Stringing

[bootlaceb]

Why do I get 4 or 5 shots in a vertical string, At 300 Yrds) ea cutting the other ?
Is it the back holding bolt ? Too tight, or too loose ?
This is with a 308 Win..if that would help at all
It was a pretty windless afternoon on the range

Cheers

 

[Tommie]

That's still some gnarly shooting at 300 yards!

Stupid question #1: Is the barrel free-floated?

 

[Bubb]

How hot is your barrel? Some times heat will make it do vertical?

 

[bootlaceb]

Thanx. Barrel is floating yes. Bedded and shooting of bags

I normally take about 3 guns to the range, to try avoid burning a barrel. How many shots can start to influence stringing?
Normally I shoot about 4 shots in a row, then cool for about 15Min or so. But then I would fire no more that 20 Rounds

 

[dtech]

Have you run your loads across a chronograph? just curious what your standard deviation is. A SD of high double-digits could give you that effect, but at shorter range, the vertical stringing will not appear.

 

[rhino]

I would shoot to warm up the barrel and then shoot your group.

If its still doing the vertical stringing. Maybe keep track of where each shot impacts.

If your getting up and down, up and down...then its an es and sd load problem and or the set-up of your rifle.

If your getting a rising or lowering straight up and down then you have a barrel fouling or some kind of stress in your barrel is causing it.

RHINOUT!

 

[bootlaceb]

"then its an es and sd load problem and or the set-up of your rifle."
Ok, now explain what that all meant please...you have lost me totally !LOL
Ps: Happy new year for all

 

[dtech]

ES = Extreme spread, the difference in velocity, from the fastest, to the slowest out of a string.

SD = Standard deviation, the average difference between shots in a string.

Take a five shot string. The highest velocity shot is 3200 fps, the lowest is 3100, and the other three were somewhere in between the high and low velocity. The extreme spread would be 100 fps, the standard deviation would be 20 fps.

Where this effects shooting at longer range is that the slower bullets will hit lower on the target, and the faster ones will hit higher on the target. This is a generalization, but the bottom line is: You can have a load that shoots one-hole groups at 100 yards, but with a high SD, your groups at 300 or 400 yards will not be good. A good group at 100 yards, with a very low SD will give you the same MOA groups at much greater distances.

 

[bootlaceb]

Ok, now this would actually make sense to me, as I have a problem with my Lyman XP1000 elec scale. It drifts all the time...thus giving me the difference in velocities. At 100 I do shoot very small groups.
I have ordered a 10/10 Rcbs. Will see if it sorts out the problem.
Thanx for the lesson, it was very interesting

Cheers

 

[Varminator]

Before you shell out for a single beam balance you might want to try one of the Denver Instruments MXX 123 digital scales.
James Phillips used to and still might be able to get a deal on one for you. You can spend a fortune on cheap scopes and scales.
I watched a bench-er,competition) use a very expensive well known powder measure to throw loads "specific" to the known atmospheric conditions without weighing the loads. When I asked if he weighed the loads he basically looked down his nose and said his powder measure was more accurate than any scale and it has been proven that weight is over rated. His vertical was not good testimony to his statement and he was convinced that it was powder fouling and violently scrubbed his barrel with brake cleaner. If you want to take powder charge out of the equation
get a really good scale and weigh every load to .04 of a grain.
If you want to load lots of rounds fast get ball powder that is as slow as you dare use and throw loads after you have verified the loads with a single beam balance. It doesn't matter to the ground squirrel if you hit him in the head or the chest.
><MM>:thumb: