Rifle twist discussion thread

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Re: Rifle twist discussion thread

Postby Al in Mi » Sat Sep 19, 2015 2:36 pm

Texas Sheepdawg wrote:If you guys could have a single shot break over 450 Bushmaster what barrel length and twist rate do you think would serve as the most versatile choice?


22" and 20t
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Re: Rifle twist discussion thread

Postby Texas Sheepdawg » Tue Mar 22, 2016 3:32 am

Okay just an update. My single shot is a 1:16 twist. I wonder how my 230 FMJs are gonna behave.... :|
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Re: Rifle twist discussion thread

Postby Al in Mi » Tue Mar 22, 2016 3:55 am

I have no doubts she's gonna do just fine buddy!!!
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Re: Rifle twist discussion thread

Postby Texas Sheepdawg » Tue Mar 22, 2016 5:45 am

If I'm not mistaken, the 1:16 twist is going to work really good with the 300+ grainers..... Right?
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Re: Rifle twist discussion thread

Postby Hoot » Tue Mar 22, 2016 6:08 am

The biggest factor I've seen with the 1:16 twist is rarely mentioned. The greater the spin rate, the greater the resistance to the bullet going down the bore, the greater the back pressure. I saw higher pressure signs in my cases at what were acceptable loads using Lil Gun and a 1:24. That should not come as a surprise when you think about what's going on in there. The solution may be one of using a slower powder, with just reducing the charge being the easier solution. Don't confuse continuous bore pressure with immediate chamber pressure. They're related but not synonymous. Also, many equate heavier bullets with faster twist rate, whereas it's more about the length to diameter ratio of the bullet. The confusion is easy to understand as in most rifle calibers, a heavier bullet is in fact a longer one. With 300gr HP bullets like we see in .451-.452, their weight increase in not proportional to their length increase.

Just my opinion though...

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Re: Rifle twist discussion thread

Postby Texas Sheepdawg » Tue Mar 22, 2016 8:35 am

Hoot wrote:The biggest factor I've seen with the 1:16 twist is rarely mentioned. The greater the spin rate, the greater the resistance to the bullet going down the bore, the greater the back pressure. I saw higher pressure signs in my cases at what were acceptable loads using Lil Gun and a 1:24. That should not come as a surprise when you think about what's going on in there. The solution may be one of using a slower powder, with just reducing the charge being the easier solution. Don't confuse continuous bore pressure with immediate chamber pressure. They're related but not synonymous. Also, many equate heavier bullets with faster twist rate, whereas it's more about the length to diameter ratio of the bullet. The confusion is easy to understand as in most rifle calibers, a heavier bullet is in fact a longer one. With 300gr HP bullets like we see in .451-.452, their weight increase in not proportional to their length increase.

Just my opinion though...

Hoot

Apply the theory of what you're saying here to a 20" barrel. Single shot. No gas system. Ejection is same as a New Englander shotgun. I know you'll probably be giving a hypothetical observations, that is, unless you turned your gas system off during your tests with the 1:16 AR barrel.
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Re: Rifle twist discussion thread

Postby Hoot » Tue Mar 22, 2016 6:56 pm

Texas Sheepdawg wrote:Apply the theory of what you're saying here to a 20" barrel. Single shot. No gas system. Ejection is same as a New Englander shotgun. I know you'll probably be giving a hypothetical observations, that is, unless you turned your gas system off during your tests with the 1:16 AR barrel.


The twist rate and semiauto vs single shot are two different phenomena, other than when the semiauto doesn't function like one it has a little more resultant velocity due to some of the gas not being ported to cycle the action as opposed to adding to the push on the bullet. I didn't chose to quantify the velocity difference other than observe it was more without the semiauto functioning. I always wondered how much real velocity was sacrificed to cycing the action. it's definitely real and if one wanted, it could be quantified.

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Re: Rifle twist discussion thread

Postby Texas Sheepdawg » Tue Mar 22, 2016 8:15 pm

That's why I bought a single shot 450 Bushmaster. I will be comparing against my previous R&D stats.
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Re: Rifle twist discussion thread

Postby BKGunsTHAL » Fri Mar 25, 2016 7:04 am

Hey guys, very new on here, but this is carter from BK Guns N Stuff. We are the ones building the single shot that sheepdawg has.

We've found that 16", 18", or 20" is the way to go with our 1:16 barrels. Do not go over 20" with this twist we've found. We had a customer that was very adamant that he wanted a 24" barrel. Note: We didn't get the chance to ever chrono that barrel, but it he had reported bsck that it had great accuracy and that it was dropping pretty quick.

We were concerned about this because our other barrels performed great. Well after some thinking, what we had come up with was that afte the 20" bbl mark It was in turn loosing velocity because of shear length of bbl. It was creating to much drag and slowing them down, all because of it using pistol powders.

That is what we've found. So we won't build over 20"
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Re: Rifle twist discussion thread

Postby Al in Mi » Fri Mar 25, 2016 9:53 am

welcome aboard and some nice work you guys do.

I'll have to dig thru my limited data from last fall, but offhand memory with factory ammo in my 24" 16t Green Mtn barrel bolt gun, it was around 100-125fps faster than the 20" Franklin upper I had out the same day. I know that's not a apples to apples comparsion because of rifle platforms, but just a observation.
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