This is the test. Cartridge is 7mm Remington Magnum and all components are from the same lot and assembled with care. Pressures were done in a lab using a pressure barrel...the only variable is the primer....66.0 gr of H4831, Winchester cases, and 169gr Sierra Spitzer boat-tail bullets. I will list the primer used and the average velocity determined using a chronograph....my list will be from higest to lowest velocity...can you rank them by pressure.

PRIMER VELOCITY PRESSURE (psi)

Win WLRM 3045 fps
Rem 9 1/2 3041 fps
CCI 250 3039 fps
Fed 215 3036 fps
Win WLR 3024 fps
CCI 200 3011 fps

I will post the pressures tomorrow along with their extreme spreads...hint top pressure was 67,700 psi and min was 54,800 psi....extreme spreads ranged from 3,200 psi to 7,500 psi. Enjoy.

[This message has been edited by DB Bill (edited 01-08-2002).]

DB Bill,
Excellent thread, since the variation of velocity is so small, i would not dare to rank them.
I plan to reload the 7mm Rem Mag within the month. Hopefully Your findings will be viable with different powder.
Also, did You compare accuracy ?

Thanks !

//Jens

This isn't somehting I've done myself, iit's from a reloading source.

Hey DB, Good thread indeed.

I don't suppose you measured the "Pressure Ring Expansion" and have those values at hand. With them, you could have listed the Lowest to Highest Pressure easily. And as you all ready know, the "velocity" can be misleading.

Yes, good thread to show the usefulness of good old PRE!

------------------
Good hunting and clean 1-shot kills, Hot Core

My guess is that the hotter the primer the higher the pressure. This leads me to the following ranking:

Win WLRM (highest pressure)
Fed 215
Win WLR
CCI 250
Rem 9 1/2
CCI 200

What you see is what you get...no additional info available......esox...you got #1 and #6 right. Will post answer later today.

Since esox got high and low, I will take a stab at the rest.

Win WLRM (highest pressure-esox)
Rem 9 1/2m
Win WLR
Fed 215
CCI 250
CCI 200 (esox)

[This message has been edited by Scott H (edited 01-08-2002).]

It's interesting. Just for reference I ran it past Quickload and out of a 26" barrel it predicted 55,157 psi @ 2955fps. Those test barrels usually seem to get more velocity. (This is also using 4831sc powder not the older h4831)

MY only dislike about this is the use of winchester brass --- even if it came from the same lot. I haven't been at all happy with the consistancy of winchester lately.
I would say to be really accurate each case should have been segregated by weight because I just don't have faith in winchester lately. Also, were flashholes uniformed and case pockets uniformed?

Hey, I want in on the fun!

WLRM
9 1/2
215
WLR
250
200

I know, no fair....... Precision Shooting did something very similar about 3 years back. For a reference, go to http://www.prfelr0.f2s.com/prfelr0/primers1.jpg

How'd I do? Dutch.

Don...don't whine about the test components

Scott & Dutch.....no cigars yet.

O.K....all the data was taken from A-Square's reloading manual "Any Shot You Want"...there is an extensive section on the effects of changing components and the differences between lots of powder, brass, bullets and primers. Here are the results!

PRIMER......AVG VEL....AVG PRESSURE (psi)

WLMR ....... 3045 fps....67,600 psi (#1)
Rem 9 1/2... 3041 fps....59,300 psi (#5)
CCI 250 .... 3039 fps....61,500 psi (#3)
Fed 215 .... 3036 fps....61,400 psi (#4)
Win WLR .... 3024 fps....64,400 psi (#2)
CCI 200 .... 3011 fps....54,800 psi (#6)

Some additional bits of information.

WLRM...velocity extreme spread(ES) was 17 fps and the pressure ES was 6,600 psi

Rem 9 1/2..velocity ES was 57 fps and pressure ES was 4,600 psi

CCI 250 ...velocity ES was 20 fps and pressure ES was 3,200 psi

Fed 215 ... velocity ES was 46 fps and pressure ES was 7,500 psi

Win WLR ....velocity ES was 23 fps and pressure ES was also 7,500 psi

CCI 200 ... velocity ES was 28 fps and pressure ES was 6,300 psi

What is especially fascinating for me is the primers esentially give the same velocity but the differences in pressures generated are pretty significant. I wonder what would happen if a large variety of powders were tested under similar circumstances.

