Thread: How to get fast twist barrels in NZ

Originally Posted by Wingman

Personally I think if I was to build another subsonic rifle Id lean toward one of @Kiwi Gregs 8.6x47 Lapua's.
Much better brass and the flexibility to load viable high velocity lighter bullet loads for longer shots if needed.
Not sure if the 1-8" .338 Shilen barrels are still available but that would be my first choice, or a 1-9" true flight would be fine in that.
Do you have the chamber reamer for that one Greg or was it just a 6.5x47 lap followed up with a .338 N&T reamer?
I considered a 6mm Norma Dasher necked to .338 with its slightly longer brass and 40 deg shoulder compared to the shorter the 6BR with the 30deg but I think this 8.6x47 Lap will make the most of a short action and multi purpose loadings.

When we made my 338 BRX AR15 upper we cocked up & used 338 Whisper reamer which meant the throat was too long for the projectiles I wanted to run & they were crap

The 160 TTSX on the other hand went fantastic, 1/2 to 3/4 moa was easily achievable at 25-2600 fps with a 20" barrel, it was an awesome upper on a 1-9 True-Flite barrel

I wanted more case capacity for its replacement only having a 11.75" barrel to get 2600 fps & still easily keep it in a magazine.

We used a 6.5 x 47 Lapua & 338 Federal reamer to make the chamber

Thanks for these responses guys it's cool to hear what people with previous experience have found to be successful.
Ruger 300blk Americans stack hornady sub x from what I have seen out of my friends with their 1-7 barrels
I would really like the opportunity to buy off the shelf top quality sub rounds like sub-x if it's just picking a case out of a hat as things seem to be between the 223 and 308 case size in all of these sub rounds. Purely for convineience and availability, I'm not interested in case forming

FWIW the Bergara B 13 takedown 308 is 1:8” twist...16” barrel.

the rifle will be on its way to Trueflight to get one of their 1-8 Prem supp barrels fitted some time in the next six weeks

When the ratio is inverted ,you don't call is a button anymore but a tap :-)

Originally Posted by Friwi

When the ratio is inverted ,you don't call is a button anymore but a tap :-)

Ha ha!
"What twist rate are you running mate?"
Errrrr... .308" BSP

Originally Posted by Wingman

Ha ha!
"What twist rate are you running mate?"
Errrrr... .308" BSP

Nah, a Witworth :-) ( if you know your rifling and your threads you ll get the idea ;-)

Sounds like the goal is to get the heaviest, highest BC possible projectile, shooting at just under the speed of sound, out of a short action. Sound about right?

Its not very unique, but personally I think when the number crunching is done, the 30cal is going to be a better choice. Arguments for the .30cal diameter are as such.

Projectiles are literally half the price of comparable .338 projectiles.
Hornady 225gr ELDM with a BC of .777 are $99 per hundred, vs .338 .300gr Sierra matchking with a BC of only .768 (thats less than the .30cal) at a cost of $99 per FIFTY.
Berger .300gr have a marginally better advertised BC of .822 but its not going to make much of difference at the ranges this gun would be capable of, and again they are double the cost of a comparable 30cal projectile.
You could shoot the Hornady 225gr .338 ELDX projectiles which are comparable in price to the .30cal ELDM but then you take a significant BC hit vs the .30 and loose the one advantage that the .338 may have, which is a heavier projectile on target.
A suitable twist barrel to stablise heavy 30cal will be much easier to come by than a .338

I ran some numbers to put it into perspective.

.30cal 225ELDM @ 1000fps.
Cost per projectile = (roughly) .99c each.
100m = zero
200m = 43clicks or 4.3mils of elevation required/17MOA elevation required. Energy at 200m = 449ft/lb
300m = 100 clicks or 10mils of elevation / 40MOA required. Energy at 300m = 428ft/lb
400m = 159 clicks up or 15.9mils of elevation required / 62.6MOA. How much does your scope have?
500m = 221 clicks up or 22.1mils / 87MOA of elevation required. 391 ft/lb energy remaining. Safe to say the effective range is well passed.

Now for the .338. Iv picked the .338berger to give the 338 as gooder showing as possible.
.300gr Berger OTM / Elite Hunter at 1000fps.
Cost per projectile $1.85 each.
100m = zero
200m = 43 clicks or 4.3MIL elevation. Exactly the same elevation required as the .30 cal. Energy = 602ft/lb. (Same elevation as the .30)
300m = 99clicks or 9.9MIL up), or 38.97MOA. Energy = 574ft/lb (one single click advantage over the .30)
400m = 158clicks or 15.8MIL up, or 62.2MOA. Energy = 550ft/lb. (one single click advantage over the .30)
500m = 21.9MIL / 219 clicks up (mil), or 86.2MOA. Energy = 527ft/lb. (two clicks advantage over the .30)

When all is said and done, there is only 2 clicks elevation difference at 500m between the .30cal projectile at 1000fps and the .338 berger .300gr at 1000fps. I cant see this setup going much further.
There is only a 136ft/lb advantage to the .338 at 500m. Is that worth literally double the cost of the .30cal projectile and the hassle that goes with piecing together a suitable setup to shoot them?
I purposely went the "reasonably priced" projectile route with the .30cal with my point being the gains arnt worth the difference in cost (imo), but if you wanted to spend ,338 dollars on .30cal projectiles then some A-tips would probably put the .30 subsonic ahead in all respects.

If you just want something cool and unique, then more power to you. Do it. There needs no justification for cool stuff. But from a numbers point of view it does not make much sense, to me.

That was the video on the 8.6 credmoor and the fast twist:
https://m.youtube.com/watch?v=RVchYB2vOjg

458 socom is another option :

https://m.youtube.com/watch?v=ijDGqYjXAiM

Thinking about this more, I think a good option could be to get a fast twist .308, throated short, so you can fit 220gr + projectile in the mag and still be close to the lands.
Brass , dies , projectiles etc will be as easy as it comes . Projectile will be real deep in the case and take up lots of case capacity, but who cares it’s not needed because subsonic, and you will still be close to the lands and mag feed = win

Originally Posted by ChrisW

Thinking about this more, I think a good option could be to get a fast twist .308, throated short, so you can fit 220gr + projectile in the mag and still be close to the lands.
Brass , dies , projectiles etc will be as easy as it comes . Projectile will be real deep in the case and take up lots of case capacity, but who cares it’s not needed because subsonic, and you will still be close to the lands and mag feed = win

You and Dean Maisy share the same opinion, I have a suppressed 308 already and just want something smaller and lighter with less case capacity for hopefully less noise
my 308 runs Roberts 151gr hollow points well, and I will use them in this 300 BLK as well as they are good projectiles and the cost factor makes shooting rabbits and things with them far more reasonable. Im not sure I would have had much success using with them in a 1-5 twist with excessive leading

I have a 450BM in the cabinet but to be honest its subs are not that quiet in comparison to 308, the 77/44 i have running 44special cow boy loads is better but they are both quite a big step up in sound

I use my 308 at least 4 days a week I just want something shorter, lighter and quieter

im still looking at doing the 8.6creed but i want to see some more components that I need become available mostly barrel, reamer, cases, loaded hornady subx. I have the donor rifle ready

till then a 300 blk will keep me more than happy

Originally Posted by Friwi

Nah, a Witworth :-) ( if you know your rifling and your threads you ll get the idea ;-)

Unf? Get it real right?

so your telling me I can just mig a whole heap of 30cal nuts together and make my own barrel? i could get into the octagonal barrel look. haha

I watched a video on those cheap buttons on youtube and they were nothing more than trash, i doubt either vulcan or truefight would even entertain the idea and risk their reputation on anything less than the industry standard