chronograph

[Hunt7112]

How do you correctly chronograph your muzzle velocity. The chrono I bought is not real expensive so im not sure how accurate it really is $100. It states to shoot between 5-15 feet away am I good anywhere in between or should I be right at 5ft for the most accurate velocity at the muzzle.

 

7mm RUM

Next I had 2 different loads 91.7 grains of Retumbo with 150 gn scirocco chrono 3350, 3325, 3341, 3325, 3341

 

85.7 grains of imr 7828 WITH 150 gn scirocco chrono at 3316, 3308, 3341, 3325, 3350, 3341, 3325

 

The IMR 7828 seemed to be more accurate.

 

If you guys were using this data for a turret what would you do? Are these velocities close enough, and if they are would you take the average, or the high.

[azslim]

back it off so you don't tip it over with muzzle blast, you aren't going to see much difference in readings with only 10 feet change that close to the muzzle.

[pwrguy]

Mine says 10 feet. I think that is going to be close enough to call it "muzzle". I don't think I want to try any closer

[matthewp45]

As long as the readings are staying within 50-75 fps of each other for each load you are fine. I usually just take the average of a 4 round string and all of my turrets have been very accurate. As said before put it out at about 10 feet from the muzzle. I have a model that cost a little over a $100 and it works great. Never had a problem with it.

[jeffro]

When it comes to your ES it depends on how far you want to shoot. As you get out longer, your loads with higher ES will start to show larger vertical spreads. This can be a real problem for long range shooting. Put the #s in a ballistics program, and it will show you your vertical spread before your human error and all the other factors that cause the groups to open up at longer ranges. Im not happy at all with my loads until I find one with an ES under 20fps, and most of mine are under 15fps. I just worked up a load for a 300WM 208 Amax @2955. The ES was 10fps over 10 shots. 75fps ES would have you all over the place at long range.

 

I put my CED M2 @ 12ft. Never have had a problem or an error reading.

[jeffro]

One thing that is very important, is to put your crony at the same distance every time.

[Hunt7112]

Thanks for the help.

[matthewp45]

We are talking about hunting situations not bench shooting. As long as you can keep all your shots in the kill zone at any yardage it is sufficient enough for any hunting situation. Some people get really anal about their stuff but the most important thing is knowing your limitations. Usually out passed 600 or 700 yards even with a bench rest sub MOA rifle an average shooter does not have the skill to make an ethical shot on a deer size animal. That is why you must practice like crazy and be able to make those long shots every time at the range before you even think about shooting at an animal.

[Hunt7112]

Thanks again! Thats why I am working with the different loads, and trying to figure out the most accurate load for my rifle. This is giving me alot of time and oportunity at the range. Once I have everything where I feel comfortable I will spend more time at different distances, and shooting positions. You pretty much answered my question with taking the average. Any other info is appreciated.

[tontotom]

I bought a Crony Alpha and for the money I love it. It's easy to keep the distance constant as it has a phone cable that allows the electronics to come up to the bench, about 15' is what my manual said. I think I've found my load now for my 300 win mag. 74g 4831 (IMR) pushes 165 grain Accubonds at 3250 fps with a max spread of 15 fps. I shot a 3 shot group at .7" this morning.

 

On my way to this load I tried 5 different bullets and 4 other powders, not cheap but I really want to work out at 600 yards with this rifle. I was able to get 1.125" goups with other combinations and this one as well. I felt like the gun would do better and listened to a couple of guys who load and shoot thousands of rounds a year. Here is what came about-

 

1- new stock, Boyds laminated thumbhole glass bedded

2- new ammunition, I was shooting Federal Blue Box 1-1/2" groups

3- chronograph to find out exactly how fast the loads were traveling

4- practice in the field and on the bench

 

Some of the loads were impressive on the chronograph but not on paper, some were good on paper but wild on the chronograph.

 

Of all the things that helped trim the last little fat off these loads was done with the brass. I weighed them all, sorted 40 keepers out of a lot of 100, trimed the flash holes and primer pockets and these will only be used in this gun from now on.

 

I still need to do a lot more shooting but I'm happy with the continued progress. Whitetail in October, Elk in November and Barbary Sheep in Feb 2010. This gun will do them all.

[jeffro]

Im not talking about bench shooting either. Im talking about longrange hunting/tactical shooting. You need to remove as many errors as you can in order to make the first shot count under pressure and in field conditions. I have, and never will shoot bench rest, but I do try to get the best out of my rifles. As said before knowing your limitations is the most important thing. Wether your good out to 500 or 1000 thats up to you to decide.

[ultra300mag]

As far as the data goes for the turret, the only thing I use any pre printed data for is to get close then I dope them at each yardage to zero and verify. Good Luck