I am hoping that someone on this forum can offer some knowledge that might help me out. I recently put together a long range bolt rifle which includes the following: remington 700 milspec 5r gen 2 in .308 win, seekins 20 moa base, seekins 30mm low rings, and a sightron sIII 6-24x50mm ffp. I boresighted the rifle and began barrel break in, shooting at 100 yards. During boresight, I only had to turn the elevation down 10 moa and then when I moved out to 100 yards I was hitting 5" low. By my calculations, I'd have to move back up 5 moa to get a 100 yard zero and I would only have 5 additional moa from my original mechanical zero instead of the 20 moa that the base should help me to achieve. Am I missing something here? I counted my internal elevation/windage capacity and zeroed the scope mechanically prior to mounting the scope. I torqued everything to spec properly too, so what is going on here?
20 moa base problems
- Thread starter Bryan Couch
- Start date
I had an issue like that on my .308 I put a 20 moa base on it and I got like 86 moa of total elevation. I know that just bc you put a 20 or 40 moa base it does NOT mean you will get that number. My Steyr has an NXS on it with a 100 moa total elevation in the scope and a 20 moa rail but I only have 64 moa elevation with a 100 yd. zero. I believe it has to do with the same of your action. What else can it be???
Good luck
Good luck
The sightron sIII 6-24x50mm ffp is rated at 80 moa, however when I counted the clicks and zeroed the windage and elevation to their respective mechanical zero points I found the following: elevation was 390 clicks or 97.5", windage was 396 clicks or 99". This of course gives me 48.75" or 195 clicks of upward elevation adjustment range and my goal in using the 20 moa base was to raise that to at least 68.75". The way I've got this figured I'm likely to only end up with 53-56" of upward elevation adjustment by the time I dial in a true 100 yard zero. I appreciate the suggestions so far, I was wondering if a call to seekins might help me to clarify what's going on here but if you guys don't think it'd be worth my time then any other suggestions you might have would certainly be of value to me.
Dusty Stevens
Shiner
A 20moa base is gonna make you be off an additional 20" at 100yds if all else is centered and perfect. It doesnt add to your scopes travel. If all youre doing is shooting at 100yd you need to go zero moa base. Youre starting out 20moa off. The 20moa is meant for you to back way up to center it up. Could be 1000yd depending on your ctg. The whole intent was to make your scope closer to optical center for long distances not 100yd
Yes sir I am aware of what the 20 moa is supposed to do but my problem is that it doesn't seem to be doing what it's supposed to. I'm shooting at 100 yards to start with for barrel break in and handload development, once I've come up with a suitable load then I'll be shooting at 1000 yards and beyond, that's exactly why I went with a 20 moa base in the first place. I expected the 20 moa base to cause me to have to dial the elevation in my scope down at least 20" in order to get a 100 yard zero. I dialed it down 10" when I boresighted it with a quality lazer device and I am 5" low at 100 yards. Coming back up 5" in elevation to get a 100 yard zero would mean that I am only getting 5 additional inches of elevation instead of the 20 moa that I expected to see. Am I wrong to expect this? Am I not completely understanding what a 20 moa base does?
Dusty Stevens
Shiner
I see. I misunderstood. Thought you were wondering why you were off at 100- sorry about that
No harm done sir, misunderstandings are very easy to come by.
