I read an article in the October issue of handloader magazine called Pressure guessing. Its written by John Barsness. Toward the end of the article he states that if you have published load data for a specific bullet and barrel length that one could add powder to reach published velocity levels while maintaining safe pressure levels. His contention is that after all it is pressure that drives a bullet. I'm wondering if this is wise advise?
If I want to reach velocity levels expected for my 7mm rem mag could I use this technique or should I get a different gun as mine seems to have a "slow barrel". Examples of velocities in my model 70 are a federal classic 150 gr bullet rated at 3110 fps but my crhono reads 2830. My loads with a 175 gr nosler and 61.5 grains of re22 only yield 2700fps. I'm quite sure my chrono is on because all by other guns are right where they should be. All the loads that I've run through this gun are 100-150 fps off the published data, and I'm not even comparing with the nosler manual. Some wise advice would be greatly appreciated.
Thanks,

Steve

If he is suggesting that when you reach published velocity before you reach published powder maximum, you should stop, that is probably not bad advice. If he is suggesting you should pass published maximums until you reach published velocity, that is a very bad idea.

He does in fact state that because of generous chamber and bore dimensions of many factory rifles that velocities will be 100-200 fps below published figures and that one can simply inrease the powder charge until the listed velocity is reached as long as your using the same bullet.

I've been doing some measurements on chamber pressure, and don't have enough data to directly answer your question. But my opinion is that what he is suggesting is dangerous.

It is not just the amount of powder, it is also the burning speed of the powder, and that varies from lot to lot. Of course, all other factors equal, a faster powder is going to generate higher peak pressure, though not necessarily higher muzzle velocity.

One thing I am pretty sure about: The pressures printed in the books are a lot different from what most people get in their rifles. As nearly as I can tell, they typically use a tight chambered rifle, and take data using several different lots of powder. The highest pressure produces is the load that gets published, generally producing a load that is on the safe side. That's a prudent way to do it. So, most of the time, the loads in the books are optimistic on muzzle velocity, but pretty safe. If you exceed them, you just never know when you're going to get a hot lot of powder, and risk scattering your rifle over the range.

A pretty reliable way to determine what is safe in a particular rifle, and no two are exactly the same, is to take a new case and load it and shoot it with the chosen load till the primer pocket goes loose. If you can get five loads through the case, it is within limits at the high end. Four or three loads only, would call for dropping the charge a bit. Two or one only, and you are on thin ice.

I've been doing EXACTLY what he seems to be preaching, and for many years. That is the principal value of an accurate chronograph to me. Never had a problem. He's not talking about different powders, either faster or slower, but exactly the same. He's apparently saying that if you have everything the same, including barrel length, the ONLY difference will be the chamber and that makes sense all the way.

I've also heard of the expanding primer pockets and have also used this criteria, except the number of reloads I've heard is seven rather than five. I think Barsness is absolutely correct. It's when you start hearing bragging about 'fast' barrels and some idiot says his will do 200 fps over published loads that I start wishing them good luck.

[ 12-14-2002, 00:52: Message edited by: Bob338 ]

I'm not a speed junky or anything but wanted to work up a load for my 7mm remminton that would drive a 175 grain bullet (preferably a nosler) to around 2900 fps. The powder that I am working with is re 22 and the recommended max load was 61.5 gr.(2700fps in my rifle) I did out of curiousity load to 63.5 for 2800 fps with no signs of pressure. I'm not trying to reach 3000 mark like when the 7 remmy first hit the market. It's just that I'd like to hit 2900 with an accurate load and have incredible confidence in this rifle. I've spent time and money on this gun to get it shooting MOA and would like to feel that I really don't need a bigger gun unless I go bearhunting or just want one.

I think that Mr. Barnsess' idea may have some merit, but it also seems to have a few holes in the theory. Namely bore condition/size is just as important to velocity as chamber size maybe moreso, otherwise how could moly coating have such an impact on velocity and pressure?

If the bore is bigger, pressures will be less, less resistance and velocity will also decrease. You need more powder. Same with moly. The same bore and bullet require more powder to achieve the pressure and velocity with the greater resistance of an uncoated bullet. If the bore is tighter, pressures rise more quickly as will velocity. Sloppy or tight chambers do the same thing. Velocity and pressure are very closely tied together. I'm in Barsness court 100%.

