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Discussion Starter · #1 · (Edited)
I decided that it was time to benchrest the ACR and try some heavier bullets. I took the ACR out to the high-power range along with some 77gr loads that shot 1 to 1 1/8" groups from my free-floated LMT M4 (1:7" twist barrel). Well, the 77gr. Nosler bullets will not group from this ACR. I couldn't keep them on a 8.5x11 target. I swapped to larger 14x14" targets to try and find some pattern, and I still had one round entirely miss the target I was shooting at, and hit the one I taped up next to it.

I started checking the barrel nut, and the scope mount nuts. I checked and double-checked to make sure the rifle rest wasn't wobbly. Everything was tight. Nothing seemed out of order, or unusual.

I fired 10 rounds of my sub-MOA 55 grain load. Although they strung out vertically, probably from shifting headwind to tailwind; horizontally, the group was probably less than an inch across. I tried some TULA 55gr. ammo that I had in the range bag, and got about a 4 to 5" group, which was about what I had expected.

I didn't get a chance to try any 69gr. MatchKing loads, or Hornady 75gr. Match loads yet. I have some Sierra MatchKing 77gr. bullets, but I haven't actually loaded any of them yet.
 

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I think you at the edge with 77 grn pills in a 1/9 bbl. (those are long rascals) The highest I have tried was 69grn match kings and they grouped better then I could do. Some folks have reported decent results with 75's, you are the 1st that has reported shooting with 77's and the results don't sound good.
 

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Discussion Starter · #4 ·
I'm pretty sure that I read about someone trying 77gr. Wolf Gold or PPU ammo, and getting adequate if not stellar accuracy. I've had several people tell me that the "common knowledge" of twist rates is often wrong. Well, I guess in this case, with these bullets, it's not wrong.
 

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I ran a very similar test on my ACR. The 75gr Hornady match bullets were the best grouping, along with the 55gr FMJ (inside 100yd). I then re-ran the test for hand loading, varring the amount of powder in each. Oddly ever single round grouped the best at the same powder load, with the 75gr Hornady matches coming out on top by far. That load is what I use for the long stages at my 3 gun matches. I can consistantly engage and hit 440+yd with it, using only my EoTech. Barrel is a 16" 1/9 twist that came with it. I did replace the A2 Flash hider with a Battle Comp 2.0
 

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From what I understand the Acr has a 1/8 twist, it's just labeled 1/9, I can't verify this myself but it has popped up on the forum a couple of times
 

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Yeah we had a couple of members measure the twist rate and they all said it was 1/8. Not sure how its measured though

Sent from my Droid RAZR MAXX
 

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Hornady uses their secant ogive on most of their slugs so the narrower profile puts more junk in the trunk, so to speak, compared to others. The Wolf 75gr pills use a more traditional ogive shape so they are squatter bullets comparatively. If you want to shoot the heavier tips I'd give them a try. I've had very good results with the Wolf Gold 75gr ammo, albeit through a 1:7 but that tells me the potential is there.

You could make I call a "light Mk262" with the 68gr or 69gr pills and these will shoot great in the ACR.
 

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I think to measure it you can use a cleaning rod and a tight fitting patch and mark the top pull it till you see one revolution. If its 8" or 9" im not positive how accurate it is. Could even be in between but I've seen it mentioned before. Marker or masking tape may work. Im curious now. I think I remember a 1/8-1/8.5ish twist mentioned in the past as well.
 

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Hornady uses their secant ogive on most of their slugs so the narrower profile puts more junk in the trunk, so to speak, compared to others. The Wolf 75gr pills use a more traditional ogive shape so they are squatter bullets comparatively. If you want to shoot the heavier tips I'd give them a try. I've had very good results with the Wolf Gold 75gr ammo, albeit through a 1:7 but that tells me the potential is there.

You could make I call a "light Mk262" with the 68gr or 69gr pills and these will shoot great in the ACR.
Do you know anyone that makes a 62gr +/- without the steel penetrator?
 

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Do you know anyone that makes a 62gr +/- without the steel penetrator?
Prvi does. You can sometimes find it loaded at Aim Surplus or Wideners, depending on availability of course. Does your range not let you use the steel core?

Also, Armscorp has in the past but it's easier to get hold of those bullets as components to load your own. I used to shoot armscorp 55gr all the time about 10 years ago and it was fine but I've heard mixed reports lately with their stuff. I suppose it'll shoot just fine.

Speer has a 62gr ball round for loading too.
 

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Well, I figure 62gr is a good mix of accuracy and range and knock down. M855 isn't that accurate because of the penetrator throwing it off. And I don't shoot at a range. Maybe you missed that thread, but my family has a lot of land. One farm that's 125-150 acres and another that's about 300 acres.
 

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Ah, I guess I did miss that. I miss being able to shoot off my back porch, it made things so much easier.
 

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Discussion Starter · #16 ·
All at 100 yards, Millet DMS-1 scope on 4X, ACR Basic w/1 in 9" twist barrel 20" long. Caldwell The Rock rest with Protektor nylon rear bag. I did not adjust the scope at all, it was sighted in with the 55gr. bullets from a previous range trip.

75gr. Hornady Match BTHP, 23.2gr Varget - 3.546" c.t.c. for 10 shots. I'm not sure why that one shot dropped so low and to the right. Best 9 shots into 1.735".
75gr. Hornady Match BTHP, 23.8gr Varget - 2.425" c.t.c. for 10 shots.
69gr. Sierra MatchKing - 2.090" c.t.c. for 10 shots.
55gr. Midway Dogtown Spitzer - 3.75" c.t.c. for 10 shots.

All these bullets do about 1.125" from my free-floated M4 upper, and have done with exact same scope and mount, 10 round groups. The Dogtown bullets are actually pretty cheap, and will do 1 M.O.A. Results from the ACR still a little disappointing. At least I didn't need a freakin' yardstick to measure the groups, like with the 77gr. Nosler bullets.

If I play with the loads some, maybe try loading shorter, the groups might improve some, but I'd still be starting behind where I started with the M4 upper. A better trigger probably would have helped some.
 

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my acr's love the handloaded 75gr rounds, my loads are about 23gr of re-15 and i was getting moa groups or under, hell my 20 shot group was about 2 inches and i was firing very quickly at 100 meters (1 shot per 1 second average)

the stock acr trigger is pretty heavy, a geissele or equivalent will shave some serious size off of your group quickly. mine dropped about half a moa when i swapped
 

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That twist rate simply isn't fast enough to stabilize much over 69gr. I would stick with 60gr or less for match bullets personally.
 

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That twist rate simply isn't fast enough to stabilize much over 69gr. I would stick with 60gr or less for match bullets personally.
In my ACR and other members copies, 69grn pills stabilize just fine. In fact I have had my best groups with 69grn federal match ammo. It's more length of the pill then weight.

Just as a side note, even barrels from the same makers will act differently with different ammo. Just variations in the barrel making process.

YMMV :)
 
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