300 Ultra Mag, Big powder charges, Weird results.......

[minniehill2]

I have been trying to work up a load that will group in my 300 RUM. I have not had much luck. I have been using 200gr AB's and Serria MK's.
What I am seeing is little MV increase for the power being fed to the gun.
All the powders at starting charge are +4 MOA
Chrono at 10-11 feet
Shooting 200 yards.

Retumbo
93gr-3025
94gr-3032
95gr-3037
96gr-3106..... best group 1.2" vertical and 1.4" overall


US869
98gr-2825
99gr-2845
100gr-2862
101gr-2871..... best group 1.3" vertical and 1.5" overall

H1000
91.5gr-3032
92.5gr-3066
93.5gr-3076.....best group 1" vertical and 1.2" overall

All the top loads show no pressure signs on the brass or primer but they are all over published.
Do I push another full grain (0.3 at a time)?

 

[pilot2001]

If you want better accuracy I would slow it down ... for a hunting rifle 1 inch at 200 yards is great accuracy ... not sure what else you want ?

 

[dero338]

your chrony is to close. it is affected by muzle blast
put it at 25 feets and you will get more accurate readings
what kind of rifle is it
what work do you do to your brass
what dies are you using
what is your col
how far is the bullet to rifling
what kind of scope do you have

 

[minniehill2]

I would run slower but the second hotest group in each powder is +1 MOA. The hot load test was only one 3 shot group, this still has to be replicated.
I do not want to accept a 1 or 2 MOA gun at published loads.
I would appreciate someone running the numbers for me.

I was thinking the massive brake on my 700 sendero would keep the blast from affecting the chrono at 10'
Brass is weight sorted and necked.
0.010 off
Vortex 6.5-20x BDC

 

[kgs]

Vertical stringing is typically barrel heat up or bedding problem and or breathing problems. If the for end is touching the barrel that is the most likely culprit. Or, a big thing, (and I could just assume that you are doing everything correctly) if the for end rest on a solid or semi-solid rest it will bounce the rifle slightly and vertically strings, if the group is more than 2 inches long this is probably it. Of course the barrel should never touch anything. One other thing to look for - when using the front rest, be sure to place the stock in the same position every time. If the stock doesn't sit in the same place for each shot, pressure on the fore end changes and can cause stringing. I have experienced the same problem before with my 300 RUM. As for loads My favorite load is IMR 4350 at 81 grains 3142 fps one inch to one and a half groups

 

[minniehill2]

I have been shooting off a bi-pod and rear bag with only my shoulder and 1 finger touching the gun.

I can do .5 MOA @ 200 yards and 5" groups at 650 yards with my 6.5mm (same viper scope).

Numbers anyone?

 

[pilot2001]

I would run slower but the second hotest group in each powder is +1 MOA. The hot load test was only one 3 shot group, this still has to be replicated.
I do not want to accept a 1 or 2 MOA gun at published loads.
I would appreciate someone running the numbers for me.

I was thinking the massive brake on my 700 sendero would keep the blast from affecting the chrono at 10'
Brass is weight sorted and necked.
0.010 off
Vortex 6.5-20x BDC

looks like you posted 1 inch at 200 yards ? but its 1 moa ? 1 Moa I agree is not that great but ... 1 inch at 200 is fine. Again your running a 200gr at almost 3100 on one of your lighter loads ... That's a lot broski

I have a friend that literally has 20 300ultra all custom built. His accuracy load for a 180 is around 3100 - 3200fps ... 200gr near 3100 is screaming. I know guys claim 3400 -3600fps with 180's on Ultras but ... Ive never seen it with accuracy