1/7 vs 1/9 accuracy at 50yds with 55gr.

[Reyn]

Would there normally be a difference in accuracy at 50yds for 55gr ammo between 1/7 and 1/9? Reason i ask is today i was shooting my Colt 6920 alongside a friends Olympic AR. They both have 16" barrels but his shot noticeably tighter groups. I was really dissapointed in the difference. The Colt was around the size of a can of dip while the Oly was almost half that with several groups the size of a quarter. This was with open sights and with both Wolf and PMC FMJs. I shot both guns back to back several times to compare. I want to compare some heavier ammo like 75gr. Im hoping the 75gr will shoot better than the 55gr in the 1/7 twist. So is this typical?

[UVvis]

There are so many variables involved here.

The differences in precision between these two guns are more related to the fact that these are two different guns over rifling twists. It simply sounds like his gun is a better shooter than yours for those loads, that is really all there is to it.

Different ammo, different bullet weights, even different outdoor temps may show a different result.

You could always have your crown inspect and headspace inspected and recut if needed.

[caporider]

At 50 yards the barrel twist rate should have no measurable effect on accuracy (unless you're shooting 75gr bullets out of a 1:12 twist barrel and your bullets are keyholing).

More likely is a difference in chambers. Your 6920 has a true 5.56 chamber, whereas the Oly probably has a tighter .223 chamber. Tighter chambers typically mean better accuracy, but at the expense of overpressure when shooting true 5.56 NATO rounds.

You might also check to see if the Oly barrel is chrome lined. Your barrel has a chrome lining, whereas the Oly barrel may not - chrome linings typically degrade accuracy a bit but offer superior wear and corrosion resistance. Chrome lined barrels also increase in accuracy over the first few hundred rounds, so if your 6920 is brand new you may not be seeing its full accuracy potential.

Finally, you may just have a 6920 that shoots at the outside of the acceptable accuracy range for rack-grade 4150 CrMo chrome lined barrels. It is not unheard of for these types of barrels to shoot 3-4 inch groups at 100 yards.

[Rifleman_04]

Olympic Arms use true 5.56 chambers and are not chrome lined. Olys are known for very accurate barrels. Maybe try comparing your groups to another brand and you may not be so discouraged. :p

[dubb-1]

Any chance he is a better shot?;)

[Reyn]

Any chance he is a better shot?;)

No sir ;) I shot them back to back and so did he. His groups with the Oly were no bigger than mine with the 6920. Thats why i shot both several times. I would shoot a 5-7rd group then pick the other up and do the same with the same ammo. We did have some light primer strikes with the Oly where the rd didnt go off. That and it has a spring vibrating sound when it goes off. That was annoying. It didnt have a collapsible stock like mine.

[dubb-1]

OK. No, it isn't typical. However, there are still a huge number of variables to consider. Age. Maintenance. Round count. Trigger. Not just accuracy issues, but "feel" issues that may affect the shooter. IMO at 50 yards, minute of dead is minute of dead.;)


New barrels are cheap. I even know someone that will sell you one if you really want to pursue it.:p

[rhino]

If the faster rifling twist is affecting anything at all (which I doubt), it is still the least of the factors as noted by the others.

[M4Warrior]

I wanted to know the answer to the same question recenlty (1/7 vs. 1/9 accuracy), so I shot my RRA Entry Tactical (1/9) and my LMT (1/7), which are both 16" and chrome lined. Both guns have an Aimpoint 2MOA and I used an Aimpoint 3x Mag.

Shot from a rest, there was no appeciable difference in accuracy with M855 green tip 62 grain, Hornady 75 grain TAP, or 55 grain American Eagle. YMMV...

[PalmerB]

For 55gr I prefer a 1/7 twist if it is an SBR, if not 1/9 works fine for me. May not be the same for everyone.

[Razorhunter]

Did the Olympic gun have a better trigger than the 6920???
I know a lot of the Olympic guns are set up for match grade, and the Colt just has a combat trigger.
Just a thought.

Also, I know for a fact that my 6920 shoots 75gr ammo MUCH tighter than that tiny lightweight 55gr crap...

