pressure and twist rate

titch--

titch--

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Hey guys. Im looking at getting a new barrel for my Stevens 223 because it seems like my groups are starting to open up now with my old one.

You ask why the heck am I posting this here, well...

My question is about pressure with twist rates of the barrel. This rifle is mainly my coyote rifle and so right now Im shooting 53gr Vmaxes through it. I have had good luck with these bullets on yotes so I would like to keep using them, that or 55gr nosler bt. Anyways with me shooting these middle of the weight range buttels, I wont need a real fast twist barrel. Ive read somewhere (I cant find it now) that I would would reach max pressure shooting in a 9twist faster than a 12twist barrel if I were to push these as fast as I could. Is that true or am I just reading internet garbage?

If I posted this is in the wrong place, please move accordingly.
 
Don't worry so much about the twist. Just get what is a standard twist for that calibre and shoot away.
The only time twist is a critical factor in any rifle, is when it is too slow to stabilize heavier bullets that you may want to shoot.
Far better to have too much twist than not enough.
 
titch-- said:
Hey guys. Im looking at getting a new barrel for my Stevens 223 because it seems like my groups are starting to open up now with my old one.

You ask why the heck am I posting this here, well...

My question is about pressure with twist rates of the barrel. This rifle is mainly my coyote rifle and so right now Im shooting 53gr Vmaxes through it. I have had good luck with these bullets on yotes so I would like to keep using them, that or 55gr nosler bt. Anyways with me shooting these middle of the weight range buttels, I wont need a real fast twist barrel. Ive read somewhere (I cant find it now) that I would would reach max pressure shooting in a 9twist faster than a 12twist barrel if I were to push these as fast as I could. Is that true or am I just reading internet garbage?

If I posted this is in the wrong place, please move accordingly.
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How many rounds have you put through your current barrel would you say?
 
Not knowing the round count kind of leaves me in the dark. So I gotta ask if you have decopperized the barrel? If not, try that first before changing the barrel. As far as twist rate is concerned, for the weight of bullet that you are shooting the standard 1:12 is fine. As Ganderite has mentioned, if you want to use a bullet that has a greater mass, take a look at a 1;9 twist. Savage makes on of those.
 
Hold up, the 53 grain v-max is a longer bullet 0.830" vs a 55 grain Nosler BT at .806". Hornady used either a secant or a hybrid ogive on this bullet to give it a higher ballistic coefficient, but that of course increased the length. They load this bullet in 223 ammunition, but not in the 22-250 due to the slower twist rates those rifles typically come with. Your rifle currently has a 1:9 twist rate, I would never go any slower than that for a 223. If you're buying a custom barrel, you could look at an 8 twist if you ever wanted to launch some heavier bullets. Keep your options open.
 
Ganderite said:
Twist has no affect on pressure.

a 1:12 will work well with 55 gr bullets. But you would have a limit of about 69 gr.
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I must disagree with you on that one, Ganderite.
In the OP case, I agree with you, but twist DOES affect pressure.
It increases drag, and a lot of long range shooters tend to take as little twist to stabilize the bullet they use, as per pressure signs don't show as fast and they get more velocity with a low twist rate out of the same load - which indicates that a higher twist rate produces more drag.

Does Twist Rate Make a Difference in Velocity?
Yes. Our tests show that, with the 80-90gr bullets, a 1:10 or 1:12 barrel will give you as much as 80fps more velocity than a 1:8 barrel, shooting the exact same loads. Fast twist (1:8) barrels have more drag and friction, which can slow the bullet down. Ideally you want to use the slowest twist rate possible that will stabilize the bullet you choose to shoot. For a dedicated "point-blank" 100/200 yard Benchrest gun, you want a twist rate from 1:13 to 1:15. But if you want to shoot both light (60-80gr) and heavy (100gr+) bullets, stick with a 1:8.
"http://www.6mmbr.com/barrelfaq.html#24639"
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Hey guys thanks for your time and wisdom.

I dont remember where I read this, Ill looking around this weekend to see if I can find it.

Moreless what this guy was saying, was that a person would start showing signs of pressure at say like 26.5grs in the 9 twist and like 27gr in the 12 twist with the same bullet. That what I gathered anyways.

cheers
 
Also I went out yesterday to shoot some more paper and....