Ok, I went out shooting the rifle again today and completed the barrel break in process, I started on it yesterday but I had to cut it short and finish it up today due to family obligations. After break in was complete, I gave the rifle a good cleaning and fired my first 3 batches of test loads. The rifle was already showing great accuracy potential during break in, I was able to produce 4 groups between .800-1.00" with a mixed variety of factory ammunition. My test loads were developed with lapua brass, cci br2 primers, varget powder, and 155 grain lapua scenars. The best load so far has produced a .752" 100 yard group with a lot of room for tuning. Also, I never changed a thing in regards to scope adjustment, every other load was shooting between 3-5" low at 100 yards and my scope was set at 10 moa below mechanical zero, like I previously stated. The lapua scenar loads were shooting either dead on or just a touch high at 100 yards, so the higher velocity and higher ballistic coefficient of these loads is definitely helping in the pursuit of gaining more upward internal elevation. Now at very least I'm looking at a 10 moa gain with the 20 moa base, it's not the 20 I'd hoped for but it's very near the results ETERNAL STUDENT said he got from a 20 moa base with his nightforce nxs. This would now give me a total of at least 58.75 moa. I expect I'll find the load I want in the 2900 plus fps area, so by running all the data together through my ballistic calculator I have found that this bullet should require about 55 moa from a 100 yard zero to make hits at 1400 yards (the point at which it will almost go subsonic too). So I guess I'm not overly disappointed after all, the 20 moa base has certainly helped me gain elevation adjustment range, the issue i'm seeing looks to be fairly common, and I'll be able to shoot this thing as far as someone could feasibly expect to shoot a .308 as well.
I think I may have this problem worked out now and thanks for the advice. To answer your question, yes sir I definitely intend to shoot this rifle at 1000 yards and beyond regularly enough to justify the 20 moa base. One of the reasons I bought the sightron was for its internal elevation range but I went with the 20 moa base to add to that. I fully intend to stretch this thing to the very limits of the .308 ' s capability
I'm glad it's going to work for you. That said, let me try to explain what you're seeing and why it's not what you expected. You are starting with the assumption that your scope at its mechanical center is going to aim at your rifle's point of impact at 100 yards. While in an ideal world we would like this to be true, most of the time it isn't. With the 20moa base you now have 59moa up adjustment left. With a flat base you would have only had 39.
When you are shooting long range and you're at the edge of your scopes elevation adjustment a lot of times that limits the amount of windage adjustment available. If it were my gun I would consider a 30 or even a 40 moa base on this particular gun. The Burris rings would work also and enable you to chance easier if your next barrel shoots at a much different elevation.
When you are shooting long range and you're at the edge of your scopes elevation adjustment a lot of times that limits the amount of windage adjustment available. If it were my gun I would consider a 30 or even a 40 moa base on this particular gun. The Burris rings would work also and enable you to chance easier if your next barrel shoots at a much different elevation.
??? The angle stays the same no matter where the rings are. Unless you're talking about the Burris rings.
Put up a 36'' target at 100 yard
Using the hundred yard Zero at the top of of the target.You should be able to move the cross hairs 35'' down the target . Without moving the gun
That should give you enough up in the scope to shoot 1000 And 100.
Depending on the ring higth and the moa in the scope it could move more.
My dasher I need only 26 1/4'' from 100 to 1000 . Larry
Sorry...you are correct...was thinking of Burris signature rings
Thanks alot, I really appreciate the feedback. I have done a little research on the side and I definitely agree with you as to why I'm not seeing what I expected to see at first. As for the base, I have decided that I'm going to run it just like it is because I only plan to shoot this rifle beyond 1200 yards occasionally. With the figures I've come up with I'll be able to shoot 1000-1200 regularly and have plenty of elevation left in the scope to remain consistent and it doesn't appear that it will effect my windage turrets at those settings either. I think I'll be ok just shooting 1400 once in a while, mainly just to say I hit that far out with a .308 lol. I'm getting back into long range shooting and this rifle is my ticket back into the game. I used to shoot 800-1000 yards regularly with a model 700p tws that I no longer have due to a divorce a few years ago. Now that I'm back on my feet and better than ever it's time to get back to doing something I love. I plan to set up a 300 win mag next for work beyond the capability of the .308 but I've got to get my sea legs back first. Thanks again and the best of luck to you sir
alf
Silver $$ Contributor
Geno nailed it. Most guys make the mistake of assuming their scope will mount up in the center of the adjustment range. I find it tends to favor the wrong side of center.
Also, comparing your scope to a clock face, the more windage you dial in to zero, the less "up" that's available for LR.
Also, comparing your scope to a clock face, the more windage you dial in to zero, the less "up" that's available for LR.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.