Mossberg 100ATR .308 Accuracy


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reklessEngi
February 28, 2011, 10:14 PM
I'm having a heck of a time trying to get tight groups out of my Mossy. I know it's a cheap rifle, but I have a cheap 223 that will print pretty cloverleafs at 100 yards with handloads, so I expected similar results from my 308.

I was getting 2" groups with my first box of factory Federal Power-Shok 150gr soft points, but the rear scope rail came loose and the scope started wandering before I knew what happened. I've since reinstalled the scope and mounts using thread locker.

I reloaded the brass several times using a collet die, and I've tried 150gr and 180gr bullets, first with IMR3031, second with Varget. I'm using CCI #200 primers. I also played around with the bullet seating depth, even seating the bullets just off the rifling. 3" groups seem to be the norm, regardless of what I try.

I would expect worse groups if the scope were busted, but I'm certainly not ruling that out.

Where do I go from here?

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guzzi
February 28, 2011, 10:55 PM
Although not the same rifle, my wife has a DPMS LR308 with a 1 in 10 barrel. And it is very accurate with 110 gr. Hornady V-Max, with 46gr. of Hodgdon H335, and a CCI200 primer.

She worked this load up just for water bottles and hedge apples.... women!

As for the ATR, I have that in 30-06 and it's right on with a 170 grain bullet.

jpwilly
February 28, 2011, 11:34 PM
Hate to say it but sounds like you may have gotten one that isn't right. Most reports from Mossy ATR owners say they are able to shoot 1.5" or better with hunting ammo. My 30-06 ATR will shoot 3/4" 3 shot groups with Fed 150gr Power Shok (the cheap blue box Soft Point sold at Wally World for $13.97) off a bench rest of course.

Skyshot
March 1, 2011, 10:06 AM
You may have a bedding problem, is the barrel free floated? Also don't rule out the scope problem also, I would try a differnt scope to rule that out as a problem. and then check for pressure points on the stock. you can cut some old credit card strips and put them between the action and stockbed and remount the barrel and test fire a group and this is a good way to check for bedding issues. Some bolt guns need a pressure point in the fore end of the stock. It's possible to have a bad barrel but I would check on how its put together first.

reklessEngi
March 1, 2011, 01:14 PM
Although not the same rifle, my wife has a DPMS LR308 with a 1 in 10 barrel. And it is very accurate with 110 gr. Hornady V-Max, with 46gr. of Hodgdon H335, and a CCI200 primer.
The twist rate is shown as 1 in 10 on the Mossberg website, and although my rifle has the older non-fluted barrel, the twist rate probably hasn't changed. I hadn't thought about trying lighter bullets...I bought the rifle in hopes of having a 600 yard coyote gun, but if light bullets are what it likes then that's what I'll just have to use.


Hate to say it but sounds like you may have gotten one that isn't right. Most reports from Mossy ATR owners say they are able to shoot 1.5" or better with hunting ammo. My 30-06 ATR will shoot 3/4" 3 shot groups with Fed 150gr Power Shok (the cheap blue box Soft Point sold at Wally World for $13.97) off a bench rest of course.
Thanks for the honesty, and for your personal range results. That is the same Federal ammo that I initially used. If my scope isn't broken, then this is by far the most temperamental rifle I have ever owned.


You may have a bedding problem, is the barrel free floated? Also don't rule out the scope problem also, I would try a differnt scope to rule that out as a problem.
The factory stock is the inexpensive injected molded type, and it seems to free float from the action forward. There is a large cavity between the barrel and stock if I remember correctly, but I may give the pressure point a try. Also, I'll be taking a red-dot off another of my rifles to test on this one at the next range session. I figure I'll just bring the target in to 50 yards and fire a group with the scope as-is, then follow up with a group using the red-dot.

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