POI Jump - costing points

[6BRinNZ]

Hi guys I'm after some input.

Shooting F-class at 500-600yrds, after 7-10 shots my POI jumped .5 MOA and pretty much stayed there, shots 20-24 looked like they were starting to creep up about .25 MOA.

I am assuming this is fowling...but maybe not - what is everyones thoughts? I sort bullets, load powder to the granule and measure base of case to ogive with a redding instant indicator for every round. The base to ogive varies less than .001, so I am confident that my loading technique won't be causing this amount of verticle.

I am thinking of getting a bore scope then realised that I don't know what an overly fowled barrel looks like, I will just be able to tell when its clean....I will get one anyways, just not sure if it will help me with this issue....what are your guys thoughts?

BTW the barrel is a custom barrel...i.e. all of my componetary is good gear...lapua cases, CCI primers...etc etc. Barrel is a 6BR with 800 rounds through it.

Any thoughts as to how I should go about solving this one? The POI jump has happened in two matches now, and I did nothing differently so that I knew I had a problem for sure.

So the next step is what is sensible to change. I was thinking of cleaning between relays to see if the POI came back down and started to climb again...although it does appear to be a distinctive jump up not something gradule. I figure this would be a good step to identify if it is fowling giving me a headache.

Oh yeah I have had the scope/mounts checked and these are fine...scope is an NF.

Anyways input welcome

Thanks

 

[wooger]

Now I'm no expert and I'm sure someone will chime in here but I have noticed that temperature can play a part in elevation gain. Are you leaving the loaded round in a hot chamber for a time period before firing? Does your rifle start to shoot high when hot?

 

[RonAKA]

Don't have the experience to help you. But, as a point of clarification, does the POI go back down from match to match, or are you adjusting the scope?

Just a guess, but could it be some kind of heating issue in the bedded part of the action and barrel. Heats up to the point that something gives or slips -- perhaps in the recoil lug area? If so, it would seem likely to respond to action screw torque. Simple barrel heating and distortion would seem to be a gradual thing, and not a granular step change.

 

[6BRinNZ]

Ron - POI returns from match to match, I clean after every match. Torque - thanks Ron something to think about here.

Wooger - I don't leave the round in the chamber long, I don't tend to muck around in my string. The barrel etc will be warming up as it is part way through a continuous string of 12 shots. There are small delays between each shot as the target is lowered, scored and raised again.

 

[dmg264]

Are you using a shield on your barrel? Barrel heat will really screw up the sight picture.

 

[6BRinNZ]

Are you using a shield on your barrel? Barrel heat will really screw up the sight picture.

I'm not currently using a shield. Maybe this would be a good thing to have but if heat was causing issues in this manner I would have expected more of a scatter effect(?) Literally I had to go down 2 clicks and stay there. There was quite a gap to the second relay and I didn't have to go back up the two clicks.
If I was to draw it as a waterline, it would have looked something like below. Shots
towards the end appeared to be creeping up but this would have been marginal.

............
......

 

[Forum Boss]

Who made the barrel?

What powder are you using?

Are you using rounds in the order they were loaded?

 

[6BRinNZ]

.

Who made the barrel?

What powder are you using?

Are you using rounds in the order they were loaded?

I don't want to say who the barrel maker is at this stage as I think that would be doing them a disservice at this stage (I don't know what the issue is, everything is just conjecture so far)...suffice to say plenty of guys are using them at the range.

The powder is ADI 2208

Yes - in terms of loading technique I size and load cases within the same day, I seat them long and do a final seating depth on the day of the match. I have read the articles about neck tension varying depending on when the cases were sized and subsequently loaded so I basically don't go there. I find seating on the day means I don't have to worry about the "weld" if the projectile has been sitting in the case for a while.

 

[watercam]

Is it always the same range? Does the wind come from 12 or 6 o'clock? Are there berms between you and the target? Seems too regular to blame wind bouncing up any berms in front of you plus it sounds like it is a recent issue.
Have you polished your bore every 500 rounds or so? In shooting Long Range and Palma I don't clean for four or five matches so as to keep the fouling consistent. I shoot with a lot of High Master (of which I am not one yet) and Palma team members who all do the same thing as does Tubb.
Hope it works out for you!
Mike

 

[Erik Cortina]

What kind of front and read bags do you use?

