Mounted my new BM 1/7 twist barrel today.  Went to the range to check zero on aimpoint.  Best the weapon would fire was 1"-1.5" groups at 25 yrds.  My other DPMS barrel with a 1/9 twist would actually shoot tighter groups than this.  I was shooting 55gr.  Q3131 both times.  Is this expected due to the twist rate of the 1/7.  I am going to try 62 gr SS109's.

Don't sound uncommon, perhaps your overlooking something......

Here's 20 rounds fired at rapid clip from a "benched" 50 yard position. Rifle is a 16" DPMS 1/7 twist chrome-lined M4 and ammunition was Q3131A:



NOTE: the 4 MOA red-dot of the Aimpoint ML2/M2 has one drawback, at 100 yards the dot covers 4" which means at 25 yards the dot covers 1" (possibly more if it's bright outside and ya got it turned up) and even if great care is taken with ones POA, the dot does not lend itself to real precision shooting.

The red-dot and the target above appear the same size at 50 yards and fwiw it's tough to be certain the dot is precisely centered each time, noted by the right/left pattern above....

For the true accuracy potential of your new barrel I recommend a good scope and 100 yard groups.

Mike

Quoted: Don't sound uncommon, perhaps your overlooking something...... Here's 20 rounds fired at rapid clip from a "benched" 50 yard position. Rifle is a 16" DPMS 1/7 twist chrome-lined M4 and ammunition was Q3131A: NOTE: the 4 MOA red-dot of the Aimpoint ML2/M2 has one drawback, at 100 yards the dot covers 4" which means at 25 yards the dot covers 1" (possibly more if it's bright outside and ya got it turned up) and even if great care is taken with ones POA, the dot does not lend itself to real precision shooting. The red-dot and the target above appear the same size at 50 yards and fwiw it's tough to be certain the dot is precisely centered each time, noted by the right/left pattern above.... For the true accuracy potential of your new barrel I recommend a good scope and 100 yard groups. Mike

I was going to try mounting a scope next.  I am not real concerned about it.  I just noted that the DPMS shot better that was all.  Gotta scrap the Y-comp though! (WOW)

Double check for proper mounting of the barrel. Check your torque and fit. It may have something to do with it.

I've got a BM 14.5" 1/7 barrel.  A couple of weekends ago, I shoot a 4 round group of 1" at 100 yards with Federal 55 gn American Eagles.

I am going to try an dig up an old scope and mount to see what it will do.  

Take a look at the brass (if you brought any home with you)...
This should give you a clue if the barrel is not mouted properly...

However, I'd guess that you were using a target that would not give you a good repeatable sight picture.  That is:

...your Aimpoint covered your target too much or not enough.
...the contrast from the red dot and your target background was throwin' you off.
...etc...

Try workin' with irons for a bit.

FWIW:  I just monted a BM 1/7 and it performed very well.

Hope this helps.