.223 twist needed for 75gr projectiles

[Willoughby]

what twist is needed for 75-80 gr projectiles in a .223 ?
will a 9 twist stabilize 75-80 gr bullets ?
or will I need to find a 7 or 8 twist ?
advise from any of you with .223 reloading exsperience greatly appreciated

[BoilerUP]

Here's a copy/paste of what I put on Sniper's Hide:

"1:9 stabilizes 75gr HPBT/77gr SMK just fine; my 26" 1:9 Savage barrel puts a 75gr HPBT out at 2860fps and has a stability factor of 1.41.

The same barrel stabilizes the 75gr A-Max @ 2950fps good enough for 0.7MOA groups at 200yd, though at 500' ASL/80°F (the environmentals for all calculations in this post) its stability factor is a razor-thin 1.01.

The 75gr Berger VLD @ 2950fps has a stability factor of 1.15.

I just had a 22" 223AI barrel arrive last week, and I ordered it with a 1:7 twist so I could have the option of 90grs if I wanted to try them, and to provide better stabilization in cold temperatures. With a 1:7 twist, the 80gr A-Max @ 2900fps has a stability factor of 1.56, 75gr A-Max @ 3000 is 1.69, and 75gr HPBT @ 2900 is 2.35."

You can do a search here and see my results with the 75gr HPBT and 75gr A-Max in a Savage 1:9 223 barrel.

[jhelmuth]

I can't agree with BoilerUP's data - but only because I do not get the same results on the 77gr SMKs. The 77gr SMKs are NOT stabil (in my 1:9 factory Savage LRPV - Bull). The 75gr VMax will work and seem stabil enough. I'd say the 77gr SMKs are border-line and will depend on the barrel. 1:9 is approx. and your barrel may vary slightly on twist rate depending (I'd measuer it to find out - maybe if it were closer to 1:8.5?).... anywho - just FYI.

PS - I don't think you'll find the 69gr SMKs lacking for most anything you want to do in the stock Savage .223 barrel. I've found that the SMKs - paired up with Varget are a very accurate combination when you find the right node for your barrel.

[kschilling]

When I started 500 yard Mid Range F Class, I used a factory 1-9 Twist .223 barrel. They held the 75 Horn BTHP at respectful groups. I switched to 70 grain Bergers and WOW!!!!!

[BoilerUP]

I can't agree with BoilerUP's data - but only because I do not get the same results on the 77gr SMKs. The 77gr SMKs are NOT stabil (in my 1:9 factory Savage LRPV - Bull). The 75gr VMax will work and seem stabil enough.

Certainly not doubting your results, but I'm very curious how the 75gr A-Max would be stable but not the 77gr SMK. In my 500' ASL/80°F atmosphere, where the 75gr HPBT @ 2860fps has a stability factor of 1.41, the 77gr SMK at the same velocity has a marginally higher stability factor of 1.42 while the 75gr A-Max @ 2950fps is right on the ragged edge (at least, in theory) at 1.01.

Guess it proves that "only way to find out is try".

[skypilot]

Sierra 69 gr SMK and Hornady 75 gr HPBT are excellent in my FLCP-K 1/9 .223, but the 75 Amax is a little squirrely @ 400+ as far as stability is concerned. I'm a try it and see reloader with regards to bullet wt/types.

[darkker]

77gr SMK's are stable in 2 FP's and a VTR, all with 9-twists.
Buddy shoots his to 1K with groups that would make the Pope jellous, Launch @ 2745fps.

[M.O.A.]

Mine shoots 68 gn bthp great haven't tried anything bigger yet but soon yo try the Berger 70gners.

[lal357]

When I the factory 26" 9t on my lrpv 75 gr amax and bthp were mo problem tried some 80 gr amax and it was a joke

[PBinWA]

I shot some 75 AMAX through my 1-9 FCP-K at 600 yards last week. Other than getting pushed by the wind horizontally they were surprisingly accurate. MV = 2870.

[Apache]

If you already have a 9 twist, try it. If not, get an 8 twist and be done with it...... or a 7 if you want to play with the 90's.

[acemisser]

77gr SMK's are stable in 2 FP's and a VTR, all with 9-twists.
Buddy shoots his to 1K with groups that would make the Pope jellous, Launch @ 2745fps.

