[Guest]

Hello,All!

I am ready to start loading for my new Super Match. My question is;
with a 1:10 twist, is there a major pressure difference for a given load vs 1:11 or 1:12?

I am likely overthinking this, but do not want to hurt her!

Thanks!

Casper

 

[JEFFJP_N_JJ]

Hello,All!

I am ready to start loading for my new Super Match. My question is;
with a 1:10 twist, is there a major pressure difference for a given load vs 1:11 or 1:12?

I am likely overthinking this, but do not want to hurt her!

Thanks!

Casper

Hi Casper. I have and just started loading for my SM, too, and have the same concerns... Look around and start low! Barrel twist is more of a bullet weight issue I think? I started with the listed loads in the Hornady 6/7 manuals and picked a couple powders and charge weights that would work with all availiable bullet weights to try and learn some.
Look at the 'ten dot' page here and you will see some of my loads
Jeff

 

[Guest]

Hi Casper. I have and just started loading for my SM, too, and have the same concerns... Look around and start low! Barrel twist is more of a bullet weight issue I think? I started with the listed loads in the Hornady 6/7 manuals and picked a couple powders and charge weights that would work with all availiable bullet weights to try and learn some.
Look at the 'ten dot' page here and you will see some of my loads
Jeff

My question should have been:
Does the 1:10 twist, being tighter, require more force to move the bullet through the length of the barrel? Would the same load used in a 1:11 twist barrel show signs of higher pressure in a 1:10 twist due to the extra friction of the tighter twist?

Casper

 

[JEFFJP_N_JJ]

My question should have been:
Does the 1:10 twist, being tighter, require more force to move the bullet through the length of the barrel? Would the same load used in a 1:11 twist barrel show signs of higher pressure in a 1:10 twist due to the extra friction of the tighter twist?

Casper

Not sure Casper as that is way above my pay grade but it does make sense to worry if you are nearing a max load? Start low; my slower loads seem to shoot better.

Jeff

 

[High Voltage]

Correct me if I'm wrong someone, but wouldn't a 1:10 twist be more pressure? Load for load, the 1:10 would be a tighter twist. I think you would be correct.

Sorry, but I am new to reloading, and learning this myself.

 

[boomerpusher]

As Jeff pointed out, the twist is more of a bullet weight factor than a pressure concern. Remember, this is a gas-operated, semi-automatic firearm and therefore cannot accept loading to high pressures-oprod issues. Go on line to Sierra and read their section on semi-automatic firearms, Then get a Hornady Manual and use the reloading data listed in there as a start point. You will find several "nodes" at which your rifle will shoot the best. Pick a middle of the road node to use_DO NOT try to hotrod the M1A, you'll pay for it! If you want to push the envelope, get a bolt action rifle. If you keep your reloads within its operating range, you will not have any problems regardless of your twist rate. Also, keep your bullets within the 150-175 grain range unless you are going to modify the rifle for heavier weights. Best to start low and slow and work up. The idea is to enjoy the platform for what it is and for how much fun it is to shoot. Have fun and keep your powder dry.

 

[nf1e]

No.

 

[lysander]

No.

This is the best short answer.

Medium length answer: For the same bullet weight, case, propellant, primer, ambient weather conditions, propellant temperature combination, you may see some slight increases in pressure, but it is generally not sufficient to get excited about, unless you are going from a 1-14 to 1-7 (even then I doubt any difference would show up without a pressure test rig). Big things that effect pressure are chamber dimensions, number of lands and grooves and the proportion of land width the groove width, forcing cone angle, seating depth.

 

[noob14s]

I am ready to start loading for my new Super Match. My question is;
with a 1:10 twist, is there a major pressure difference for a given load vs 1:11 or 1:12?

No.

 

[MitchAlsup]

This is the best short answer.

Medium length answer: For the same bullet weight, case, propellant, primer, ambient weather conditions, propellant temperature combination, you may see some slight increases in pressure, but it is generally not sufficient to get excited about, unless you are going from a 1-14 to 1-7 (even then I doubt any difference would show up without a pressure test rig). Big things that effect pressure are chamber dimensions, number of lands and grooves and the proportion of land width the groove width, forcing cone angle, seating depth.

Slightly longer answer: For the same bullet weight, case, propellant, primer, ambient weather conditions, propellant temperature combination, the major difference in twist rate is encountered when the bullet is being engraved on the rifling. After being engraved, the difference in bore friction is very close to zero. So after the bullet jumps from the case to the rifling there is a slight increase in pressure, but after the entire shank has been engraved, the pressure curve will follow the same pressure curve as the slower twist barrel.

You might ask: Isn't the twist rate part of barrel friction: yes, but not in the way you are thinking. After the bullet has engraved itself on the rifling, it has been spun up to the twist rate and from here on in its spin increases linearly with the velocity it has in the bore. Thus, the difference in friction cannot be more than the added shank helical distance of the engraving compared to that part of the shank that is in contact with the groove of the barrel. Since the shank to bore is very much greater than the added helical engravement, the difference in friction is almost immeasurable.

 

[JEFFJP_N_JJ]

IMHO is it not worth worrying about. Just load up some 'mid-range' ammo and go out and have fun!