Chasing my tail with a load...

G

Ghys_T3LSS

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Sherbrooke, QC
Hi,

I wish there was plenty of H4350 available...

I had a recipe that gave me consistent 1/2 MOA shooting sessions. Now I need to duplicate that using IMR 4350 (Best Bet I had given what was available

243, Tikka varmint, 1:10 twist, SBK 85 HPBT... (For the record...)

here's my question. With my previous experience, i never really gave sh** about COAL and lands. I was around 0,010 from them, for what it worth...

now, i can't find a load that i Like. always around MOA, 3/4 MOA... never better. worse, I started to chrony them, and I didn't like what I was. ALWAYS a flyer (in speed). Always around 50 fps ES. sometimes 70-75. I believe I am reloading correctly, I am super patient and make sure every load is perfect...

So I loaded the best recipe I had, and loaded in increments of 0,003 or 0,005 (Can't recall... notebook is elsewhere..)

my question is:

From your experience, is that common to get this type of results:


Looks like my loads 5 and 6 can be interesting. Grouped together, they give me a SD of 9,5 for 9 shots...
But do you often see this type of difference with COAL variation?

load 1 ES 35
3192
3201
3220
3205
3227


load 2 ES 57
3165
3219
3217
3193
3222

load 3 ES63 (or 22 IF i disregard the flyer)
3212
3205
3193
3253
3190

load 4 ES 75!!
3226
3237
3240
3273
3202

load 5 ES21
3218
3217
3201
3220
3222

load 6 ES 26
3231
3205
3227
3220
 
Sierra 85 Grain HPBT is not a match bullet but it has shown well in my 243.
38.0 grains of IMR4064. This is the load used when my 11 years old grandson shot a 0.83" 3-shot group at 300 yards.
Re22, IMR7828 and IMR4831 have been reserved for heavier bullets (95 and 100 grain).
 
COAL surprisingly can make a huge difference when load developing. I suppose though "difference" is subjective and one's rifle needs to be precise enough to realize those differences. At times if I like what I see on the target I will ignore what the chronograph tells me. Depends on the application. Short range - I don't care. Long range - I care much more.

One method I employ for load development is to find the OCW with seating depth just touching the lands. I then adjust seating depth in .003" increments for powder charges above and below that OCW. Say 1 gr in .2 gr intervals and shoot 3 shot groups on a grid target at 100 yards. Powder charges across and seating depth down. Whatever, just so long as you have all your groups on one target and organized. You've found the correct seating depth when the group's position on the target doesn't change, or very little, with changes in powder charge. Line that seating depth column up with the powder charge column that shows best groups. There's your load for a given velocity or accuracy node. Sometimes that correlates with consistent velocities and sometimes it doesn't. At least that's been my experience. The more precise the rifle the easier it is to interpret the results. For short range I'll call it there. For long range I'll confirm powder charge by shooting 5 or 10 shot groups at 500 and make sure there isn't any vertical. I'll adjust powder charge as required but I won't mess with the seating depth.

Of course you should have some way to read the wind between the bench and target so you're doing your best to shoot in the same conditions from group to group. Most people think flags are a waste of time for various reasons. If you ask me, a shot during load development without wind flags is a wasted shot. :stirthepot2:
 
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my concern would be throat erosion - if you consistently fire shots in succession eventually more sooner than later you will have throat erosion and fire cracking in your barrel. It would be worth a look with a borescope that may answer your question. It's not your load but your barrel that may be causing this.
 
Clean your barrel real good, make sure no carbon ring
Check neck tension -
Load all rounds in same brand cases the same length
try again!

I agree a borescope will help you here -
 
Start by doing a full barrel clean , using a good copper remover. Try some new quality cases, and check the neck tension, around .002" is ideal. Then try seating at around .010" off the lands for a start.
 
H4350 is a unique powder - IMR4350 and Accurate 4350 have similar Burn Rates, but are completely different powders, not the same powder as H4350 just rebranded (like HP-38 and W231).

So while that Burn Rate worked well in your application, you might never get the same satisfcation with IMR4350. I have found Reloder 16 and Reloder 17 to be much closer in Burn Rate to H4350.

Best Wishes!
 
You know your rifle more than anyone else, however it could be a multitude of issues, from that lack of accuracy and increased extreme spread of velocity. Check your brass, measure it in all aspects, inspect barrel (thoroughly clean), check head-space, check bullets, age of powder and primers, expansion of primer pockets, check guard screws for tightness, did you remove swivel studs (catches on front and rear rests).

The 243 Winchester is a very inherently accurate cartridge where several powders will make that rifle shoot very accurate, sub half inch. You can narrow down your powder selections by checking reloading manuals or other sources of load data on the computer.
 
I've had good results with IMR 3031 with the 85 grain Sierra hpbt. You might want to try that if imr 4350 fails. But go through the neck tension suggestions first because they are the likely cause of your velocity spreads.
 
9/10 times imr 4350 shoots better out of a 243 win then does h4350 for me. With 100 gr bullets and under.
Try a magnum primer. Seat the bullets deeper in the case too.
 
Looking at your load 5 you have excellent ES and SD, which means you have good combustion. If I were you, I would keep working on seating depth.
 
Thank you all for your answers.

I'll try to answer to as much as I can in one post.

All the brass I use are Lapua. the last shooting was their 2nd load. FL sizing "shoulder bump" 0,002". Very consistent brass and length. all trimmed. good powder, new primers, etc.

I don't care about neck tension. BUT Given the brass all are the same batch, sized at the same time, with the same expander, there is no reason they would end up different. (I don't control the value, but I am sure they are equal)...

Barrel is free of copper fouling, but has shot maybe 50-60 rounds already (i always prefer a "not too clean" barrel. I think it may repeat more than starting with a very clean barrel, and seeing an increase in carbon fouling...)

As far as shooting strings of bullets... I always wait 2-3 minutes between shots. depending on weather / temperature / cartridge.

long story short, My question was: can there be a difference as big as 70-80 fps between two different seating depths?

next loads i'll prepare will be :

- duplicate of my load #6
- 0,003 less
-0,006 less
etc
maybe 5-6 loads...

thanks again for inputs!
 
Seating depth is an issue when you are in the rifle, touching the rifling or very close. Once you are 20 thou off it does not have much effect on ES and SD unless you are working with a light load that need the bullets in the rifling.
 
Ganderite said:
Seating depth is an issue when you are in the rifle, touching the rifling or very close. Once you are 20 thou off it does not have much effect on ES and SD unless you are working with a light load that need the bullets in the rifling.
Click to expand...

Makes sense. When you are in a zone where it jumps, jumping 0,020 or 0,025 doesn’t change a lot. Barely touching vs touching «#more#» impacts more...

I always try to stay in areas where it allows for more latitude. Meaning I would prefer a 1/2 MOA load I can repeat with some variables, or for example not annealing, no neck turning, etc, THAN a 1/4 MOA load that I hate to reload because it is sooo picky in every aspect...

Thanks again
 
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