Who said 6BR is easy to tune?

[marchx]

Gentlemen
@Clancy
@SPJ
@CharlieNC
@JEFFPPC

I will try to record a short video to address the questions on (a) setup, (b) my process, (c) rest of your questions.

 

[Nick Caprinolo]

Using new brass could be the problem. I would never try tuning my load with it. Needs to be fireformed for you rifle.

 

[Sundown]

First...I would get a good Front rest and rear bag. Second...actually measure the twist rate of your barrel. I had a barrel that was listed at 8-twist that was actually 8.5-twist. The only thing that would shoot in that barrel was 90 gr. Bergers. I also had problems shooting 105 hybrids out of my 8-twist barrel. Seems like they need a faster twist. Try a few 108 Bergers with the same charge. Third...don't be afraid to seat bullets out to 30 .0030". I had a 6 BR that absolutely hammered at (.0030") off the lands.
Good luck on the trip!

 

[Kracken McGraw]

A straight 6br shouldn’t need much fire forming on the brass, should it?

 

[6fatrat]

Everybody i know.
Steve Bair

 

[PracticalTactical]

Last week I tested different seating depths using 30gr of N140 in 6BR. The most promising was .010 off the lands showing ¼ MOA for a 4-shot group.

Yesterday I loaded 5 rounds to repeat the test in different weather conditions. What came out was a disaster 0.88 MOA (see below). It was a vertically dispersed group.

It was virgin Lapua brass trimmed to length, mandrel expanded, graphite lube. I measured the powder chargé on 2 scales and the charges were precise up to 0.02gr. CBTO was consistent up to 0.0005”. 105 Hybrids. I was shooting off F-class bipod and SEB rear bag using x60 magnification.Seeing the heart rate on my reticle but still my point of aim was within the X zone.

Would using a front rest (like seb neo) increase my accuracy or should I stick to my setup and review my reloading process (or is it shooting technique)?

https://imgur.com/04lA0l3

https://imgur.com/QY22U82

Lots of suggestions here, but I'm thinking about mirage refraction. Mirage refraction is where the image you see from the firing point appears to move, even though the target is not really moving.

This leaves two choices...
1) Wait for fog, and shoot just as the fog clears. (Not very practical)
2) Measure target displacement caused by mirage refraction

You can observe how much mirage will appear to move the target by watching through your rifle scope, but then once you see it move, what exactly can you do about it? Each time you fire your rifle you will loose your point of reference.

What you need to minimize the effect of mirage refraction is to use a second rifle scope on a tripod with a phone scope behind it.

If you watch the phone scope you will see the reticle will move relative to the bull as mirage does its thing. Wherever that reticle moves relative to the target is the current relative point of aim for your rifle.

I hope this makes sense.

I welded up a one piece tripod for this purpose with spiked feet so I can jam it into the ground, but hey, you can use whatever you think works for you if you shoot from a bench. You just need to mount the tripod on a surface you know will not move during your shot string.

I think mirage refraction is the number one reason most shooters cannot get inside 1/2 MOA.

 

[marchx]

Lots of suggestions here, but I'm thinking about mirage refraction. Mirage refraction is where the image you see from the firing point appears to move, even though the target is not really moving.

This leaves two choices...
1) Wait for fog, and shoot just as the fog clears. (Not very practical)
2) Measure target displacement caused by mirage refraction

You can observe how much mirage will appear to move the target by watching through your rifle scope, but then once you see it move, what exactly can you do about it? Each time you fire your rifle you will loose your point of reference.

What you need to minimize the effect of mirage refraction is to use a second rifle scope on a tripod with a phone scope behind it.

If you watch the phone scope you will see the reticle will move relative to the bull as mirage does its thing. Wherever that reticle moves relative to the target is the current relative point of aim for your rifle.

I hope this makes sense.

I welded up a one piece tripod for this purpose with spiked feet so I can jam it into the ground, but hey, you can use whatever you think works for you if you shoot from a bench. You just need to mount the tripod on a surface you know will not move during your shot string.

I think mirage refraction is the number one reason most shooters cannot get inside 1/2 MOA.

What kind of mirage do you have at 8.00am, 2 degrees Celsius?

 

[Murray Brook]

At 2 degrees C the heat from you barrel can cause problems.

 

[BoydAllen]

A straight 6br shouldn’t need much fire forming on the brass, should it?

