Load Development Question

[64Rambler]

In 2 Different Cartridges ( My 6 XC and, 6.5 Creed ) I found that, the BEST Powder / bullet accuracy Nodes were about, One to 1 1/2 grains, under Max charge, of StaBall 65, produced the Best, REPEATABLE, Groups.
I'd replay, Powder Loads,.. #4, #5 and, #6 with some Bullet,.. "Tuning".
Some Bullets like to be, "Jammed" others,.. .050 to .130 "Off" Jam point.
Keep in Mind that that, the 7 MM-08 chamber reamer, HAS a 3* Throat angle and HATES "Some" VLD style, Bullets. My Son had good Luck with, 150 grain, Sierra GK's and, Hornady ELD-X's "Jumped" .060 / .070

I had Manson grind a custom reamer with 0.100" Freebore @ 0.2841" rather than 0.2845", and 1.5* leade,
Here's Load #6 with a much deeper seating depth range. Still not happy with group size - maybe this bullet isn't going to happen... have longer seating and 2 other powders to do a quick check before giving up.

	2	3	4	5	6	7
Jump	0.035​	0.040​	0.045​	0.050​	0.055​	0.060​
CTBO	2.215​	2.210​	2.205​	2.200​	2.195​	2.190​
47.00​	2772​	2789​	2745​	2773​	2756​	2781​
3X	2758​	2760​	2761​	2738​	2763​	2773​
	2745​	2781​	2776​	2765​	2767​	*
Avg	2758.3​	2776.7​	2760.7​	2758.7​	2762.0​	2777.0​
ES	27​	29​	31​	35​	11​	8​
SD	13.50​	14.98​	15.50​	18.34​	5.57​	5.66​
Group Size	0.550​	0.673​	0.701​	1.077​	0.945​	0.684​
2 touching @	0.185​

 

[Idaho-Lefty]

Great !!
You have, a MUCH better, Leade Angle than, my son's Rifle, had !
And a Shorter ( .100 ) Free Bore you might TRY backing Off the Powder about, 1/2 grain and Jamming, this Bullet .010 to .015 ( Light Jam ).
If that, doesn't "Work" ,.. switch to, another Bullet.

 

[Dimner]

I agree that 47.8 is the one to investigate. Further. You have similar horizontal POI with the load weights before and after it. As well as a close to similar POI two load weights before 47.8. That's the key to this method, showing that you gave a stable load and can be further refined by seating depth testing. Good luck!

 

[Idaho-Lefty]

My son's 9.25 Twist, 3 * throat, did NOT Like the,.. Long, High BC, 162 grain, Horn. Bullets !
You may need to Try, the Sierra 150-160's or, the shorter, Hornady 150 gr. ELD-X's or, M's.
Might look seriously at, the Sierra #1915 for,.Target / Steel or,.. #1920's.

 

[Idaho-Lefty]

After pulling most of his Hair out with, the 7mm-08 and 162's gr. eld-x's, my son ended up with, a 7 PRC, Proof barrel, 8 Twist, that shoots, High BC, 180 gr. ELD-M's , in the low, 3's to 4's.

 

[Fuj]

Hows the pressure ?? When I was still fooling with the 7/08, my loads
were 2810 fps with Reloder 16 and the 150 SMK. .140 freebore on a 10
twist Hart. Doing my part, I could clover leaf the groups. I had since
wild catted the 284 Winchester down to 7/08 length and currently
running that in 9 twist Lilja with a .200 freebore I call it my SA284.
BR2 primer, 50 grs. H-4350, 150 SMK, in .005. Easy bolt lift. It's my
7/08 on steroids......Note.....A talk with Sierra has me informed that
the 150 SMKs should be back online, first quarter of this year.

With your .100 freebore and 9 twister, drop down to a 140 Berger and
get some Varget.

