1:10 twist with 155 gr A-Max?

[CBRpilot]

I'm starting my first batch of handloaded ammo this weekend with my 300 WSM. I have 178 gr A-Max, 180 gr Nosler/Barnes, 208 gr (A-Max) and 178 gr A-Max. I know the 208's will probably cause me some grief but I'm willing to work through it. Anyhow, I wanted a hot load for varminting and decided on the 155 gr A-Max (for now). I'm under the impression that a 1:12 is ideal for this bullet. Will my 1:10 over-stabilize this round @ approximately 3150 fps?

 

[agbm]

Try bergers Twist Rate Stability Calculator, http://www.bergerbullets.com/litz/TwistRuleAlt.php, To see if 1-10 will work for 155 gr. I'm shooting 137gr GSC bullets out of 1-12 @3200 fps and it should work by bergers Twist Rate Stability Calculator, will be shooting out to 1000 yards . These 137gn bullets are 1.25 inches long. GSC told me if the stability factor (twist rate) is too high the bullet will just keep going and not come down where you want it to. Also at what distance are you looking at shooting the 155gr?

 

[AKONA]

There is not such thing as over-stabilizing with commercial bullets and cartridges. Even in extremes the difference on the pitch would be indistinguishable in the printed results even at 1000 yards.
However there is the potential loss in speed, increase torque, and if speeds are too high and jackets too thin the risk of potential jacket separation.
That will not be the case with a 155gr amax. BTW a nice versatile and consistent bullet.

 

[CBRpilot]

Thanks guys. I can't imagine finding somewhere to varmint beyond 400 yards in the next year or two, and I only have access to a 300 yard range for practice. I want to have a 0.75 MOA load worked up for 155 A-Max and 208 A-Max, as well as a 180 grain just to have something in the middle of the road. I'd love to be consistent at 600 yards with these 3 loads. I'll let you know how the loads work out for me.

 

[AKONA]

No problem. 10 twist is pretty much a standard all the way to 220gr-230gr excluding solids. for those 1:8 is the most popular.
I wanted to build a new round for extreme LR but I am currently working in two new ones one in 7mm so I will have to leave it for later.
Too many pots on the fire and not so much time right now.
The 155gr will do great at even much larger distances. Extra speed, great flier for the given grain, and specially very consistent and well priced.
Also try the berger 168 hybrid. Very nice little bullet too.

 

[CBRpilot]

Also try the berger 168 hybrid. Very nice little bullet too.

Interesting you say that. I keep reading about the merits of that bullet in particular. I may have to try these out after I have settled on a load for the 155 and 208.

 

[JGorski]

I'm starting my first batch of handloaded ammo this weekend with my 300 WSM. I have 178 gr A-Max, 180 gr Nosler/Barnes, 208 gr (A-Max) and 178 gr A-Max. I know the 208's will probably cause me some grief but I'm willing to work through it. Anyhow, I wanted a hot load for varminting and decided on the 155 gr A-Max (for now). I'm under the impression that a 1:12 is ideal for this bullet. Will my 1:10 over-stabilize this round @ approximately 3150 fps?

My 10 twist 308 doesn't shoot 150/155s well. It does like 178s, though.

 

[bschneiderheinze]

Im gonna try some 155 lapuas in my 10 twist tomorrow just happen to have some laying around

 

[AKONA]

My 10 twist 308 doesn't shoot 150/155s well. It does like 178s, though.

The 155 amax, 155 lapua and berger 168 hybrid are not picky at all but you an always play a bit with COAL and loads if you haven't done that already.
start 5 to 10 thousands off and with a milder load and take it from there and see what happens.
I am not sure if you are using a commercial chamber or not but sometimes it really depends on the specific reamer used to cut the chamber the 155 might need more work to get them right.
Whether you have a SAAMI chamber or not find out max COAL and then start whit those parameters.

 

[AKONA]

Interesting you say that. I keep reading about the merits of that bullet in particular. I may have to try these out after I have settled on a load for the 155 and 208.

Amax and 168 berger H. and obviuosly lapua 155 are able to produce match winning loads.
The Amax 155gr is well priced and also a great extreme cold/winter bullet. paired with varget it makes a great consistent load in all weather, including extreme conditions.

 

[VITA per Veritas]

There is a significant amount of research and science involved in stabilization factors for particular bullets based on Cross sectional density, bullet profile and other factors as well. The 10 twist is too fast for the 155 gr class of bullets. If you look at Berger bullets, they list a minimum twist rate. The minimum rate is typically the proper rate of twist. Other factor that is very pertinent is velocity. Calculating the RPM is helpful. If you are shooting very fast, you can slow your twist rate and achieve proper balance w/o ripping off jackets. I won't bore you with my diatribe on reduction of linear velocity without balanced reduction of rotational velocity.

The twist rates DO matter and they will affect accuracy.

There are many who skate by with twist rates too high with good performance, but there is a reason why one of the 600yrd BR records is held by the Lapua Scenar being shot from a 14 twist barrel.

BTW - Lots of opinions here, and mine is only one. Be careful to note what verifiable experience someone has before trusting what they say re: things that are often unknown by those in the blogosphere.

 

[CBRpilot]

There is a significant amount of research and science involved in stabilization factors for particular bullets based on Cross sectional density, bullet profile and other factors as well. The 10 twist is too fast for the 155 gr class of bullets. If you look at Berger bullets, they list a minimum twist rate. The minimum rate is typically the proper rate of twist. Other factor that is very pertinent is velocity. Calculating the RPM is helpful. If you are shooting very fast, you can slow your twist rate and achieve proper balance w/o ripping off jackets. I won't bore you with my diatribe on reduction of linear velocity without balanced reduction of rotational velocity.

The twist rates DO matter and they will affect accuracy.

There are many who skate by with twist rates too high with good performance, but there is a reason why one of the 600yrd BR records is held by the Lapua Scenar being shot from a 14 twist barrel.

BTW - Lots of opinions here, and mine is only one. Be careful to note what verifiable experience someone has before trusting what they say re: things that are often unknown by those in the blogosphere.

Good points and they're definitely noted. I do understand that a twist rate of 1:10 will stabilize a bullet differently at different velocities. If you have more you'd like to add I will definitely try to understand. I'm all about learning these things.