Years ago, a friend was trying to work up a very accurate load for a new 6BR that had a top level barrel and had been bedded correctly. He was getting a bit frustrated when the best that he could do were groups in the 3s. This was a slow twist varmint application. It turns out that he was working his way through new brass. I advised him to pick of set from those that he had already fired once and use those to continue his work. Problem solved. After that everything went as he had
expected.

 

[BoydAllen]

Lots of suggestions here, but I'm thinking about mirage refraction. Mirage refraction is where the image you see from the firing point appears to move, even though the target is not really moving.

This leaves two choices...
1) Wait for fog, and shoot just as the fog clears. (Not very practical)
2) Measure target displacement caused by mirage refraction

You can observe how much mirage will appear to move the target by watching through your rifle scope, but then once you see it move, what exactly can you do about it? Each time you fire your rifle you will loose your point of reference.

What you need to minimize the effect of mirage refraction is to use a second rifle scope on a tripod with a phone scope behind it.

If you watch the phone scope you will see the reticle will move relative to the bull as mirage does its thing. Wherever that reticle moves relative to the target is the current relative point of aim for your rifle.

I hope this makes sense.

I welded up a one piece tripod for this purpose with spiked feet so I can jam it into the ground, but hey, you can use whatever you think works for you if you shoot from a bench. You just need to mount the tripod on a surface you know will not move during your shot string.

I think mirage refraction is the number one reason most shooters cannot get inside 1/2 MOA.

I disagree about that being the reason that most shooters can't get inside 1/2 MOA. For years most of my varmint and benchrest rifle groups have been well under 1/2 inch, and I have spent a lot of time on the range with shooters whose results were not nearly that small. There are a variety of reasons for their performance, but given what a lot of us have been able to do when there is mirage, I would have to say that it was not their primary limiting factor.

 

[dcali]

Even off an F Class bipod you shouldn't see that. I agree that you shouldn't see a heartbeat, so figure out what's going on there. That you have so little horizontal is a puzzler. This doesn't look like a load issue to me. Either a gun issue or a rest/stability issue.

 

[Forum Boss]

Let someone else shoot the gun. Check the way it fits in the front rest and rear bag.

Sometime ago we did an interesting three shooter test. A buddy had a rifle and he was complaining about horizontal stringing. He shot the rifle and sure enough there was a horizontal string. Then I shot the rifle and I had a vertical string, mostly because my hand/head placement on the high comb stock was inconsistent. Then a third shooter shot the rifle with the same ammo and he got a perfect three shot group that was in the high ones followed by a nice round 0.22 four shot group.

When we analyzed the video of the guy with the horizontal stringing, we diagnosed poor trigger technique — he had arthritis in his fingers and was pulling the trigger laterally, not straight back.

When I corrected my head position and my hold on the rifle, my vertical string disappeared.

What I see on the OP’s target suggest user errors, bouncing in the bags, or a scope issue as others have described.

 

[JEFFPPC]

Let someone else shoot the gun. Check the way it fits in the front rest and rear bag.

Sometime ago we did an interesting three shooter test. A buddy had a rifle and he was complaining about horizontal stringing. He shot the rifle and sure enough there was a horizontal string. Then I shot the rifle and I had a vertical string, mostly because my hand/head placement on the high comb stock was inconsistent. Then a third shooter shot the rifle with the same ammo and he got a perfect three shot group that was in the high ones followed by a nice round 0.22 four shot group.

When we analyzed the video of the guy with the horizontal stringing, we diagnosed poor trigger technique — he had arthritis in his fingers and was pulling the trigger laterally, not straight back.

When I corrected my head position and my hold on the rifle, my vertical string disappeared.

What I see on the OP’s target suggest user errors, bouncing in the bags, or a scope issue as others have described.

Very first sentence. One of the few ideas in this thread that make sense.

 

[marchx]

Let someone else shoot the gun. Check the way it fits in the front rest and rear bag.

Sometime ago we did an interesting three shooter test. A buddy had a rifle and he was complaining about horizontal stringing. He shot the rifle and sure enough there was a horizontal string. Then I shot the rifle and I had a vertical string, mostly because my hand/head placement on the high comb stock was inconsistent. Then a third shooter shot the rifle with the same ammo and he got a perfect three shot group that was in the high ones followed by a nice round 0.22 four shot group.