 

[Idaho-Lefty]

@ Fuj,.
Why shouldn't, the OP be shooting those, 150 gr. SMK's, too ?,.. IF, he can find them,.. in his 9 twist bbl. ??
They should shoot every bit, as good as, most Berger's do and are, quite a bit, cheaper.
The 7-08 really "Hum's" velocity wise with, StaBall 65 as it's, a 4350 Burn rate, powder.
StaBall 65, shoots pretty Small, in my 6 XC and 6.5 Creed with, medium to heavy bullets at, near Max Velocities.

 

[Fuj]

As it is, he would be better off with the SMK's. I don't shoot Bergers
at all. I just mentioned the 140 to get some speed up and again work
with his .100, and keep the bullet above the neck/shoulder junction.

Keep checking the Sierra site itself for when that bullet comes back in
stock.

 

[64Rambler]

Hows the pressure ?? When I was still fooling with the 7/08, my loads
were 2810 fps with Reloder 16 and the 150 SMK. .140 freebore on a 10
twist Hart. Doing my part, I could clover leaf the groups. I had since
wild catted the 284 Winchester down to 7/08 length and currently
running that in 9 twist Lilja with a .200 freebore I call it my SA284.
BR2 primer, 50 grs. H-4350, 150 SMK, in .005. Easy bolt lift. It's my
7/08 on steroids......Note.....A talk with Sierra has me informed that
the 150 SMKs should be back online, first quarter of this year.

With your .100 freebore and 9 twister, drop down to a 140 Berger and
get some Varget.

With H162 ELD-M, SB 6.5 @2.215" CTBO (0.035" off lands) I was seeing signs of pressure at 48.1 gn and 2860 fps with 1 of 3 hard bolt lift. 48.4 gn gave me 2870 fps, all hard bolt lifts and a clicker. 47.8 is listed max at 2810 fps, I was seeing 2821 from that load at 12', 2839 corrected to the offset I was getting with a Garmin.
With 150SMK, I was getting 3 touching with a low load of IMR4350 at 2660 fps.

 

[dkhunt14]

Agree. If it posts, this was from fireforming primed Norma brass using Sierra MatchKing 150 gr, 0.016" from touching the lands (brand new barrel) with 14 yr old IMR 4350, a low load of 45 gr, MV at 2660, ES of 72 (3 shot groups are touching at 100 yds). Not sure what happened on shot #6 (x-ring), but I KNOW I pulled #10, so the rest are in a vertical column matching the ES, but width-wise it's less than 1 moa. This is why I'm hesitant to go straight to the smallest group. I'd be happy with a group that's only as tall as this is wide, hence the focus on ES.
Unfortunately, I am just about out of the SMK 150's, and they seem to be unobtanium now, as are Bergers. I can get rudolf's all day long, so trying to make it work with those. See updated original post for current load details.
Thanks for the reply.

You really need to shoot it at 3 or 400 yards. It's not far enough that you can't keep conditions under control somewhat, but far enough to see what 100 yards can't show. Matt

 

[J_idaho]

Observations,
150gr smk group size average.67”

162eldm group size average .95”

162eldm after seating .82”

Also I would like to note you probably shouldn’t be seeing pressure signs unless your brass is not completely fire-formed and your jamming bullet. I wouldn’t set shoulder back until 3rd firing. You say they changed lead angle to 1-1/2 from saami 3. But your rifle shows signs of not liking vlds. I would visit smks or Berger classic hunter hybrids

 

[64Rambler]

Observations,
150gr smk group size average.67”
View attachment 1513163
162eldm group size average .95”
View attachment 1513164
162eldm after seating .82”
View attachment 1513165
Also I would like to note you probably shouldn’t be seeing pressure signs unless your brass is not completely fire-formed and your jamming bullet. I wouldn’t set shoulder back until 3rd firing. You say they changed lead angle to 1-1/2 from saami 3. But your rifle shows signs of not liking vlds. I would visit smks or Berger classic hunter hybrids

Thanks for your input and group analysis. What software or app do you use for this? The 1/11/24 targets were from once fired brass and didn't need bump to get the bolt to close. There's also the possibility that this powder may not be what the barrel likes. I shot a few groups with IMR4350 and H4350. IMR gave me a bigger group than SB 6.5 and H4350 gave me a noticeably small group than SB 6.5. I also followed Berger's method for gross seating depth and got a couple pretty small groups...