I have been shooting 26.5gr of varget with the 53gr Vmaxs and I could get lucky sometimes if I did my part with a group around 5/8" (3 rounds). Then it seemed like later on the best would be 1.5" and thats after I scrubbed the barrel down with bore solvent.

So since it was nice out yesterday and I was out shooting yotes, I decided the I would try out 26.7, 26.9 and 27.1grs of varget. Low and behold 26.7 and 26.9 were shooting really good which anyone would be happy with in a factory barrel. So whats up with that? Having to increase like that to shoot good again?

thx
 
A couple things to note.

Was there a big difference in temperature when you were shooting last compared to now (temperature compensation)?

How many rounds between then & now (throat erosion)?

Google OCW

Maybe not time to spend $'s on a re-barrelling job quite yet.

Take some of your savings & buy some Berger 53-55 gr. target/varmint bullets first.

Also, epoxy some steel rods in the fore-arm of your Tupperware stock, presuming you haven't changed that.

Presume you're using some quality brass (Norma, Lapua, RUAG, &c.)?

Are you using wind flags when you're working up loads?
 
jamesharrison said:
A couple things to note.

Was there a big difference in temperature when you were shooting last compared to now (temperature compensation)?

How many rounds between then & now (throat erosion)?

Google OCW

Maybe not time to spend $'s on a re-barrelling job quite yet.

Take some of your savings & buy some Berger 53-55 gr. target/varmint bullets first.

Also, epoxy some steel rods in the fore-arm of your Tupperware stock, presuming you haven't changed that.

Presume you're using some quality brass (Norma, Lapua, RUAG, &c.)?

Are you using wind flags when you're working up loads?
Click to expand...

But aint Varget suppose to be none temp sensitive?

Only 10 rounds since I last shot it with bad groups. I think it aint my shooting because I was shooting my 243 and was shooting it real good.

When I find a new load. I shoot a 26, 26.2, 26.4, 26, 26.2, 26.4 etc

My Stevens 200 has a devcon bedded Boyds stock on it already.

Lake city brass

Wind is calm

EDIT: Ive even went as far as taking my wheeler fat wrench out with me and playing with different action settings
 
Just my experience but the fast twist .224 barrels don't shoot light barrels particularly well. I have both .223 and 22-250 with 7-8 twist barrels and have tried to get the lighter stuff to shoot. A rifle that will hold .25" for 5 rounds with an 80gr can barely hold .75" with a 60gr...just an example from load testing this week. Also, I haven't shot bullets as light as 40gr with the 7 twist but I'd imagine there's a real possibility of them coming apart shortly after exiting the barrel. As for the accuracy, I don't know the science behind why they don't shoot as well.... I just know what I've observed. I'd be interested in learning why if anyone has some understanding of this.
 
Yeah it seems that I just had to up the charge alittle more.

Im going to shoot another 26.7, 26.8 and 26.9 to make sure everything tickety boo.

Still wanna check out a new barrel though. :)
 
Limitations imposed by increases in rate of twist is where the theoretical runs head long into the practical. Few of us restrict ourselves to a single bullet weight, so the fastest twist allows us to shoot the greatest variety of jacketed bullets. There is no practical downside through the choice of a fast twist barrel, and no measurable difference is accuracy when compared to slower twist barrels of equal quality, regardless of bullet weight. My 28" .308 target rifle with a 1:8 twist drives 210 gr VLDs at 2650, and it shoots bug holes with any match bullet I've tried regardless of weight. Would velocity be higher with a 1:12? At one time I had a .222 with a 1:7. this was until then the most accurate rifle I had owned, yet most of the bullets I sent down the pipe were short little 52 gr MKs. Any difference in velocity or pressure would be meaningless because the interior dimensions of the barrel matter more than the rate of twist, it takes energy to spin the bullet. Spin drift increases with the rate of twist, but is a constant and easily predicted and adjusted for even at long range.
 
Thanks guys for taking the time here



Ganderite said:
Sounds like throat erosion was reducing pressure.
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That sounds like new barrel talk to me. heh

I know someone with a one of those mini camera snakey thingys. Ill have to pop over there sometime and take a look.

Also if this was cause by erosion and me having to bump up the charge a bit, does this mean that after a little while this newer charge will soon start to open up aswell?
 
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