Twist rate for 220 gn .308 bullet

I have 2 Rem 700 .308. One with a rate of twist of 1-11.25 and the other with a rate of twist of 1-10 their suppose to stabilize heavier bullets.



Jonnybender
 
JonnyBender said:
I have 2 Rem 700 .308. One with a rate of twist of 1-11.25 and the other with a rate of twist of 1-10 their suppose to stabilize heavier bullets.



Jonnybender
Click to expand...

Most refer to heavy as being 190-208. 220 is.... well. yea.

If nobody responds try a 1-10 and see what happens.

Why do you want to shoot such heavy rounds?
 
1-10, out of 308 should work fine with 220 but bits on the edge depending on velocity and overall bullet design. If it was a 300wm you would be okay but the velocity on the 308 will be much lower. As asked above, why a 220 out of a 308? You can always try and "stretch" things but a 1-8 twist would be a sure thing, but again I don't know the bullet you want to shoot. 220gn is a little vague.
 
What would the velocity of that bad boy be.... I suspect it would drop like a stone at further distances... I know there is the big arguement of velcoty vs weight, but at one point you are getting out of it... I think 220 would be that.

2250 to mid 2300 fps?
 
I heard a few years ago that down in the Southern US some F'ers are using 220 gr bullets in 1:7 twist running @2400 fps in their .308's. The B.C. at that velocity is around .629. Just to compare the 6.5mm, 142 gr SMK's has a B.C. of .595 @ 2850 fps. The barrel life on the .308's was also about 5 times longer.
 
I haven't chrony'd my 225 load yet, but I'm hoping I can get 2450 out of it. With that speed, it's still no 7mm 180gr, but the numbers it gives back are pretty darn good. For KD shooting it'd be tough to beat without cranking up the punishment.
 
You can always use the Greenhill Formula to get an approximate ideal twist, since gyroscopic stability is a function of length and diameter:


Twist = (150\(Bullet Lenght\Bullet Dia)) x Bullet Dia

EG for 5.56 62 gr round:

Twist = (150\ (.908\.224)) x .224 in
Twist = (150\4.054) x .225 in
Twist = (37) x .225 in
Twist = 8.325 inches
 
take a look at

h t tp://www.riflebarrels.com/products/caliber_twist_rates.htm

The Problems you have with such a have bullet are
Throat
Load data where do you find it
Will it fit in the mag > seat it deep and loose case capacity

200g plus are being loaded in the 300 Blackout and shot sub sonic
 
rimfiremac said:
I haven't chrony'd my 225 load yet, but I'm hoping I can get 2450 out of it. With that speed, it's still no 7mm 180gr, but the numbers it gives back are pretty darn good. For KD shooting it'd be tough to beat without cranking up the punishment.
Click to expand...

Let us know what you find out. I assume compressed powder charges too?

I'm starting to test 190gr SMK's, but I have been wanting to play with Amax 208's as well.
 
Many barrel makers (Shilen for instance) post a list of calibers/twist and weights on their website.

Caliber Twist:

.172
- 9" for bullets heavier than 30 gr.
- 10" for bullets up to 30 gr.

.204/20
- 9" for VLD bullets
- 10" for bullets up to 45 gr.
- 12" for bullets up to 39 gr.

.222 RF
- 10" * 60 gr. bullets Ratchet rifled 4 groove
- 14" * Twist for pistol barrels
- 15" * Special twist for rifle barrels
- 16" Standard twist for rifle barrels
- 16" Ratchet rifled 4 groove
- 17" * Special twist for rifle barrels

.224 CF
- 7" for bullets heavier than 70 gr.
- 8" for bullets heavier than 70 gr.
- 8" * Ratchet rifled 4 groove
- 9" for bullets up to 70 gr.
- 10" * for bullets up to 65 gr.
- 12" for bullets up to 63 gr.
- 14" for bullets up to 55 gr.
- 14" * Ratchet rifled 4 groove

6mm/.243
- 8" Special for VLD bullets over 100 gr.
- 8" * Ratchet rifled 4 groove
- 10" For bullets up to 95 gr. and VLD under 100 gr.
- 12" for bullets up to 85 gr.
- 13" * for bullets up to 75 gr.
- 13.5" * for bullets up to 70 gr.
- 14" * for bullets up to 70 gr.
- 14" * Ratchet rifled 4 groove
- 15" * Special for bullets up to 70 gr.

.257
- 9" for bullets heavier than 100 gr.
- 10" for bullets up to 100 gr.
- 12" for bullets up to 90 gr.
- 13" * for bullets up to 80 gr.

6.5mm/.264
- 8" for bullets heavier than 130 gr.
- 8" * Ratchet rifled 4 groove
- 9" for bullets up to 130 gr.

.270
- 10" for all bullets
- 11" * for all bullets - 4 groove

7mm/.284
- 8" for all bullets-customer discretion 180 gr. VLD
- 8" * Ratchet rifled 4 groove
- 9" for bullets heavier than 140 gr.
- 11" for bullets up to 140 gr.
- 12" special for high velocity

.307
- 13" * Special size and twist

.308
- 7" * for heavy VLD bullets and/or subsonic ammo.
- 8" for bullets heavier than 220 gr.
- 10" for bullets up to 220 gr.
- 12" for bullets up to 170 gr.
- 13" * Ratchet rifled 4 groove
- 14" * for bullets up to 168gr.
- 15" * for bullets up to 150 gr.
- 17" * for bullets up to 125 gr.

7.65mm/.311
- 10" for all bullets

8mm/.323
- 10" for all bullets

.338
- 8" for all bullets
- 9" * Ratchet rifled 4 groove
- 10" for all bullets

9mm/.355
- 14" for low velocity wad cutters
- 16" for all other bullets

9.3mm/.365
- 12" for all bullets

.38/.357
- 14" for low velocity wad cutters
- 18" for all other bullets

.358
- 12" for all bullets
- 14" for all bullets

.375
- 12" for all bullets

10mm/.400
- 16" for all bullets

.411
- 14" for all bullets

.416
- 14" for all bullets

.44
- 20" for all bullets
- 16" for low velocity wad cutters

.451
- 16" for all bullets

.458
- 14" for all bullets

* Stainless Steel only


Black Powder Barrels (1.250" x 30"):

.32
- 14", 16" .320 groove

.38
- 20" .379 groove

.40
- 20" .403 groove

.457
- 20" , 14" .457 groove
 
I thought I read somewhere that to get to 1000 you should always stay at or above 2500 fps not possible for a 220 gr I have a 1-12 twist and it shoots 185 gr nice so I think a 1-10 would be a minimum but you still want your bullets going supersonic at a 1000 or so I have read
 
I ran it in my ballistic jbm and you are looking at 850 fps at 1000 my 185 vld is still going at 1200 fps at that range I don't think you would get much accracy past 600 with this bullet and 70 MOA at 1000 drop you would need one hell of a scope and rail combo
 
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