6mm question

[sbhooper]

I have a Remington 6mm that I have been shooting for many years. I have gotten into doing a bit more target practicing with it out at 300 yards. I sight the rifle in at 200 yards. I shot a group yesterday at 300 yards that measured 2.25 inches, which is very acceptable for what the rifle is used for-deer culling. The bullet used is the Hornady, 100-grain Interlock.

The 300-yard group measured three inches below the center of the bull. This is real good except that the load chronos at 3070 fps and all ballistic programs show that it should drop 6.5 inches. Is it the barrel lift that makes the difference, whereas the programs are figuring for straight flight with no barrel jump?

I have seen this with my 7 mags, too, and figured this was the only explanation. Am I wrong?

 

[Ledd Slinger]

Where it 'actually' hits, is where it hits and that's all that really matters. Can't always trust ballistics calculators. They are just a tool to get you close on paper where you can fine tune from there.

I find that if you leave all the atmospheric conditions in a calculator at the default settings and elevation at 0 ft for any area, they will give you much closer data. Also measuring the center of your scope to the center of your bore to get the proper scope height is very important for the accuracy of a calculator. That is one piece of information for the calculator you do not want to guess on.

 

[sbhooper]

I ran the numbers again using 2 inches of scope height instead of the 1.5 inches that I was using and it only changed the impact point about .5 inches. Not significant.

This is not real critical, as it is still well within acceptable parameters, but it seems a bit odd to me.

 

[LHSmith]

It's not a great idea to draw conclusions from one group in one outing. It could be many things that caused it including mirage, barrel induced( you are not specific on how many total shots were fired before getting the group mentioned) or field mirage.
Not sure what you mean by barrel jump. One method of guaranteeing high shots is resting the barrel on the rest.

 

[sbhooper]

This has happened for a long time. I didn't start shooting yesterday. I just started taking an interest in why this is what it is. I know better than to rest the barrel on anything. I am referring to just what I said, the barrel jump when the rifle recoils.

I have killed over 100 deer with this rifle out to 400 yards. This phenomenon is not going to change anything. I just found it interesting that there was that much difference. I was using the G-7 Ballistic Program.

 

[Ledd Slinger]

This has happened for a long time. I didn't start shooting yesterday. I just started taking an interest in why this is what it is. I know better than to rest the barrel on anything. I am referring to just what I said, the barrel jump when the rifle recoils.

I have killed over 100 deer with this rifle out to 400 yards. This phenomenon is not going to change anything. I just found it interesting that there was that much difference. I was using the G-7 Ballistic Program.

The bullet is long gone from the barrel before it ever jumps.

 

[CJ6]

Is the 300 yd target at a incline/decline from the shooting point?

 

[Tim Singleton]

Is it possible the bullet you are using has a better BC than as advertised or than what is entered into the program?

Is it possible the chronograph being used isn't correct ?

To you question of barrel jump I don't think this is a factor. You have it sighted at 100 so even if it could be a factor you have corrected for it when you sighted in at 100.
I would think it's one or both of the two things mentioned above

 

[sbhooper]

The target is dead level from the shooting bench. I guess that I could check the chrono with another one, but I would not think that load could be much faster than what it indicated. If it was slower, then it should drop more at that range. The BC should be pretty close. That bullet has been around forever. I get it about the barrel jump, too, but I am just throwing around all ideas.

Thanks for all of the ideas and input.

 

[Ledd Slinger]

I got an idea...you've been shooting the rifle for years out to 400 yards. Should know it very well by now...throw out the calculator and forget about it. Seems to be creating problems that never existed before

 

[sbhooper]

LOL. Good point. Bottom line is that it is a great rifle that has ruined the day for lots of white-tailed does! Technology is great, but not always perfect.

 

[fredo]

"believe the bullet"...

 

[mongochicago]

Think of all these ballistic programs as "ball park figures". They are a good place to start from but rarely are "on the money"

 

[doctorh]

ON A LIGHT RIFLE BARREL YOU CAN GET A DIFFERENT BARREL WHIP WITH DIFFERENT BULLET WEIGHT.

 

[Dusty Stevens]

ON A LIGHT RIFLE BARREL YOU CAN GET A DIFFERENT BARREL WHIP WITH DIFFERENT BULLET WEIGHT.

 

[people]

Think of all these ballistic programs as "ball park figures". They are a good place to start from but rarely are "on the money"

As a person shoots more they can tune the application and then they are far better than "ball park figures".

 

[Nomad47]

6.5" drop sounds like from a 100 yard zero. You said your rifle was sighted in for 200 yards.

 

[jcampbellsmith]

.. Can't always trust ballistics calculators. They are just a tool to get you close on paper where you can fine tune from there. ...

I don't agree. I've worked with my Applied Ballistics App and 6XC for about a year now. I'm now getting the results I expect when I plug in correct data to the App. The App's aren't easy to drive and like everything else there is a learning curve.

It's a Borden Alpine action with Remington style bolt handle and a Wyatt's Extended Box Magazine fitted. Throated for 105 A-Max with .274 neck. Jewell Trigger with top safety. 1:8 twist True Flite barrel. Barrel length – 23.5 inches. AU-SL5 moderator. Harris bipod. Pillar bedded Darrell Holland stock. A March scope with Burris mounts sitting on a Third Eye Tactical 0 MOA rail.

First shot on Saturday afternoon in the fading light hit the centre of the gong at 400 yds. 3 shots for an ~2.25 inch group.

Regards JCS

Regards JCS