My .30-06 180gr Sierra GK Load development

[ericwh]

A few discussions on load development recently so whoever wants to follow along with me and give advice is welcome.

I wanted a middle of the road toughness bullet for max shot of 500 yards at elk. Something that would be easy to find a good load for. I had good performance from the Sierra 165 SBT on cow elk before so I just went with the 180gr SBT.

Remington 700 BDL Left Hand .30-06. DIY Devcon and pillar bedding.


Hand me down R-P brass from my father. Trimmed, chamfered, deburred, primer pocket uniformed, flash hole doohickey.
WLR Primers
H4350

Found load data online. Sierras load data was significantly lower than noslers and Hodgdon. Hodgdon data was specifically for Sierra bullet so I went with it.

The bullet has a long boat tail and I didn't feel like I could really seat it any longer than book length and get much bearing surface in the neck. According to my measurements I have a little less than .30" of bearing surface in the neck. I loaded to book length.

I loaded 1 cartridge of 52, 53, and 54 grains to "work up" and make sure things were progressing safely without using up components. Then I went in .5 gr increments from 54.5-56 (3 shot groups). Then .3 gr increments from 56.3 to the boom max of 57.5 (3 shot groups). This got me from something definitely safe to book max in 30 shots, with 3 shot groups over a good range and .3gr increments in the region I hoped to end up in.

57.5gr seemed awfully close to 100% capacity with my casings.

 

[Deer hunter]

You can never go wrong with Sierra bullets I use the match Kings for hunting and let me tell you what they do so damage put the elk and deer down hard.

 

[ericwh]

Went to the range and it was fairly windy so I decided to stick to 100 yards. I have the cheap Caldwell chronograph and it gave me errors on 2 shots of 54.5 gr early. I adjusted it and didn't have any errors after.

I shot them all in groups, in order. Broke position fairly often in between groups. Waited for calm conditions (wind flags at 50, 75, 100). I shoot off the bench with a bipod and a rear bag. Piece of carpet under the bipod legs.

and the targets:

 

[Deer hunter]

From looking at your data you have a node at 56 and 56.3 on your first shots I would stick around there and seat the bullet -2k off the lands and groves and I bet you can get sub moa shots. This is my wife gun I did it’s a ruger 6mm creedmoor 5 shots at a 100

 

[ericwh]

56 and 56.3 have the lowest SD and ES. But they really didn't shoot that great. And I can't get anywhere close to the lands with this bullet and rifle.

How can I ignore 56.9?! That group is .32" center to center. The deviation and spread is only slightly worse than 56 and 56.3 and I don't have the greatest amount of confidence in my chronograph.

I will shoot 5 shot groups of 56.9 and 56.2 at 400 yards over the chronograph.

 

[MrTim]

I wouldnt stress about the amount of bearing surface in the neck at this point if thats the only thing keeping you from loading longer than book coal.

 

[Deer hunter]

That group is awesome. I had a cheap chrono at first and I had to upgrade to a magnetospeed and that helped me out a lot and also neck tension.

 

[ericwh]

I wouldnt stress about the amount of bearing surface in the neck at this point if thats the only thing keeping you from loading longer than book coal.

How far can I push this without causing issues? At book length I have ~.300" of bearing surface in the neck and I am .098" away from the lands.

If I were to seat .005" jump I'd have .207" of bearing surface in the neck.

 

[ericwh]

Well today was less than inspiring.

56.9 - 10 rounds at book length
56.2 - 3 rounds at book length
56.2 - 3 rounds .04" longer than book length
56.2 - 3 rounds .08" longer than book length.

Accuracy: At 100 yards, 56.9 group was not as good as last time but still best of the 4 options. Seating depth variance on the 56.2gr charge didn't show much promise at 100 yards.

SD/ES:
For 56.9, SD was about the same, ES got a little worse.

It definitely seems like the SD and ES data is repeatable and definitely best between 56 - 56.3 area. If I lump the book length and the +.04 length of 56.2 together I get SD of 7 and ES of 16 which seems quite good (for me). The SD/ES of the +.08 length was significantly worse so I didn't group it with the other two.

I shot 4 shots of the 56.9 at 400 yards and it was pretty disappointing. The velocity spread was only 50, which according to my calculator would be less than like 1 inch of spread... So I don't know what to make of that.

Not sure where to go from here. Probably load some more 56.2 and shoot them at distance?

 

[MrTim]

I currently have 180 grain NPTs seated .250 into the neck. I haven’t had any issues with the bullets not staying secure in cases in the magazine under recoil. I seated even shallower with the old Speer Grand Slams and didn’t not have any issues either. YMMV

 

[ericwh]

My longest cartridge (.080" over book length) had bearing surface ~.160" in the neck = SD of 37 and ES of 74. So I'm thinking that's too little bearing surface, maybe causing inconsistent neck tension?

.040" over book length had bearing surface ~.200" in the neck. SD 7 and ES of 12 so that still seemed fine.

I'm thinking I could've skipped over something accurate in my seating test? Were my increments too large? I got the increments from Berger testing suggestions. Maybe I will try 56.2 at smaller seating depth increments - I see .003" recommended...

 

[ericwh]

I've been following this series of articles on the subject of seating depth and I think I'm going to try between Book Length (.098 of jump) and .045 of jump, in .010" increments. 4 shot groups. I will exclude .058" of jump as I have already shot it. So that will be another 20 shots bringing my total to 67...

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

 

[MrTim]

Going back to square 1 with seating depth...
My recommendation would be seat as long as you can and still fit in your magazine. Use this as your baseline and work back from there adjusting seating 0.015” increments. If you aren’t limited by magazine length then use the lands as your baseline, again working back from that point in .015 increments.
Since you are using a bullet with a soft point, you would benefit from using a comparator that measures from the bullet ogive instead of the tip.

 

[ericwh]

I am measuring from the ogive.

I am not limited by the magazine. I am limited by bearing surface in the neck before I get close to the lands.

.080 longer than book length is 2.798 cbto and had a jump of .018 to the lands but only had .160 of bearing surface in the neck.

 

[ericwh]

Think I got somewhere. I just did a seating depth test in .005" increments. I was hoping to find 2 consecutive depths that performed better than others. My thought is this if I seat at the longer of these two lengths I will move from one to the other, maintaining performance, as the throat erodes .010" over a couple hundred rounds. That way I can load a couple hundred and not worry about it.

Important to note that .018, .058, and .098 were shot on a different day (previous post). My .005" test went from .063"-.083". I am going to load at .078" jump.

These jumps are large because of bearing surface limitations with this rifle/bullet combination: