice, etc. Very rarely have I ever shot enough to have any "signs" other than a loose primer pocket. I then discard it. Now, that works for "me", someone else might grit their teeth and run backwards at anything "over book max". That's fine with me. I know that some books ( er...Hodgdon?) are pretty slow. Brass material/capacity, of course, comes into play also. More often than not, when I find a hot load, the next time or two I check it again the accuracy falls off. The first was the fluke, so it pays to shoot several groups/different days before I settle for any load, but for sure one "on the fence".

I'm finding similar results with CFE 223....if the typical pressure signs are absent go for it. We know that some powders generate greater velocity over others because of their burn rate and while I fully disagree that pressure does NOT equal pressure....it's certainly a sign to be considered along with other indicators.

An example as to why I say pressure does not equal velocity.....(a far out example) it would be darn wrong to keep adding Bullseye powder to a .30-06 case topped with a 180 grain bullet of any kind until a 2800 FPS velocity was achieved.....velocity is indeed a pressure sign but not to be used alone.....to be used in conjunction with several indicators.

I'm a guy that still uses CHE (case head expansion) and have purchased a mitutoyo blade micrometer just for the task....

I find such powders as superformance and CFE 223 to be a step up in the overall reloading experience.....especially if one is dealing with a modern push feed bolt action rifle that fully enclosed the case head.

Knowing the SAAMI pressure specs s also to be considered.....we find that certain cartridges can be improved by simply shoveling in a few more grains of powder.....the .257 Roberts among them and to a lesser extent the .308 Winchester and the .30-06.....

Your question is to be commended.....you have "street smarts" about reloading.....but there is a better question.....at what point do we generate limiting returns on our investment.....or to put t differently.....at what point does the additional velocity offer me a real advantage in the field?.....I have a dead deer.....you have a deader deer.....our buddy has the deadest deer.....sometimes we just become addicted to velocity and for no discernable advantage.....

Velocity does not directly correlate with pressure but absent a strain gauge setup it's by far the best thing reloaders have that we can measure. Book data showing 2877 out of a 24" barrel and getting 2712 out of a 20" barrel with no pressure signs? I'd shoot that all day long, it wouldn't worry me a bit.

CFE223 is a bit more energetic than other powders. It's the canister grade of the powder used in the M855 ammo for the M16. It's a bit temp sensitive but does give excellent velocity in my experience.

A few comments:

In general, these days .308 data for 165-168 grain bullets shows around 2800-2900 for 165-168 grain bullets as top velocity from 24" barrels. Sometimes the highest-velocity powder is CFE223, but sometimes it's something else, such as TAC, Big Game, Power Pro 2000, Vihtavuorhi N550, or whatever. The one thing all the zippiest powders have in common is being double-based and pretty dense. (Nosler's manual shows the highest velocity, 2910 fps, using Big Game.) 2700+ from a 20" barrel is right in there with the best powders, since around 25 fps per inch is about average for velocity loss. In fact I wouldn't be surprised at close to 2800 from some 20" barrels.

Pappy, I don't know of ANY powder or bullet company that doesn't use some form of pressure-test equipment anymore, including Barnes. The last company I know of that used traditional "pressure signs" for working up data was Speer, and they haven't done so for years.

Vapodog, I don't recall ANYBODY saying velocity is equivalent to pressure with ALL powders. As for traditional "pressure signs," including CHE, they've all been proven unreliable in one way or another in pressure labs. If you feel CHE is somehow better than chronograph results, then congratulations.

John, I was simply responding to this statement



I fully understand that most reloaders understand this.....but one never knows.

Great question and you are wise to ask it.

What is the accuracy like?

As an old mentor of mine used to say, When reloading and working up loads always keep in mind that "EVERY RIFLE IS AN ENTITY UNTO ITSELF."

I have a .250 Savage built on a Howa 1500 action with a 26" Krieger barrel. My intention from the get go was to use heavier than average bullets for deer and hogs and get as much velocity as possible out of it. So when I got the rifle back from the gun smith after rebarreling to .250 (It was originally a .22-250) I slowly worked up a load for it over about 6 months with 115 Grain Combined Technologies Ballistic Tips and ended up with over 41 grains of RL-17 that was mighty impressive velocity wise. I saw no signs of pressure at the range. However I had bunches of brass and didn't load the same cases for quite a while. But later when I got around to reloading some and I was repriming the once fired cases the new primers about fell in. The primer pockets were loose as a goose. I backed off a couple grains of powder but slowly worked it back up to 40 grains. I still have great velocities for a .250, though some what less than with 41 grains. However, they're certainly impressive for that heavy a bullet in a lowly .250. But now the primer pockets are nice and tight 3 or 4 loadings down the line. And that brass was all new when I started and the primer pockets loosened after just one firing. No sticky bolt, no flattened primers. Just loose primer pockets. You have to look at every sneaky aspect of pressure when hand loading.

Now before you go attempting to make your whatever into a Weatherby Rocket, there's a couple points I need to stress here that aid in my quest for higher velocity. Remember, my rifle has a 26" barrel which gives it a little extra whoomp! Plus my gun smith gave it an extra long throat. I can probably get an extra grain or two powder in it safely. And one more key thing is the powder itself. RL-17 is often compared to Hodgdon's and IMR 4350. But I'm here to tell you, it ain't your grandpa's 4350. They're comparable on the starting end but RL-17 has a slower pressure peak. It's a modern powder akin to Hornady's Superformance Powder. You can go farther out on the limb without it breaking. Just don't get carried away with a good thing.

And you were reading a lot more into it than was actually there--as you are with CHE.

Pressure and velocity are correlated. They are not equal.

Anyone who says they are equal is demonstrating their ignorance.

