Highest B&C bullet for a 12 twist 30cal.

[distantfoe]

I'm having a 300 jarrett built. My initial thoughts were to shoot 165gr Nosler BTs so I ordered a 12 twist barrel, big mistake. So I'm stuck with a new 12 twist barrel and would like to push the range envelope. Any thoughts on weight limitations for this twist? The rifle should push the 165gr at around 3500fps so should be able to push heavier bullet to relatively high velocities as well.

Thanks in advance

 

[sewwhat89]

Berger lists 1/12 all the way up to their 190 gr VLD.

 

[älg]

rather than weight you should be looking at bullet length when talking about twist. there are some formulas around that may give you an idea of how big/long bullets will your 12 twist accept at a specific velocity.

 

[DougH9]

I am in the same boat as you (except mine will be a 30-338). I picked 12 because I had good luck shooting 190's in a 308 12 twist at 1K. I am planning to use 180 BT's exclusivly (this is a deer rifle). Once underway, I wished I had picked an 11 twist, mainly because I might be forced into unleaded bullets in the future (endangered birds around here). I did a lot or reasearch, including asking here (very helpful), and my fears have been put to ease. My current take is that a 12 twist is probebly ideal for a 180 grain BT (or similar) bullet, fired out of a magnum. Just for kicks, I tried 200 SMK's in my 308 12 twist, and shot the smallest 100 yd groups it has ever done.

 

[Warren Barrett]

1-12 twist is used somewhat in the 1000yd br crowd up to 200- 210 vlds.

 

[Michael Eichele]

I shoot 200 grain accubonds out of my 12 twist 300 RUM and they stabilize just fine. BC of about .590 Probably not the highest but high enough.

Try the 178 AMAX. I get a SUPER HIGH bc with that one. I dont care what the published bc is. At 3100 FPS and a 300 yard zero that bullet fired from my rifle drops 37.75" at 600 yards. That is real world testing not a computer telling me this. My 200 grain accubonds at 3150 dont hold a candle to that! If you were to use the published bc in a computer program, the velocity has to be around 3465 for it to equal 37.7" at 600 yards. I am working on a load that should reach 3450. I wonder how little the drop at 600 yards would be then??

 

[distantfoe]

I want to thank everyone for their insight/advice. You've made me feel better about my situation. /ubbthreads/images/graemlins/smile.gif

 

[Mysticplayer]

Meichele, another shooter with gravity defying Amax results. Bizarre isn't it.

Any chance you can launch some 220gr MK to see if they will stabilize? I have a lead on a 'cheap' match 12 twist but am concerned the 220 will not work in that slow of a twist.

Jerry

 

[Michael Eichele]

Jerry,

Its good to know I am not alone in the 178 BC phenomenon.

I would love to shoot some 220 SMK's. I will look around Anchorage and see if they have some and if so I will give them a try. I wouldnt hold your breath though!!

It might be a week or 2 before I can get to the range and test them as work is going crazey right now.

What results are you getting with the AMAX's and which ones??

 

[jb1000br]

My only experience with the 178 amax showed them to work as they say.

velocity of a buds rifle was about 120fps slower than me 175SMK load and it was consistantly hitting lower than my load to 1040yds.

at 1040, side by side, i hit with 39MOA and it took him 43

178@ 2580 and 175 @ 2700

YMMV,
JB

 

[sewwhat89]

From tests out to 535 yards, the 178amax shoot flatter than the 175smk. the amax needed 9.75 MOA while the smk needed 10.25 MOA to hit the same zero.

The smk have shot better than the amax for me out to 535 yds, 1.44" for SMK compared to 2.20" for the AMAX out of my 300 SAUM.

 

[Mikecr]

It's pretty even between SMK/Amax. Both right near .500G1BC as claimed by their makers. Henry Childs tested the Amax @ .495 using his Oehler system. JB's numbers support this.

How the Gun Nutz & Alaskys here get a G1BC of >1.00 out of a 178Amax is a mystery. Imagine what such a bullet would be worth if REAL!!!

 

[sewwhat89]

Plugging the numbers with my setup, the AMAX have .520-525 while the smks post about .510-515 for me. They both proboly transition into a lower bc category by the time they reach the target. Maybe the AMAX just stabilize faster? It is of no concern really. The difference in drift was less than 1/2 an inch on paper. The smks shoot a tighter group, repeatidly for me; therefore, I will use the smks.

I am waiting to get some Wildcat bullets to see if I can take advantage of a lighter bullet with equal or higher bc than the smk and shrink my groups. I'll post all the results after I get the groups shot.

 

[Michael Eichele]

jb1000br,

I also used the 178 AMAX at about 2550 and found it to be nothing special as far as trajectory. It was .318 on the G7 curve for my circumstances which is close to .475 on the G1 curve. Published at .496. The interesting thing though is when I use the 178 AMAX in my 300 RUM 12x at 3100 FPS it follows the G7 curve at .496 which is truly an unbelivable trajectory!

Mikecr,

You mentioned someones claim of 1.00 with the 178 amax and if you convert from G7 to G1 1.011 is a close match in trajectory between .495 (G7) and 1.011 (G1) Trust me its happening!

I think there is a pattern here. Seems like when guys are shooting the 178 AMAX at medium to lower velocities they dont see any special trajectories. When they launch them at higher velocity, the trajectories are inperpotionatly flatter when compared to other bullets.

Any other thoughts or experiances??