Reply With QuoteWhy wouldn't it work?
I tried afew this morning at 250 yards with wind and rain
using reloader 15 powder and winchester cases..cci 200
primer..Near max load..More testing will be needed to
be sure I want to continue the use of them at that price.
Why wouldn't it work?
I don't know,, why should a 155 work in a 1 in 10 twist..Originally Posted by helotaxi
Not all of them will because they are not long enough..And the above is longer than a 175 Seirra MK...
Not everyone on here knows all ...So I would like to hear your opinion as to why they should work...
I've used the Berger 155.5 fullbore, the Sierra Palma 155 s (2156), and the Nosler 155 Custom Comp in my Savage .308 with a 1 in 10 twist 26" and all of them have preformed VERY well out to 800 yards. The Sierra load is what allowed me to ring steal for the 1st time ever @ 1220 yards. The Bergers and Nosler gave me the SAME and best group @ 100 ( .35" 5 shot). The Bergers are great but I settled for the Nosler 155 CC due to the clearance price I picked them up for 20$ per 100. Funny thing is both the Bergers and the Noslers have the same POI out to 700 after that the Bergers exhibit less drop.
Savage--I find that truely amazing that you have gotten such extrem accuracy with the above
mentioned boolets...My Rem.700 SPS with 20 inch barrel and 10 twist will not shoot any of
them boolets...Now the 175 SMK boolets work real good out to the 250,which is all we have
to shoot at the range..
I was a bit skeptic about placing an order for the Lapua 155 grainers..I am still surprised at how
good they shot.But then again the boolet is longer than the 175 SMK...
Because as we stated earlier, twist does not dictate accuracy, only stability. But I think you you said something about not agreeing with and had to prove it to yourself.
For some reason here people think that if you have a fast twist rate then you can't shoot lighter bullets. Not sure why they do, but they do. IF you still don't believe it, have a look at the group below. This is what a 1:8 twist Rock River (yeah an AR) will do with Ramshot Hunter and 55 grain Nosler Varmegeddon bullets. Don't think I will try to argue with the rifle much, it knows what it likes.
Not every barrel shoots every bullet the same. Each barrel is its own and each one will tell you what it likes to shoot.
Last edited by Jamie; 11-03-2012 at 11:09 AM.
Jamie--Thats a very good group...I understand now whats going on. If it weren't for
some of you guys on the forum,I would still be in the dark about.I appreciate the
time you have spend making it more understanding for me...
Hell, I can't fault you for not listening. There is so much crappy advice given out on the interwebs that I wouldn't trust it either. Which goes back to more shooting time, less typing time.
Both of those groups were shot with a 1:10 twist barrel and Nosler 155gn Custom Comps, the first at 300 yds (measured 1.65") and the second at 100. Like Jamie and I have said, barrel twist only tells you the longest bullet that the barrel can stabilize. Nothing else. I've got a bunch of 125gn OTM bullets that I want to build a load for just to prove the point...
Just think if they only made a super long 110 grain bullet...
They do, but it's a .243 cal :D
What good would it do in .30 cal? The BC would be better than a short, fat 110gn but not as good as a 155gn of a similar shape. You don't need a long bullet to get a relatively fast twist barrel to shoot well, that's our point.
Your not far out of the range for the general twist to bullet weight chart, and it's still a good starting point that all barrel makers use, but poly tips, and material density changes the general rule :-)
Just remember if you over spin it may show up at longer ranges or when weather and/or altitude changes....
Bottom line, if it shoots good it shoots good
No such thing as "over spin" outside the point blank benchrest game.
Don't know about you but I have seen many bullets go poof....what do you call it when the rpm is too fast?
Plus the bullet should not spin any faster than need be, here is a couple of ways to calculate spin:
MV x (12/twist rate in inches) x 60 = RPM or MV X 720/Twist Rate = RPM
Last edited by FUBAR; 11-10-2012 at 05:12 PM. Reason: Add
Don't start this again.
First, for anyone needing a twist rate tool, Don Miller's Twist Rate Rule page is excellent: http://accurateshooter.net/Blog/millerformula.xls
For the avg shooter most barrel and bullet makers provide the twist rate recommendation for particular bullets, there are exceptions, but it's a good starting point, beyond that it's researching the subject and testing.