If we assume accuracy was comparable I think I would choose to use the CCI 250 primer.

I am immediately skeptical of the test data, but (that aside) I am intrigued with your choice of the CCI 250. Given a velocity difference of only 28 fps but a pressure reduction of 11% I would opt for the mild mannered CCI 200.

I do remain skeptical of the results. I would like to see this sort of test repeated by another independent lab (or even by the same lab). I would expect to see more velocity variation for one thing. That seems uncannily tight.

If all true and accurate, this test seems to repudiate the conventional wisdom regarding hot primers for "magnum" loads. I tend to always use the slowest powder that will fill the case and on the basis of this experiment I would be inclined to use also the mildest primer that would ignite it.

I chose the CCI250 because of it's low extreme spread for both velocity and pressure.

About the test...I've never reloaded for the 7mm RemMag so I don't know if the powder they chose is appropriate or not AND I think it would have been interesting to see what the velocities would have been if they loaded all the primers to the same pressure BUT they didn't...the point they were trying to make, and it is a very important one, is that whenever you changes any component you need to start over with load developement or else you can run into problems with pressure.

CCI recommends their magnum primer for all ball powder loads. There may be a reason. I've always used non magnum cartridges so I figured that magnum primers weren't necessary.

It's not surprising that peak pressure variations and velocity variations are not tightly correlated. Peak pressure is one point measurement, the velocity incorporates the entire action of the gasses on the bullet
over a much longer time period.

I'm still surprised, though that the Rem 9.5 can do such high velocity with a lower pressure.

Surprising indeed! One has to wonder if the tests were conducted under identical ambient conditions and if the loads were also constructed similarly, particularly humidity.

If you read my first post (or read the A-Square manual), the tests were done using a pressure barrel...I would assume this was done indoors in a lab and I would also assume, taking into consdideration Art's background that the ammunition was prepared in the most meticulous manner possible.

If you haven't read Art's reloading manual I would suggest you get a copy...especially if you like big-bores. The information about how to set up your equipment as well as why things happen (and how) is the best I've read.

Very interesting. Also instructive is the difference between this test and the very similar Precision Shooting test I linked earlier.

Thanks for the post. Dutch.

I dont know if this test is reliable,if it is so,my choice wiil be CCI 200,considering the lowest pressure...

The Speer reloading manual uses CCI primers and mostly 2" shorter barrels than the other guys. Speer manuals generally show lower velocity for a given powder charge than other sources (which use mostly WLR and Fed 210) 30 fps for primer plus 40-50 fps for barrel length is fairly close to the difference I've noticed for .30-06.

It would, indeed, be interesting to see data for constant pressure vs velocity and primer type. It seems that the cooler primers might get more velocity for a given peak pressure (start the powder slower, but longer burn).

DB Bill,
Did the report specify Rem 9 1/2 or 9 1/2M?

Loren, that's where I was going with my thought. The only arguments that I have heard in favor of magnum primers is consistent ignition with tightly packed (and especially ball type) powders to improve accuracy and to ensure good cold weather ignition. I would hate to squander performance because I was using a hot primer needlessly.

Major question: What method was used to find these pressures? One issue that seems to have been ignored so far is the natural random variation (error) of the measurement system.

The best estimate I can come up with is that the old CUP method has so much variation that you can still only hit within about 5,000 PSI or so after averaging 10 shots. That would put the 95% confidence intervals of the measurement at the square root of 10 times 5,000 PSI, or something above plus or minus 15,000 PSI for any single measurement.

If we don't know the characteristics of the measurement system, all the posted results might be exactly the same reading, mixed with random noise.

Given that the values are in PSI, we can rule out copper crushers (CUP). Ballisticians typically baseline their transducers against known reference loads and calculate an offset to be applied against later redaings from test loads (or so says the Speer manual). I would be surprised if they tested differently.

It would be interesting to see the curves and the rise times for each load.

Martindog

Martindog...

Of course, you are right that we can probably rule out copper as the measurement system, but my point was a little different from that. I have muddied the water a bit. My reference to the CUP system was just to illustrate that a mediocre measurement system can mask the real variation of the process. Until and unless we can characterize the measurement system, we don't know anything about the measurements.

A couple of us are already hard at work doing the statistical gauge study for a strain gauge system. That study will answer the question for that one type of system. Of course, results will be posted when we have them... probably several weeks away.