How fast is TOO fast?

[Texas Solo]

Can a bullet be over spun? I'm now looking at a .223 for mid-range, 500yds. I have a choice of 1/9 or 1/7 with the Savages I'm looking at.
I called Savage on this and they said 69gr needs a 1/9 twist, but the 77gr needs 1/7. Berger says 1/8 for the 69's and doesn't recommend 1/7 until you get to 90gr bullets.
I seem to think that a 1/8 would be best, but Savage doesn't make it. I'm hoping to use either/both the 69's and 77's. So, which is the lesser of two evils? Being under spun or over spun? Will the 1/7 over spin a 69gr bullet? Totally confused why Savage doesn't make 1/8 twist. From 1/9 > 1/7 seems like a big jump.

[M.O.A.]

Over spin is really only a problem with the lighter bullets like light varmint bullets they can come apart after leaving the barrel when spun to fast.

Like lets say a 36gn varmint grenade out of the 1-7 twist barrel at like 3800fps and yeah you'll have a problem .

But with a 69gn bullet at 2900fps out of a 1-7 well be ok if.

[acemisser]

I shoot the 69 gr SMK out of my 22-250 with the 7 twist with no
problems..Have not tried anything heavier than those..

[BoilerUP]

I know this has been beaten to DEATH recently, but you simply don't need a 1:7 twist to shoot a 77gr SMK or a 75gr HPBT...both shoot just fine from 1:9 Savage barrels.

[82boy]

I have a test target from Savage, on a gun that they sent me, a 10 Percision carbine, in 1in 9 twist that they used Federal gold match ammo loaded with 77gr Sierra Match King bullets. I am sure if the bullet would not work Savage would not use it to test a rifle. I bought a box of them, and they shot very well out of that same gun, actualy it was one of the best shooting bullets I found.

Now a bit of information on the Sierra 77gr bullets, I talked to Rich Machholz (Bulletsmith at Sierra.) last week at the IBS 600 Nationals he told me that this bullet is considered a special bullet, that is why it comes in boxes of 50 instead of 100. The bullet was designed for AR15 rifles, they never intended it to be used in a bolt gun. (This is why you will not find loading data for it in Sierra manual except for a AR15, and Sierra's test rifle is a 1 in 7.) The reason why it is considered a special bullet is because they have to keep closer tolerances on the bullet to ensure that it will fit , and function in a magazine.
Now with that all said, the lable on the box says for 7-8 twist barrel only.

[nsaqam]

Don't be afraid of a quick twist.
Why not retain the option of the super heavies?

[darkker]

Can a bullet be over spun?
Personally I have 2 10FP's and a VTR with 9-twists that are perfectly happy shooting the 77 SMK.

The answer to THIS question is YES. EVERY bullet has an RPM limit, NOT just varmint bullets.
Call the bullet manufacturers. I did this several months back albeit with varmint bullets; here are the responses:

Here is a listing of RPM limits for 22-cal bullets I have discovered(talking with bullet makers) over time. This is a general guide for the curious, not meant to be the "end-all".
As with all things, YMMV

MV * 720 / twist = RPM

Dogtown bullets:
@ 260,000 RPM - Midway wouldn't "admit" who builds them, but had me call Sierra, as they "are familiar with them". NOW they claim that Nosler makes them. Don't know if this changes things or not.

Varmint Nightmare bullets:
@ 260,000 RPM - This is based off of my personal reloading experiences with them. The rumor is that they are identical to the Dogtowns, but I can't confirm that.

Speer TNT's (low velocity):
@ 240,000 RPM - Based off of info in their loading manuals, and personal experiences. When I have talked to Speer on the phone(last time was a month ago) The people that take "technical" questions really do seem to be clueless, and not particularly helpful with this info.

Hornady V-max & SP's:
@ 290,000 RPM - Hornady told me last week that the V-max bullets, and SP's have the same rating. While I'm not as big of a fan of them as of late, they are quite helpful on the phone in this arena.

Hornady SXSP:
@ 240,000-260,000 RPM - One of my children drew me a lovely picture, over my notes; so this figure is difficult to make-outhttp://shootersforum2.survivalistboard.netdna-cdn.com/images/smilies/wink.gif

Sierra Varminter:
@ 216,000 RPM - The Sierra tech "didn't have his calc sheet in front of him". But told me that the velocity limit was 3600 FPS in a 12 twist barrel, so the calculation gives this RPM.

Sierra BlitzKing:
@ 352,000 RPM - Same tech as above, claimed the ceiling is 4400 FPS from a 9 twist barrel.

Nosler BT's:
The Nosler folks are full of....... They claimed that NONE of their bullets failed in a 6-twist at a speed of 4600fps. In theory that means 552,000RPM. I know from my experiences with my 223 WSSM's that this is NOT true. At some point the Centrifugal force overcomes the Centripetal force, ALWAYS. My personal experience puts the BT's somewhere around 320,000RPM.

[nsaqam]

Spin a Barnes to 600,000 and it'll hold together.
Varmint bullets are fragile compared to most hunting bullets.

[darkker]

Any monolithic bullet is a totally different animal. Whether Varmint based OR NOT, "standard" bullets have dissimilar metals that WILL begin to slip relative to each other. That friction will induce heat, and that will change the dynamic balance of the projectile. That begins a failure, as does the relative differences in densities and hardness, as the tensile strength is not the same.

