BLOG CLOSED

Due to the death of Ronald "Mac" McLeod in September of 2021, this blog is no longer in effect. Feel free to read what is here. I (his wife) still have several of his books. If you would to order one, please contact me at my email: cwdancerlady@yahoo.com.  His other email address of mcleod.right.rifle is not current anymore.  

Marilyn McLeod

Specific Impulse.

Let's talk about specific impulse for hand loading rifle cartridges. By following some basic rules, you can extract the most velocity and accuracy from any rifle. Here is what I have found to be the truths of hand loading cartridges.

Your cases, your powder, and your bullets all have to match a criterion. So here's some basics from which to start. The smaller the case, the faster the powder. The larger the case the slower the powder. The smaller the sectional density of a bullet, the higher the heat explosion of your powder, the higher the sectional density of your bullet the lower the heat explosion. The lighter the bullet the higher the heat explosion of powder. The heavier the bullet the lower the heat explosion of powder. 

The VMD (volume measure density) is given in thousandths, such as .0651 (example) and the density 15.337 (example). You must find a powder that fits this criterion, but also the powder will have to fill the rifle case to the neck.  Too small a density, filled to the neck may give too much powder, and too much pressure.  Also too large a density powder will not be enough to give the velocity you want.  

Specific Impulse is directly related to your VMD and the DENSITY of your powder, your BULLET weight, and your CASE size.  You may ask, what about ballistic coefficient (B.C.) of the bullet?  BC only relates to the bullet in flight.  The higher the BC,  .509 (example),  the flatter, and longer, the bullet will stay in flight.  Less air drag will be on the bullet, so the less drop the bullet will have. 

Even though all this is true, it is problematic because every powder is different, no two are the same. Each one will have a different effect. By following all the guide lines above you can achieve success.  As all hand loaders know, or should know, you must start 5% below your neck level and work up your load cautiously. You must take full responsibility for your actions.  I hope this gives you some knowledge of Specific Impulse.       

Mac

And time passes............

Times sure passes quickly, and things happen in life that make the wheels move slower.  I understand I've been away for some time now.

Life events:

• Hunting 2013 - (no luck)
• Christmas 2013 and visiting kids 5 hours away (several times)
• Spring 2014 and the beginning of house hunting (to buy)
• Late Spring, 2014 - enjoying some awesome sunsets (see below)
• Summer 2014 - house hunting continued......(no luck)
• Late Summer 2014 - finding a new rental at the last minute
• October, 2014 - moving to new rental
• October, 2014 - hunting in Central Oregon (see below)
• October, 2014 - wind storms and fallen trees (see below)
• November, 2014 - gathering firewood

No photos have been retouched!

One thing that may be of interest to some of you. I took a .308 model 88 Winchester and had a .338 Federal chambered barrel put on it.  That gives you quite a bit more energy for Elk hunting in the brush on the coast, or in the thick timber anywhere.

As all of us know, this is not a long range cartridge, but comes into its own at short to medium range.  You can take any short action rifle in .243, .308 and others, in any action you find those calibers in.  You can find many sights on the .338 Federal on the internet.  I find them interesting.  I hope you will too.

I did go deer hunting around La Pine, OR this year (where I live), and not to any surprise, the season around here is way too early, it was way too warm and the deer were not moving.  It was a full moon, so needless to say, it was a bust for me. 

I am seriously thinking of moving back to the Oregon coast (anywhere west of the Cascade Mountains), where my luck has been much better in years past.

My La Pine hunting area - north and west of La Pine, not too far from the Deschutes River.

High winds and lots of rain (which is unusual for this area) caused a huge pine to topple in our new rental's front yard. Lots of cleanup... kept my busy... and much needed firewood.

And of course, no buck sightings in the mountains around here, but they come right into our yard!

Oh well.... nothing fills your hands better than a well-loved wife and your favorite rifle......

Good hunting............oh... and hope you've had a chance to take a gander at my book. I still have plenty of copies to go around. You can purchase one right here on my blog... would make a great Christmas gift for someone who's into hunting and shooting, or just likes some good stories.

...........and I'll try to make my next post happen sooner, than later... unless life gets in the way.

Mac

VOLUME MEASURE DENSITY.

Here's some info I wanted to kick out there that wasn't in my book.

VMD is "Volume Measure Density".  When working up a load, you must know your case capacity at the bottom of the neck of your cartridge.  Fill a primed case with water to the bottom of the neck. Then dump the water into the charge pan and weigh the water.  This will give you the grains of water.

Photo from castbullet.com.  Go here to see how they figure the water weight.

Next, you have to convert grains into grams.  15.4 grains = 1 gram.  Thus, you divide the water weight in grains by 15.4 to convert to grams.  Next, you have to divide the bottom of the neck case capacity by your powder's VMD value. 