Helotaxi-- "don't start again"? Your the one who used the phrase, "no such thing as over spin...."
Might should have said--exceeding the correct Gyroscopic Stability Factor (GS), but I wanted to keep it simple.
Try defining what would be a "correct" Miller number.
Not enough RPMs underspin, too many RPMs overspin, need info to determine that....so the correct "Miller number" is whatever it takes to get to get to a GS of 1.3 - 1.5
GS *is* the Miller number or Miller index. The idea that anything outside 1.3 (which is considered marginally stable, btw) and 1.5 isn't "correct" is silly. In fact, the stability index increases as the bullet travels downrange and its velocity decays and the bullet doesn't go crazy as a result.
The 168SMK shoots very well from a .308 with a 1:10 twist. That bullet has a stability index somewhere north of 2.1 from such a rifle. My 1:9 .243 is way sub MOA out to 375yds shooting 58gn Vmax over 4k fps with a stability index of 3.3. By your assertion, those are both "incorrect". On target results would seriously disagree with your assertion and my results are normal.
Last edited by helotaxi; 11-13-2012 at 11:47 PM.
No you said what is the correct Miller number...not what will still shoot to some assumed level of accuracy. Plus you need to re-read what I wrote--the correct/desired number is 1.3 to 1.5, if you want to define 1.3 as marginal that's fine.
Never said the bullet will go crazy, and i did not come up with the to strive for GS number--Bryan Litz says the desired SG is "1.4" is the Army says "1.5" and I just used a spread.....
If some of the variables are not considered, caliber, bullet length&weight, MV, twist, atmospheric conditions, one can end up with a bullet that might shoot ok in hot humid weather and then not work well in cold dry weather. Moreover it may or may not work as expected.
What's acceptable to a hunter may not at all be acceptable to an IBR shooter...
The Don Miller formula is an excellent tool and shooters may want to understand what's the correct/desired SG and then they can research why.
You said there was no such thing as overspin, overspin is not overstabilization, don't know how a bullet could be overstabilized. Overspin happens more often with cast bullets, but it still happens, and some define it as excess velocity for the bullet / barrel twist rate, however to me that's the same thing...the bullet goes poof in flight, and/or hits the target or ground in fragments.
No, he said the "minimum" was 1.4. You need to go back an read that chapter. He plainly stated that once the minimum was reached, barring a bullet failure, there is no maximum.
Not in the context of what SG we are trying to achieve:
...."In Figure 3, we found that the benchmark requires a 1:8.6 twist to achieve the desired Sg of 1.4 at 2950 fps. Table 1 shows what happens to Sg if we keep the 1:8.6 twist and change other conditions. Notice that for higher speeds and temperatures, the Sg goes up. For lower speeds and temperatures, the Sg goes down. Decreasing barometric pressure and increasing humidity also make the air less dense. These things have the same effect as increasing temperature....."
You are thinking of minimum twist?
"Minimum twist required for an Sg=1.4. You may get away with slightly slower twist, but itís not recommended. Higher twist rates are generally ok."
I disagree with you on the 168 SMK shooting so well in the 1 in 10 twist...I know of 2 other guys plus my own rifle will NOT shoot this bullet worth a hill of beans..Different powders tried,and OAL.....nothing...
Acemisser:
That's the point, and I'm sure your example is correct, but Helo Taxi's example may also be correct, it's just anecdotal back and forth without understanding the why....it's not just bullet length or bullet weight, not one thing at all...
The combo might shoot to some level of accuracy in some situations, it's totally dependent on many variables...and with you shooting Benchrest it's good to understand why.
he 168 SMK and 168 NCC and 168 H A-Max all shoot well in my rifle out to about 700 yards after that the 155s and 175s all shoot better. What other 168s have your tried? its highly possible that your gun just doesn't like that one bullet. Can't imagine as to why but it could. If you are talking about the SMK past 600 yards that's the reason right there. Its boat tail has given it issues at atime when it starts to go threw the trans sonic barrier it just get wonky. Depending on velocites that barrier is usually between 600-800 yards.
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