Short .308 stabilizing with 1in12?

[HonkeyMcGee88]

I have been wanting to cut my AI down to 16.5in for a while now and while the velocity loss wouldn't be a concern I am wandering about stabilizing the bullet. I am shooting 175 matchkings and 178 amax bullets out of the factory AI 24" 1in12 twist barrel with no problems. Would chopping it down to 16.5" possibly cause the heavier bullets to not stabilize with the slower twist?

Thanks in advance for any advice.

 

[briang7511]

I have a rem 700 with a 12 twist that I had cut to 18 in and I have no issues with heavier bullets.

 

[JBM_DC]

I also "had" a Remington 700 SPS Varmint in .308 with 1:12 twist cut to 18" and never saw a problem shooting 175 SMK handloads.

 

[redbullitt]

It COULD cause issues if velocity drops to a point where the bullet is not wanting to stabilize in your shooting conditions.

Generally I would say no issue at all, but I think it COULD be a possibility with a 12 twist depending where you will be shooting.

FWIW 43.0g of varget and a 175 will get around 2400 fps out of my 16 inch barrels here.

JBM puts a 1.225 inch long 175 smk at 2400 fps, 60 deg F at 1.681 stability factor at 20 deg f that is dropping to around 1.5 stability factor

According to that you should be okay. I have not personally used a 12 twist short barrel.

 

[HonkeyMcGee88]

I will be using CFE 223 and 178amax, should get a little more velocity than varget. At 24" currently I am pushing 175SMK 2775fps with a can.

 

[briang7511]

I am at 43.5 of varget with a 178bthp. I also use 43.2 of rl 15 with a 178bthp but its been a while since I have seen any of that stuff.

 

[JBM_DC]

I also "had" a Remington 700 SPS Varmint in .308 with 1:12 twist cut to 18" and never saw a problem shooting 175 SMK handloads.

I should have stated, I ran with 44.5gr Varget in that particular rifle without excessive pressure. I would think with CFE 223 you would be in better shape than using something like Varget. I would not hesitate chopping it to 16.5" with a 1:12 twist. Really there is only one way to find out if it will cause issues or not and I say go for it.

 

[patrol120]

My 17" 700 with the 1:12 barrel really likes 178 Amax. The accuracy at 100yd is nothing to write home about, but at distance, its wholly acceptable.

 

[HodgdonExtreme]

You'll be fine, unless you dip below ~2400fps at 0°F at sea level. Even then it'll probably be OK.

 

[softcock]

I have been wanting to cut my AI down to 16.5in for a while now and while the velocity loss wouldn't be a concern I am wandering about stabilizing the bullet. I am shooting 175 matchkings and 178 amax bullets out of the factory AI 24" 1in12 twist barrel with no problems. Would chopping it down to 16.5" possibly cause the heavier bullets to not stabilize with the slower twist?

Thanks in advance for any advice.

-
I think 16" is ultra-short for achieving good working Vel. for 175 sierras .To short of barrel @ 16" with Reloader 15, and Varget if your looking for minimum of 2600 fps with 175's .

BIG difference doing loads from and 18" & dropping to 16" barrel for .308 with 175 sierras . getting the Vel. up to taking advantage of the 175's . I had to drop the usual powders and go to 3031 . Then the short length barrel with a sweet workable powder burn-rate all fell into place . Had No problem getting 2600 fps & even more vel. with 175's out the 16" length & good accuracy .
.

 

[popeye089]

The problem with a shorter barrel as stated is you loose a lot of velocity. Contrary to what some people are saying, it is still accurate and is stabilized fine at distance using the 175 SMK. The problem is that you hit transonic and subsonic closer.
Here's some quick numberConditions
16" gas gun
Velocity 2500FPS
TBH 85 degrees F, 29.67 inHg, 78% humidity

I hit transonic that day at around 690 and went sub at around 865. Now some people might say and be happy with that but lets look at the numbers. At 800m my hold is 9.55 mils and at 700m my hold is 7.51 mils. That's a difference of 2 mils At that distance that means my data is changing approximately .2 mils or .66 moa every 10 meters. So if I am shooting and am holding for a 740m target and say realistically am off my range by 30 meters so the target is at 770m. That's a difference of .6 mils. Because of loss of velocity I just missed my target by about 18" low. I didn't even factor how since you loose velocity your time of flight goes up so now wind has more time to impart it's effects on your bullet so your wind drift is greater. Instead of using 4mph for a baseline you're using 3mph. Now even with just a 3mph full value wind you would be holding close to a mil. In my humble opinion 18-20" is just about ideal for a 308 bolt gun. But that's my opinion, different strokes you know