I have a fairly new Bushy 20" A3 HBAR flat top.  I have been really happy with the rifle to date and have had zero malfunctions.  Last week I mounted a scope on it (a Springfield 10 x56 with Badger rings).  I was real dissappointed with the results.  I'm shooting Rem/UMC 55 gr fmj's.  My dissappointment is that the best groups (100 yd) were aprox. 6-8 inchs on average.  I had also been shooting my Rem 700's (which were shooting 1/2" to 3/4" with handloads).  Is this the accuracy I should expect, or may this be ammo related in that this ammo is crap.  I have shot this in same ammo in a bolt rifle in the past and was not impressed.  
Thanks for any responses,
Sleepy  

Ouch that's bad. The UMC rounds could be the problem, try another couple of brands.

Expect about 2" groups or less. I shoot five or more rounds to form a group. More is better. Often you can expect sub one inch groups with an AR.

what kind of accuracy were you getting prior to mounting the scope?  is this the first time you've used optics or are you a veteran with them?

also, just because you line up the dot or crosshairs on center target, doesn't mean it's going to hit there.  you have to make sure that you're looking straight through and head on down the line of the scope.  also that the distance from your eye to the scope is the same everytime, as well as the height and lateral position of your eye relative to the scope.  (my apologies if you're an optics vet and already knew this.)

i agree that the ammo could be a problem.  

6-8" groups?

Trade it for a Mini-14...they get at least 5" groups or better!

Just kidding, of course.
Change ammo brands.
I think things are OK with the gun.
That ammo thing is weird like that.

Let us know what works.
Good lucks.

I third the ammo.  I have used UMC a few times and found it to be quite bad in the accuracy department but it is real cheap.

Keving67

Thats horrible accuracy.  My 20" Bushy Hbar A2 floated with TA01 Acog shoots 3/4"  at 100 yds with South African Ammo, around 1" with PMC.  You should be around 1" with just about any ammo.  Are you using a sling and pulling down on the barrel or bench resting it and putting too much weight on the front?  Some of this could cause a slight bend in the barrel and stray shots. Maybe your scope isn't tight enough, did you locktite it, I've seen that cause shots the jump around many times.
Bill3508

Expect around 1 MOA.  Everyone here has mentioned ammo, change that first.

Second look at your scope.  I have heard of at least one SA scope's crosshairs that wouldn't stay put.

I have a Colt SP1 20" AR15 and a few weeks ago Deadeye47 and I went shooting and I put 10 rounds in a 1 inch x-ring at 100m using UMC 55gr .223 ammo and I was keeping solid 2-3 inch groups at 200m. Yesterday I went out there with my wife and kids and I was using some American Eagle Federal 62gr .223 and I was only getting 2 and 3 inch groups at 100m and at 200m I was having some 2 and 3 shotgroups that were sub 1 inch and then it would throw a few 4, 5 or 6 inches off. What I am saying is that each and every rifle is different and will like its own ammo different than its brothers and sisters. You will just have to invest in several different types of ammo and the time to shoot them and see what yours prefers to be fed.