7prc load question

[BarelyThereOuterwear]

I just got past what I would call the barrell break in point and I'm working up loads for the 7 prc for my bergerra carbon ridge. It won't group factory loads and today I shot the first groups from it that I have loaded. The only to worth a second look in my opinion were h1000 at 66g under a 175 gr eld x at 3.34 ol and 63gr of 7828sc with everything else being same. Both loads using hornady brass and a fed 215 primer. I'll attach the 2 groups at the bottom.
The question I am asking is do I mess with the ladder or try playing with the ol first.

 

[Article 4]

Both patterns have bullet strikes that are the same with the second being larger. Are the impact patterns the same?

Do ladders. Absolutely. Always a good idea with a new rifle and new development.

 

[BarelyThereOuterwear]

Fairly new to reloading or at least still in semi early stages but what are you meaning by impact patterns?

 

[dukeball33]

There is a bunch of info in the painless load development thread and others, but I would answer a few questions first: 1.) what is the intended range of the load and 2.) how much do you like to tinker…

Im a new reloader but I would use a ladder to find pressure or safe operating range for load and rifle. If 66 grains H1000 isn’t showing pressure I would load 7-10 more and see what the 10-13 shot group looks like… if that group looks good I would probably call it a day. Maybe shoot 1 at 67 to see if pressure is there, assuming you’re not at pressure at 66. This would let you know if you’re on the edge of max.

If you like to tinker and have components, try seating depth tests, more ladders of both powders, etc, etc.

 

[Article 4]

Fairly new to reloading or at least still in semi early stages but what are you meaning by impact patterns?

Which bullet are shot 1-2-3 in each target. Are the impacts the same?

 

[Harvey_NW]

Shoot 10 and see how consistent they are. Dropping the powder charge (significantly, like 1-1.5gr, not .3) can shrink the amount of dispersion if it's worth the velocity sacrifice. But with the 7 PRC throat geometry and their high BC bullet, it's highly likely you won't be able improve anything by adjusting seating depth. Trying different component combinations is much more beneficial than tweaking the same combination and shooting small samples.

 

[padenlac]

I am currently in the load development process for a 7 PRC +P. I started with the 180gr ELD-M but it was not grouping that great so I switched to the 180 berger hybrid target and it has been much more consistent. Seems to like either 15-20 thou off or 80-100 thou off.

 

[Article 4]

I am currently in the load development process for a 7 PRC +P. I started with the 180gr ELD-M but it was not grouping that great so I switched to the 180 berger hybrid target and it has been much more consistent. Seems to like either 15-20 thou off or 80-100 thou off.

I have a 7/300 PRC and I always recommend, whenever shooting any new rifle and especially overbore magnums, a 15 shot ladder is always a good idea.

 

[philcox]

@BarelyThereOuterwear check this out.

My Summary of the “groups to small” “painless load dev” and Shoot2Hunt

Overall, that is a good summery. For the above, that is correct. Other than barrel mirage, if the barrel is properly stress relieved and the rifle is assembled correctly there is no difference in cold, warm, or hot bore shots or groups. If the barrel isn’t properly stress relieved, or if the...

rokslide.com

I spend 200+ rounds on a CarbonSix 7PRC barrel that I sent back, and got another setup. A quick summary:

1. Set realistic expectations (listen to "your groups are too small"). For me I want a 1.5 MOA 20 shot group (also listen to
   )... there is no such thing as a .5 MOA rifle, a 1.0 is RARE, a 1.5 is realistic but expensive.
2. I shoot 10 round groups to see what the ammo is like (actually 2x5 to minimize shooter fatigue variable)
3. I shot Factory 180 ELDM and 175 ELDX to figure out what rifle+factory+shooter (me) are probably capable of. Both right at 1.65MOA (so I have my baseline)
4. Doing load dev. I do a ladder at 1g increments to find pressure, then back off at pressure, and load 10 and see how it groups (again 2x5)
5. I am in comifornia, so have to use Mono, so I settled on 168LRX. I tried Ramshot Magnum, and neither load had acceptable accuracy, so did 67.5g RL26 2975 20" barrel. I found that is a load that I can use 1.65 MOA (close enough to 1.5 for me).
   1. With that said, I am a tinkere, and in my old barrel, 66.5g H4831SC shot a 1.23 10 round, but hard bolt lift. I did a pressure on it, and seemed OK in this barrel, so going to shoot 10 at that load. I will go with RL26 or the H4831SC depending on the results

In summary: Shoot 10 with the Factory and set a baseline of what the rifle/shooter/round is roughly capable of. Then 10 round load dev.

