Bullet Stability ... Need help

[Magnum61]

Hello everyone - I've discovered I have purchased the wrong barrel for my custom 300 win mag, 10 years ago.

The gun has grouped well and I've filled tags at long range with the gun but I've also had some funky random results as well. Well... after 20 years of reloading and long range shooting I learned about bullet stability with rifle twists in detail. I always knew of the basics but I was shown the calculator on Bergers site yesterday.

After a day of piling in and running data, I'm finding that the 26" - 1/11" twist barrel on my 300 win mag wasn't a great choice for long heavy bullets.

My current load is with a 210 Berger at 2840 and according to that calculator, I'm right on the edge of stability. I'm using 500ft, 20 degrees as my baseline worst-case environment to trust the gun.

So instead of getting more frustrated, I wanted to put this in front of all of you and see what information and advice you would be able to apply to this situation. My goal was to try a few new bullets this year, the big ELD X's, a 200gr Accubond, etc.. for a do-all deer/elk load. After running that calculator for stability, the bullets below are what I'm showing I need to pick from:

180 Accubond
200 Sierra Gameking
190 Berger VLD
200 Nosler Partition

Thank you in advance. I'm happy to listen to everything you've learned. I'd rather lean on humility and do this right.

 

[WildRose]

Hello everyone - I've discovered I have purchased the wrong barrel for my custom 300 win mag, 10 years ago.

The gun has grouped well and I've filled tags at long range with the gun but I've also had some funky random results as well. Well... after 20 years of reloading and long range shooting I learned about bullet stability with rifle twists in detail. I always knew of the basics but I was shown the calculator on Bergers site yesterday.

After a day of piling in and running data, I'm finding that the 26" - 1/11" twist barrel on my 300 win mag wasn't a great choice for long heavy bullets.

My current load is with a 210 Berger at 2840 and according to that calculator, I'm right on the edge of stability. I'm using 500ft, 20 degrees as my baseline worst-case environment to trust the gun.

So instead of getting more frustrated, I wanted to put this in front of all of you and see what information and advice you would be able to apply to this situation. My goal was to try a few new bullets this year, the big ELD X's, a 200gr Accubond, etc.. for a do-all deer/elk load. After running that calculator for stability, the bullets below are what I'm showing I need to pick from:

180 Accubond
200 Sierra Gameking
190 Berger VLD
200 Nosler Partition

Thank you in advance. I'm happy to listen to everything you've learned. I'd rather lean on humility and do this right.

Hence my advice for anyone building a custom today to go at least one turn faster on the twist than they were planning. If I were building a new .30 of any kind today I would at least go a 1:9.5 or 1:9.

I've had great results in my Rum's and WM's shooting the 183gr VRG 4 from Peregrine and very good results with both the Accubond LR and Hornady Interbonds.

Stick to the 180-195gr bullets and you should have no problems at all.

 

[6.5x47hunter]

can you speed up your 210"s any? Im running a 300Norma Mag 230gr Berger Hybrid tgt a 2930 with 11tw just fine

 

[Magnum61]

can you speed up your 210"s any? Im running a 300Norma Mag 230gr Berger Hybrid tgt a 2930 with 11tw just fine

Unfortunately, 2840 is near pressure in that gun. I would need to try a different powder. This is H1000

 

[Wedgy]

The heavier bullet may shoot well on paper but not have enough stability to perform/expand & penetrate when it hits an animal. Realistically speaking the heavier bullets do not have an advantage until past ~1,100 yards most of the time.

 

[dougduey]

I have a Sako 75 300 WSM with a 1:11 twist. It has no problem shooting a ragged hole with the 200 gr ELDX. I use it or the 180gr Accubond for everything. The ELDX made short work of a NM bull elk this past season. It was bang flop. I've been very impressed with the ELDX accuracy and performance. Give the 200 gr ELDX a try, I think you'll be very happy

 

[lancetkenyon]

Unfortunately, 2840 is near pressure in that gun. I would need to try a different powder. This is H1000

I can usually get around 2920-2980 in .300WM pushing 210 HVLD over 75.0-78.0gr H1000 before I hit pressure in SAAMI chambers.