[Reyn]

Well,i took it out again and stuck a cheap scope on this time. I bought some 75gr TAP,75gr BT from Hornady and some Sellier and Bellot (sp?) 55gr FMJ. I was shooting off a rest off the hood of my car and think i could have done better with a more solid rest and no coffee not counting i had been up for 24hrs. Anyway i mostly shot 5shot groups. At 100yds the largest was 2 1/4in. Most were between 1.5 and 1 7/8 outside to outside. I then shot a 10shot group with the 55gr that was around 1 7/8. I saved the targets and im trying to recall my measurements. Anyway none with the exception of that 1 group was over 2in. I was very happy with the 10shot group being under 2MOA.1 group with the 75gr 3of the 5 were 1 hole.I then went back to 50yds and open sights and shot a 5shot group where 4 of the 5 cut one hole. I dont mean 1 little hole. They were horizontal side by side close enough to cut the paper inbetween. The wind was also up a little and my campaign sign kept swaying a little moving my bullseye. Considering the circumstances i was shooting under im very satisfied. I was expecting 3-4inch groups at 100 before i started.

Paul,i dont know about the trigger on the Oly but i can say it didnt stand out over my trigger which i assume if it was a match i would have noticed a difference. It did have a heavy barrel but i just didnt think that would make that much of a difference at 50yds. The Oly did have several light primer strikes where the rd didnt go off.

[BigEd63]

It's been my experience that 1/7 or 1/9 in themselves will make zero difference.

As already mentioned there are too many other variables to contend with.

[M193 BALL]

At range yesterday

Shot at 50 yard range

LMT Defender 2000 M4 14.5 SOPMOD 1/7 twist ML2
&
Bushy lower/VLTOR + LMT M4 14.5 551


I tried several types of ammo

Win USA 45gr JHP + boy I had no IDEA just how accurate this ammo is out of my M4`s

I would buy more if I had a good deal!

Also had found a old box of ULTRMAX 40gr N BT had orange tip about 8 years old

I never buy this brand but it shot pretty tight also for a 40 gr bullet in a 1/7 twist

Wolf M193 by P.P. that stuff is great ! Very clean and very accurate
shoots better than my STASH of Q3131,Q3131A,XM193

Best groups were Black Hills 77 smk B.B. eats out the 10ring red dot on 50 yard small bore Target

The Defender 2000 also was makeing ragged hole with the Blue Box 75gr

My Bushy/LMT cant seem to do as good with the 75 ? But close

maybe because of trigger and 9mm buffer in the Defender 2000

the Bushy/LMT kicks alot or should I say jumps a bit off Target


LC M855 From Ammo Man NON PD Black marker came in CANS with Wire thingy!!

it shot okay but got alot of BIG FLYERS shooting 10rd groups

Like to get it Chrony Tested

ADCOM M855 1998 ammo Looks so good and is seald up

but I dont care for my groups at 50 yards over 2 inches

Maybe if I had a REST and SAND BAG !


Im going to get a Rest and a sand bag and get it right




A fellow AR15 shooter had a TACTICAL Carbine by Colt with aimpoint magnifier aimpoint x2 dont know the model
and also a GRIP POD I love it

I gave him 10 rounds of BH 75 he made a nice little groups at the 100Y line



But yes I think lite bullets can do well in 1/7 twist


and the GRIP POD really works well on a little carbine

[M193 BALL]

Would there normally be a difference in accuracy at 50yds for 55gr ammo between 1/7 and 1/9? Reason i ask is today i was shooting my Colt 6920 alongside a friends Olympic AR. They both have 16" barrels but his shot noticeably tighter groups. I was really dissapointed in the difference. The Colt was around the size of a can of dip while the Oly was almost half that with several groups the size of a quarter. This was with open sights and with both Wolf and PMC FMJs. I shot both guns back to back several times to compare. I want to compare some heavier ammo like 75gr. Im hoping the 75gr will shoot better than the 55gr in the 1/7 twist. So is this typical?



Id still would rather have your 6920 any day over oly

Could just be you had a bad day? it does happen !

I use LMT M4 14.5 wich is close to Colt Quality

and it shoots better than I can

did you use a rest! Standing up,Prone

I know that Black Hills 77 gr Blue box should give you a ragged hole at 50 yards

Good luck