I got my .300 Win. Mag. back yesterday after a year getting customized. Boy she looks good. Well I went to the range to try out some new loads and use my new chronograph. The last load confused me. Powder is IMR 4350. Bullets are Nosler Ballistic Tips.

70 grains under 165 grain bullet 2950FPS
70 grains under 180 grain bullet 3023FPS
71 grains under 180 grain bullet 3125FPS
72 grains under 180 grain bullet 3050FPS

The first load is the load I have used for years. It will clover leaf 3 at 100 yards. Loads 2+3 fell apart two holes each one inch apart and load #4 was great it is a one holer. Three shots in a dime.

I don't understand the loss in velocity in the last load though. Now I will admit I only shot a couple rounds of each load. I only had a few 180 grain bullets left and this was my first stab at a new load. My friends want me to try H4831 and I always wanted to try IMR7828 But If I can get this accuracy with 4350 why try harder? The book don't even call for the 180 grain loads to break 3000 FPS.

Any input?

Jacobite, Were there any pressure signs, sticky bolt, flat primers? The loss of velocity sometimes occures at max or just over max pressure. The Nosler 5th edition shows 70.0 gr of IMR4350 with a 180 gr bullet as max, you`re 2 gr over. This isn`t to say your load is over max, the Speer book shows your load of 72 grs as max, but it may be something to consider.

Ol Joe,
My Speer book shows 73 grains as max. My case's show no signs of over pressure. No sticky bolt either. Maybe I am right there at the max. Hey it shoots good with 72 no reason to try to go higher.
Might back off a couple 10ths at a time and see what happens.

High pressure or not, it may simply be a matter of: Dimminis, diminnis, diimming (oh what the heck, little or no) return. Burn more powder of a slow kind and it'll show no signs of pressure "regardless" of filling. Boils down to adequate/reliable pressure/burning at each shot.
If it works don't fix it!

May cost you a dime or two extra a shot. But save on: Childrens clothes/toys, womens clothes/gifts, food, taxes (tell them you'd like to unsubscribe!), electricity, heat etc. Stuck up om petfood and ammo, a dog and a gun can be/are a man's best friends.

[ 04-19-2003, 02:29: Message edited by: The Dane ]

I have observed this before and other than the comment about max loads can offer no other suggestions. Just wanted you to know that you're not the Lone Ranger. "couple of rounds" may not be enough for reliable data, plus temperature or ammo laying in the sun(or not) prior to firing can influence this. In the past when I've noted this behavior it was with ball powders. More common is the point where velocity gains for charge begin to diminish. Rough rule of thumb in my world is that velocity gain should approximate charge increase as a percentage. When that return falls off I back off. It is one of those things that is trying to tell you something but I'm not sure how to explain it. I generally do not rely on velocity data with a sampling of less than 10 rounds and consider that a very small sample. Most would recommend at least 25-50 rounds.

If these velocities are not averages of a number of shots at the respective charge levels, they really don't provide useful information.....

[ 04-20-2003, 18:21: Message edited by: eldeguello ]

A couple of thoughts about chronys and load data

I don't know what kind on chrony you have but they can give erroneous results from time to time. I have a two Shooting Chronys they are particular about bullet travel angle and light sources.

Here is what I have learned.

One

Always shoot strait across the chrony. I get mixed results otherwise. I found this when shooting at two different 2'x2' target at 100 yds. Out of laziness and respect to my fellow shooters I did not want to close the firing line to change the target. I was working up a load for a wildcat and the velocity started droping as the charge went up. No signs of pressure at all. All previous data indicated I was nowhere near max. I changed the target and got squared up again then the numbers went right back to my expectations.

Seems to make sense. The chrony works on time and distance across the sensors (only 2 feet of distance.) Changing the angle changes the distance.

Two
We started shooting the same load for a 10 shot string for my kids school science experiment on BC. We were taking pictures and recording data, ... At least 2 minutes between shoots. I had prevoiusly recorded a 10 shot string with a SD in the range of 6 and the load shoots very well.

I looked at the data at the range and noticed after 3 rounds that the velocity was increasing.
Started where expected but climbed over 150 fps during the string. Got very concerned. What was going on? Had I screwed up the load?

I took a good look at the setup again and noticed sonething. As the Sun came up the shadow of the building had receded and now the chrony screen closet to the target was in the full Sun but the one closest to the gun was still in the shade.

I moved the chrony back about two feet (both in the sun now) and the numbers came righ back to my expectations.

When we developed the picture, you could see the shadow move across the chrony.

Three

I have placed my two chronys back to back and gotten numbers for the same shot consistantly within 10 fps.

About the loading data.

I notice Nosler gives the same data for both the BT and Partition of the same weight. I would expect that given the different bullet designs that the max load would differ. I expect the Partition max to be lower(more bearing area and solid web). Anyway I expect Nosler to publish the lower of the two numbers for max. Might explain why the BT can run at a higher max.

In any event - be careful of the load you have when the temperature goes up this summer. Could get a nasty surprise.

Good luck

eldeguello makes a good point. Two shots of each doesn't tell you anything. Shoot twenty shots of each load then tell us what the velocities are. As of now you're drawing conclusions with inadequate data.