Twist Rate Affects Pressure?

[HL]

I've been reloading for over 26 years. I just have one simple question, that will hopefully have a simple answer.

Reloading manuals show loading info for 223 based on specific barrels and twist rates. Most have their loads based on a 1-12 or 1-10.

In developing loads for a barrel with a 1-8 twist, I plan on starting with the lowest load listed in the reloading manual and working up to find an accurate load.

My question is with a 1 in 8 twist, should I really be concerned with the difference in pressure developed by a twist rate tighter than the manual calls for in their development loads, say with a 1 in 12 twist.

Any input would be appreciated.

HL

[charles p]

Makes sense to me.  Seems a tighter twist rate would cause a slower initial acceleration and maybe the pressure would be greater at first.  Just an opion, mind you. 

[Lloyd Smale]

yes ive seen where a faster twist increased pressure. Even in a handgun.

[Grumulkin]

Though I have no proof of it, twist probably does affect pressure but, as long as you start at the lower end of the recommended loads and work up as you should do with ANY firearm, watching for signs of excess pressure, you should have no problems.

[HL]

That's pretty much what I was thinking, but I've never had a rifle with a 1 in 8 twist before in this caliber. Mine have always been 1 in 12.

thanks for the replies.

HL

[huntducks]

That 1-8 will need bigger and longer bullets.....

[HL]

I Plan on using 64gr bullets. It's for my AR-15, my new hog gun. 

Guns and Ammo had a good article with the AR I bought, and it looked like 63-64gr bullets showed the best accuracy with the 1 in 8 twist, using factory ammo. So, I figured I would load up my own and see just how accurate it can be. Factory ammo 63gr was getting .75" 100 yd groups and 1.3" 200yd groups from a bench rest.

[SHOOTALL]

I think the books state the equipment used so the reloader will know what was used. Other books don't list such some so skechy as to list "jacketed " or Lead " bullets no brtand name. I would doubt they would offer loads that could not be used in all weapons with out noting exceptions. Another reason to start low and work up.
 When the gun is fired the bullet has to jump from the case or crimp if one is present - the first peak in pressure . The bullet enters the forcing cone the second peak, At some point the powder is consumed and pressure has reched its peak which may be as it leaves the bbl or part way down it or the 3rd peak is reached. Does the bullet move faster ? or peak higher ? Maybe a bit of both depending on bullet, rifling , bbl length , bore size , lead or jacketed bullet, case size , powder type , temp at time of shot , humidity etc.
 It might be the peak occures in a different section of bbl . But consider that a bullet spinning faster might travel at the same forward speed depending on where pressure peaks .
All that said in reality it has little effect , check out Greenhill caculations

[helotaxi]

That 1-8 will need bigger and longer bullets.....

It can shoot longer bullets but it certainly doesn't "need" them.

[helotaxi]

All that said in reality it has little effect , check out Greenhill caculations

The Miller formula is a better indicator for modern bullet designs moving at supersonic velocities.

[HL]

Well, the magazine will pretty much dictate the bullet seating depth for the 223. I am able to seat the bullet .01 longer than published and still have positive feed.

[SHOOTALL]

All that said in reality it has little effect , check out Greenhill caculations

The Miller formula is a better indicator for modern bullet designs moving at supersonic velocities.

Couldn't remember that name yesterday , old age ya know . But point is it has little effect .

[HL]

I appreciate the input, guys.

Good shooting!