 

[northernalpine]

I just got past what I would call the barrell break in point and I'm working up loads for the 7 prc for my bergerra carbon ridge. It won't group factory loads and today I shot the first groups from it that I have loaded. The only to worth a second look in my opinion were h1000 at 66g under a 175 gr eld x at 3.34 ol and 63gr of 7828sc with everything else being same. Both loads using hornady brass and a fed 215 primer. I'll attach the 2 groups at the bottom.
The question I am asking is do I mess with the ladder or try playing with the ol first.

Those loads don’t look bad, like others have said loading 10+ rounds and shooting either for a single group would give you a better sample size.

Something else to consider. It would be worth measuring your mag well and max COAL to figure out if you can seat your bullets longer for your specific rifle. Factory loads and the 3.34” COAL SAAMI spec are kind of a catch all length, you may find better overall and repeatable accuracy by adjusting your seating depth. I’ve had pretty good experiences tightening groups up with minor adjustment to depth once you get a powder charge working.

 

[BossGobbler2024]

Those loads don’t look bad, like others have said loading 10+ rounds and shooting either for a single group would give you a better sample size.

Something else to consider. It would be worth measuring your mag well and max COAL to figure out if you can seat your bullets longer for your specific rifle. Factory loads and the 3.34” COAL SAAMI spec are kind of a catch all length, you may find better overall and repeatable accuracy by adjusting your seating depth. I’ve had pretty good experiences tightening groups up with minor adjustment to depth once you get a powder charge working.

Do you find moving the seating depth farther from the lands tightens groups more than moving closer?
IE making the COAL longer or shorter?

 

[BarelyThereOuterwear]

Those loads don’t look bad, like others have said loading 10+ rounds and shooting either for a single group would give you a better sample size.

Something else to consider. It would be worth measuring your mag well and max COAL to figure out if you can seat your bullets longer for your specific rifle. Factory loads and the 3.34” COAL SAAMI spec are kind of a catch all length, you may find better overall and repeatable accuracy by adjusting your seating depth. I’ve had pretty good experiences tightening groups up with minor adjustment to depth once you get a powder charge working.

Still working the load dev I will try seating depth once I'm semi happy with a powder charge..thanks or the input

 

[Harvey_NW]

Do you find moving the seating depth farther from the lands tightens groups more than moving closer?
IE making the COAL longer or shorter?

When taken to a valid sample size the changes typically eclipse themselves and shoot the same sized cone, especially with high BC bullets in modern chamber designs. The differences you see in 3-5 shot test groups is from random distribution and falls within the variability.

 

[northernalpine]

Do you find moving the seating depth farther from the lands tightens groups more than moving closer?
IE making the COAL longer or shorter?

What @Harvey_NW said is accurate, more of the modern high BC bullets are agnostic to seating depth. However, there is validity in saying factory ammo loaded at SAAMI length from a given rifle/barrel can shoot poorly, and with minor adjustment to seating depth in a similar performing bullet/component combo, you can get better overall accuracy for a given bullet. There’s no guaranteed formula that’s universally applicable as far as moving closer or further.

I don’t recommend spending countless hours trying every possible combination and wasting a bunch of components. I do recommend (1) measuring your individual rifle’s maximum COAL/mag length vs SAAMI specs and using that to make an informed decision when starting a load development cycle, and (2) looking at a limited number of seating depth adjustments with the chosen powder charge weight if it shoots poorly before moving on.

 

[BossGobbler2024]

What @Harvey_NW said is accurate, more of the modern high BC bullets are agnostic to seating depth. However, there is validity in saying factory ammo loaded at SAAMI length from a given rifle/barrel can shoot poorly, and with minor adjustment to seating depth in a similar performing bullet/component combo, you can get better overall accuracy for a given bullet. There’s no guaranteed formula that’s universally applicable as far as moving closer or further.

I don’t recommend spending countless hours trying every possible combination and wasting a bunch of components. I do recommend (1) measuring your individual rifle’s maximum COAL/mag length vs SAAMI specs and using that to make an informed decision when starting a load development cycle, and (2) looking at a limited number of seating depth adjustments with the chosen powder charge weight if it shoots poorly before moving on.

Good to know. I have only reloaded for 3 guns and none are "Modern"