When you go to the line and set your gun on the bags, make sure you press down on the gun as you slide it back and forth a few times to make sure it settles on the bags. If you don't, as you shoot the gun starts to settle in the bags and therefore changes the way your gun slides in the bags, changing your POI.

One more thing, make sure your front bag ears are tight enough to provide good tracking and minimize torque, but loose enough to allow gun to slide properly. If front ears are too tight, your POI will change as the match goes on and stay there, then when start over again, it will usually go back to the original POI because it has not settled in the bags yet.

Hope that helps.

 

[6BRinNZ]

Is it always the same range? Does the wind come from 12 or 6 o'clock? Are there berms between you and the target? Seems too regular to blame wind bouncing up any berms in front of you plus it sounds like it is a recent issue.
Have you polished your bore every 500 rounds or so? In shooting Long Range and Palma I don't clean for four or five matches so as to keep the fouling consistent. I shoot with a lot of High Master (of which I am not one yet) and Palma team members who all do the same thing as does Tubb.
Hope it works out for you!
Mike

Thanks - the ranges I have been shooting are 500 and 600 yards, yes there are berms from the other yardages, I am confident (as I can be) its not wind, the wind theory was in part why I didn't change anything from match to match. I actually think the problem has been around for a while but I have always put it down to me, but now that I am getting my head around this game and all of its nuances ....I am very confident there is an issue.

Cleaning - no I don't polish the bore, I will get a bore scope before I go down this track...my OCD won't let me do something like this unless I can measure or verify it

 

[6BRinNZ]

What kind of front and read bags do you use?

When you go to the line and set your gun on the bags, make sure you press down on the gun as you slide it back and forth a few times to make sure it settles on the bags. If you don't, as you shoot the gun starts to settle in the bags and therefore changes the way your gun slides in the bags, changing your POI.

One more thing, make sure your front bag ears are tight enough to provide good tracking and minimize torque, but loose enough to allow gun to slide properly. If front ears are too tight, your POI will change as the match goes on and stay there, then when start over again, it will usually go back to the original POI because it has not settled in the bags yet.

Hope that helps.

Thanks - yeah I definitely have improvements to make here and now that I have established a problem I will look to change my setup. Maybe this would be a better place to start than changing my cleaning regime (?).

 

[Forum Boss]

Erik raises some very important points. I would also suspect POI walking as the barrel heats -- something not uncommon with factory barrels. You may also have a scope problem. Try shooting with a different scope to eliminate that possibility.

 

[6BRinNZ]

Erik raises some very important points. I would also suspect POI walking as the barrel heats -- something not uncommon with factory barrels. You may also have a scope problem. Try shooting with a different scope to eliminate that possibility.

Thanks - it definitely isn't a factory barrel, to be honest if it was a factory barrel I wouldn't even bother posting. The scope and mounts etc have been checked out. I feel I have covered off the basics - everything tight, scope box test, attention to detail with loading.

What I will do is replace my current rest setup (I need to do this anyways)...I will get one of the experienced guys to check my rest setup. If the problem still occurs then I will look to clean between relays to see if that changes the behaviour at least. Does this sound like a good approach?

 

[Larryh128]

Is this a switch barrel rifle? If so, it really sounds to me like the barrel could be loosening up. I experienced something like this in the past & after 20 shots you could move the barrel by hand. Last time that I didn't cut my own threads.

 

[jo191145]

Try not cleaning it for a match. See if it remains steady.
If its fouling POI should remain high where it left off after barrel cools.
If its heat it should drop back down.

Not uncommon to see POI changes due to fouling in factory barrels.
If your custom is doing that it simply means its not overly happy with your choice of powder.

Toying in factory class shoots I learned early on to have at least 20rds through the bore before going to the match. (Usually 100+) All load development is done with a fouled bore. Loads are tweaked, checked and retweaked if needed. Barrels are never cleaned unless fouling was an issue.
Takes a little work to find a powder that your specific barrel considers a happy medium. Custom barrels are generally much more forgiving but they still have preferences.

 

[6BRinNZ]

Is this a switch barrel rifle? If so, it really sounds to me like the barrel could be loosening up. I experienced something like this in the past & after 20 shots you could move the barrel by hand. Last time that I didn't cut my own threads.

