If you are really bored with nothing to do....

[DirkTejan]

If you are really bored with nothing to do maybe you can help me ponder a few questions (or not).

Rifle is a 6XC I use for F class and tactical matches. Scope is a Leupold VariX III 6.5 to 20x 50mm Obj. All targets shown were at 100 yd. Rifle was zeroed for 36.7 grains of H-4350 behind a 108grain Berger BT. I am thinking about switching to Sierra 107s. The reason that I don’t use Berger 105 VLDs is because with a previous barrel I got tired of bullets getting stuck in the throat and powder spilling out into the action. This rifle only has about 300 rounds through the barrel.

The first target (10-17-08) was shot in sunny conditions at 90 degrees. Elevation at Boulder City was 2200 ft. I was shooting off of a bench. Previously the rifle had been zeroed and these rounds should have impacted at the center of the X (but they didn’t for some odd reason). Upper two targets are Berger 108 BTs - 10 rounds apiece with powder charges varying from 36.2 to 37.2 grains. – 1st target bullet .020” off lands- 2nd target bullet into lands. Lower two targets are Sierra 107 MK – 1st target bullet .020” off lands- 2nd target bullets into lands. Same drill with the varied powder charges. The last group is only 4 rounds.

OK – I get it- we like the bullets touching.

This was meant as a chrony test to see if there was a sweet velocity spot. Unfortunately I was using a “Shooters Chrony” which meant that I didn’t get much useful data. I returned home with a surprisingly intact Chrony.

I decided on 36.7 grains of H4350 and loaded some Berger 108s for the next Las Vegas tactical match. Well I didn’t do so well at the match today, for a number of reasons (primarily the nut behind the buttplate). I had some strange missed shots that I thought were unexplained. Match elevation was 3300 ft. Match conditions were 70 degrees with light switching wind (0mph to 5mph) The match was shot prone w/ bipod. Because we were shooting at steel and I didn’t have a spotter it was impossible for me to see which direction I was missing most of the time. I have never thought that lighting conditions affected me all that much, but it was mostly cloudy.

Later during the day I decided go to the desert to check my zero. Elevation was 3200 ft. (11-1-08) These two targets were shot prone at 100 yards. Conditions were cloudy. According to my windmeter the wind was a pretty consistent 8mph sometimes dieing to 4mph (left to right). I set elevation for 100yd and put 2 clicks left on windage. I put 5 rounds downrange with one unexplained flyer. First thing I noticed was that I was impacting about .5” low and a little left. I put 2 clicks on elevation and removed one left click windage. Another big flyer! Hmmmmm.

Thoughts? Ideas?

Thanks,

Dirk

 

[DirkTejan]

This is the second target that I shot today.

This is the second target that I shot today.

Dirk

 

[mike in co]

was the flyer right after scope adjustment ? the scope adjustments settling in ?

 

[Steve Shelp]

Dirk,
The first 2 things that popped into my head was this:

you mentioned your first targets where you tested seating depth were shot off from a bench. Was this with sandbag's or still with your bipod, just off from the bench?

Either way a rifle fired from a bi-pod resting on a hard surface will give you different impact points. The heavier the recoil the more pronounced the change. At least that is my experience. I use an older Harris a lot for field use and when sighting-in I always try to shoot prone with it placed in soft dirt or put several layers of rags under the legs if I'm on a bench or shooting from a hard surface. I've seen this change with my 223 and mostly with my heavier 30s such as a 30-06 or the 300 Winny. For me and my hold, my shots have a tendancy to go higher and left with a harder surface.

The other thing is the scope is ALWAYS in question no matter what brand name or age it is. But 1 or 2 flyers here and there in the middle or end of a group typcically isn't a sign of a bad scope. Were these flyers the first round or two after making a click adjsutment?

Steve

 

[bsl135]

I agree with Steve

My guess is that the different shooting platforms are causing your shift in POI.

 

[DirkTejan]

Thanks for the help guys.

I think some of your theories may have merit. First groups (ten round groups) were shot off of a Harris bipod from a concrete bench. This was at a lower altitude and a higher temp. Match was shot off of a harris bipod- prone on concrete. Second set of groups was shot on the same day- prone with harris bipod with the legs on a brick. The brick was slanted away towards the target about 15 degrees. All three times I used a little sandbag in the rear.

I don't believe that the flyer was the first round in the second group. As a matter of fact- no- I remember the first round of the second group impacting just below the "X" and thinking "good call on scope adjustment".

I got to thinking maybe I had the bullets just barely touching the lands and the flyers were caused by bullets not quite touching. I dont know. Even if that is the case the 10 shot groups show that the POI is very close to the same either in or out of the lands. I could almost see the first 5 round group flyer- but the second one? I don't think so. That is VERY strange and aggravating.

Anyways thank you all for your efforts.

Dirk

 

[DirkTejan]

Bumpy surface of concrete.

maybe that is it. I think you are on to something Steve! Thanks!

Dirk

 

[bob3700]

Dirk,

A couple of thoughts from a HP shooter.

First, always try to establish a zero from the position you will be shooting from. Each position a HP shooters fires from may have a unique sight setting due to pressures on the gun.

If firing from the ground with a bi-pod, get it zero'ed up exactly that way so the bi-pod reacts to it's base in the same manner.

Check out your zero's when the firing point slopes away, or toward you. See how/if the rifles POI changes.

Know these things in advance before the event. That way you can compensate for a good first shot hit. Ask the fellows who shoot "No Sighter" matches. Where that first shot goes if pretty important for your overall score.

Scopes are a whole nother kettle of fish. I am sure there will be those who disagree, but I never trust the clicks on a scope untill a couple of shots have been fired. The PIO can move until the erector assy settles down. Check out the BR folks and see what some of the trends have been. A locking screw to freeze the erector assy. Frozen erectors with adjustable mounts. Well, you get the idea.

Hope some of that helps.

Bob

 

[STP]

This something that was pointed out to me back in 2003 just prior to my attending my first F-Class match. "Get off the bench and practice as you intend to compete."

I had been bench shooting 168SMK`s in my 700VS for groups and recently switched to 175`s and the difference in recoil to this "newbie" was considerable. The advice was timely, as my groups improved and things pretty much fell into place after that.

HTH...