Hey y’all, I have a fairly new AR-10 308 with an ATN 5X20 4K PRO scope mounted on it with a Shepherds outdoors high mount. So after a few trips to the range I have finally decided on zeroing the scope at 200yds. I use the ABL1500 and ballistics calculator to shoot 300yds. At 200yds it seems to be dead on the money but at 300yds it is a good bit looser grouping. I was reading and watching YouTube videos about trueing the upper receiver to the barrel. Can anyone tell me if that is necessary or is this something PSA already does? Is it worth doing?
Ive never needed to do it. Today’s CNC machines are also much more accurate than how receivers were machined 20-30 years ago
1 Like
Three shots is not a statistically significant grouping. Do at least 5-10 groups on different days and a cold barrel. After 100 or so shots yo will have an idea of what your rifle, and your ability, is capable of.
3 Likes
Thanks for the replies y’all. Well with what y’all said it might not be the rifle, it might be the scope instead. The gun groups good at 200yds where I have it zeroed but the using the atn scope’s Ballistic calculator the group is way looser as you’ll note in the pictures.
I lap all my upper receiver faces, it is easy, and every one I have done, various manufacturers, have visibly shown high sides.
I agree with GuitarGuy’s comment about modern CNC machines being very accurate, but, I think the anodizing isn’t applied evenly.
Anyway I look at it, the lapping is always obvious where the high side is.
I have spoken to many people about this, and everyone has said that is very possible.
I don’t know… but again, it is easy enough to do. So, its why not, for me.
That said, I also make sure I have a snug fit between upper and lower, and Loctite my barrels in.
I might have really good luck, ( riiiight ) but it seems to work for me.
I also, feel, that shooting a LFAR accurately, takes more practice and trigger time than a AR15 or bolt gun.
I didn’t see, what ammo are you using ?
And as mentioned, I also suggest you fire 10rd groups, I know it isn’t cheap, but it will give you a better idea of what to expect from your ammo used.
Double check all mounting screws is an easy thing, and torque them appropriately.
And… fwiw, I shoot better groups off of a bag, rather then a bipod.
Here are some of my results from a PA65 upper…
https://www.ar15.com/forums/Industry/-ARCHIVED-THREAD-PSA-PA10-GenII-lower-w-PA-65-review-START-at-the-beginning-again-UPDATED-with-Tn-G-results-/301-285762/?page=1
What weight round are you using? 147s spread loose in my AR10, but 175s and 180(?) are TIGHT
1 Like
I have torqued my mount screws with a torque driver. I might have to consider trying to do that lapping. The ammo is Winchester Deer Season XP 150gr
Maybe I need to try 180gr instead. I have tried a few different rounds and so far they are all similar.
Oh and I’m shooting from a lead sled.
Also try zeroing using irons. It may be an issue with the scope not holding zero.
Thanks, i thought of that, but it’s holding zero perfectly. It’s when I use the ballistics calculator that i wonder if it’s just the bc on that scope
Hey guys, I went to the range today. The very first thing i did was make sure the ballistics calculator was turned off on my scope so it was like a normal scope with a 200yds zero. I shot 5 rounds at a huge silhouette target at 300yds a red Square sticker on it for a bullseye. I did this first so the barrel wouldn’t be hot causing me to think it could be the barrel temp. The farthest two shots in the group were about 7 inches apart. And this is shooting from a lead sled steady as a rock. I’m thinking about maybe going to Kershaw County tomorrow to paladin machine services and let them check out the head space, bore diameter, receiver face etc. I have no idea what else to do. I even tried my old Bushnell scope on it and it didn’t group very good.
1 Like