No -1 action 1 barrel

Try not cleaning it for a match. See if it remains steady.
If its fouling POI should remain high where it left off after barrel cools.
If its heat it should drop back down.

Not uncommon to see POI changes due to fouling in factory barrels.
If your custom is doing that it simply means its not overly happy with your choice of powder.

Toying in factory class shoots I learned early on to have at least 20rds through the bore before going to the match. (Usually 100+) All load development is done with a fouled bore. Loads are tweaked, checked and retweaked if needed. Barrels are never cleaned unless fouling was an issue.
Takes a little work to find a powder that your specific barrel considers a happy medium. Custom barrels are generally much more forgiving but they still have preferences.

hmmm, thinking about it the POI didn't drop back in the second relay, there would have been about a 30min wait maybe more. To be honest my intuition FWIW says its to do with the barrel but I need to keep an open mind so I don't go chasing my tail.

I have already cleaned the barrel so I think a good start will be to work on the rest setup like Erik has suggested and then look at the barrel cleaning.

I have always completed my load development on clean barrels and after thinking about this problem I came to the conclusion that maybe I should do my load development on a fouled barrel. Is it a common practice to not clean so much....this question is in relation to F-class as I realise each discipline is different? I have to admit, it seems weird to not clean after each match .....sooo much to learn

 

[jo191145]

My methods are never considered normal ;D
Just what I've found works for me.

The first comps I ever shot were a fun egg shoot.
Shoot both yardages 200+300yds and its possible, not likely to fire 100rds a day.
To find a powder/fouling condition that would allow that takes effort.
When I finally found a powder willing to let me go that far I also found POI would change slightly after 6-10rds in a clean barrel.
At 300yds slightly is enough to miss an egg. Eggs suspended in air can't tell you where that miss went. With paper you can compensate. Start shooting holes in air and your all done.
Last time I still shot factory eggs I ran a 204 Ruger all season without seeing a rod.
400+ naked bullets. Accuracy remained.

I do the same in a 6PPC and 6BR 1/14 with different powder and HBN coated pills.
I'm not setting the IBS league on fire but thats my choice. Formal BR I do for fun and offer support to the league. No n-133 for me. It can't go the distance without a rod.

 

[6BRinNZ]

My methods are never considered normal ;D
Just what I've found works for me.

The first comps I ever shot were a fun egg shoot.
Shoot both yardages 200+300yds and its possible, not likely to fire 100rds a day.
To find a powder/fouling condition that would allow that takes effort.
When I finally found a powder willing to let me go that far I also found POI would change slightly after 6-10rds in a clean barrel.
At 300yds slightly is enough to miss an egg. Eggs suspended in air can't tell you where that miss went. With paper you can compensate. Start shooting holes in air and your all done.
Last time I still shot factory eggs I ran a 204 Ruger all season without seeing a rod.
400+ naked bullets. Accuracy remained.

I do the same in a 6PPC and 6BR 1/14 with different powder and HBN coated pills.
I'm not setting the IBS league on fire but thats my choice. Formal BR I do for fun and offer support to the league. No n-133 for me. It can't go the distance without a rod.

Thanks - I appreciate the input. I am a varminter turned F-classer....those x's are tantalising

 

[6BRinNZ]

Shot 3 yardages today - 300 500 and 600. Total of 9 shots at each range 1 relay each...27 rounds all up

I totally replaced my bag setup and had one of the top national shooters check it over.

Well - I took out the 300yrds (its just a club day), not sure on the 500 and 600 yrds yet...I only mention this so you know I'm not a complete babboon pulling the trigger.

Sure enough at 500 yrds first shot it jumps two clicks worth....I come down two clicks and there it stays for the 500. we move to 600 I take my drop chart less two and I am on the money.

So, there is definitely a problem. I don't believe it is rest setup. It is round count related but not heat related(?)

Where to from here? The only thing I can think of is to do as Joe suggests and not clean or go into matches with 10 rounds down the spout...as yet i don't know where accuracy will drop off or if it will?

Its going to be a while before my bore scope arrives so I am catching up with a mate of a mate who will let me borrow one tomorow...maybe this will shed some light?

Would it be fair enough to contact the barrel manufacturer now? Is there other gunsmithing type things i should get checked out....seems to me that it is barrel related though.

again thanks for any responses.