Question on how much precision needed ?

powdergun

powdergun

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I'm on a slow learning curve around this precision game so please pardon my lack of knowledge . My next goal is to be able to hit a 5" circle at 500M. Just how precision does my rig need to be in order to hit this consistently ( assuming no wind to worry about ). Right now I get groups .75" or less at 100M consistently with my current set up. I can drop the rams at 500M but want to hit much smaller targets.

The rig is a savage BVSS in 300 wsm. The scope is a Bushnell Legend ( I know I cheaped out on the scope but thats what I have for now )
 
The rifle and groups you have should be "precision" enough to hit a 5" target at 500 yards. It is in fact the wind and other variables that come into play that make holding minute of angle or less at that distance much harder. Trajectory, hold over, wind and conditions all come into play when shooting beyond 300 yards and are amplifies the further out you get. It sure is fun trying though.
 
I have developed loads to do what you plan many times. The problem is that 100 yard groups to not extrapolate very well. If you want a load that will shoot well to 500 or more yards, the shortest distance that will give you useful information is 300 yards. I don't know what kind of facilities you have available, but if you can shoot groups at 300 or 500 yards, that would be so much better than shooting 100 yards.

Dead calm days are rare, so I shoot groups and measure only the vertical. Groups typically look like footballs lying on their side.

A 5 shot group does not give useful information (unless it is a big group). You need to shoot 10 shot groups to have a statistically valid group that means anything.

You will help your cause by choosing the right match bullet. I would try 175, 180, 190 and 200 grain bullets. All will buck the wind well and your rifle should show a preference for one or two of them.

Your rifle should be bedded. This will not only improve accuracy, but greatly impove repeatability and holding a zero. You have a very good rifle. The abrrel should last about 1500 shots. Then you can install a better barrel and even change the bolt head, should you prefer a different case size.

I test 308/7.62 ammo out of a rail gun. This sits on a concrete pad and has zero aiming errors. Testing is done at 525 yards. 10 shot groups run in the 2" to 4" range. I think the best ever was in the order of 1 3/4".
 
5" at 500 is one minute of angle. Go try it. Your rifle is certainly capable of it. You'll have to learn how to read the wind though.
 
Consider these changes. Use a match primer as this really helps to reduce stringing at LR. CCI BR2 or Fed 210M is ideal. Use a hodgdon extruded powder like h4831SC and H1000. Collet neck size your cases to eliminate any runout during sizing. Measure runout on your loaded ammo. There should be no more then 4 thou - less is better.

With a 165gr/180gr SST, 155gr/168/178gr Amax, you will have no issue with a load that can shoot MOA or better at 500m. Try and test at least 200yds away. 300yds is ideal but not always available. You should be able to shoot 1 to 1.5" at 200yds in calm air.

Bed that action especially around the lug. Should be fully supported. Get the trigger as light as possible. Free float that barrel. I will bed under the nut and first bit of barrel but not critical. Controlling the lug and around the action screws is critical. You will not need to he man the action screws once the bedding is properly done.

There is little wrong with your scope as long as it holds zero. In fact, shooting further might be advantages due to parallax (unless you can dial it out with a AO).

Use a target with a big cross which you staple up level. The cross should be large and thick enough so your reticle just covers it at 500m. There will be enough aiming error due to mirage without making it tougher following the 'bouncing ball'. You can draw a 5" circle around the center of the X so you know you are in the zone.

To start, aim dead center and work on consistency. If you can, have a look every few shots where they have landed relative to your POA, wind, mirage. If all is well, you will have a horizontal group with little vertical. Try for 3" of vertical. The horizontal is not important until you learn consistent form.

if the load is good, your shooting form will control vertical.

Once you are consistently shooting vertical 3" and under, you can work on your doping skills to bring the groups into center.

You have a rig that can shoot MOA as far as you want to go. Good ammo and lots of practise will get you to your goal.

Jerry
 
I agree with Mystic, but make two comments:

The Federal 210M primer is now made by a new process. Some benchrest shooters have commented that it is not as good as it was. I don't know. I am still shooting old stock.

But when I get new ones, I will try them and CCI BR2 to see which is better.

500 yard aiming mark. I use the old FN zero target. This has a black rectangle aiming mark, about 10" x 8". I find the cross hairs can easliy be lined up on each of the four corners of the aiming mark. On a good day I can shoot 4 groups at the one mark.

If you have to aim at a solid black aiming mark, see if you can put a 5" white square on it. The cross hairs will easily fit well inside this square.
 
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