Bullet weight verses barrel twist

[Tech09]

I have a Precision Firearms 6.5 Grendel Neptune V (Five) Lilja 24 inch upper with 1 in 8 twist rate
I am wondering what weight bullets would be best for both hunting and punching hole in paper with this twist rate
I am still developing my own loads for paper punching with 123 SMK, but am open to use what ever would be good with my 1 in 8 twist rate
I also like to work on a hunting load for deer or maybe something a little bigger

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[Drifter]

123-grain A-max shoots very well in an 8-twist barrel for me (and also in my 8.5 and 8.75 twist barrels). The bullet is excellent for paper-punching and reasonably good as a deer bullet at typical Grendel velocities.

[PrecisionFirearms]

Until Hornady releases the 123 SST, the best bullet to date is the 120 Grain Nosler Ballistics for deer and similar game. The 130 grain Berger is also good but more costly and tends to be pickier on the rifles. 130 Nosler Accubond are also very good for heavier game like elk and hogs.

I cant wait until Hornady releases the 123 SST. We have 50,000 bullets ordered from them!

We are also urging Nosler to make a 123 grain BT.

[txgunner00]

Your 1:8 should be able to stabilize anything available in 6.5.

[fanofflyn]

BTW, the twist rate should be increased with increasing bullet length, not necessarily weight.

[Tech09]

To those who responded

Thanks to all who have responded so far
And by the way a special thanks to Precision, my upper shoots so well it makes me look like a pro, tight tight groups, I love it
Again thanks for the input all, I will look at developing a good hunting load based and all your input as well as future input

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[BluntForceTrauma]

Dang! Good shootin' and good on Precision Firearms!

John

[PrecisionFirearms]

BTW, the twist rate should be increased with increasing bullet length, not necessarily weight.

This is absolutely correct! Thanks for mentioning this. Often bullet weight is proportional to the bullet length but not always. For example Barnes Copper Bullets are longer since the material (copper) is less dense than regular jacketed bullets (copper being lighter than Lead cores). This also is common in M855 5.56 Bullets with Steel cores. The Military has gone to 1-7 Twist for this very reason. A lead core 62 grain will easily stabilize in 1-9 twist but the steel core makes the bearing surface of the M855 so long that it will not stabilize in the 1-9 twist and needs the 1-7 to make it work.

Since the diameter of the bullet must remain the same in any given caliber, the only way to increase bullet weight is to add to length provided that the composition of the materials and ratio of lead to copper jacket remains the same. Thus heavier the bullet, the longer the bullet and faster the twist needs to be.

[Variable]

The Military has gone to 1-7 Twist for this very reason. A lead core 62 grain will easily stabilize in 1-9 twist but the steel core makes the bearing surface of the M855 so long that it will not stabilize in the 1-9 twist and needs the 1-7 to make it work.

Splitting hairs somewhat, but I thought it was actually required because of the M856/L110 tracer projectiles?

[LRRPF52]

Splitting hairs somewhat, but I thought it was actually required because of the M856/L110 tracer projectiles?

Yeah. Not tossing egg, but the M855 has a lead core, with a smal steel cone in the tip. It behaves much like a 62gr lead core bullet. The 1/7 rifling is to stablilize the M856 tracer, which is wicked long. I've dissected many a M855 projectile to show my Joes at the time, and they clearly have a small steel cone in the front, with a lead core. Everyone I've seen shot with it had pretty devastating tissue and or bone damage.



I would also title the thread bullet speed versus bullet weight in the Grendel, since speed has a lot to do with the RPM's upon exiting the muzzle, and subsequent stability in-flight, so a tighter twist helps shorter barrels stabilize long pills in the Grendel, whereas longer pipes don't need the same tightness.

A 123gr NBT or Nosler Accubond would be cool for the Grendel. Hat's off to Mark for supporting this cartridge so well. I have some Precision Firearms 123gr Lapua Silver Scenars that shoot great out of my 16" AA Grendel, with 7fps Extreme Spread and .79 MOA at 100yds from a button-rifled barrel, at substantial velocities.

When I had the barrel in another upper with an H1 buffer, that load chrono'd as high as 2584fps.

[PrecisionFirearms]

Yes - M855 are lead core with steel nose in the core per LRRPF52. But the Steel "nose" makes the bullet Longer to gain the weight. I suspect it also makes the bullet unstable the rotations must be higher to keep it true in flight but quick to tumble if it strikes a target. (just a theory - not based in research). The 62 grain bullet in the M855 is the same length +/- .002 as the 68 grain Hornady BTHP.

[Dogue]

The 62 grain bullet in the M855 is the same length +/- .002 as the 68 grain Hornady BTHP.

Both of which work fine in 1/9 twist barrels. It's not until you get to the 75 or 77g bullets where some 1/9 barrels cannot stabiliize the bullet due to it's length, but others will (I know mine actually likes the Hornady 75 BTHP bullet).

[Variable]

.....It's not until you get to the 75 or 77g bullets where some 1/9 barrels cannot stabiliize the bullet due to it's length....

Or you use a long for weight projectile like the M856 tracer or other exotics.

Interesting gel shots of M856 and side by side projectile photo comparison: http://ammo.ar15.com/project/Ballist...est7/Test7.htm