Struggling with Seating Depth Precision - 300 PRC - Monometals

[btuley]

Friends,

I'm struggling to get precise seating depths with my 300 PRC loads. There are a number of places I could look to make improvements and wondered if I could get your advice as to where to look first.

In a ten round group of loads I'm getting CBTO spreads of 0.008 to 0.01 inches. Given that Winning in the Wind and Eric Cortina suggest a depth node is about 0.006 long it seems like I should be trying to get more precision (correct me if I'm wrong).

I'm using a Forster Co-Ax press with the stock shell holder jaws.

I'm using new Lapua brass neck sized to 0.002 neck tension.

I'm using a Whidden micrometer die with a custom stem to the Barnes LRX 208 grain bullet. (also tried CX 150 grain).

I'm using a Hornady COAL gauge with the 30 caliber insert and a Mitutoyo Absolute Digimatic Caliper.

I've tried seating with no lube on the interior of the case. I've tried seating after lubing and neck sizing with some RCBS case lube in the neck with a light cleaning with alcohol on a q-tip after sizing.

Should I look first at swapping the shell holder jaws for a regular shell holder? Or a precision shell holder? Should I full length size with expander ball? Should I just wait patiently until i'm on the brass once fired and full length sized and annealled? Should I get tools to see if my bullets need to be separate by seating stem to ogive variance? A different approach to measuring CBTO? Different approach to neck interior lubing? Or something else?

What would you recommend?

 

[Shane Lindsey]

Have you shot any of these or are you just not getting the consistency you are looking for in the loaded round?

Have you measured just the bullets? Are they consistent enough to know that they are not the culprit. I have never measured a batch of bullets for consistency. But I don't compete and they don't pay my bills, so not that important to me. Instead, I am looking for a forgiving load.

Since it is a Barnes, how far are jumping them? I jumped them a good bit when I was using them. At least .050" or as long to fit in a mag. I also had times when a bullet would not seat with enough pressure to hold it in place (neck tension) due to surface area of the bullet. That may be your issue.

 

[cajun]

I would check the bullets. I would bet a lot of it is there.

 

[entoptics]

EDIT after reading OP more carefully.

Last few batches of Barnes I've loaded (0.284 LRX) had fairly variable tip lengths. Even though it's a custom stem, confirm it's not hitting the tip instead of ogive.

 

[Dmagna]

I have had a few batches of Barnes where I have to seat each bullet separately. Adjusting the die every time, then back the die off .020 then seat the next

 

[btuley]

@Shane Lindsey Thank you for your response. Yes, I am hoping to get more consistency. It's not terrible, but I should be able to do better with a Masterpiece Arms Lighweight Hunter with a Nightforce NX8 and parallax set correctly. Currently 5-8 round groups are at 1.6 MOA off of front and rear bags on a cement bench at a 100 yard range sheltered from wind. I was able to hit 3 of 4 milk jugs at 600 yards when I was checking dope before fall rifle hunt, and 6/6 targets in a PRS style sharpshooter tryout with Colorado Parks and Wildlife. So, the rifle is shooting ok or well. I'm just looking for 'better'. Yes I know some of the 1.6 MOA is me, but I feel I could get better out this with the right load and my seating depth is highly variable right now.

No, I haven't measured the bullets. That is at the core of my question because if I'm going to measure from where the seating stem presses to the ogive I will need some new tools. I'm interested in measuring this, but it will be come flow. It that's the most likely culprit then I may need to invest. Or if entopics is correct that the tip lengths are variable on these bullets I saw in another post the idea of seating half way and sorting by length and then seating the remaining depth in groups. This could deal with the tip length variability without tools.

I've tried seating at a few different depths. I don't remember for sure what depth these were at, I think the target jump was 0.020".

Thanks again for your reply.

 

[btuley]

I have had a few batches of Barnes where I have to seat each bullet separately. Adjusting the die every time, then back the die off .020 then seat the next

Do you think this was due to tip length variation, or seating friction, or something else?

 

[btuley]

EDIT after reading OP more carefully.

Last few batches of Barnes I've loaded (0.284 LRX) had fairly variable tip lengths. Even though it's a custom stem, confirm it's not hitting the tip instead of ogive.

There is a pretty clean clip or stop when the seater hits the contact point part way down the bullet tip. I'm not feeling anything that feels like the plastic tip may be hitting the back prior to the metal to metal contact.

But, if you've seen a variable tip length it may include variability of the profile where the seater attaches. These post lead me to believe there is a high chance it's the bullet variability.

 

[Barehandlineman11]

I would toss the whidden in garbage can. Ive had nothing but issues with them from sizing to inconsistent seating.

 

[btuley]

Well, that stinks. They weren't cheap.

 

[Barehandlineman11]

Can always sell them.

 

[Barehandlineman11]

Bullet Central carries the micron seater. Best otc dies ive used actually been hornady besides the micron

 

[Pdyson]

Some guns like the copper bullets and some don't, but a different seater die is in order. heck, A Lee seater is more repeatable than 8 to 10 thou. My FA universal micrometer seater is dead-nuts accurate and I can write down the setting and repeat my desired CBTO every time…even after switching over to a different caliber and bullet combo. could your powder be compressed? I've seen that cause inconsistent depths and they can grow longer over night.

 

[TRG65]

1.6 moa at 100 yards for 5 round group? I don't think seating depth variation is the issue. My AR 223s give that kind of group, but I use unsorted range brass and load that on a Dillon 1050 with Dillon dies. I use Whidden dies for several calibers. I've had very good luck with them. Whidden is one of my preferred places to by equipment. I've had a custom die set made by them for a wildcat off the reamer spec including the hydro form die in 6.5 Addiction. That is an awesome set. I also use Whidden for my 6 Creedmoor PRS rifle and a combination of Whidden and Redding for 6.5 Creedmoor. For my bolt gun and precision gas loads, I'm using a Dillon 650 to do all my sizing steps and seating on a co-ax. I fairly typically get +/- .002 or .003" variation on my CBTO measurement. However, seating on the co-ax whether I use Redding, Whidden, or RCBS that is about what I get. On a load that is worked up, my 5 shot group (bolt) should be .6 moa give or take using a bipod and rear bag and precision gas gun I try to keep sub moa, because that is good enough for me.

If you are trying to get from 1.6 moa to 1moa or .5 moa your dies should be fine. If you want to get to .25 moa I'd start looking to LE Wilson.