Hey Steve, This is one of the most misunderstood subjects concerning Reloading. The problem is, the misunderstanding can damage fireams and the person yanking the trigger.

...John Barsness...states that if you have published load data for a specific bullet and barrel length that one could add powder to reach published velocity levels while maintaining safe pressure levels.

It is rare for me to disagree with Bob338, but in this situation I completely agree with Denton - it can be dangerous.

The real problem is that the statement is not 100% accurate. In "some" firearms it would be SAFE to do just as Barsness suggested, but there are other firearms where it would NOT BE a SAFE thing to do. Due to that inaccuracy, it is best just to consider that concept as potentially hazardous for a person who is just beginning to reload.

His contention is that after all it is pressure that drives a bullet. I'm wondering if this is wise advise?

"Expanding Gas" Pressure does drive the bullet. But just dumping in powder until you hit an arbitrary value picked from a Manual, without proper reguard for "ALL" Pressure Indicators has the potential to be a serious mistake.

If I want to reach velocity levels expected for my 7mm rem mag could I use this technique or should I get a different gun as mine seems to have a "slow barrel". Examples of velocities in my model 70 are a federal classic 150 gr bullet rated at 3110 fps but my crhono reads 2830. My loads with a 175 gr nosler and 61.5 grains of re22 only yield 2700fps.

You can use the technique, but you need to "use it in conjunction with the other traditional Pressure Indicators".

And, NO, DO NOT trade off that rifle, cause it is exactly the opposite of what you think it is. Only looking at your Velocity indications(which is not a good thing to do), your rifle appears to have the potential to actually be a "Fast Barrel" rifle. "IF" the other Pressure Indicators indicate things are SAFE, you might be able to load beyond the Powder recommendations in the Manuals and still be SAFE. This results in a "Faster than normal" rifle.

Loads that will possibly work well in "your" 7mmRemMag would probably lock-the-bolt in my 7mmRemMag.

I have a "Slow Barrel" 7mmRemMag which reaches a SAFE MAX using 4.0gr less powder than a previous rifle I had in the same caliber. And, when "less fuel" reaches the SAFE MAX Pressure Limit, this translates into lower Velocity - aka "Slow Barrel".

I'm quite sure my chrono is on because all by other guns are right where they should be. All the loads that I've run through this gun are 100-150 fps off the published data, and I'm not even comparing with the nosler manual.

Excellent observation on your part, but don't allow the Velocity figures to overwhelm you. "Velocity alone" is a poor and UN-SAFE indicator of how close to the proper operating Pressure you have come for a specific cartridge.

[ 12-14-2002, 04:20: Message edited by: Hot Core ]

I've heard it recomended to move up until you hit either max load or max velocity... but never going past one to reach the other. I have broke the rule though.

I Had loaded my Ruger 416wby up with RL22 and 400gr X bullets, I was 12.0gr over max load at 120gr when I hit 2700 fps, bolt lift was slightly felt at 122gr so 120 was where I loaded them up at. Max load I remember was 108gr, so when I got a new lot of powder I went down to 106gr and worked back up, 118gr was a bit more stiff bolt lift than before at 122gr! 115gr gave me 2650fps and .75" groups so there it is now. I got 4 lbs of that lot# on the shelf left. I bought the Oehler 43 and measured 63,500 psi when I got a gage hooked up and checked it... go figure.

I was recently testing RL25 in my 300 Ultra with the Oehler 43 with 180gr Sciroccos and Nosler BTs and found 96gr was 65k psi and just .5gr more went over 70k psi, another .5gr was at 70k psi too so I stopped. Velocity was 3250 then JUMPED to 3350 when it went to 70k psi too.

Norma at one point had an excellent idea. They realised that handloaders had no instruments to measure pressure They then made cases precisly made so that they would give pressure signs at the maximum permitted pressure for that cartidge. These cases are marked with Re on the headstamp. Unfortunately there are too many dummies out there. Some thought Re meant that the cases had been reloaded, not true. Others used to loading 70,000 thought the cases far too soft. Norma then dropped it.

Norma cases are still too soft. Interesting.