Seating depth advice

[JohnyRingo]

Where should I go from here? 300 H&H Mag. 180 grain Accubonds. 67.5 grains of IMR 4831. CCI primers and Nosler brass. 3.652" OAL to lands.

3.585" OAL. ES=100 fps. 1.5 MOA (3-shot group)
3.595" OAL. ES=25 fps. 0.9 MOA
3.600" OAL. ES=15 fps. 0.7 (2-shot group and a big flier)
3.605" OAL. ES=14 fps. 0.8 MOA
3.613" OAL. ES=47 fps. 0.6 MOA
3.625" OAL. ES=25 fps. 1.18 MOA
3.640" OAL. ES=14 fps. 1.15 MOA

Obviously, the 3.613" created the best group. I am surprised it shot so well with the ES being 47 fps. Should I try any other lengths to try to get better than 0.6 MOA? I am kicking around trying 3 shots at 3.610" and 3 shots at 3.620". I don't have a big surplus of reloading supplies to be messing with load development without eating into my supplies a little. This is the first time I have ever messed with seating depths as my other rifles seem to shoot great with advertised OAL. The advertised OAL for this load is 3.600", but I got a huge flier (2") out of it.

 

[lennywd87]

I see you started .01 off the lands. Have you tried .01 into the lands then back down .006 to where you started? I’ve had pretty good luck like that with quite a few other loads, as long as you aren’t on the max end of your powder charge. How did you decide on the 67.5 charge weight? Was it listed as the most accurate load for that powder or no?


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[JohnyRingo]

I actually started at 65 grains and then worked up by 0.3 grains until I found a velocity node. I believe Nosler lists 66 grains of IMR 4831 as the most accurate load. With Nosler's recommended COAL of 3.600", that load didn't impress me. The accuracy was never better than 1--1.25 MOA until I started messing with the seating depths.

 

[Couescrazy33]

Custom rifle? Or production rifle.

Also hunting rifle or bench rifle?

Are you measuring c.o.a.l or c.b.t.o. if not using cbto, I would try using that measurement to get a more consistent length since bullet lengths vary

Me personally, I would be ok with the 3.605 for hunting

 

[lennywd87]

Custom rifle? Or production rifle.

Also hunting rifle or bench rifle?

Are you measuring c.o.a.l or c.b.t.o. if not using cbto, I would try using that measurement to get a more consistent length since bullet lengths vary

Me personally, I would be ok with the 3.605 for hunting

I’m right there with you @Couescrazy33 for the amount of energy that caliber is packing. Hunting with half moa is far better that the old method of dinner plate at 100 yards , but I am also a hunter that seeks raged hole groups at 200.


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[bsnedeker]

Shoot a 10 shot group with the one you feel most confident in, zero your scope to that group (big fliers included) and go hunting.

 

[Couescrazy33]

Also per noslers load data, you can also go lower in the seating depth and see if you hit a node around 3.580.

 

[Bearizona]

Custom rifle? Or production rifle.

Also hunting rifle or bench rifle?

Are you measuring c.o.a.l or c.b.t.o. if not using cbto, I would try using that measurement to get a more consistent length since bullet lengths vary

Me personally, I would be ok with the 3.605 for hunting

I’d have to agree with 3.605 being comfortable to me for hunting.

 

[Wrench]

3 shot groups are begging for disappointment.

Don't be afraid to sink them deep.

Consider your max distance. 47fps is unnoticeable at 300 yds, but stretch it out and things change. Personally if I have a .8 rifle in hand, any animal inside 600yards should be nervous.

 

[JohnyRingo]

I loaded up 5 rounds at 3.605" and 5 rounds at 3.610". I did adjust the powder charge to see how 67.3 grains will perform.

 

[JohnyRingo]

Custom rifle? Or production rifle.

Also hunting rifle or bench rifle?

Are you measuring c.o.a.l or c.b.t.o. if not using cbto, I would try using that measurement to get a more consistent length since bullet lengths vary

Me personally, I would be ok with the 3.605 for hunting

It's a factory Browning XBolt with some mods on it...McMillan stock, glass bedded, MCarbo trigger spring, BOTW muzzle brake. Just a hunting rifle. Something that gives me 5" groups at 500 yards for big game and something that allows me to shoot rocks out to 1000 yards.

 

[N2TRKYS]

I’d try a different powder.

 

[RLam]

I think you are on the right track and good to go with what you have already seen. Just my opinion.

 

[Couescrazy33]

In theory if your group at 3.605 is under 1 inch then you should be at 5 inches at 500 or just under... But you wont know until you shoot out to 500.

That's up to the shooter and elements though. A lot of variables that you could be chasing and wasting compents on.

 

[HiMtnHntr]

What is the listed max charge?

 

[LaHunter]

Where should I go from here? 300 H&H Mag. 180 grain Accubonds. 67.5 grains of IMR 4831. CCI primers and Nosler brass. 3.652" OAL to lands.