What is your charge weight?
You could go to Retumbo, RL26, RL33 and probably pick up some more speed also.

 

[gohring3006]

If you don't want to change barrels, push a 185 Berger to 3000 fps or faster.

 

[Magnum61]

I can usually get around 2920-2980 in .300WM pushing 210 HVLD over 75.0-78.0gr H1000 before I hit pressure in SAAMI chambers.

What is your charge weight?
You could go to Retumbo, RL26, RL33 and probably pick up some more speed also.

Great info. I'm at 75.5gr of H1000 with this load. What would you suggest with those other powders?

For info: the barrel is 26" Lilja 3 groove #4 in 1/11"

 

[WildRose]

Unfortunately, 2840 is near pressure in that gun. I would need to try a different powder. This is H1000

Try RL26. It routinely gives 100-150fps more velocity than H-1000 with less pressure.

If you are loading into or very close to the lans you can can also set the bullet back a bit to reduce pressure and increase velocity.

 

[can1010]

you have a stability problem not a velocity problem changing powder does nothing you would have to gain over 500 fps or increase the temp and/or altitude to stabilize that bullet. try the 190 vld if you want berger they were the first bullet I used in my 300 or 178 ELD X they will work in an 11 twist

 

[lancetkenyon]

To be honest, running your numbers through Berger's twist rate calculator, you are right at 1.50 for your stability factor. Right at the point of stable/marginally stable (at sea level and 59°), which should not cause flight issues at only 1.50. Go up in elevation, and you should be fine.
2000' AMSL = 1.61
4000' AMSL = 1.73
6000' AMSL = 1.87
Adding 100fps takes it to 1.52 @ sea level.

Unless you are hunting coastal ranges in winter time, you should be fine. If you have been using them for 20 years, and only had the occasional weird results, not sure why you would want to change. I am betting it was factors other than a stability issue that gave you those results.

By going with a 190 VLD, even with no other changes in velocity, temp, altitude, you go up to 1.66. You will also gain speed, which will help. But you will lose BC for downrange performance a bit. Still should kill anything you point it at if you put the bullet where it needs to go.

 

[sable tireur]

Your bullet is MARGINALLY STABLE.

Your bullet stability is marginal. You may (can and will) shoot good groups under these conditions, but the BC of the bullet will not be optimized.

This does not tell you that the bullet will be UNSTABLE at all, it is simply stating that the BC is not optimal. Don't read more into this than what is really meant. When you didn't know about these calculators you were happy and content to shoot your load and harvest game. Don't let some math throw you off your course.

We just finished a series of tests using the very same bullet in the 300 Win Mag case through a 26" barrel with H-1000. Optimal load (3/8") was 2947 fps and safe pressure. We shot 100, 600 and 1,000 yards with all targets showing round holes and minimal signs of pressure. We're at sea level but it was probably about 80 degrees when we shot. August doesn't allow for shooting in cold weather.

If the potential of your load bothers you after all these years, switch to a slightly lighter bullet as suggested above and quit trying to split hairs. I doubt you're shooting at 1,000 yards to harvest your elk. Try the 190s or the 185s and go hunting! Enjoy the experience!

 

[Magnum61]

Wow, this is all great information. Thank you.

So to back up a little to understand this "Marginally Stable" label, I just want to be as disciplined and ethical with this weapon as I can be.

I have a second 300 Win mag (700 PSS) that I have 1st round hit many times out to 1000 with 190 Matchkings on targets from a bipod. I haven't been able to do that yet with this custom gun that I hunt with and I've stayed under 600yds with hunting for that reason.

I know the gun is capable I'm just trying to figure out what to do next and a lot of this advice is helping.