What do you figure? 300rum problem/mystery

knockturnal

knockturnal

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So, I got out on Saturday to do some shooting. Shot at 100 to make sure everything was still all good after Jerry bedded my rifle. And it was good. I need to do some more load development now though. Anywho, I ranged a rock at 640 and then another one at 900. Started with the 640 and had to dial up to 8.25 moa. Then the 900 I had to dial 14.5. I took into consideration the angle, which was 8degrees according to isnipe. The last time I shot through a chrony was shooting with Jerry in the summer and his chrony said my average was somewhere around 3160. If I punch that into isnipe, I don't get anything close to what I have to dial. I've shot 420 and dialed up 4moa and shot 475 and dialed up 5moa. Now, by trial and error, I've come up with my rifle to be shooting more along the lines of 3600fps according to my drop at those ranges. Could the chrony have been off? Could my scope be messed up? Can my rifle even shoot that fast given my loads??

Loads are as followed : Sendero 300ultra mag, 26" bbl.
91gr of rl25 under a 180gr Accubond
Federal 215 primers.
Scope is a leupold mk4 6.5-20x50.
 
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Put up a tall target at 100. Fire a group. Raise the sights a number of minutes. Shoot another group. Repeat. Repeat. Repeat. Etc.
Measure the change in elevation from group to group. Compare this to the minutes that you applied to the scope.
This will tell you how the calibration of your scope compares with actual changes in elevation.
If you shoot you way back down, it will tell you how consistantly your elevation is tracking. Shooting a box or square is also a useful test of scope repeatibility.
If you stop and think about it, knowing the actual come ups on your scope for various ranges is important, and it really doesn't matter how many minutes on the dial they are.
See the target, range it, consult your range table, set the elevation and windage and away you go.
 
Your rifle, given a 26" barrel, will easily shoot 3160 with that load. Mine pushes 180 AB over 93.2 gr RL25 and 3280 fps, so your load and velocity seem about right. I would confirm your scope is accurate for 1/4 MOA adjustments by shooting groups at 100 yards at your zero, then 10 MOA up, 20 MOA, 30 MOA and 40 MOA up and see what you get for an average adjustment. I had a similar issue with a scope and found the 1/4 MOA was more like 1/3 MOA, although I would be surprised if that is the case with your Mark 4.
 
I have the same rifle and used the same rl25 powder behind a berger 210gr VLD. I have switched to H1000 powder because it does better during the changing seasons i.e. temp as the rl25 does have changes in velocity and compression during tempurature changes. I have had my sendero for 3yrs now changed the barrel out once since then the H1000 was consistent in both winter and summer and after the barrel swap. I also use Hodgdon (VARGET) in my remington 5R. Long story short try Hodgdon H1000 powder. But if you decide to switch to Hodgdon powder and you notice that Hodgdon RETUMBO is cheaper and you might want to try it DON'T DO IT!!! spend the extra money and get the H1000, it has more consistant powder grains then the RETUMBO. Hence the reason the RETUMBO is cheaper.
 
Told you, you would like the bedding. Gave you an extra 500fps as a bonus :)

As was said, check the actual movement of the scope at 100yds.

I set up a tall cardboard at least 3 ft tall at 100yds. Put a target right at the bottom. Zero dead center. Dial up one full revolution - take one shot. Dial another rev - take one shot.

By the 4th rev, you have likely maxed out your scope and you have that many holes in the cardboard. Measure between the holes. The distance should be the same and the row of holes in a vertical plumb line.

Assuming your load is shooting sub MOA at 100yds, tolerate up to 1/2" variation between hole centers. Close enough. Does the distance between holes equal the amount of mins/MOA of each scope rev? How far over/under?

If you find that one rev is bigger or smaller then the rest, repeat the test and if the holes land in the same places, you have a problem with your scope. If the scope adjustments are not consistent or repeatable, you will get large groups at each scope rev.

If all is well, your scope will likely work just fine for 1/2 revs, etc. If things are landing all over the place, then the scope is mechanically not so happy and needs to get fixed.

many scopes do not move exactly the amount listed but as long as it is repeatable and consistent, doesn't matter. You will adjust the drop chart to fit your set up.

Jerry
 
Haha. No flinches. Doesn't bother me a whole lot. I shot 25 rounds out of it, 30 rounds out of a 270 and then 100 rounds out of my 12ga. A couple marks on the shoulder but I was fine the next day. So fine I actually went out and shot another 100 rounds from my 12ga. What can I say. I love the smell of gun powder in the morning haha

by the way Jerry, saras 270 shoots way tighter groups. I loaded a 5rd and 3rd, then the last 2 rds. For a total of 10rds in under 5min. All shot into smaller then a 3inch circle at 100 yards. Which is way better then the previous all over the place groups with the crappy Winchester factory loads.
 
Proper bedding will always help but I am surprised that you only shot 3". Rifle must really not like that ammo.

I bet handloads will get that beauty under 1".

That is a really nice balanced and handling rifle.

Snow is melting. time to go burn some powder. We will get that drop chart figured out.

Jerry
 
that ammo is garbage. i will be doing up some handloads asap!

and i thought about changing bullets and such. maybe ill just work on some loads and work up my own drop chart to see whats what. no point in quitting now!
 
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