Barnes, which are a heat-treated monolithic bullet SHOULD have a much higher RPM limit. However they too will have a rotational limit do to minor imperfections inherent in the construction.
I never called Barnes and spoke to them about rotational limits.

On a somewhat side note:
I find it curious, that many are so concerned with sectional densities, and using heavy bullets to ensure penetration on large animals. Yet are perfectly happy to use lighter(SD & gr) Barnes for said task. Barnes heat-treats their bullets to ensure that they will be tough enough to not just yard sale upon impact. It seems what people understand is that Equal weight Vs. Equal weight: Barnes penetrate better, so you CAN use lighter.
What they generally don't understand, is that it is due to construction. And also they REQUIRE a higher velocity window for proper operation. THAT is why lighter bullet weights get recommended, to ensure proper functioning.
Not saying it is a good/bad thing, just a curiosity.

[Texas Solo]

Don't be afraid of a quick twist.
Why not retain the option of the super heavies?


This is what I'm thinking, as I might give the 80gr a whirl. But I just wanted to be sure that a 1/7 would still shoot the 69's OK.
So, from what I've read here, you "can" over spin a bullet, but you would have to work at it. And since I'll never be shooting the light varmint stuff from this particular rifle, that doesn't apply to me.
I should be good to go with 69 and up in a 1/7.

It's also worth noting that my Colt 6920 AR15 shoots 62gr M855 from a 1/7 twist real well @ 100yds. Then again, it's a 16" barrel that I've never shot over 100yds.

[Luckus]

I have read, that if a bullet spins too fast any imbalance or imperfection in the bullet will be magnified and accuracy can suffer. I can't site the article but it was probably in some benchrest article somewhere.

[darkker]

Call Berger:
714-447-5424
Ask what the RPM limit is, then use the formula.

MV * 720 / Twist = RPM

[kevin_stevens]

Barrels will heat up more with a tighter spin, don't know if it's appreciable enough to be an issue.

KeS

[lal357]

I've got a LG shank 1/9 sitting in the safe that loved the hornady 75 gr pills used it to shoot 300 yds f class with . My other 223 has a cbi 1/8 so I can shoot 80 gr pills

[jhelmuth]

I won't even comment on the lager (than 69gr SMK) pills in the 1:9 Savage barrel....


Something to consider... the Savage barrels I've had in .223 are throated pretty long. If I want to seat a 69gr SMK in my latest 1:9 LRPV, I have to go to a 2.340" COAL (1.943 OAL) to put the bullet at the lands. I've never had a 1:7 Savage .223 barrel (I think these are only avail. in LS - correct?), but I would be a bit curious to know if the 1:7 had any longer throat (since it would be targeted more toward the longer/heavier bullets). If it did, I think you'd possibly be giving up some seating depth and may need to avoid seating the 69gr SMK to the lands (and I have found that this typically works the best when using the 69gr SMK in the Savage 1:9).

Just a thought...


BTW... the bullets I have tried (and looked at) which are 75gr and higher ALL recommended 1:8 to 1:7 twists. I would ALWAYS go with their recommendation as they know considerably more than anyone else what it will take to get the best performance from their bullets.

[Texas Solo]

I won't even comment on the lager (than 69gr SMK) pills in the 1:9 Savage barrel....


Something to consider... the Savage barrels I've had in .223 are throated pretty long. If I want to seat a 69gr SMK in my latest 1:9 LRPV, I have to go to a 2.340" COAL (1.943 OAL) to put the bullet at the lands. I've never had a 1:7 Savage .223 barrel (I think these are only avail. in LS - correct?), but I would be a bit curious to know if the 1:7 had any longer throat (since it would be targeted more toward the longer/heavier bullets). If it did, I think you'd possibly be giving up some seating depth and may need to avoid seating the 69gr SMK to the lands (and I have found that this typically works the best when using the 69gr SMK in the Savage 1:9).

Just a thought...


BTW... the bullets I have tried (and looked at) which are 75gr and higher ALL recommended 1:8 to 1:7 twists. I would ALWAYS go with their recommendation as they know considerably more than anyone else what it will take to get the best performance from their bullets.

This is good info, thanks. The rifle will be either the #12VLP/DBM (available in either 1/7 or 1/9) or the F/TR. I primarily want to shoot the 75/77 grain stuff (I think), but of course I want to keep my options open. Once I order this rifle, it's mine. So I'm just trying to look at all the variables, ie: bullet brand/type/weight/BC...powder brand/velocities/pressures. I've already worked up 216 loads on the computer, using 9 bullets and 8 powders.

My head hurts.

[helotaxi]

Like lets say a 36gn varmint grenade out of the 1-7 twist barrel at like 3800fps and yeah you'll have a problem.

Hmm...all the ones that I've shot would beg to differ. The VG is a very tough bullet with regard to spin. The really low density of the core probably has a lot to do with that. Now a 35gn bullet designed for the Hornet is a totally different story.

As far as dis-similar metals and shifting with relation to each other, look at a bonded bullet. It isn't shifting at all and you aren't spinning one apart.

[helotaxi]

I have read, that if a bullet spins too fast any imbalance or imperfection in the bullet will be magnified and accuracy can suffer.

This is true; however, you'd need a top quality benchrest rifle to realize it. If the bullet is out of balance enough that you'll notice the difference under practical conditions, it's going to shoot so poorly to begin with thou tyou'd be talking about the difference between 5 MOA and 6 MOA between a 1:9 and a 1:7. Shoot a good bullet to begin from a good barrel and as long as it is adequately fast, twist becomes essentially irrelevant.