Now what makes you think the Pope will be jealous...You need to explain this in better detail..
I doubt the Pope even has a gun,but then you never know...

[devildogandboy]

what twist is needed for 75-80 gr projectiles in a .223 ?
will a 9 twist stabilize 75-80 gr bullets ?
or will I need to find a 7 or 8 twist ?
advise from any of you with .223 reloading exsperience greatly appreciated

hope this will be useful to you.
http://www.savage-barrels.com/calibers.htm

[darkker]

Now what makes you think the Pope will be jealous...You need to explain this in better detail..
I doubt the Pope even has a gun,but then you never know...

.... If I have to explain why THE POPE would be jellous of being able to shoot groups that tight, it's isn't worth explaining....

[MZ5]

Certainly not doubting your results, but I'm very curious how the 75gr A-Max would be stable but not the 77gr SMK.

Just a guess, but I think it's because he cited the V-Max rather than the AMax.

I agree with your first post, that the 77 SMK will be adequately stabilized by the 9-twist Savages. My 26" FP-UV runs then well. The 75 AMAXes seem to work at least for a couple hundred yards. At the 300 yard mark, when I lived and shot at ~4,800 feet, wouldn't hold as tight as the SMKs. I can't be positive whether that was a stability issue showing up, or just a better load for the SMK, because I hadn't worked with the bullets that much by then. Either way, even here at ~1,200 feet and HIGH temps, the 75 Amax is doing just 'okay' for me at 500 yards. The SMK is a clearly-better choice.

[BoilerUP]

Just a guess, but I think it's because he cited the V-Max rather than the AMax.

Considering there's no such thing as a .224 75gr V-max, I think surmising he was talking about an A-Max to be a fair assumption.

[jhelmuth]

Twist rates and bullet compatibility are actually based on the bullets bering surface and NOT it's grain weight. Clearly ther is SOME relationship there, but as each bullet is not made with the same profile(s) there is an expected difference in resluts from one bullet to the next. One cannot comapre the 75gr AMax (or VMax) to the 77gr Sierra BTHP MatchKing... they are just not the same design from the start even though their grain weight is very similar. Stability is all about angular momentum and as long as one can achieve the needed rate for a given bullet design, great. For the most part, the Savage 1:9 twist factory .223 barrel will stabilize MOST bullet weights up to about 72-73gr accurately. After that, it's a crap shoot and will depend more on the bullet design and it's requirements along with the actual twist rate (which is not always identical to the factory engraved spec.)

All the best,

Jim

[jhelmuth]

Considering there's no such thing as a .224 75gr V-max, I think surmising he was talking about an A-Max to be a fair assumption.

You are correct.... there is a 55gr VMax, the 75gr is an AMax in Hornady. My bad for misposting that.

[MZ5]

I had surmised the 7 as a type-o for a 5. Thanks for clarifying.

I'm a little fuzzy on your assertion regarding how "(s)tability is all about angular momentum..."

The 'amount of' gyroscopic stability required for a given bullet is primarily a function of its length. Weight is a factor, but a minor one in comparison to length. The primary reason why the 75 Amax will _always_ require a faster twist than the 77 SMK is that it's a _much_ longer bullet. If you can shoot the 75 Amax and get adequate gyroscopic stability for a given purpose/function, then the 77 SMK will always have greater gyroscopic stability under the same conditions. Therefore, if the 75 Amax will group and the 77 SMK won't, it ain't because of stability. :)

[Westcliffe01]

My Savage 10PC in 223 (20" barrel) shoots the Hornady Superformance 75gr BTHP 0.5MOA. However the Amax and Berger bullets are a no-go. Perhaps I could shoot those if I re-chambered to 22-250 since the higher MV requires less twist to achieve a given RPM. For the moment, I will leave it as is, since it shoots very reliably and the scope on it has a custom elevation turret for the 75gr boat tail bullet. For me, 55gr is a waste of time because I too often have the wind blowing and shooting 250yd + the wind drift on the lighter bullets is a joke. Meanwhile I also have a model 12 in 243 and that will be shooting even better in the wind, so I do have alternatives.