 

[J_idaho]

Thanks for your input and group analysis. What software or app do you use for this? The 1/11/24 targets were from once fired brass and didn't need bump to get the bolt to close. There's also the possibility that this powder may not be what the barrel likes. I shot a few groups with IMR4350 and H4350. IMR gave me a bigger group than SB 6.5 and H4350 gave me a noticeably small group than SB 6.5. I also followed Berger's method for gross seating depth and got a couple pretty small groups...

SubMOA app
I see why you’re not shooting the 150’s as they are no where to be seen.
I thought you said you once fired brass and then set back .002”. I’m just saying you may see higher pressures if cases are expanding more than .005” and inconsistent case sizes would affect velocities.

 

[64Rambler]

SubMOA app
I see why you’re not shooting the 150’s as they are no where to be seen.
I thought you said you once fired brass and then set back .002”. I’m just saying you may see higher pressures if cases are expanding more than .005” and inconsistent case sizes would affect velocities.

Yes, set back 0.002, but easy bolt close @ fired length. I debated leaving it at 0 because of the easy bolt, but decided on the bump. Should I only take it to easy bolt close?

 

[J_idaho]

Yes, set back 0.002, but easy bolt close @ fired length. I debated leaving it at 0 because of the easy bolt, but decided on the bump. Should I only take it to easy bolt close?

Honestly your probably fine I’ve just seen brass take 2-3 firings to fit a chamber if running light loads. The first time you fire it is when you’ll see higher pressures and sticky bolts if running closer to max load. I’d probably recommend loading up a few of the 150 smk with imr4350 and see if they shoot the same as they did the first time you shot them. If they don’t then maybe something else is causing the groups to open up. If they shoot the same then just find a different bullet and powder combo. I hope that makes since. You can’t assume it’s the ammo without retesting.

 

[64Rambler]

Honestly your probably fine I’ve just seen brass take 2-3 firings to fit a chamber if running light loads. The first time you fire it is when you’ll see higher pressures and sticky bolts if running closer to max load. I’d probably recommend loading up a few of the 150 smk with imr4350 and see if they shoot the same as they did the first time you shot them. If they don’t then maybe something else is causing the groups to open up. If they shoot the same then just find a different bullet and powder combo. I hope that makes since. You can’t assume it’s the ammo without retesting.

I just checked the remaining resized, once fired brass (26 cases) and found all were at 1.6230" +0.0005" (no minus) right where I set them to be, except 3 that were 1.621".
I did as you suggested with the SMK and IMR combo and found the same group size, and getting smaller as I went up in powder charge. For the H162ELD-M with SB6.5 powder ladder I did, I did not run into the same pressure signs at the same powder charges that I did with the new brass, so I may go back and find the new max load. I got a 0.376" group with one seating depth, but 0.003" on either side was 0.9"+ groups, so not there yet. I've read these ELD-Ms are quite sensitive to seating depth, but that's nuts.
With the single 3 shot group I got with H4350 and ELD-Ms at 0.385" (as in; I only loaded 3 rounds with this powder at a single seating depth), I'm definitely going to play with that powder some more.

 

[J_idaho]

I just checked the remaining resized, once fired brass (26 cases) and found all were at 1.6230" +0.0005" (no minus) right where I set them to be, except 3 that were 1.621".
I did as you suggested with the SMK and IMR combo and found the same group size, and getting smaller as I went up in powder charge. For the H162ELD-M with SB6.5 powder ladder I did, I did not run into the same pressure signs at the same powder charges that I did with the new brass, so I may go back and find the new max load. I got a 0.376" group with one seating depth, but 0.003" on either side was 0.9"+ groups, so not there yet. I've read these ELD-Ms are quite sensitive to seating depth, but that's nuts.
With the single 3 shot group I got with H4350 and ELD-Ms at 0.385" (as in; I only loaded 3 rounds with this powder at a single seating depth), I'm definitely going to play with that powder some more.

