Home Forums Hunting & Shooting Ask The Gunwriters Swapping Primers

Gentlemen:

I've been a cautious handloader over the years, and I'm getting more cautious as I get older.

Here's the situation:

I've got Sierra bullets I want to load for my .308. I've got the Sierra manual, Edition 5. I've got Winchester cases - not the Federals listed in the manual, but I'm not too concerned about that.

But I don't have the Federal 210M primers called for in the manual. Can't buy those anymore, it seems. I've got some CCI 200 - a precious few. And I've got a stash of WLR (standard) that are about 10 years old, but have been constantly stored under cool and dry conditions.

Here's why I ask:

In the August/September 2005 Handloader, Mule Deer wrote an article on pressure. He included a sidebar about a primer experiment on a 7mm Magnum where primers were swapped on otherwise identical handloads.

Results included a reading of 54,800 psi for the CCI 200, and 64,400 psi for the WLR (standard), for essentially the same velocity. (Fed 210M not tested).

So here's my dilema:

I can begin with the starting loads - swapping the WLRs for the Fed 210Ms - and carefully monitor the velocities on my chronograph. But if I'm getting book velocity (less 100 fps, give or take, for my 20" barrel) as I approach the max recommended powder charge, am I going to be running higher pressures than is wise?

WLR (standard) ran a higher pressure in the test than Federal 215 (magnum)!

I'm getting a headache. Thanks for any insight, here. I would buy the Federal 210Ms if they were available.

- TJM

I hope someone, in the know, can shed some more light on this. I seem to recall an article in Handloaders Digest by M. L. McPherson where he performed a similar experiment with a different cartridge and got different results. His experiment showed primer generated pressure increases matched by higher velocities. Maybe this is the reason the 7mm magnum has a reputation as a "touchy" cartridge?

Tim

I don't know. And there is a related thread in Reloading: Big Game Rifles that adds to the confusion.

Remember, Pressure is Velocity. Don't exceed recommended corrected (for barrel length) velocity and you should be ok.

But then, Murphy is alive and well.

Good Luck!!!

I wouldn't worry too much about it in your situation. The .308 is notoriously well-mannered. Just work up to the same velocity you've been getting with F210M's and you wil be fine.

It is indeed a good idea, however, to work up ANY load again from a few grains below if changing anything, even lot of powder. I have been caught on that one more than once, but primers can do it too.

JB

MD:

Many thanks for that reply. Will do.

Samthedog:

It seems that higher pressures don't always show themselves with higher velocities. At least, that's what I'm taking away from the extensive research MD has been doing on the subject for a number of years. Hence my post.

- TJM

Thank you for your response. I learned something new.

I have been under the impression that while there might be pressure excursions when changing components they would largely be insignificant as long as the new loads velocity was close to the original loads velocity. I understand that pressure measurment is largely an artform masquerading as a science and that all data is likely suspect because the techniques are largely gross approximations to real time actions.

I don't mean to demean the pressure measurement systems in use today but realize that tomorrow's systems will provide better answers to our questions.

This is why we always start low and work up watching for any signs of high pressure - such signs being suspect as we all know. John Barsness is on record as suggesting that the use of the chronograph is a much better way to determine safe operating pressures based upon velocity - keeping in mind that max velocity is not the goal but rather load safety being the goal. He also places several other caveats on using the chrony when changing load parameters which I won't bother listing as I don't remember all of them and would have to go back and reread his articles before being comfortable in passing them on to others.

Once again, thank you for your response and for posting the interesting question.