3.585" OAL. ES=100 fps. 1.5 MOA (3-shot group)
3.595" OAL. ES=25 fps. 0.9 MOA
3.600" OAL. ES=15 fps. 0.7 (2-shot group and a big flier)
3.605" OAL. ES=14 fps. 0.8 MOA
3.613" OAL. ES=47 fps. 0.6 MOA
3.625" OAL. ES=25 fps. 1.18 MOA
3.640" OAL. ES=14 fps. 1.15 MOA

Obviously, the 3.613" created the best group. I am surprised it shot so well with the ES being 47 fps. Should I try any other lengths to try to get better than 0.6 MOA? I am kicking around trying 3 shots at 3.610" and 3 shots at 3.620". I don't have a big surplus of reloading supplies to be messing with load development without eating into my supplies a little. This is the first time I have ever messed with seating depths as my other rifles seem to shoot great with advertised OAL. The advertised OAL for this load is 3.600", but I got a huge flier (2") out of it.

This was asked earlier and I may have missed your answer, but how are you measuring OAL? If not CBTO, you are 'pissing in the wind' trying to find optimum seating depth. You need to measure from Cartridge Base to the bullet ogive.
What chrono are you using, the lower priced models are notorious for not being super precise.
In my opinion, 3 round groups are not enough for load development.
How are you measuring powder charges? If you are looking for ES in the teens and SD in the single digits, you better have your reloading procedures dialed in pretty good and really understand the entire process.
Since you are limited on reloading supplies, the 3.6"-3.613" OAL seems to be a range you can work with, for hunting purposes, assuming that 'big flier' was operator error.

Good Luck

 

[JohnyRingo]

This was asked earlier and I may have missed your answer, but how are you measuring OAL? If not CBTO, you are 'pissing in the wind' trying to find optimum seating depth. You need to measure from Cartridge Base to the bullet ogive.
What chrono are you using, the lower priced models are notorious for not being super precise.
In my opinion, 3 round groups are not enough for load development.
How are you measuring powder charges? If you are looking for ES in the teens and SD in the single digits, you better have your reloading procedures dialed in pretty good and really understand the entire process.
Since you are limited on reloading supplies, the 3.6"-3.613" OAL seems to be a range you can work with, for hunting purposes, assuming that 'big flier' was operator error.

Good Luck

Which CBTO tool do you recommend using? I have just been using the OAL.

 

[LaHunter]

Hornady makes the one that I use. They also make a tool for measuring base to shoulder / headspace that is useful.

 

[Vern400]

Where should I go from here? 300 H&H Mag. 180 grain Accubonds. 67.5 grains of IMR 4831. CCI primers and Nosler brass. 3.652" OAL to lands.

3.585" OAL. ES=100 fps. 1.5 MOA (3-shot group)
3.595" OAL. ES=25 fps. 0.9 MOA
3.600" OAL. ES=15 fps. 0.7 (2-shot group and a big flier)
3.605" OAL. ES=14 fps. 0.8 MOA
3.613" OAL. ES=47 fps. 0.6 MOA
3.625" OAL. ES=25 fps. 1.18 MOA
3.640" OAL. ES=14 fps. 1.15 MOA

Obviously, the 3.613" created the best group. I am surprised it shot so well with the ES being 47 fps. Should I try any other lengths to try to get better than 0.6 MOA? I am kicking around trying 3 shots at 3.610" and 3 shots at 3.620". I don't have a big surplus of reloading supplies to be messing with load development without eating into my supplies a little. This is the first time I have ever messed with seating depths as my other rifles seem to shoot great with advertised OAL. The advertised OAL for this load is 3.600", but I got a huge flier (2") out of it.

My best 100 yard groups don't have the best ES. ES makes more difference at ranges beyond your point blank range. Still 100 is high. And you probably need to send 5 to really know your groups. I get that your gun is a kicker, and barrel life aint infinite. your groups are so good it doesn't matter while hunting because all the other variables like having a briar bush in your rear while your trying to twist and shoot matters more. And a big thing i have found is my 30 cal throws 2 flyers on a clean barrel. So I clean it, go outside and pop 2 in the dirt. So clean it, shoot it to find out what it does and if the groups are good quit messing with it. What you are doing looks good. remember the stuff that will kick you in the teeth. Like I shoot about 1/3 of my deer left handed cuz I hunt in tight sometimes, and have no better choice. In that regard, spending your time on a bench aint helpin ya. The rifle has to do its job(and you're there), but in the field most times it aint the rifle that misses.

 

[CastIronSkillet]

Seating depth test tunes your group sizes. I would bet that over a larger sample size all of those seating depths would produce similar ES #'s. If you were to graph your seating depth group sizes you would see that they follow a perfect wave. I would call 3.608-3.614 your seating node and use a final depth of 3.610 and leave it. You will see that your rifle will shoot well over time even as the rifling wears.

Ignition tunes your ES...ie your powder charge and primer selection. You have two choices. Do an OCW test around 67.5 grains in .2 grain increments. Start with 66.9, 67.1, 67.3, 67.5, 67.7, 67.9 and see which one has the best SD/ES. Or you could stay with 67.5 and shoot as many different primers as you can find for better SD/ ES.

You are almost to your final load. Don't give up. May the force be with you.