When we analyzed the video of the guy with the horizontal stringing, we diagnosed poor trigger technique — he had arthritis in his fingers and was pulling the trigger laterally, not straight back.

When I corrected my head position and my hold on the rifle, my vertical string disappeared.

What I see on the OP’s target suggest user errors, bouncing in the bags, or a scope issue as others have described.

@Forum Boss In fact I let someone else shoot the gun. It was veteran army sniper with 20 years of shooting experience. A month ago he shot one ragged hole with my ammo and my rifle setup. It was in the .3s for a 5-shot group (also 105s).
on the mirage/scope issue- I doubt that because with 2 degrees Celsius at the range and 1 minute pauses between shots it is unlikely considering 1.1" diameter at the muzzle. March scope is mounted lege artis as well.

My assumptions- (a) bipod-rear bag tracking problem, (b) maintaining the same position behind the gun from shot to shot (head on the comb, shoulder against the buttstock), (c) trigger pull- although I concentrate to pull it straight back every time.
I hope I will be able to upload a video tomorrow to visualise this for you.

 

[Matt_3479]

A straight 6br shouldn’t need much fire forming on the brass, should it?

All calibers should have a lighter-middle load fired once through their rifle. It’s not fire forming to change a drastic measurement like an ackley improved, but it still should be fired to your chamber once for optimal load work. A lighter/mid charge firing also strengthens the web and primer pocket without over working anything on first firing. A hotter charge first time around can give you lower brass life in the long run.

 

[Darwin]

Not repeating precise stock location over the rear bag can do that.
It’s strange you have pulse in the scope and no horizontal.
I’ve got two 6r’s and that sure ain’t the new brass.

 

[S Miller]

On the up side take away a bullet diameter and you’re at .625. Better than I can do, but I’ve been known to shoot groups without my rest knobs tight and barrel barely touching the rest front stop. If I shot that I would be looking at my rear bag ear fill especially if that group printed low to high. Good luck!

 

[Colnagotex]

#1 FLAGS???
#2 How did you come to choose 30.0?????
#3 (related to #2) Describe your process to tune or do you have a process?

A lot of comments here about the rifle, handling, front rest, and rear bag, but I haven't seen a response to #2 or #3. I shoot F Class TR exclusively off a SEB Joypod and SEB rear bag in competition and load development, and I've experienced many vertical and horizontal groups during load development similar to this one that can always be eliminated with either a powder adjustment or a seating depth adjustment. What did 29.9 and 30.1 look like? How many seating depths did you try? Do you have pics of your load development targets? Assuming this is at 100 yards, I didn't see where you identified the yardage.

 

[PracticalTactical]

I disagree about that being the reason that most shooters can't get inside 1/2 MOA. For years most of my varmint and benchrest rifle groups have been well under 1/2 inch, and I have spent a lot of time on the range with shooters whose results were not nearly that small. There are a variety of reasons for their performance, but given what a lot of us have been able to do when there is mirage, I would have to say that it was not their primary limiting factor.

Interesting that you would disagree. Not sure where you live or what kind of weather, but mirage on a typical day at my range is good for 1/4" at a hundred yards easy... more when it gets heavy.

I don't know how you can possibly dismiss it as a primary factor. When all else is perfect, its the last thing on the list anyone thinks of.

Now, from my perspective, I have actually used the method described in my post to observe and compensate for mirage displacement in real time, and shot tiny groups in heavy mirage because of it, and that would otherwise not have been possible with any degree of consistency.

All shooting is the result of the combined effects of ALL variables. To dismiss any variable as a factor is counter productive, especially in the context of sub 1/2 MOA.

 

[BoydAllen]

Boyer has written that he does not shoot mirage, which leaves flags. If you see someone at the range shooting over flags, typically he is a short range benchrest shooter. Your assumption about our mirage conditions is just that. I have seen it so bad that at 200 that we had to aim at the square, because the rings were not visible most of the time. Many years ago, I was tuning up factory Remingtons in the smaller varmint calibers. Floating the barrels, skim bedding the actions, adjusting the factory triggers, and working up loads with RCBS one piece dies, using thrown charges. My scope was a Leupold 10X and with all of that I expected my rifles to be able to shoot comfortably under 1/2". I totally agree that people not being able to shoot under half inch is typically due to multiple factors. Where I disagree it that mirage is as important as you think it is.