I have several 30 cal rifles, including a 30-378 Weatherby. Plenty of powder for good velocity, but only a 1:10 twist rate. My groups have been a little too inconsistent, and I'm wondering if a 1:10 twist rate is fast enough to stabilize the bullet. I haven't tried a full pallet of powders yet, but N217, H1000, and Reloader 33 have not always yielded the greatest groups. Sometimes yes....sometimes no, and I'm not sure it isn't just "luck of the draw" sometimes.
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200 Gr Barnes LRX Stability
- Thread starter hawlejr
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Yes, that bullet in a 1:10 twist barrel leaving the muzzle at 2,600+ fps should be stabilized fine.
sable tireur
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There may be more here than just the twist rate also.
If this is a factory Weatherby barrel, the freebore may influence that slight inconsistency you are referring to. But trying to correct this can complicate matters by exceeding the magazine length for these long bullets leaving you with a single shot. Yes, I'm aware you can run to the Wyatt's boxes to partially solve your problem, I'm just not a fan.
Depending on the shot count for your barrel, you could get a 1:9" twist which is what the various calculators call for.
While I appreciate the California laws for no-lead bullets, if you are not there, you can consider the Nosler 200 gr. Partition. Others solutions can use the Hammer Hunter designed for 1:10" twists or the Barnes 190 gr. LRX instead of the 200 gr.
Enjoy the process!
If this is a factory Weatherby barrel, the freebore may influence that slight inconsistency you are referring to. But trying to correct this can complicate matters by exceeding the magazine length for these long bullets leaving you with a single shot. Yes, I'm aware you can run to the Wyatt's boxes to partially solve your problem, I'm just not a fan.
Depending on the shot count for your barrel, you could get a 1:9" twist which is what the various calculators call for.
While I appreciate the California laws for no-lead bullets, if you are not there, you can consider the Nosler 200 gr. Partition. Others solutions can use the Hammer Hunter designed for 1:10" twists or the Barnes 190 gr. LRX instead of the 200 gr.
Enjoy the process!
Thank you. (unfortunately) I AM in the Peoples Republic of California. I have some 180 gr TTSX bullets I might try along with some 180 gr Nosler E-Tips, and some heavier Hornady GMXs as well. Your comment about the 1:9" twist is along the lines of what I expected. I was thinking 1 in 9.5", but 1:9 would be better. Is there a calculation for that, or did you go by the Barnes website, or how to come up with a number? I know that longer bullets ( or higher length over diameter, or l/d ratios ) require faster spins in general, and ogives and boat tails also impact the stability to some extent. I think I'll try the lighter non-leads and stop messing with different powders as a next step.
sable tireur
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I think this will give you a lot more information to get going with your project.
There are a few twist rate calculator available online. The Berger Stability Calculator is very popular along with their bullets. You can substitute variables in the calculator for other bullets or use the Berger list above the calculator field. The Berger Stability Calculator de-emphasizes the velocity changes that were more prominent years ago.
https://bergerbullets.com/twist-rate-calculator/
It is important to note that the Berger calculator states that even though a slower twist is stable, the change is in the Ballistic Coefficient not whether the result will show in your groups. Here is an example from your Barnes 200 gr. LRX:
The Berger Stability Calculator does not incorporate necessary adjustments for bullets with plastic tips, as none of their bullets have them (but Barnes LRX does). As a result, the Berger calculator will underestimate stability of bullets with plastic tips.
Use the JBM calculator for bullets with plastic tips. It shows that even at velocities of around 2,600 fps and twist of 1:10 the Barnes LRX 200g has a stability factor of 1.5, meaning no loss of BC.
www.jbmballistics.com
FYI, if you're unsure of the length of the plastic tip itself, you can get estimates from JBM's site also:
www.jbmballistics.com
Use the JBM calculator for bullets with plastic tips. It shows that even at velocities of around 2,600 fps and twist of 1:10 the Barnes LRX 200g has a stability factor of 1.5, meaning no loss of BC.
JBM - Calculations - Stability
FYI, if you're unsure of the length of the plastic tip itself, you can get estimates from JBM's site also:
JBM - Bullet Length List
acourvil
Well-Known Member
I've shot the 200 LRX in my 1:10 300WM @ ~2800fps with good results, no stability issues.
Rrpro
Active Member
I'm shooting 200lrx @3084fps with my 30-378 Weatherby v with 1:10 twist been great
epoletna
Well-Known Member
Don't get too comfortable with your all-copper bullets. I give it 3 years before some tree hugger in CA discovers pure copper is poison to the blue-tail butterfly and you have to find another element for bullets.
sable tireur
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The Berger Stability Calculator does not incorporate necessary adjustments for bullets with plastic tips, as none of their bullets have them (but Barnes LRX does). As a result, the Berger calculator will underestimate stability of bullets with plastic tips.
Use the JBM calculator for bullets with plastic tips. It shows that even at velocities of around 2,600 fps and twist of 1:10 the Barnes LRX 200g has a stability factor of 1.5, meaning no loss of BC.
JBM - Calculations - Stability
FYI, if you're unsure of the length of the plastic tip itself, you can get estimates from JBM's site also:
JBM - Bullet Length List
There is no Calculator which is perfect right out of the gate. They all need to be fiddled with and tested before accepting what should be a correct set of data. You still have to shoot in your choices and collect the data, plastic tip or not. No way around it.
This will depend upon your chosen definition of Stability, there are several which often get used interchangeably when one specific definition would be the proper one. Just looking at a target will only provide a visual clue as to whether the bullet hole is round, oval or a profile of the bullet.
SSgt G Cody
Well-Known Member
In my modified R700 300 WM the 200 Barnes LRX shoots great in my 1:9 twist barrel, as do the 180 Hammers. I shoot near-mag velocities with 1/2 MOA groups. Very accurate to 600 yards (my range max).