Pappy, I don't know of ANY powder or bullet company that doesn't use some form of pressure-test equipment anymore, including Barnes. The last company I know of that used traditional "pressure signs" for working up data was Speer, and they haven't done so for years.

Thanks. I supected that was the case, but good to know.

antelope sniper,

Yes, there is considerable correlation between pressure and velocity--within certain parameters.

I first heard about this years ago from the head technician at a major piezo-electronic pressure lab, which does considerable experimenting with various aspects of pressure. He made the comment that "a chronograph" is a handloader's best friend." We started talking about that, and what he has seen, over and over again, is that with the same powder and bullet, anytime the velocity goes above what pressure-tested data shows (given an allowance for difference in barrel length) then the pressure is higher--despite what traditional "pressure signs" indicate, including CHE. As long as velocity is in the data's range, then the load is within SAAMI pressures. Partly this works because velocity and pressure also vary with seating depth, primer and case.

This means there are no magically fast barrels, but also means that if we use a different bullet of the same weight, then the correlation isn't nearly as strong. But with the same powder and bullet it is.

This same lab also has performed experiments on traditional pressure signs, including CFE, and has found that while sometimes they result in spot-on pressures, just as often the pressures are considerably high--or low. So yes, they found a chronograph is a far better indication of pressure for handloaders--as long as they're using the same powder and bullet used in pressure-tested data. And in general a chronograph is still a better indicator even with a different bullet of the same weight.

Thanks for the comments all!



vapodog - that's my real inquiry here. I'm just trying to make sure that I'm not risking "gotchas" that I cannot see. I'm not really that guy that is a velocity seeker but if I can get more velocity with as good (or better accuracy) then that's a good thing, as long as I am not missing something. In this case - it is for elk hunting and I'm about as green as they get, I've just decided I'd rather take my 308 at that altitude than my larger, heavier, louder, and much harder kicking 300 Win Mag.



Temperature sensitivity does have me a little concerned. With both of us being Southerners we know how ridiculously hot it can be during hunting seasons. I've had two range sessions with CFE-223. One was during 50 degree temps the other 75 degrees. I recorded about 15 fps faster the second trip (in warmer temps) but I also reduced the seating depth a bit which could be the reason more than the temps. I don't plan do deer hunt with this load and expect the temps on "game day" to be anywhere from 20 to 40. I'm trying to pick a few more days when temps are 50 or below this winter to finish and put it on the shelve until the time comes.



Aha! Thanks for this MD, this is something I hadn't considered. Being a bit stodgy in my reloading practices all my experience with 308 have been with extruded powders, I hadn't really thought about the difference it could make with double based more dense powders. I suppose I'm a bit guilty of thinking of "classic" published loading data and not realizing how many good higher energy powders have become available for use in classic cartridges.




Quite good actually - about as well as this guy can normally shoot monometal bullets in a light / thin stocked rifle on a day with variable winds approaching 10 mph.

100y


100y


200y




This makes me feel much better. My load certainly is within the loading data's range, I just wasn't considering the nature of the powder I am using compared to what I've traditionally used. There have been cases in my past where certain powders produced oddly higher than published velocity (like the IMR 7828 thread I made) and in that case I was pretty sure that even though I wasn't getting sticky extraction or the other instances of voodoo pressure indications, it most certainly was "hot"

In my opinion, Velocity is all about pressures. However, you don't necessarily have to be in an overpressure situation to have a higher velocity. I feel like fast powders tend to give a fast pressure peak. Slow powders have a steady increase and get more efficiency out of their energy. It's like comparing a Diesel to a gas engine. A Diesel engine's fuel is burned in a constant Pressure while a gasoline is burned in a constant Volume. When ignition in a gasoline engine occurs the pressure on the piston is pretty instant. In a Diesel when ignition occurs the flame front is sustained nearly all the way past the mid point of the stroke because the injection of the fuel is over a longer period of time than an electrical spark from a plug and with gasoline's properties it explodes rather than burns. That's why all things being equal a Diesel gives a much better torque curve than a gasoline engine. If all the fuel is burned at the top of the stroke, the power surge is akin to hitting the piston on top with a sledge hammer. However, if your power surge is controlled by the fuel entering the cylinder and it continues well down through the power stroke, you will get a much steadier surge of power, or if you will, Push on top of the piston giving you more usable torque. Same thing with a bullet in a gun barrel. A steadier push is more efficient.

Just downloaded the Barnes data. I'd happily hunt with any load on that table, at any charge level, if the accuracy was there.

That's only half of it. It's about pressure and time...which is where burn rate makes its presence known.

Thank you, that is the point I was trying to make. If someone wants to read the few sentences I posted in context, it's not rocket science. The OP's question was about one specific bullet, one specific powder, loaded in a .308 Winchester. When using a specific bullet with a specific powder, your velocity vs. published pressure-tested velocity data is your best indicator. Not case head expansion, flattened primers, or any of that other crap.

And anyone who uses the example of loading bullseye behind a heavy bullet in a .30-06 to "prove otherwise" is an idiot.

MD pretty well nailed it. Just a couple of follow up comments....

CHE simply doesn't work well enough to be useful. There is far too much variation in the hardness of brass, even brass from the same lot, for it to work well. In order to get acceptable precision, you'd have to average hundreds of rounds.

Primer flattening doesn't work well enough to be useful. I once started off to write an article on using primer flatness to indicate pressure. I made a bunch of ammunition, ranging from starter to maximum loads. Then I popped the primers out, and under a microscope sorted them from least flat to most flat. The resulting order had no correlation with powder charge. It was a complete bust.

Not seeing pressure signs doesn't mean you have a safe load. As rough rules, pressure signs kick in at about 70 KPSI and primers fall out after the first firing at about 80 KPSI.

A chronograph is indeed your friend. Speed is a pressure sign.