weird consistencies in different loads?

rk_barber

rk_barber

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Ok I have a 300 Win Mag. and have been working up a load for my spring grizzly hunt and noticed some weird consistencies between different loads and am wondering if anyone can explain why this is happening.

I am using 70gr of IMR 4831 and I started with Barnes 165 TSX bullets found after awhile that 70grs powder was a good match for me. Then switched to 165 MRX bullets with similar results but not quite as good. I have finished the load with 168 Tipped TSX.

The consistency is that in all loads mentioned my groupings are 1/2" left at 100 yards, and 1/2" right at 200 yards. All shot on different days with different wind conditions. Can anyone explain? My only thought is the axis of rotation is not down the centre of the bullet but slightly off. Or it's just me, I don’t know.
 
First, I am not an expert on rifle shooting but I like to read gun articles.

I recently read about how a barrel resonates & moves when it is fired. We cannot see it but it is there. Certain factors such as bullet weight, speed, rifling twist etc will determine if & when a bullet " goes to sleep ". I understood this to mean when it settles down into a straight trajectory.

Sometimes a rifle will shoot smaller groups at say 200 yards than at 100 yards becuase it has not stabilized at 100 but does before 200.
I assume that this can also cause shifts in the point of impact at different ranges.

Exterior ballistics can be a fascinating study.
 
When you give these dimensions, are your referring to a mean point of impact?

How big are these groups at each of these distances? How many rounds in each group?

It sounds more like normal random dispersion. 1/2" at 100 yds is .5 MOA 1/2" at 200 is .25MOA, so what it sounds like is that all rounds are falling within a predictable pattern of grouping, considering you are using hunting bullets, not match/precision bullets.
 
rk_barber said:
Ok I have a 300 Win Mag. and have been working up a load for my spring grizzly hunt and noticed some weird consistencies between different loads and am wondering if anyone can explain why this is happening.

I am using 70gr of IMR 4831 and I started with Barnes 165 TSX bullets found after awhile that 70grs powder was a good match for me. Then switched to 165 MRX bullets with similar results but not quite as good. I have finished the load with 168 Tipped TSX.

The consistency is that in all loads mentioned my groupings are 1/2" left at 100 yards, and 1/2" right at 200 yards. All shot on different days with different wind conditions. Can anyone explain? My only thought is the axis of rotation is not down the centre of the bullet but slightly off. Or it's just me, I don’t know.
Click to expand...

IMR 4831 can make for a twitchy load in the 300Win.
Try H-4831, RL-22, RL-19.
Note RL-19...You will have to look hard to find a better powder for the 168gr.

I don't understand your choice of bullet?
I have owned half a dozen rifles in 300Win (still own 3) and they all shoot 165/168 grain bullets best at 3000-3100 fps....The 3300fps potential has never rewarded me with anything but marginal and inconsistent accuracy.

Seat a 180 grain bullet over 74-76 grains of RL-22 and prepare for 3000-3100 and I guarantee one little hole in the target....A better choice for Grizzly IMHO.

Load the 200 Partition, 200 Accubond or 200 TSX over H-4831, H-1000, or RL-22 and experience the only significant reason to select a 300Winchester over the 30-06.
Optimal accuracy will occur between 2900 and just under 3000fps. I get sub 1-1/4 inch groups at 350 yards with this combo.

In my opinion you are better off using a bullet that both matches the game at hand and optimizes the flight characteristics, downrange energy, downrange velocity, and penetration capabilities of the 300 Winchester....Not a bullet best suited for suited the 308Win and deer.

Good luck!
 
The difference in POI between 100 and 200 is 1", or a half minute at 200 yards and your intended target is an 8' tall grizzly. Don't worry, the bear won't know the difference, but you need to get off the bench and start shooting from field positions. In preparation for bear hunting you should also shoot groups at 10, 15, 25 and 50 yards just so you know in advance how the rifle behaves at short range.

If you are just curious as to what is going on, shoot a group at 300 and see if you can detect a pattern. Perhaps, but not necessarily, your POI will still be a half minute right, if so simply adjust your scope for the half minute. It might be that the bullet needs to get out there aways before yaw is stabilized and it goes to sleep. Often close range impacts differ from impact at longer ranges. If you can recover a bullet from a close range impact, the amount of yaw at impact can be detected by the expansion of the bullet. If the mushroom is angled, the bullet was in precession at impact.
 
Thank you all for the responses.
I think exterior ballistics and the discussion of them is fascinating.
X-FAN, I have tried R-22 with poor results, I haven’t tried R-19 I think I will have to go buy a tub and try it to see its response. Also do you think the Barnes 165 TSX bullet is too small for Grizzly? I would have to disagree if that is the case. If it were any other kind, acubond, partition I would agree that a 165 gr bullet is too small, but not for a TSX. They are a very destructive bullet, I have shot, deer, moose, and elk all with a 165 TSX, all three animals dropped almost instantly.
The target range in velocity I am going for is in the 3000-3100 range, and all of my rounds have been around that. This present load is pretty consistent at 3010-3030 FPS
 
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