Sight in problems.

[bjones870]

I'm considering buying a bolt action .308, and have a question. If I were to buy a 18-22" barrel rifle, would I have a problem keep the rifle sighted in? What helps a rifle hold it's sight? In other words, how would I make SURE that my rifle won't lose sight in. Thanks!

[mc223]

how would I make SURE that my rifle won't lose sight in

Once you have it sighted just the way you want it. Don't touch it! Don't move it! Don't let anyone else touch or move it!

Or Don't fret over it too much. If you did your part and the mounts and rings are properly mounted and the screws are torqued properly it shouldn't change.
Accidents happen so after transporting the rifle it is good practice to check zero when you get to the hunt sight if possible.
It is also good practice to set a target to be kept separate from others for the first cold shot at each trip to the range. This will give you the info on scope change vs where the barrel will shoot when cold or clean.

[the rifleer]

The barrel doesn't have much to do with it. If you put decent glass on it and get it sighted and then shoot it at a known distance when you sight it, it should hold its zero as long as you use the same ammo and keep it in a good case when you transport it.

If you shoot your rifle under the exact same conditions and circumstances every time, the rifle will always shoot the same. If you change anything at all, it will shoot differently.

Guns do not shoot in strait lines. They also shoot differently with different ammo. At long distance, humitity, air pressure, elevation, distance, rate of twist, muzzle velocity and other things all play a factor in where the gun shoots. if you change anything at all, you will change how the gun shoots; however, at shorter ranges (pretty much anything under 300 yards or so) this stuff isn't a huge factor. If you sight your rifle in at 100 yards, then don't change anything and always use the same ammo and transport it in a good case, it should hold its zero.

[JSJ127]

A good quality scope mounted properly in good rings and bases is the answer. There are other variables such as ammo the rifle likes, keeping it clean, bedding, etc. The biggest variable is the guy behind the trigger.

[geetarman]

There some things to consider that CAN change your sight in.

A poorly fitted stock/bedding can almost guarantee a problem.

Junky mounts and a junky scope are sure fire ways to keep you on the move tracking a phantom zero.

Poor trigger/breath control will contribute.

For the most part, not ALWAYS, but mostly, if you have a quality rifle, decent glass and good mounts, you should be able to get and achieve a good zero.

If you reload, then you have taken a big step in controlling one of the variables that contribute to poor performance.

For a given weight bullet and a particular load, once the rifle is zeroed in, it will pretty much stay there. If you drop the rifle or clunk the scope, it is time for a trip to the range to check your zero. It may not have changed but you will not know for sure. If you don't know, check and find out.

If you change the load for a particular weight bullet, you are apt to get a vertical change in POI barring the effects of wind or other anomaly.

If you change the weight of the bullet you may see a horizontal change as well as vertical change in POI.

I see that in my bolt .308 when I move from 168 to 175 gr. bullets.

Your experience may differ. When I change bullet weights, I am usually shooting groups and I don't shoot for the bulls eye per se. I shoot for the same point of aim. The difference in bullet impact is a combination of the bullet, the powder, the charge weight, the primer and me.

Sometimes the process is in control and sometimes on the verge of chaos.

The fun is finding the sweet spot for your rifle and trying to sweeten it up.

Screws get loose and things shoot loose. Usually when that happens, there is a MAJOR shift in impact.

If you KNOW nothing/or no one has monkeyed with your rifle, then look for something loose.

Don't over engineer the solution. It is usually something simple.

Take a log book. Log the data. Log the brass, the bullets, seating depth. powder type and charge weight. Log the ambient conditions and write down how the load performed for you.

Keep the log book and refer to your notes when working up a load.

You can NEVER know too much about shooting or your rifle.

If you experience difficulty at the range, ask one of the older guys who have been shooting since flintlocks were the latest and greatest.

They are a wealth of information and it is all available for just asking politely.

I hope you have an absolute ball working with your rifle. If you have a question, post it and someone will get back with you.

There are some people on this forum that have forgotten more than I will ever know about rifles and shooting. I troll this forum everyday to see what little nugget I can find and how I can use it to become a better shot.

You can do the same.

Geetarman:D

[mrgoodwrench76]

Not to highjack the post but could you explain why this is?


If you change the weight of the bullet you may see a horizontal change as well as vertical change in POI.

I see that in my bolt .308 when I move from 168 to 175 gr. bullets.


I see the same in my bolt .308. I 'think' (dangerous, I know) that I see a small amount of this when going from 17 - 20 grains in the 17HMR. Just lookin for a 'nugget' myself.

