Should my AR 15 Have a 1:7 twist or a 1:9 twist

[AIRret]

Yes we are going to buy an AR 15 while we still can. But which one will be best
for a SHTF scenario.
The 1:7 that will shoot all ammo
Or the 1:9 that is more accurate.

[MDH65]

A 1/9 will not be more accurate over a 1/7 per say.
It depends on the ammo you plan on shooting.

If you want to shoot 75/77gr then you will need to go with 1/7.
On the otherhand if you wont shoot anything over 68/69gr then 1/9 will be fine.

As far as accuracy goes, I've got a 1/7 Colt that shoots nice tight groups out to 200yds with 77gr Federal match. The wife has a Colt with a 1/9 and it will do about the same size groups with 69gr ammo.
The 1/7 has the potential for greater accuracy at longer range just from the greater ammo compatibility.
Both are 16" barrels with 556 chambers chrome lined.

Now if going for a shtf type then the 1/7 gives you more versatility overall.

[PYROhafe]

I just went through this myself and after lots of research I went with the 1:7 twist. It works with almost any ammo except the really light varmint stuff. Also most of the stuff you can pick up at wally world or sporting goods stores is in the perfect range for the 1:7 twist. YMMV but I hope this helps.

[AIRret]

Thanks for the information folks, it does help.

[Charlie98]

My Colt H-Bar 20" has a 1/7 twist, it's intended as a target rifle with at least 55grn bullets (although it does much better with 62's and up.)

My RRA build has a 1/9 16" barrel, spec'ed specifically for 55 and 62grn ammo; it's my SHTF rifle. I don't expect to shoot it beyond 200M (I have something else for that... ;) )

TBH, at 100M, they shoot as well as each other, even given the shorter barrel of the RRA.

[AIRret]

Do any of you reload 5.56?
About a month ago we bought reloading equipment and are set up to reload our handguns. Unfortunately, we can't get up and running until we get home around the 15th of Oct. However, we are considering purchasing the dies, bullets ect. to also reload the 5.56 and we are looking for specific suggestions.
Thanks

[josp]

I have a bolt action 223 that shoots one hole at 100 yards with 55 grain. It's 1:12. I know it's not an AR but it gives you an idea

[CJB]

In 1879, George Greenhill (http://en.wikipedia.org/wiki/George_Greenhill), a professor of mathematics at the Royal Military Academy (RMA) at Woolwich (http://en.wikipedia.org/wiki/Royal_Military_Academy,_Woolwich), London, UK[9] (http://en.wikipedia.org/wiki/Rifling#cite_note-8) developed a rule of thumb (http://en.wikipedia.org/wiki/Rule_of_thumb) for calculating the optimal twist rate for lead-core bullets. This shortcut uses the bullet's length, needing no allowances for weight or nose shape.[10] (http://en.wikipedia.org/wiki/Rifling#cite_note-9) The eponymous Greenhill Formula, still used today, is:
http://upload.wikimedia.org/math/d/8/9/d897ff3697a3bbde34972528dbaf3dc4.png
where:


C = 150 (use 180 for muzzle velocities higher than 2,800 f/s)
D = bullet's diameter in inches
L = bullet's length in inches
SG = bullet's specific gravity (http://en.wikipedia.org/wiki/Specific_gravity) (10.9 for lead-core bullets, which cancels out the second half of the equation)

[Bawanna]

Oh well if you put it like that it makes it plain as a marshmallow in a cup of hot chocolate. :confused:

[Tinman507]

http://2.bp.blogspot.com/-0XsAnAUTSW8/TYTgiThqHrI/AAAAAAAAFs0/9oOBjR9cynM/s1600/proog.jpg

[Charlie98]

Do any of you reload 5.56?
About a month ago we bought reloading equipment and are set up to reload our handguns. Unfortunately, we can't get up and running until we get home around the 15th of Oct. However, we are considering purchasing the dies, bullets ect. to also reload the 5.56 and we are looking for specific suggestions.
Thanks

I reload for mine... although I didn't for a long time. Surplus used to be cheap and it didn't make sense time-wise to reload. The trade-off is loading long-range or target ammo, very little of that is available and what is is quite expensive. So I buy bulk 55grn FMJ ammo and reload the 62grn BTHP's (etc) for my H-Bar.

Be careful when you are buying ammo or components... depending on where you shoot. Some ranges won't allow magnetic or steel core ammo (like M855 62grn 'Green tip penetrator' ammo, or a lot of the cheap 55grn FMJ ammo) and will test your ammo to ensure compliance.

If you have never reloaded before, starting with a bottleneck cartridge like the 5.56mm is a little difficult, there are a number of parameters you must adhere to to produce good, safe ammo, particularly for use in an autoloader like an AR. If you have a pistol you shoot, consider starting to reload for that (straight-walled pistol cartridges) and then move up to rifle cartridges.

[siginu]

Also consider that the faster twist keeps the bullet more stable upon impact. The early M16 had 1 in 14" twist for use with 55 grain bullets, they were barely stable, but inflicted greater damage due to quick tumbling. The faster rates used these days were a response to marginal long range accuracy and cold weather accuracy.

I guess what I'm getting at is that the 1 in 9" has a better chance of not zipping straight through the target for a given bullet weight.

[MDH65]

Also consider that the faster twist keeps the bullet more stable upon impact. The early M16 had 1 in 14" twist for use with 55 grain bullets, they were barely stable, but inflicted greater damage due to quick tumbling. The faster rates used these days were a response to marginal long range accuracy and cold weather accuracy.

I guess what I'm getting at is that the 1 in 9" has a better chance of not zipping straight through the target for a given bullet weight.

Yes and no
The faster twist, say a 1/7, is better able to stabilize a longer bullet compared to a slower twist like a 1/12.
A standard 55gr fmj is fairly short at around .72 compared to a 70gr tsx at over an inch long. But with todays bullet designs, there are some long, lighter weight bullets that do real well in a 1/7 twist.

[ripley16]

Ahhh, the AR.

http://i72.photobucket.com/albums/i186/ripley16/funny%20stuff/M4likrbarbie.jpg