I would like to build a varmint upper and am curious about barrel lengths. From what I have read, accuracy isn’t much affected whether I choose a 16”, 20” or 22”. What is gained, is muzzle velocity. From one study of a 223 bolt action, going from 16 to 22 gained aprox 230fps and from 20 to 22 gained about 50fps.

The 50 fps doesn’t sound like much but the 230 fps certainly does. Why then do some people choose the longer barrel length rather than a 20” which seems almost optimum? What am I missing here?

Thanks - Brad

This may help:
[img]http://www.bushmaster.com/images/faqchart.gif[/img]

I like 24" for my "varmint" AR and an even longer barrel for Rem 700 223 (26"+) bolt rifle, keeping all the bullet velocity I can, to extend the "useable" range. YMMV

Mike  

That IS useful information. I wonder how that translates to bullet drop at longer distances?
Brad

Here's a come-up chart for my rifle using 77grn. SMKS:
100- zero
200-1 1/2 min
300-3 3/4 min
350-4 min
400-5 1/2 min
450-7 1/2 min
500-9 1/4 min
550-11 1/2 min
600-12 3/4 min
700-17 3/4 min
800-23 min
900- no target
1000-35 1/2 min (34-36 depending on humidity)

When compared to the charts in the [url]www.ammo-oracle.com[/url], and converted into minutes, (which is easiest way to deal with come-ups, IMO)

Range/ 20" bbl/ 16" bbl/ my 24"
200  / 3.8 min/ 4.2 min/ 1.75 min
300  / 6.3 min/ 6.9 min/ 3.75 min
400  / 9.2 min/ 10.2min/ 5.5 min
500  / 12.6min/ 14  min/ 9.25 min

Please note: this is NOT a decent comparision as figures above for the 20 & 16 inch bbls. are drops for M193 ammo, not the [red]red-line[/red] 77 SMK round I'm tossing and while they leave the barrel at a faster velocity, they do not have the kinetic energy of the heavier 77SMK downrange.

One can see the differences though, between the 20" and 16" bbls, using the same load and tell "WHY" velocity is a consideration for varmint/long-range ARs.

Using my load in my rifle (CR6724), I can reach the 1000 yard line with around 36 minutes of come-up, (this is 360 inches or 30 feet of drop). Round goes sub-sonic between the 900-1000 yard mark, but it's the best we can do, as ya can't push the 77SMK faster without poppin primers and other pressure signs, and we like using mag-length rounds which ya can't do with the 80s and 90s.

Hope this is some help,
Mike

Very interesting Mike. Now what about barrel materials? I like the idea of a chromed barrel but understand that accuracy (I think precision is the really the correct term) is adversely affected. But is it effected enough to really be concerned about for a varmint rifle? Also, the only chromed barrels I have been able to find are of the 20” HBAR configuration installed in a varmint type upper. I wonder how much precision would suffer by the combination of a chromed bore and HBAR barrel as compared to, say, a SS bull barrel. My main reason for the chromed bore is for longevity, I’d like to use the barrel for a long, long time and not worry about replacing it. Also the parkerized exterior would make it reasonably resistant to the environment given proper care with CLP. I believe Bushmaster has a 24 inch chromemoly barrel available now, although without the chrome bore.

Thanks - Brad

The advantage to a longer barrel really comes into play when reloading.  Yes, using the same loads in longer barrels gives you better velocity than in shorter barrels.  However, working up loads with slower burning powders with longer barrels gives you MUCH better performance.  I have never reloaded .223 so this might not be an issue in such a small case.

I have a 24" Oly SUM in 6mm PPC.  I like the extra length for the velocity, but I also like the extra weight... I can hold it VERY steady with sandbags or a bipod.

As for barrel material, it seems the best barrels are all in stainless.  I read somewhere (probably here!) a chrome lined barrel will increase group sizes over a similiar chrome-moly barrel by 1/2 MOA.  That is OK for combat, definitely not for tiny critters at 300 yards.

Scot

While "chrome lined" chambers and bores are preferable in SHTF, plinking and CQB shooting, the subject was "varmint" or long range, if I understood correctly.

Stainless steel is what you want if long range accuracy is what your seeking. According to my gunsmith and friend his CR6724 has seen 15,000+ rounds and is showing throat erosion. (Spotting for him and uncle, shooting newer CR6724 against the older, shows decided difference between bullet strikes on steel at the 1000 yard line, definite proof and additional indicator throat is in need of attention, no problem for him as he builds our bolt rifles) Re-chambering this barrel while causing the lost of approx. 2+" of barrel length, gets one a new throat and the potentional for and additional 10-15,000 rounds as the barrel is not the problem only the throat is. While your concern is warranted, ya can't go both ways here. Stick with stainless if LR accuracy is your goal, ya won't regret it.

My opinion, YMMV,
Mike

Hey Brad, I'm in the process of doing the exact same thing you are. (though mine's stalled until next semester) I think it comes down to how "flexible" you want your rifle to be.  If it is a dedicated varminter, to be used with a bipod and seldom if ever shot off hand, then 24" is the way to go.  I've decided that for my purposes a 20" stainless varminter (I'm building a RRA Rifle) is the best compromise, because I will frequently shoot offhand.  While you may get modest gains in precision at long range, with a 24" vs. a 20" barrel.  Chances are the 20" barrel is going to be a better shooter than you are anyway.  (don't take offense to that, it's a better shooter than 99% of shooters, myself included)  

Cheers,
Shawn

Most everyone that has posted here has very good information to digest.
In my view, the .223 has good bailistics.
Out to 375 yards.
With a 40 gr at 3900 fps in a 1 in 14 twist or a 70 gr in a 1 in 8 twist at 2600fps, it's a compromise.

"My" best was a 40 gr Ballistisc Tip at 3800 fps out of a 1 in 14" 24" Douglas barrel. 700 action. 5.56m Nato chamber.

Thanks for the replies everyone. Now let’s talk about barrel fluting. I do understand that fluting increases the surface area for better cooling. In fact, a black fluted barrel would dissipate heat better than SS due to higher black body emissions. However, for a varmint rifle, which wouldn’t be used in rapid fire situations, you would think an unfluted heavy barrel would give greater stability from its increased weight. Fluted barrels score higher for good looks, but are they really worth the extra $$?

Brad