[the rifleer]

The weight of the projectile effects the muzzle velocity. If it has a lower velocity, it will take longer to reacher the target, thus it drops more.

All objects fall at the same rate (9.81 meters per second squared, not considering air resistance), regardless of weight. If it takes bullet number one longer to reacher the target than bullet number two, bullet number one will drop more.

[mrgoodwrench76]

Maybe I should have been more clear. I was reffering to the horizontal change.

[the rifleer]

That would have to do with the rifle twist I believe. All rifle twist rates have an "ideal" bullet coefficient/weight. There is a formula to calculate it it, but I don't know what it is. if you change the bullet weight considerably, you will see a noticeable change in accuracy.

It may also have to do with the cartridge tolerances. Not all ammo is equal. Some is better than others. Some cartridges are longer than others and burn different powders... there is dozens, if not, hundreds of factors that effect how a gun shoots.

[mrgoodwrench76]

I had assumed that the twist rate was the cause but was shocked at just how much deviation it caused.

Before advancing beyond a .22 as a child, I assumed weight only changed the vertical POI. :D Live and learn.

[geetarman]

I am not sure why the change horizontally except that my hold might be different for a heavier bullet and the bullet spends a little more time in the barrel.

If I had a mechanical rest, I might be able to prove or disprove the reason I see what I see.

I do not notice it so much with my 25.06 going from say 100 gr. to 120 gr. bullets. But I certainly see it in the .308.

Anyone else have any ideas why this happens?

Geetarman:confused:

[mc223]

Time in barrel. Position of barrel when bullet exits. Barrel contour and twist rate. Usually more noticeable when going from heavier bullet to lighter.

See this: http://www.varmintal.com/amode.htm

[mrgoodwrench76]

I read all the information on that link.............and now Im more confused. :confused:

[Picher]

I'm considering buying a bolt action .308, and have a question. If I were to buy a 18-22" barrel rifle, would I have a problem keep the rifle sighted in? What helps a rifle hold it's sight? In other words, how would I make SURE that my rifle won't lose sight in. Thanks!

There are a few things that will assure keeping a rifle zeroed. First, a free-floated barrel will minimize wandering zero, especially in wood stocks. Pillar bedding will also help, regardless of the stock material.

Shoot the same ammo, or ammo types that shoot to nearly the same point of impact.

Use a mounting system that is very stable. I like Weaver Detachable Top Mounts, but the ones that have four screws per (solid) ring. (The two-band rings are junk). That system allows removal of the scope and accurate replacement without re-sighting. Stay away from see-thru mounts and cheap one-piece mounts those that only have screws at the top of the rings and at the base (people will probably have negative comments about this statement, but I'm sticking to it).

A good scope will hold it's zero almost forever. Leupold MKII, Bushnell 3200, 6400, Burris, and Weavers Accu-Trac and other medium priced scopes made in Japan tend to work well. Less-expensive, Chinese-made scopes are suspect, though I like my new Mueller for my varmint/range rifle. There are few people who complain about their MKII and MKIII Leupolds.

[rickyrick]

If you have zero'ed your rifle .... and ... at some point In the future if you notice a change ... don't go cranking on the adjustment until you check that the mount hadn't come loose.

I figured that out too late


:o

[mapsjanhere]

My recipe for solid mounting is simple: Warne bases and rings, a drop of loctite red into the mount screws, tightened with a torque screw driver. Put a Leupold VX-II or better scope on it, and you'll set for life.
Now, some people will argue that that's a $500 package, more expensive than their rifle. But, at least to me, it's easier to find a well shooting cheap rifle than to find a trustworthy cheap scope and base combo.

[Doyle]

Not to highjack the post but could you explain why this is?


If you change the weight of the bullet you may see a horizontal change as well as vertical change in POI.

I see that in my bolt .308 when I move from 168 to 175 gr. bullets.



It has to do with barrel harmonics. The barrel is actually vibrating as the bullet travels down it. Going to a different weight, shape, brand, etc. of bullet changes the harmonics which can affect side-to-side travel as well as vertical travel.

Bottom line, ALWAYS sight in with what you intend to use and don't change ammo types without re-signing in.

[Picher]

There is no such thing as a scope that will never fail or will never change it's zero, no matter how much is spent for it. All scope mechanical and optical units fail at sooner or later; hopefully not for many years, but they can go bad from recoil, from poor assembly, or from poor design.

I recently mothballed a Baush and Lomb Balvar 8B whose eyepiece lens couplet was coming apart from age of the glue that held it together. Another like it was getting very dim. Those scopes had never lost zero (to my knowledge) in nearly 60 years of use, but they finally are not worth using. May they rest in peace.