Load Development Help - Rifle Went Out of Tune

[treillw]

I'm relatively new to tuning rifles to have great accuracy. I have a 300 win shooting 215 bergers with 75 grains of H1000 at 2740 fps. For the past couple years it has been a half minute rifle. This year it has gone out of tune and is shooting about 1.1 moa. What is the best approach to finding the tune again?

My first guess is to chase the lands - they are probably wearing by now. So I loaded up a few rounds with the same powder charge and started seating the bullets longer in .005" increments. You can see in the photo below that things didn't improve. I'm confident that the fliers in the original load are not my fault. I have shot a lot of shots with it since it has gone out of tune and seen many fliers on shots which feel solid.

What would you try next? I almost feel like I should go shorter with the OAL, since the original load still shows so much promise. Maybe vary the powder charge slightly?

I've also thought about playing around the 3.920" length, but I would need to shoot quite a few more rounds to confirm that load is indeed in the .7 moa ballpark; it could very easily open up to 1.25 moa with another shot.

What would you do from here?

Thanks!

 

[Homerange]

Anything changed in your loading methodology ?
Scales accuracy double and triple checked ?

New powder batch ?

 

[GuitarmanNick]

Has the rifle been disassembled? Check the action screws and barrel for contact with the stock. Wood can warp in humid conditions.

 

[JFrank]

That’s not a lot of speed for what I’m assuming is a 300 win mag. Although 3.910 looks like a decent depth I would definitely revisit the charge ladder.

 

[INTJ]

If you don't clean the barrel at least every 50-100 rounds, then clean it. Otherwise....

At the best seating depth you just found, run a powder ladder.

 

[NZ_Fclass]

Time for a bore scope

 

[Ned Ludd]

It looks like the original load (top, left) had one pulled shot out right, otherwise it would still have been about 1/2 MOA. Perhaps the load is still ok and it is the trigger puller that needs some work.


How many rounds have you put through the rifle in the last year? That number should give you some indication of whether it is time to re-visit load development. If it is only a couple hundred rounds, my first observation probably holds true. If the number is closer to 1000, measure the distance to "touching" the lands and see how it compares to the last measurement in terms of COAL or CBTO. If you decide to continue tweaking the load, I would also suggest using a finer increment in seating depth testing like .003". It is sometimes possible to miss a fairly narrow seating depth optimum when using a seating depth test increment as large as .005".

How does the current muzzle velocity compare to what it was when you first worked up the load? Likewise, a noticeable change in velocity due to temperature differences or other sources can also be an indicator that you need to re-visit charge weight as well as seating depth. If so, I'd probably start with that first, and leave the seating depth where it was until you find a [new] optimal charge weight. Then you can re-visit seating depth using the most recent optimal charge weight, and slightly finer increments.

Keeping meticulous records during load development is critical. If you have good records, the rifle will usually tell you whether it is time to re-develop a load. Accuracy/precision is only one indicator that it is time to re-work a load that has been in use for a while. Other indicators such as round count, the distance from bullet to lands (i.e. land erosion), and muzzle velocity can also provide useful clues when something has changed sufficiently to warrant closer inspection and possible load re-development.

Finally, how good are you about cleaning the rifle? Build-up of carbon at the end of the case neck (i.e. "carbon ring", or in the throat and first couple inches of barrel can also do bad things to accuracy/precision. If you don't own a borescope, a good cleaning regimen after every use of the rifle is strongly recommended, so as never to let significant carbon/copper fouling build up in the first place. I'd be cautious about suggesting to everyone that they should run out and buy a borescope. The Teslong borescopes have certainly brought decent quality borescopes into such a low price range that almost anyone can own one if they wish. However, the downside to that is that there is also tendency for new borescope owners to reach a state of high anxiety over every little speck they find in the rifle bore or chamber. I refer to this as "Borescope Anxiety Disorder" (i.e. BAD), and it can sometimes be almost as much a problem as not looking at the bore at all. Nonetheless, it is not a bad idea to have one, even if it is used most often simply to ensure the chosen cleaning regimen is working satisfactorily.

 

[gdbleb]

Cold weather (10/14/21) this year vs. warm last year perhaps?

 

[treillw]

So it's a new powder and bullet lot. I've been shooting 1 pound jugs of powder and 100 round boxes of bullet up until now - couldn't find anything in stock to order a larger quantity. That almost has to be the reason, I'd say. Now I have a batch of 1000 projectiles and an 8 pound jug of powder, all the same lot.

Nothing has changed with loading methodology. Action screws tight. Scope screws tight. I will check the scale. Synthetic stock.

 

[treillw]

Cold weather (10/14/21) this year vs. warm last year perhaps?

It has been consistent through various temps over the past few years.

 

[treillw]

Time for a bore scope

Holy crap they are expensive!

 

[6MMsteve]

Holy crap they are expensive!

50 bucs will get you a teslong borescope very good borescope,

 

[6MMsteve]

 

[treillw]

It looks like the original load (top, left) had one pulled shot out right, otherwise it would still have been about 1/2 MOA. Perhaps the load is still ok and it is the trigger puller that needs some work.


How many rounds have you put through the rifle in the last year? That number should give you some indication of whether it is time to re-visit load development. If it is only a couple hundred rounds, my first observation probably holds true. If the number is closer to 1000, measure the distance to "touching" the lands and see how it compares to the last measurement in terms of COAL or CBTO. If you decide to continue tweaking the load, I would also suggest using a finer increment in seating depth testing like .003". It is sometimes possible to miss a fairly narrow seating depth optimum when using a seating depth test increment as large as .005".

