Are these tumbling? 225 gr Hornady BTHP's in 300 WM

[cowboyarcher]

Hi Fellas,

Finally got out to shoot my new to me Browning A-Bolt in 300 Win Mag. I had hopes of making this a good, light weight, mid to long range hunting rifle so when I found a screaming deal on some 225 gr Hornady BTHP's I jumped on them and loaded them over 75, 76 and 77 gr of Retumbo and headed out to test them out. COAL was 3.461" average and they were loaded in 1x W-W Super cases w/WLR primers.

I was shooting at the lower left target (8.5x11 paper each) and you can see what appears to be impact from debris (first shot was a big puff of dirt in front of the target) and then two long holes in each of the right targets. Are these tumbling and not stabilizing? I only shot the 3x of 75 gr given what I saw on target.

The only other load I a had on hand was a 150 SGK over a light load of 760 just to sight with. They printed normally and in about a 2" group.

Thanks for the help as always and God bless you all,

Adam

Here are some photos:

 

[tonedaddy]

First question, what twist?

 

[Tommie]

Any idea what the barrel twist is? Oops, I see tonedaddy beat me to it...

 

[cowboyarcher]

22" barrel 1:10" twist...

 

[Turbulent Turtle]

Are you sure it's a 1:10 twist? I would measure it just to be sure; stranger things have happened.

Also, any way you can get a close-up of the impact holes?

 

[cowboyarcher]

Yes sir, I measured it w/a cleaning rod, very close to 10" per one twist. . .

Here are the impact holes, you can see the 2" group w/the 150s in the first also:

 

[rickiesrevenge]

They don't look stable to me. Not even close. How long is the bullet?

 

[cowboyarcher]

It's about 2 miles long, no seriously, it's huge.

I don't have one handy to measure now, but they have to be somewhere around 1.6". . .

 

[fdshuster]

They sure look like keyholes to me. On the top photo with 4 diamond tgts. if you were aiming at the center of the diamond, the 3 elongated holes aren't even close to your aiming point. The close up with the "normal" 3 shot group with the elongated keyhole underneath clearly shows you have a problem with those heavyweight bullets.

You answered your own qustion when you said the 150 gr. were normal. Maybe the bullets weren't such a bargain after all.

 

[cowboyarcher]

They sure look like keyholes to me. On the top photo with 4 diamond tgts. if you were aiming at the center of the diamond, the 3 elongated holes aren't even close to your aiming point. The close up with the "normal" 3 shot group with the elongated keyhole underneath clearly shows you have a problem with those heavyweight bullets.

You answered your own qustion when you said the 150 gr. were normal. Maybe the bullets weren't such a bargain after all.

That was the conclusion I came to also but wanted some input as I have never seen a bullet do this before. Just wanted to get some opinions before I trade the remainders off for something lighter.

Thanks for all the help fellas, look for these in the classifieds!

 

[Turbulent Turtle]

I'm not convinced those are keyholes, but there is an issue. According to JBM, that bullet is 1.558 inches long. I also used the JBM stability calculator to figure out the stability quotient. I guesstimated a muzzle velocity of 2800 FPS and it showed a very stable 1.63.

I reduced to 2700 FPS and it's still a very stable 1.61. Even at 2400FPS, it's a very stable 1.55.

So I think there is something else going on here or we don't have all the data.

 

[cowboyarcher]

I'm not convinced those are keyholes, but there is an issue. According to JBM, that bullet is 1.558 inches long. I also used the JBM stability calculator to figure out the stability quotient. I guesstimated a muzzle velocity of 2800 FPS and it showed a very stable 1.63.

I reduced to 2700 FPS and it's still a very stable 1.61. Even at 2400FPS, it's a very stable 1.55.

So I think there is something else going on here or we don't have all the data.

Should be more like 2500-2600fps but I cannot verify as I do not have a chrono. I'm at 8000 ft and it was 75 degrees today, though both of those should help stability.

These are the first rounds I shot though this rifle. I'm just utterly confused since the 150's will group.

Could these have been dropping so much more than the 150's that they were ricocheting into the target?

 

[queen_stick]

How far were you shooting?

 

[cowboyarcher]

How far were you shooting?

Just 100 yards. . .

 

[queen_stick]

Try them again, but zero the scope, so you're not hitting dirt. Just try a couple rounds... no need to waste components or barrel life if they simply won't work.

I'd also recommend using thicker paper for targets. It will give you a much better picture of what's happening when the bullet passes through.

 

[Nvreloader]

If you have the "Shooter" ballistic program, you can Zero at 100yds (on the nose) then move back to 300yds and shoot a group.

Save target, then measure the difference of the drop and input the correct info into the ballistic program and it will you a real close guess.

Tia,
Don

 

[Turbulent Turtle]

I'm going to go with GS on this one; try again and this time, aim higher. I reread your original post and the fact you mention "big puff of dirt in front of the target" and wonder about ricochet just rings alarms bells too loudly to ignore. Also, those impact holes do not look like any tumbling or keyholing bullet I have ever seen. Granted I have not seen every keyholing bullet but your pictures remind me of impacts on the long range targets when the shooter hits the berm and skips the bullet into the target, along with other stuff.

I rechecked the stability numbers I posted earlier and I am convinced that in your rifle, provided nothing is broken and it is as you described, these bullets should perform very well. But if you hit something before the target, then all bets are off.

 

[Tommie]

I've seen factory 300WM rifles with 1-12" twist. Not saying yours is though.

Long story short, those pics sure look like under-stabilzation to me.

Tom

 

[cowboyarcher]

I'm going to go with GS on this one; try again and this time, aim higher. I reread your original post and the fact you mention "big puff of dirt in front of the target" and wonder about ricochet just rings alarms bells too loudly to ignore. Also, those impact holes do not look like any tumbling or keyholing bullet I have ever seen. Granted I have not seen every keyholing bullet but your pictures remind me of impacts on the long range targets when the shooter hits the berm and skips the bullet into the target, along with other stuff.

I rechecked the stability numbers I posted earlier and I am convinced that in your rifle, provided nothing is broken and it is as you described, these bullets should perform very well. But if you hit something before the target, then all bets are off.

I agree, unless something is wrong with the barrel, these bullets should stabilize.

I've got a little free time this morning, I'll head out and test another group with a higher point of aim and a bigger target.

 

[cowboyarcher]

Well I am embarrassed to say it, but this is the group I just shot, with ruler to indicate how much they were dropping:

Do the holes still seem a bit odd?? It is clear from how much lower they are hitting that these were doing exactly as you thought.

These were at 100 yards w/ some cross wind and were over 76 gr of Retumbo. These gave me sticky extraction so it looks like I need to go no higher than 75 gr and work with seating depth some.