OK, I've got my Oly Arms pre-ban lower and may have enough money soon to get the upper done.

Would some of you mind answering a few questions?

1 - difference between 1:9 and 1:7 twist?

2 - Difference between chambering for 5.56 vs. .223?

3 - I'd like to get the 16" M4 barrel, threaded, with flash suppressor (not permanent, in case I ever get a suppressor) - should I stick with this idea, or would getting a different barrel/length combo be better?

4 - Would like handguards that have rails on them, but can't see paying $350+ for Knight's RAS ones.  Would the Oly Arms FIRSH or some other style be cool?  Rails just on the top and bottom or each side would be fine with me.

5 - I'm still undecided on whether to get front sight post or get the 4 rail gas block with the rails.  That way I could put on a flip up if/when I need to.  I'm going with a flat top upper for optics, but may get a flip up rear site as well.  Opinions?

Thanks, guys!

BTW - any manufacturers to avoid altogether for any of these items?

1/7 can stabilize heavier bullets.

Hi there Greywolf...

1- as David said, 1-7 will do the heavier bullets better...I think original twist was 1:12 for 55 gr FMJ. 1:7 was for 62 + gr rounds. so there could be a happy medium, 1:9 was done so that the shooter could do both for the most part. if you are building a dedicated match gun for longer ranges, go with the 1:7. if you are just building a plinker/target shooting gun then go 1:9.

2 - 5.56 and .223 measure their chambers differently. you can safely shoot .223 in a 5.56 chamber but according to SAAMI yo should not shoot 5.56 (milspec NATO ammo) in a .223 chamber. It isn't safe according to them.

3 - I'm in Canada so we are not stuck barrel length issues. You guys have the restriction (unless you have the right licence - I stand to be corrected if I am wrong on this one)so go with the 16 inch.  once again depends on what you want to do with it. close in work, the 14.5 is a little handier, 16 is better if you are going to move further out. accuracy and terminal ballistics are better when further out with the 16.

4 - hate to say this, but ...save up the cash and get a KAC FF RAS or ARMS FF SIR...they appear to be the best choices. once again if accuracy is an issue then the Free Float feature is a must.

5 - if you are getting a RAS of some sort, then why go railed G.B.? stick with front sight post and a flip up rear or something like the LMT SOCOM rear sight. the A2 type rear sights are good as they give you adjustablility and sturdiness (Like BM, LMT, DPMS BUIS) if you need small. then go flip up like GG&G, ASA, ARMS,etc.

I hope this helps ya out.

Ruff

[url]ammo-oracle.com[/url]

[url=ar15.com/forums/topic.html?b=3&f=12&t=147348]SIR, FIRSH, RAS test[/url]

ARMS #40

Thanks for some of the advice, guys.

Question - the reason I don't want a front site post is because I don't want to look at it in my scope or red dot - I would think it would tend to get in the way? :)

Notack - excellent links - thanks!

BTW - if I plan on using subsonic rounds through a suppressed AR eventually, and I assume they will be heavier bullets, should I go ahead and get the 1:7 twist barrel?  Am I losing anything by getting the 1:7 vs. the 1:9 twist?

Difference between 1:7 and 1:9 is 2.

Difference between 5.56 and .223 is 5.337.

I don't know about the rest.

The 1/7 twist will reduce your barrel options.  I can only find two manufacturers with 16.1" 1/7 chrome-lined barrels, DPMS and Colt.  Several people are *very* pleased with the 16" DPMS:
http://www.cmmginc.com/inventory_a/uppers_tbl.html  
http://www.cmmginc.com/cmmg_images/tbl_images/uppers_images/M4_A3_16.jpg

I agree with TacticalConcepts: don't go cheap on the FF assembly.  
According to the people much smarter than me in the Ammo forum, the 1/7 will stabilize up to 100gr ammo.

Go look at the CMMG upper.  It's got a lot of what you are looking for: 1/7 twist, 556 chamber, 16.1" preban.  CMMG also lists the other options you mentioned and may be able to package them together.

Best of luck.

I called CMMG about their gov't profile 20" upper, looking into it myself. I was concerned because I have a 1:9 Post Ban Oly, and the 1:7 Gov't profile upper is only offered in preban config. They said it's no problem to order it, then put on a brake instead of flash hider, pin and silver solder it onto the threads (can be removed if ban sunsets) and the dogs on the bayonet lug can be ground down, reparked. That’s probably what I will do, to get my 1:7 ratio, which is currently the standard for US Armed Forces.

its near the bottom of the page:

http://www.cmmginc.com/inventory_a/uppers_tbl.html

By the way, I have ordered several items from CMMG, always satisfied. They always answer the phone, too, no recordings.

Let me ask you guys this:

If I have a flat top, will the front site post block my view when using optics (red dot, scope)?  This is the reason I was thinking of getting no front site post and having instead the 4 rail gas block up front, where I could mount a flip up front sight.

Greywolf..I don't know about the scope but the red dot (with a proper mount) should co-witness with the post itself...ie:line up...it isn't a distraction when you train with it..you learn to ignore the post. I suspect that with a good scope the the magnification may not even allow the sight tower to show up in the scope...but you will have to ask someone else on that. I am used to scopes on bolt guns only.

Ruff

Your front sight post is going to be there when shooting with the irons.The red dot will co-witness so you get the same site picture but your eye is drawn to the red dot/crosshair quicker and you don't have to line up the rear site w/ the front post.This means you get a faster sight aquisition.If you have to have a folding front site, you might check into the PRI or GG&G folding front sights.

Grey,

Totally concur with a 1/9 twist which gives you the best of both worlds on bullet selection.  I would opt for a 1/7 twist on a 20" or 24" but not a 16" barrel.  The 16" is considered more tactical than target.

I really like the flat tops because they look cool but to tell you the truth, I've mounted a number of scopes on standard uppers with no isssues except a $10 mount.  For some unknown reason, I just don't like the front sight sticking up into my optics and the thought of paying more to look better doesn't appeal to me as well.  I see this option as a matter or preference and is just not mine.

As for the handguards, there are a number of options.  First and foremost I feel the barrel you want should take precedence over any consideration.  I would compare pricing that with and without and then the cost to modify the without to what you want.  I picked up a rail mount for my 20" at the last gun show for $20. It bolted into the handguard and works fine.  A number of aftermarket handguards with rail mounts are also available on the market.

BTW, are you planning on going to Coal River tomorrow?  Besides a good time, this is right up their alley.  They have a number of neat add ons for the AR including a rail mount that I'm interested in.  Take your cell phone and come on up.  You can still take calls from your car.

Tj