I know from personal experience that eld or vld bullets like to be close to the lands.

 

[64Rambler]

How many shots in the group ?? Was that ES of 62 spread around
or was just one shot way out of the norm ?? What powder and
bullets are you using, let alone equipment your shooting with ??
Most assuredly you can have an ugly group with a real tight ES but,
I think there is something else going on.

There was! I spec'd the reamer based on a bullet diameter of 0.2840" and tried the 6.5 Needsmore use of 0.0001" over bullet diameter for the freebore. In reality all the bullets I'm using are measuring (micrometer, not caliper) at 0.28420" and larger (Berger at 0.28450") so everything was interference fit or very close. So I got the throat opened up to 0.2845" and ended up with a bit more free bore in the process, now at ~ 0.155". Now I'm seeing that most of the 7-6.5 PRC (7-PRCW) chamber drawings are showing a freebore diameter of 0.2852"....

 

[64Rambler]

Fast forward a bit; the throat was way too tight and I was basically at interference fit for most of my rounds. Got that corrected, and gained some freebore length in the process, now at ~ 0.155" Couldn't get Staball 6.5 to shoot consistent, so tried a few other powders, the better looking of the groups coming from N555! On the SB6.5 inconsistency, same load, same seating depth, same cases and primers, one day I'd get in the low 2's, then next weekend I'd get high 6's and a variety of velocities and SDs. Per the suggestion, I followed Cortina's 100 yard load development, but Jam -0.020" was a mess, so I backed up a bit and followed Berger's gross seating depth test, and went from there, finding the smallest groups at ~0.045" jump, and consistent 3 range trips in a row. I did a powder ladder seated at the average Jam length, but also not consistent. (When seating at Jam, do you actually seat longer in the die and let the lands finish the seating every time, or do you seat to a CTBO?) So here is the target from a powder ladder with N555, Berger 168 VLD-Hunter (VLD-Target unobtanium at the moment) at 0.046" jump, and the chrono data to go with it. The question is, which load would you chose for seating depth adjustment? Length listed is CTBO, and 48.0 gn starting to get slightly firm bolt lift.
Thanks for your time.
Scott

 

[Straightshooter1]

Fast forward a bit; the throat was way too tight and I was basically at interference fit for most of my rounds. Got that corrected, and gained some freebore length in the process, now at ~ 0.155" Couldn't get Staball 6.5 to shoot consistent, so tried a few other powders, the better looking of the groups coming from N555! On the SB6.5 inconsistency, same load, same seating depth, same cases and primers, one day I'd get in the low 2's, then next weekend I'd get high 6's and a variety of velocities and SDs. Per the suggestion, I followed Cortina's 100 yard load development, but Jam -0.020" was a mess, so I backed up a bit and followed Berger's gross seating depth test, and went from there, finding the smallest groups at ~0.045" jump, and consistent 3 range trips in a row. I did a powder ladder seated at the average Jam length, but also not consistent. (When seating at Jam, do you actually seat longer in the die and let the lands finish the seating every time, or do you seat to a CTBO?) So here is the target from a powder ladder with N555, Berger 168 VLD-Hunter (VLD-Target unobtanium at the moment) at 0.046" jump, and the chrono data to go with it. The question is, which load would you chose for seating depth adjustment? Length listed is CTBO, and 48.0 gn starting to get slightly firm bolt lift.
Thanks for your time.
Scott

Before testing seating depth, I'd retest 46.4 - 47.0. If you get the same result (looking at group location and vertical dispersion), then try to improve with seating depth testing. IMHO