The best VMD chart I've found is Lee Precision, Inc's VMD chart which you can view HERE.  You can visit the Lee Precision, Inc. website HERE. For an example, I'll use the .308.  It turns out there are 52 grains of water to the neck in the .308.  So you would divide 52 grains by 15.4 which equals 3.37.

Then you take 3.37 divided by your powder's VMD, which is .0655.  .0655 is Winchester 748 powder's VMD.  3.37 divided by .0655 equals 51 grains of powder.  This is 99%, and way too hot, and is over the 94-97% maximum.  The pressure that will occur will be way too high.

Therefore, I drop down to 49 grains of 748 and come up with a value percent that is within the tolerance range. 

To find the percent figure, we take the powder charge times the powder's VMD (49 x .0655 = 3.20).  The powder charge times VMD = 3.20.  We take that value and divide it by our max value, which was 3.37.  It looks like this: 3.20 divided by 3.37 = .9495, which is very close to 95%.  This percent figure falls perfectly into our 94-97% margin, which gives us a maximum velocity with a pressure curve under maximum pressure.

Thought you'd like this little tidbit of information.

Mac McLeod

SOME PHOTOS FROM MY BOOK.

Here are some of my favorite photos from my book.

I grew up and learned most of my hunting and shooting skills on the Sixes River in Southern Oregon. This is one of the "houses" I lived in from 1958 to 1967. (Pg. xx of my book).

My cousin, Jerry Lively, is mentioned alot in my book! His knowledge and expertise in prairie dog dusting and bench rest shooting astounds me! (Pg. xix of my book).

Mountains of SW Washington where I've hunted for years.  Note the thick stands of timber and Jack Fir, and areas where deer will come out to eat along the edges of the timber. (Photo by Eric Fossm)  (Pg. 6 of my book).

My cousin, Jerry's, 6mm/.284 Winchester with Pac-Nor 30" barrel. (Pg. 13 of my book).

My mom and dad with a Black Bear that my dad shot by Sixes River in 1948.  He used his 32 Winchester Special for a quick and easy shot. (Pg. 30 of my book).

(Pg. 38 of my book).

One of the many reloading manuals I've used throughout the years. (Pg. 83 of my book).

One of the many charts I use in my book. This is in my chapter entitled "Making a Case for the Right Powder". (Pg. 174 of my book).

My old Weaver K4 post reticle - great for brush! (Pg. 236 of my book).

A good kneeling position. Notice how my elbow rests on the inside of my knee. This photos is in my chapter entitled "Making a Case for Shooting Skill", where I picture proper and improper shooting positions.  (Pg. 261 of my book).

My dad killed uncountable game animals. I can't count how many deer I've seen dad kill, on the run, in their beds, uphill, downhill, and across draws.  He was a surgeon with his rifle. (Pg. 276 of my book).

From my chapter entitled "Making a Case for the Truth". (Pg. 322 of my book).

My old hard to find .22 Semi-Auto Remington Model 66 Nylon.  This photo was in my chapter entitled "Making a Case for my Top Picks".  (Pg. 330 of my book).

Well, there you have it - just a smattering of my photos and illustrations in my book (there are over 100 photos and illustrations).

Here's a chapter title page:
 

Here's a page from my book so you can see how it is set up:

That's it for now!

Mac McLeod

BOOK DEDICATION

I dedicate this book to the memory of my father, Arlie McLeod, who in my early years, helped and guided me in learning to hunt and shoot.  The skills he taught me were invaluable.  The memories will never wane.

My dad in 1950, tapping trees for pitch (southern Oregon).

I also dedicate this book to my stepson, Eric James Fossum, who passed away in 2009.  Eric loved the mountains where he lived, especially Silver Star, so we've named our publishing company after the mountain, Silver Star, in honor of him.  Eric loved guns and rifles as much as I do, and we spend many happy hours discussing and sharing our love of them.

Eric in 2008, at age 24. He loved the outdoors.

Mac McLeod

IMPORTANT POWDER INFORMATION

Important Things to Know About Powders and Your Caliber and Cartridge Case

You must know that the slower the burn rate powder, the higher the powder load, for a given muzzle velocity in a given barrel length of a given bore diameter, with larger case capacities. Moreover, it is important to remember that the quicker (faster) the burn rate powder, the higher the velocity for a given powder load, and a given bore diameter.

This diagram is from page 183 of my book.

Therefore, you know that the larger the bore, the quicker the powder must be for a given muzzle velocity, and a given powder weight.  This is where using V.M.D. (volume measure density) charts come in handy to a reloader.

Go to: Precision Reloading for more information.

Coming soon:  Using V.M.D.                           

~Mac~