How does the current muzzle velocity compare to what it was when you first worked up the load? Likewise, a noticeable change in velocity due to temperature differences or other sources can also be an indicator that you need to re-visit charge weight as well as seating depth. If so, I'd probably start with that first, and leave the seating depth where it was until you find a [new] optimal charge weight. Then you can re-visit seating depth using the most recent optimal charge weight, and slightly finer increments.

Keeping meticulous records during load development is critical. If you have good records, the rifle will usually tell you whether it is time to re-develop a load. Accuracy/precision is only one indicator that it is time to re-work a load that has been in use for a while. Other indicators such as round count, the distance from bullet to lands (i.e. land erosion), and muzzle velocity can also provide useful clues when something has changed sufficiently to warrant closer inspection and possible load re-development.

Finally, how good are you about cleaning the rifle? Build-up of carbon at the end of the case neck (i.e. "carbon ring", or in the throat and first couple inches of barrel can also do bad things to accuracy/precision. If you don't own a borescope, a good cleaning regimen after every use of the rifle is strongly recommended, so as never to let significant carbon/copper fouling build up in the first place. I'd be cautious about suggesting to everyone that they should run out and buy a borescope. The Teslong borescopes have certainly brought decent quality borescopes into such a low price range that almost anyone can own one if they wish. However, the downside to that is that there is also tendency for new borescope owners to reach a state of high anxiety over every little speck they find in the rifle bore or chamber. I refer to this as "Borescope Anxiety Disorder" (i.e. BAD), and it can sometimes be almost as much a problem as not looking at the bore at all. Nonetheless, it is not a bad idea to have one, even if it is used most often simply to ensure the chosen cleaning regimen is working satisfactorily.

I respectfully have to say it's not the trigger pullers fault I've been down that road many times and am confident I can shoot and it's the gun haha.

I would say I have 250-400 rounds though the barrel. Guessing - I could probably get a more accurate number if needed. I should have kept better track of it.

So I haven't shot it over a chronograph, but I've validated my trajectory out to 740 yards and it is the same - therefore the velocity should not have changed.

I could have been a little more diligent with my cleaning regiment over the past couple of years. The gun was shooting well, so I did not clean it. Once things started acting up, I clean it and then continued shooting. These groups are after cleaning. I don't know that I cleaned it to spotless bare metal, but I tried to clean it well with butch's bore shine. let it soak pretty long and scrubbed it well with a nylon brush.

BAD - that's hilarious.

Thank you for your help.

 

[treillw]

I would have to think it is due to changing powder and bullet lots. Where does that lead me?

It's kind of funny how going through other bullet and powder lots in the past didn't make an appreciable difference. Guess my current stuff might just be more different.

 

[treillw]

50 bucs will get you a teslong borescope very good borescope,

Any recommendations on a good model? Seems like they have a few.

 

[INTJ]

I would have to think it is due to changing powder and bullet lots. Where does that lead me?

It's kind of funny how going through other bullet and powder lots in the past didn't make an appreciable difference. Guess my current stuff might just be more different.

It leads you back to what I suggested earlier. Clean it if you aren't cleaning it at least every 50-100 rounds.

Assuming the barrel is not grossly fouled, pick the best seating depth and run another powder ladder. It can be as simple as .5 grains on either side plus your current powder change.

If that still doesn't work, then it might be time for a new barrel. A 300 Win is only going to last 900-1200 rounds while keeping its best accuracy, depending on how it is shot.

 

[Ned Ludd]

I would have to think it is due to changing powder and bullet lots. Where does that lead me?

It's kind of funny how going through other bullet and powder lots in the past didn't make an appreciable difference. Guess my current stuff might just be more different.

Changing Lot #s of any component is a big unknown. Using a different Lot # of some component can make a huge difference, or virtually none at all. Many reloaders make the assumption that changing even a single component Lot # means starting out from square one, and completely re-do the load development process when a component changes.

One potential issue with sporadic cleaning is that carbon build-up over time can turn into what basically looks like black volcanic glass through a borescope. Once accumulated, it can be difficult, if not impossible, to remove without using some kind of abrasive bore cleaner. A proper cleaning regimen will not harm a barrel, or cause the rifle/load to shoot poorly, so it is better to clean after each use and never let that stuff accumulate in the bore to begin with.

 

[STS]

I respectfully have to say it's not the trigger pullers fault I've been down that road many times and am confident I can shoot and it's the gun haha.

I would say I have 250-400 rounds though the barrel. Guessing - I could probably get a more accurate number if needed. I should have kept better track of it.

So I haven't shot it over a chronograph, but I've validated my trajectory out to 740 yards and it is the same - therefore the velocity should not have changed.

I could have been a little more diligent with my cleaning regiment over the past couple of years. The gun was shooting well, so I did not clean it. Once things started acting up, I clean it and then continued shooting. These groups are after cleaning. I don't know that I cleaned it to spotless bare metal, but I tried to clean it well with butch's bore shine. let it soak pretty long and scrubbed it well with a nylon brush.

BAD - that's hilarious.

Thank you for your help.

I'll step out on a limb here and suggest that your barrel in not thoroughly clean. If it's a factory barrel, and you put enough rounds through without cleaning that it finally quit shooting, then you aren't going to get it clean Butch's and a nylon brush. At the very least you'll need a bronze brush and likely will need an abrasive and a good copper solvent. As mentioned above, a bore scope would be helpful.

 

[hicap40]

Run some bore paste down the tube with free all, made a Big difference bringing my groups back

John