1 in 7 twist with a 55grain bullet

[steelejones]

Any issues shooting this bullet with this twist that you can see ?

[Michael C]

I assume that your talking 223....and the answer is no problem at all.

[earl39]

With a 223 i don't think you can push a 55 grain bullet fast enough for the 1/7 twist to cause a problem. This is not the case with lighter 40 grain bullets. I have seen them come apart in a grey puff within 50 yards using a 1/7 twist.

[Dennis]

I have seen them come apart in a grey puff within 50 yards using a 1/7 twist.

x's 2

[savageboy]

I shoot 55's all the time w/ my 1:7 twist AR

[Dennis]

What's your barrel length with the 7 twist?

[savageboy]

18" SPR Configuration. Rifle length gas tube. Prob. Dosen't get the velocity of a 26" obviously, but shoot good, not as good as the 77's , but cheaper

[Dennis]

Maybe my 26" make a difference!

[steelejones]

Dennis it would be a 30" barrel of a Mod 12 F T/R

[JW]

I shoot 52 gr SMKs with good success out of a 26" Shilen 1 in 8 twist

[Mallard57]

JW

I shoot 52 gr SMKs with good success out of a 26" Shilen 1 in 8 twist

My AR with a 1 in 7 twist has shot 45 gr factory loads very well. My 1in 8 twist shoots 55 V Max very well also.
Jeff

[Michael C]

OP: Why do you want to use 55g bullets out of a 30 inch target rifle? Are they match bullets?

[amamnn]

Apart from vaporizing a very light bullet with a too fast twist/velocity combination, the concern for matching a bullet to a barrel twist rate is one of accuracy. The faster the bullet rotates on its way to the target the more times it rotates before impact. The more rotations it makes, the more chances any imbalance in the bullet has to affect accuracy. So, the idea is to match up the bullet/twist/velocity for the fewest rotations for the best accuracy. 1/7 is a fast twist meant to stabilize heavy bullets which do better than lighter ones at longer ranges. It is not necessary to stabilize a 55 gr. 224 bullet. 1/14 works best according to the formulas. It boils down to fast twist-long (heavy) bullet-long range. Slow twist-light (short) bullet-short range.

http://www.shilen.com/calibersAndTwists.html

All this can seem quite academic and maybe even backwards, since most people seem to buy the rifle off the shelf and worry about the twist rate sometime after they get it home. Still, it is worth knowing especially when it comes time to rebarrel.

[steelejones]

Thanks for that last post Amamnn.

And Micheal C.

The reason im asking is I have a 100 55grain shells sitting here doing nothing and was curious if it would hurt. And also, im not reloading anything yet, so I dont have access to much for higher grain cases straight off the shelfs here.

To begin with I anticipate 100yards and moving out from there to 600 yards.

[Delaware_Ken]

I also have the Savage F TR with the 30" barrel, and it just loves those 80 gr Berger VLD's behind 24.4 grains of Varget.

Ken

[Michael C]

Steeljones, now I understand. I thought you were talking about a 24 inch rifle. You will not hurt the rifle at all by shooting the 55's. The accuracy is not going to be very good, and they may actually come apart at distance (the jacket can come off the lead core and the bullets dont make it to the target) since that long barrel is going to give max velocity.
Loading for the 223 is very easy, and it's a great round to learn on. I shoot NRA high power rifle and Palma (308). I load about 3000 to 4k 223 a year for my service rifles which all have a 1x7 twist; but, they are 20 inches long. You might want to try the 80g Amax when you get up and loading that is what I shoot at 600 with my service rifles and it seems to do well. You cant really buy ammo that is going to work in that rifle as good as you can make it. Savage rifles are making a showing at the 1000 yard matches in Sacramento Ca. I think last month a guy was running the same rifle you have with good effect. Michael

[steelejones]

Im pretty excited to get started..unfortunately winter is about here...Im ordering the gun on Thursday so hope to have it in a few weeks.

[Sundo]

...The faster the bullet rotates on its way to the target the more times it rotates before impact. The more rotations it makes, the more chances any imbalance in the bullet has to affect accuracy...


Thank you for that explanation. I have been waiting to read something like that. It fits with the reports I've heard.

The original M-16 had a 1:14 twist for 55 gr bullets. It was changed to 1:12 to work in cold (Arctic) conditions where the lower temps reduced muzzle velocity. The lower muzzle velocity required a faster twist rate to achieve the same spin rate. Most current M-16/M-4 rifles have a 1:7 twist, but only because the 5.56 tracer round requires that twist rate.

In reading various forums, I get the impression that the Sierra 77 gr Match King is most accurate with a 1:8 twist while the 69 gr Match King is most accurate with a 1:9 twist. With insufficient twist, the bullet is not stable and starts tumbling end-over-end. With too much twist, a weak construction bullet can come apart while an imperfect bullet will manifest its imperfections.

This explains the reports I've read regarding over stabilized bullets. What I've read is that as long as you're using high quality bullets (i.e. uniform, concentric, balanced, etc.) you can use a faster-than-necessary twist and still get high accuracy. With a low quality bullet, an unnecessarily fast twist magnifies the effect of the bullet's imperfections, reducing accuracy.

That said, a high quality 55 gr bullet should be quite accurate in a 1:7 barrel, while a low quality bullet will be less accurate. The reports I've read suggest bulk 55 gr ammo fired from a 1:7 barrel can be expected to achieve 2-3 moa accuracy while a high quality 55 gr bullet can do much better.

[darkker]

As has been hinted about with regards to rotation.
EVERY bullet has an RPM limit. Speed (short of 5000fps) doesn't affect bullets, spin does.
Not sure I caught WHAT bullets you are talking about. As a good example:
A few years back I bought a pile of 55 gr. Dogtown bullets, Midway says "keep them under 4000fps and they will probably outlast your best barrel". Well BullShiggen!! In my 1:9 twist they were puffing.
After a long series of phone calls and emails, they told me to call Sierra. Sierra told me the approx RPM limit for those bullets. In a 9-twist barrel the rpm limit kept me at @ 3050fps.
Midway has STILL not posted the rpm limit.

IF you are talking a Hornady SX bullet, the rpm limit is MUCH lower than a FMJ(around 240,000). IF the manufacturer "doesn't know" or "won't" tell you, WHAT the rpm limit is(Speer, Hornady) then they (to me) don't have a good handle on what they make.

RPM = MV*720/twist IE: 3200fps*720/7 = 329,600RPM

[poncaguy]

I have a AR with a 1x7 twist, shoots 1/2" 40 Grain with Hornady and Fiocchi VMax's...........also does well with 77 grain and all in between.