I have the opportunity to snag a new upper for a pre-ban I was given for Christmas.  It is currently a AR15A1, but I want to convert to a M4.  Which chromed upper would you choose, the Bushmaster preban or RRA preban?  For a semi-auto only rifle, which would be your choice?  One better than the other?  No difference?

Thanks.

The pre-ban DPMS 16" M4 chrome-lined upper that CMMG sells on the EE might make a good choice for ya, it's a 1/7 twist and will shoot the newer heavy 77 OTM Nosler NATO rounds.

As to the 1/9 twist uppers you mentioned, while their both good uppers, I'd prefer the Bushmaster.

Mike

How does the 55gr/M193 stuff do with a 1/7 twist?  And what is the pricing like for these 77gr rounds?

I just got a Rock River with chrome lined barrel from Adco. Very nice.

This is what I would do... first of all the 77 grain stuff is $.60 a round so its only something to get for defense and then in limited quantities.  You can get reloaded 75 grain ammo for $225 per 1000 which is very cheap for match ammo.  If the military goes beyond the current smaller batches of MK 262 Mod 1 77 grain ammo you will certainly want a 1/7 barrel.

The main point is you want a 1/7 twist in case you want to use the "best" ammo or the price of that ammo drops if its adopted as a standard round.

Now the least expensive solution in 1/7 is a 14.5" M4 barrel from Bushmaster.  You will have to call to get the barrel (its special order as 1/9 twist is standard) but its only $195.  Bushmaster will assemble the upper for you or you can use someone elses upper to mount that barrel on.  For a price comparison the CMMG/DPMS barrel was $225 last time I checked.  Keep in mind the 14.5" barrel needs a permanently attached muzzle device like a Vortex, Phantom, Bilock etc. to be legal.

The cost of the attaching of the muzzle devise offsets the discount somewhat though with the Bushmaster barrel.  If you want a 16" barrel then the CMMG barrel is the best choice.  Bushmaster is doing a group buy for a 16" for dirt cheap but youd have to pay for machining to M4 profile and threading.  You would have to talk to Kurt of KKF in the industry section to see whats more affordable to you.  I doubt the Bushmaster barrels will be produced however as there is a 200 unit minimum before they start making them.

The 55 grain M193 is no less accurate in my Bushamster 14.5" 1/7 twist barrel than my previous 16" 1/9 Bushmaster.  Its a small enough difference I cant measure it.

In the end I recommend Bushmaster for a 14.5" and CMMG for a 16" 1/7 M4 profile.  
Use whatever uper reciever and other parts you feel comfortable with but I recommend building the upper yourself instead of a whole complete unit which is less than you want for more than you want to spend.


Oh also keep in mind Bushmaster uses forged front sight posts and CMMG uses a cast one which can be switched out for a substantial upcharge.  If it must be 16" and you not in a hurry get on the Bushmaster barrel group buy if it must be done NOW get the CMMG.

I have shot plenty of the M193 and even a box or two of the cheap Winchester white boxed 45 grn. HPs through mine. They shoot very well.

As to the cost of the 77 OTMs, devl covered the commercial cost above, but I reload and while I cannot say for certain how much their coming out to per round, they are cheaper for someone into reloading. There's even a guy on the EE that'll sell ya "cannelured" versions of the same bullet, although I'm having no problems and can't detect any differences in the non-cannelured ones.

FWIW, I'm still tweaking on the load I intend to use and am using the testing/shown velocities by brouhaha and Tat on the "Ammunition" forum as a guide which is very, very good and worth reading. I have yet to reach their velocities outta my 16" barrel, but then I'm only above 60 fps shy and still not done testing, besides their load is in special brass and uses military powders, I'll get there tho.

Hope this helps,
Mike

   

Thanks very much for the info folks.  A lot of knowledge in here [;)].  For my education, what is the difference in the 14in vs 16in barrels with this ammo (55/62/77gr stuff) and how does it affect accuracy if at all?  I am going to go out on a limb here and guess it affects velocity in some way?  I also like the idea of building the upper my self - never done it before.  Good idea for me to do so?  Might be a good project to undertake and it seems like the tools are somewhat cheap to purchase.

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

Accuracy will not be affected, velocity drops for standard M193 and M855 shown above.

Mike

Sweet.  Thanks for the chart.  Since the barrel has to be 16in (I really don't want to mess with the NFA rules) I will most likely look at the CMMG barrel.  I have a post-ban Fulton Armory AR15 flat top 20in style rifle too.  Would it be worth it to change the barrel out on the Fulton and put the old A1 upper on the Fulton receiver?

Just for info purposes the 77 grain NATO MK 262 is 2660 from my 14.5" M4 and 2750 from a 16" barrel.  You are not messing with NFA rules if you permanently attach the flash hider to a 14.5" barrel and make it 16".  There is no difference in accuracy.