1/7.7 twist rate, bullet grain recommendation

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00Swfit

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Hi everyone,

Very new to the precision shooting, and newer still to reloading. I have done some research but looking for some advice related to projectile weights. I currently using a 6mm cm RPR with a 1/7.7 twist rate. It appears bullets for the twist rates range from ~95-110grs. I have shot the hornady 108gr that was okay. Any recommendations or advice. Thanks again everyone. :cool:
 
00Swfit said:
Hi everyone,

Very new to the precision shooting, and newer still to reloading. I have done some research but looking for some advice related to projectile weights. I currently using a 6mm cm RPR with a 1/7.7 twist rate. It appears bullets for the twist rates range from ~95-110grs. I have shot the hornady 108gr that was okay. Any recommendations or advice. Thanks again everyone. :cool:
Click to expand...

I had a almost identical 1/7.5" 6mmx47 Lapua and I could go up to 115gr VLD with this barrel twist.
The best choice is often a Berger 105gr hybrid or a 95gr - 107gr - 115gr Sierra Match King as they are very easy to get an accurate load for (both have tangential ogive).
Many higher BC bullets such as Berger VLD have secant ogive and are trickier.
 
A fast twist barrel will stabilise a heavier (longer) bullet.

It will shoot shorter bullets too, but with a small loss of accuracy.

Stability is a function of RPM - which relates to twist rate and velocity. Air density matters too. A marginally stable bullet in Toronto might be just fine in Calgary.

At long range the longer bullets with higher BC handle the wind better. If you shoot long range (say, beyond 600 yards) try to get a heavy bullet to shoot well.

If a bullet is too long, it will tumble. One shot at 100 yards will tell you if it is a keyhole or a round hole. If it is round, it is good enough. A bullet gains stability as it moves down range.

BTW, we call those pointy things "bullets". They are not "projectiles" until shot.
 
Ganderite said:
A fast twist barrel will stabilise a heavier (longer) bullet.

It will shoot shorter bullets too, but with a small loss of accuracy.

Stability is a function of RPM - which relates to twist rate and velocity. Air density matters too. A marginally stable bullet in Toronto might be just fine in Calgary.

At long range the longer bullets with higher BC handle the wind better. If you shoot long range (say, beyond 600 yards) try to get a heavy bullet to shoot well.

If a bullet is too long, it will tumble. One shot at 100 yards will tell you if it is a keyhole or a round hole. If it is round, it is good enough. A bullet gains stability as it moves down range.

BTW, we call those pointy things "bullets". They are not "projectiles" until shot.
Click to expand...

thanks for the correction, greatly appreciated
 
AlexF said:
I had a almost identical 1/7.5" 6mmx47 Lapua and I could go up to 115gr VLD with this barrel twist.
The best choice is often a Berger 105gr hybrid or a 95gr - 107gr - 115gr Sierra Match King as they are very easy to get an accurate load for (both have tangential ogive).
Many higher BC bullets such as Berger VLD have secant ogive and are trickier.
Click to expand...

Thank you for the advice, this has been helpful. I will look into picking these up and start load development asap.
 
105 Berger Hybrids.

Bergers have great consistency, and it's super easy to develop a load around a Berger bullet. I load Bergers for all of my cartridges now, as I've learned it's not worth the time to experiment with other projectiles. Hornadys are okay, RDF's are garbage, and the Sierra's are really finicky. You will never hear anyone complain about the ballistic capabilities of the Bergers. I would also give the 115 DTAC's some thought - they are more consistent than most Sierra's (supposedly) and have a shape that's more forgiving than the other Sierra projectiles.
 
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I've been running 110 SMKs in 2 different barrels (a 7.5 twist and a 8 twist) and they shoot I both guns although I know others that have had issues getting them to group tight. The bc on them is much better than any of the 105-108 class 6mm bullets. I've proved them out to 1600 yards running a 0.317 G7 bc. I've been meaning to try some 115 DTACs as well (they're manufactured by Sierra for Tubb) and I also know that the 108 ELDMs shoot in one of my barrels but the bc is much lower (like 0.270) than the 110s. Try a few and see what shoots.
 
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