AXMC sighting in advice / Ballistics help

[Viper1973]

Just received my AXMC and am in the process of getting everything setup. After getting my scope mounted it dawned on me that zeroing is going to be more complicated than I thought. Therefore I figured I better ask first rather than wasting a ton of ammo since many of you guys swap calibers/barrels frequently.

Since my AXMC is truly multi-caliber with a single scope I’m trying to decide WHICH caliber I should use for sighting in at 100yrds so that all of my other calibers will just be a positive elevation change regardless of range. (Since my Nightforce scope has a zero stop, I don’t want to have to constantly be changing it. And there’s no way to dial below it once set)

The barrels / ammo I have available to shoot are:

.300 Win Mag 26” — Federal Gold Medal Match 190g SMK
.308 Win 24” — Federal Gold Medal Match 175g SMK
.338 Lapua Mag 27” — Federal Gold Medal Match 250g SMK
6.5 CM 24” — Hornady Match 147g ELD

What is going to be my best choice here to minimize scope monkeying and simplify caliber changes?

Also, on an unrelated note....

I noticed in the AI manual they actually recommend WD40 to lubricate and maintain the trigger mechanism... WTF??? I was always told never to let that stuff anywhere near a gun because it makes a gummy nasty mess. What does everyone else use for this?

 

[redneckbmxer24]

It's not quite as simple as an elevation change. No barrel is perfectly straight and the curve can be to any direction.

Pick the barrel you will be shooting the most and zero it as your baseline zero. Make a logbook to zero the POI shift for all of the other barrels from that zero. It will be simple to track and just turn/reset the knobs each time. If you set your zero stop 1mil below zero you should have plenty of travel for any of the barrels without having to mess with it each time.

For repeatable POI between barrel changes, consistency in changing the barrel is critical. Any debris between the barrel shoulder and action can throw it off. Remove the hand guard when installing a new barrel so that no debris from the hand guard and get pushed down with the new barrel. Make sure you wipe down the barrel shoulder and action face very well. Seat the barrel with the muzzle straight up, I also recommend snugging it ever so slightly with a wrench on the flats just to get a nice hard seat.

If everything is consistent, your shift will be consistent.

WD40 is made from fish oil and is actually a great lubricant for some applications, but I don't use it on triggers. I douche mine out with zippo lighter fluid and lightly hit it with air to dry it out. I use zippo fluid for all of my bolt gun triggers, it flushes the crap out and leaves a nice dry film of lubricant.

 

[Night Assassin]

Redneck explained the process perfectly !

 

[Viper1973]

Compiling a lot of the changes barrel to barrel was what I was thinking. I realize that windage would potentially change. My concern was mainly with the zero stop interfering with the process.

So it doesn’t matter which caliber I do the initial zero with? I guess I figured one would potentially be better than the others.

 

[redneckbmxer24]

The zero stop can if you set it right at zero, but most people (even if they don't run a switch barrel) set the stop 1mil low or so just to have some wiggle room below zero. This can be to account for using a different load that may impact higher, suppressor on/off causing a higher impact, or a Magnetospeed chrono if it causes an upward shift. You absolutely should not see more than a mil. This is one of the reasons that I like scopes with turrets with hard stops built in and not ZS clutch like S&B. There's no ZS to fool with.

It honestly doesn't matter one bit which barrel you use for the base line so long as everything is recorded and when changing barrel to barrel it's all accounted for even if not going back to the POA settings for the baseline barrel. It's just logical to be to use your go to barrel that you will shoot the most as the baseline, or perhaps whichever barrel is the original barrel/caliber your rifle was configured in.

 

[GIXXER2000]

I have the PSR version of the AXMC. I was lucky as all 3 barrels that came with the kit had the same windage hold. I zero using the 300wm as the 338lm is .2 mil less and the 308 was .3 more so when I used my FFS software I just add or subtract the difference.
I did add a 6.5 cm and it was off on both elevation and windage. I have since added a AI-AT for short action stuff and now only shoot the 300 and 338 out of the PSR.

 

[Covertnoob5]

Because you have a NF you have the luxury of setting the zero stop where ever you like. I also have an axmc. I have my zero stop at 1 mil below zero so my 6.5 is my main 0 then I record the offset in my ballistics app. Very easy this way.

 

[texag0842]

I did mine like Gixxer

AT for the 6.5CM for PRS
AXMC set-up for .308, .300, .338

 

[Bradu]

As mentioned, I set my zero stop about 5 moa low so I don't have to worry about changing it when switching barrels.

 

[Long Range 338]

I read somewhere here that ideally you would zero for the 338LM as the other cartridges should all be "ups" from the 338 zero. However you would have to verify this with all of the barrels to make sure - it is the case with my AXMC.

 

[Covertnoob5]

I read somewhere here that ideally you would zero for the 338LM as the other cartridges should all be "ups" from the 338 zero. However you would have to verify this with all of the barrels to make sure - it is the case with my AXMC.

Yes that is typically the case and if you don’t care about which barrel is your home barrel then zero your 338 first. But for people like me, I hardly shoot my 300wm and spend 90% of the time at 6.5 and 308 so I rather zero the 6.5 because I don’t want to mess with offsets for comps.