Help with verticle stringing

[hoythitman]

So I have a Remington 700 AAC-SD in 308. I had the barrel cut to 18", threaded and re-crowned. Worked the factory trigger down, put a Nikon scope on it and started shooting. I got it in the .5 - .7 MOA range. Decided it was a heck of a shooter so I put it in a chassis. Took it out tot he range this weekend. Figured out the scope is going to need to be changed because it tracks like crap. Good hunting scope not good for dialing elevation and windage. Anyway, while shooting strings yesterday I noticed, especially at 200 yards a lot of vertical stringing. Hand loads with precise load charges and the projectiles are all same weight.

I've shot lots of long range before but I was more of shooting just for MOA at steel or silhouette. This type of precise paper shooting I'm somewhat new to. The gun us grouping very good, at 100 yards I shot several .2-.3" groups. The string pictured is one of about 4 groups at 200 that were all just about identical. left to right .1-.3" which is lights out, but stringing .6-1.1" vertically.

[Cajun Blake]

did you skim bed the action into the chassis stock ?

[kck]

At 200 I don't know that I'd really consider that vertical stringing that I'd be concerned about. You may just chalk that up to a barrel warming up. I would be more concerned about your cold bore grouping as in marking your first shot every time you go shoot. If your cold bore shots are grouping well then I wouldn't get terribly fired up as that's still a 1/2 min to sub 1/2 min group at 2 bills. By no means am I trying to be the guy that says "Ah, that's good enough" but assuming that it's still a stock rifle, I'd say that's still pretty solid. Perhaps bedding it if you haven't already may give a little assistance though if you plan to leave it stock?

[hoythitman]

did you skim bed the action into the chassis stock ?

No sir, not yet. I wanted to shoot pre bed and see what it was like. I chalked the action and torqued then removed. All chalk was off, seems to be a very solid fit. The folks at XLR said you can bed but they haven't noticed much difference unless the action is out of spec. I am going to skim bed it this week to see how much it changes. I'm thinking its barrel warming or the trigger. I'm still factory trigger, just lightened and tightened.

[hoythitman]

At 200 I don't know that I'd really consider that vertical stringing that I'd be concerned about. You may just chalk that up to a barrel warming up. I would be more concerned about your cold bore grouping as in marking your first shot every time you go shoot. If your cold bore shots are grouping well then I wouldn't get terribly fired up as that's still a 1/2 min to sub 1/2 min group at 2 bills. By no means am I trying to be the guy that says "Ah, that's good enough" but assuming that it's still a stock rifle, I'd say that's still pretty solid. Perhaps bedding it if you haven't already may give a little assistance though if you plan to leave it stock?

I've heard that heat can alter groups but noting specific. Can you explain or point me in the right direction. I'd like to read about it. I did a google search and I've seen people talking about it but not explain it. Does heat slow the bullet, speed it up, de-stabilize it?

[BrianL]

Might try backing off powder .1 grain at a time and see if it brings them in. Still pretty dang good

[Cajun Blake]

No sir, not yet. I wanted to shoot pre bed and see what it was like. I chalked the action and torqued then removed. All chalk was off, seems to be a very solid fit. The folks at XLR said you can bed but they haven't noticed much difference unless the action is out of spec. I am going to skim bed it this week to see how much it changes. I'm thinking its barrel warming or the trigger. I'm still factory trigger, just lightened and tightened.

install a Jewell and don't look back

[Cajun Blake]

of the 4 bullets , what was the 1st shot , and 4th shot

wind will effect bullet impact

when shooting benchrest and for groups, this chart is always on my bench





you can even use a wooden stake with 18" of surveyors tape tacked on to read wind direction

look at the various wind directions from this bench

many times it's not the powder or load , but wind that screws up groups

[hoythitman]

of the 4 bullets , what was the 1st shot , and 4th shot

wind will effect bullet impact

when shooting benchrest and for groups, this chart is always on my bench

In order of shot from top to bottom

2
1
3
4

[gumbl3]

Are these shots 1, 2, 3, 4 in order from the bottom to the top?

Did you chrono to see what the ES is?

[hoythitman]

install a Jewell and don't look back

I will get there. lol. I've been building the rifle since February. Once addition at a time. The ol single parent budget makes things a little drawn out. But bedding tonight. Trigger in the next 2 months.

Then I'm going to shoot it till the barrel is worn out. By then I'll have enough saved up to get the action and bolt trued with a new barrel.

[hoythitman]

Are these shots 1, 2, 3, 4 in order from the bottom to the top?

Did you chrono to see what the ES is?

from top to bottom 2134

I haven't run these loads through chrono in a while (broke it with arrow) But when I did they had a variance of 15-25 fps max. Not using a thrower for final load. It throws about .5 grain low, use trickler to get the load precise.

[kck]

I've heard that heat can alter groups but noting specific. Can you explain or point me in the right direction. I'd like to read about it. I did a google search and I've seen people talking about it but not explain it. Does heat slow the bullet, speed it up, de-stabilize it?

I have a straight 284 that will start moving down just slightly after a 7-8 shot string and a 6br that climbs just a hair after 10. I'm sure CajunBlake can speak to this much better than I can but from what I gather, barrel harmonics will differ from a cold to hot barrel. However, I DO NOT know what that critical temp is and/or how it may/may not relate to barrel contour or pressure. A buddy of mine has a 7.82 Lazzeroni that shoots lights out for the first 3 shots, but has a pencil thin barrel with flutes (don't have a clue why he did that) and starts moving all over the place since the barrel is smoking hot after 4 shots. As to not ramble aimlessly anymore, I will leave it at that in my VERY humble opinion, my concern lies in my first, fouled bore, cold bore shot grouping and letting the barrel cool to after strings of no more than 4-5 shots. Hopefully keeping data on your strings will give you insight how that particular gun behaves.

[hoythitman]

I have a straight 284 that will start moving down just slightly after a 7-8 shot string and a 6br that climbs just a hair after 10. I'm sure CajunBlake can speak to this much better than I can but from what I gather, barrel harmonics will differ from a cold to hot barrel. However, I DO NOT know what that critical temp is and/or how it may/may not relate to barrel contour or pressure. A buddy of mine has a 7.82 Lazzeroni that shoots lights out for the first 3 shots, but has a pencil thin barrel with flutes (don't have a clue why he did that) and starts moving all over the place since the barrel is smoking hot after 4 shots. As to not ramble aimlessly anymore, I will leave it at that in my VERY humble opinion, my concern lies in my first, fouled bore, cold bore shot grouping and letting the barrel cool to after strings of no more than 4-5 shots. Hopefully keeping data on your strings will give you insight how that particular gun behaves.

I appreciate it. I am keeping data on each string. Still figuring the gun out. I'll get it figured out for sure. As far as banging steel and shooting pigs / coyotes at long range. Its more than good enough already.

[bboswell]

of the 4 bullets , what was the 1st shot , and 4th shot

wind will effect bullet impact

when shooting benchrest and for groups, this chart is always on my bench





you can even use a wooden stake with 18" of surveyors tape tacked on to read wind direction

look at the various wind directions from this bench

many times it's not the powder or load , but wind that screws up groups

Excellent info Blake