Just curious Jaggy13 if you bedded your barrel extension into the upper receiver with blue Loctite or similar substance. I’m a firm believer in bedding the barrel extension and gas block on my AR-15’s. I figure you’ll see between 20 FPS and probably closer to 40 FPS change going from 20” to 18” 6.5 Grendel. The Hornady Black 123 grain ELD-M seems to be a little slower than the previous 123 grain Hornady A-Max factory I chronographed. I used a Magnettospeed and got 2500 FPS to 2510 FPS out of my 20” Shilen with Factory 123 grain A-Max and SST.
Some FNG and hopefully not so FNG questions.
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The reason I asked if you bedded the barrel extension is if there is a loose fit between the upper receiver and the barrel extension there is a greater chance you could see verticle stringing in the groups. There is no guarantee this will improve your groups but there have been several members who have experienced improvement after bedding. All my future build will have the front of the receiver lapped to ensure the receiver is square. I have used Permatex blue thread locker on two of my 6.5 Grendel builds and I have been pleased with my results.
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Originally posted by VASCAR2 View PostThe reason I asked if you bedded the barrel extension is if there is a loose fit between the upper receiver and the barrel extension there is a greater chance you could see verticle stringing in the groups. There is no guarantee this will improve your groups but there have been several members who have experienced improvement after bedding. All my future build will have the front of the receiver lapped to ensure the receiver is square. I have used Permatex blue thread locker on two of my 6.5 Grendel builds and I have been pleased with my results.
Also I do have significant vertical stringing.
My OCD doesn't allow me to make both changes at once. I need to be able to document the change so that I can apply to other scenarios.
I am looking forward to trying this out!
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20" barrel was 2450 FPS
18" barrel is 2400 FPS
Used the blue locktite "extension bedding" technique.
shooting just over 1/2" now at 100 yards (5 shots groups)
but there appears to be some parallax in the group so I'm going to throw on another optic for my next range trip to see what the rifle can do.
Same factory Hornady black ammo,
.255 seems to still be accurate for the BC, 4.5 mils was my correction at 550 yards.
And it looks like I was able to eliminate the vertical stringing as well as the mystery .5 mil change in elevation after several rounds fired.
I'm feeling much better now. I'll take .55 MOA with factory ammo any day of the week!
Thanks for all the imput! This build came together very well based on your help.
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I was able to throw down a couple of decent groups today.
I had to muscle the gun a bit to keep the groups tight.
If I used too loose of a grip I would get a flier in every group.
sorry for a 3 round group, it was the end of the box of ammo.
I had some american eagle 120grn that goes about 2500 fps
and the hornady black that was right at 2400 fps.
both grouped about the same.
I think the rifle is capable of a little tighter than I shot today based on how hard I had to drive it to keep it tight.
But I'll take .44 moa all day long!
here are some pics.
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