Buy a chrony!

stubblejumper said:
Just one more thing to ponder.If the chronograph really was a reliable way to estimate pressure,why would oheler,probablly the most respected name in chronographs, even bother to manufacture their m 43 pressure measuring equipment?
Click to expand...


Great point!! I was wondering that to. Where are you guys getting the idea that it measures pressure? It does not measure pressure it measures velocity. Pressure is a whole different ball game. There are specific tools used for measuring pressure and the chronograph is not it. It may help out in the calculation of pressure for all of the given components used by supplying the velocity reading of a given combination. These calculations end up being just that, calculations.

The variables that contribute to pressure increase/decrease or velocity increase/decrease are forever changing. The only reliable way of measuring the pressure is with the appropriate equipment and that is only as reliable as the conditions present. We also have to remember that these are done probably done under lablike conditions.
 
Last edited:
What else do you use as a pressure indicator,case head expansion? primer radius? primer pocket expansion?And don't even go into bolt lift or burnished heads.As much as I check these,I have seen far too much variation in brands to go by any of them.Until we hook up a Pressure Trace to our barrels,the chrony is still the best indicator of pressure.If you have more velocity than the book,you have more pressure.

You have to understand the book pressures,whether they are SAAMI or CIP.Both the 264WM and the 8x57JS change pressure maxs when they cross the Alantic.
 
If you have more velocity than the book,you have more pressure.
Click to expand...

Maybe,maybe not.And which book do you use when you have several books that vary by 100fps to 200fps using the same barrel length and identical components?
For the record,I do pay a lot of attention to case head expansion and primer pocket expansion.Even some of the loading manuals explain how to use case head expansion to estimate pressure,speer being one of them.Or do you suddenly not trust those loading manuals anymore because they disagree with Barsness?:p
 
With the coming of strain gages,such pressure indicators as case head expansion have proved very inaccurate,the data of Denton and Stan Watson,both are scientists,shows.The reason Speer and others used casehead expansion was because they didn't have anything better.Could it,also,be the reason they vary so much, is that they are using casehead expansion for pressure?If you are saying that you are getting 200f/s more because you have fast barrel,maybe you should buy a Pressure Trace,they are cheap enough.Buy yourself an eye-opener.:p

An example of using a chrony as a pressure gauge.The 338.06 doesn't have much published data,(some of it is wrong to boot),but using Lee's powder company data,average max for a 225gr is around 2700,take off 50 for the 22" barrel and I'm at 2650. Guns and Ammo with a strain gauge arrived at the same number. Using a series of Varget loadings, I end up at 2725,I call that too high a pressure.
 
The reason Speer and others used casehead expansion was because they didn't have anything better.Could it,also,be the reason they vary so much, is that they are using casehead expansion for pressure?If you are saying that you are getting 200f/s more because you have fast barrel,maybe you should buy a Pressure Trace,they are cheap enough.Buy yourself an eye-opener.
Actually the speer data falls toward the middle of the pack.I didn't say that I was getting 200fps more than than any manual,I said that the manuals varied by up to 200fps.You either are having a problem with comprehension or you are seeing things that don't exist.:confused:Even more ironic is that the high or low readings are not consistant by manual.For example with the 7mmremmag,the nosler manuals list the higher velocities while the hodgdon manuals list much lower velocities.Yet with the 7mmstw,the hodgdon manual lists much higher velocities than listed in the nosler manual.So therefore you can't attribute the differences to one companies pressure measuring equipment simply reading higher than the other companies equipment.The only logical example is that some barrels simply produce more velocity than others with the same pressure.
Click to expand...
Click to expand...
 
To bad Stan Watson's page went missing,he's not in the best of health.

What you are saying,Stubble, "what numbers do you use?"

My answer is "as suspect as the manual numbers maybe,they are still the best pressure indicator we have" short of glueing a strain gauge on.
 
My answer is "as suspect as the manual numbers maybe,they are still the best pressure indicator we have" short of glueing a strain gauge on
Click to expand...

You are still avoiding the question which is;

Given that you have several manuals that use the same components with the same barrel length,yet the maximum velocities vary by up to 200fps,which manual do you use when you try to match your rifles velocity to the velocity listed in the manual?Do you use the lowest velocity,the highest velocity,or the average velocity?
 
I'll bring in another factor for you.

Moly coating - bullets or barrel.

The velocity changes, as does the pressures.

Now what are you going to do
Click to expand...

Then we can bring in the barnes tsx with it's grooved shank that reduces bearing area.
 
RePete said:
I have a PACT Professional = $350 delivered after the exchange and duties.

Shooting Chrony is good for most people.

You have, in addition to the above - CED, Oehler, Competition Electronics.

There may be others too.

RePete.
Click to expand...

I've got the CED Millennium, $USD 305, in hand. It works, even talks to you, and the wiring is plenty long enough so the unit sits beside you on the bench while in use.

These guys also offer "Pressure Trace", a contraption for specifically measuring pressure using a gauge strip glued to the barrel. I'm tempted :rolleyes: .
 
downwindtracker2 said:
What else do you use as a pressure indicator,case head expansion? primer radius? primer pocket expansion?And don't even go into bolt lift or burnished heads.As much as I check these,I have seen far too much variation in brands to go by any of them.Until we hook up a Pressure Trace to our barrels,the chrony is still the best indicator of pressure.If you have more velocity than the book,you have more pressure.

You have to understand the book pressures,whether they are SAAMI or CIP.Both the 264WM and the 8x57JS change pressure maxs when they cross the Alantic.
Click to expand...

I'd submit that no one really cares what the actual pressures are, or whether they fall within the SAAMI specs or not. As long as it functions well in your gun with not pressure signs - primer looseness or casehead expansion or what have you - who really cares? SAAMI is the lowest-common-denominator, and works well as a liability limitation mechanism for manufacturers. But to the end user, you may find that SAAMI is on the low side of what your gun can handle. Competition shooters - benchrest & IPSC guys - regularly exceed SAAMI. And don't forget the ancient rounds like the 45-70 that are loaded well over pressure as a matter of course (in modern firearms). As long as you have some experience and use your head, just load to whatever shoots best in your gun.
 
martinbns said:
I knew I shouldn't have mentioned the theory of using the Chrony as a pressure gauge.
Click to expand...

No, I agree it's good as a (rough) indicator of pressure. I just don;t really care what the pressure is if my gun is shooting well.
 
You must log in or register to reply here.
Back
Top Bottom