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Post by mosigdude on Jun 9, 2015 20:38:15 GMT -8
Before I get into details, and I will but I just don't want to lead anyone, I want to ask a question: Those of you shooting the 6.5x6.8 and the Nosler 123gr Custom Competition bullet, what is your barrel twist rate, what is your measurement to the lands and what is your loaded OAL? I'm having performance issues with this bullet using 8208 and everyone else seems to be enjoying success with it. I guess maybe include your velocity notes on your most accurate as well, although I think I'm in the ballpark on this aspect.
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Post by Deleted on Jun 10, 2015 15:12:04 GMT -8
Before I get into details, and I will but I just don't want to lead anyone, I want to ask a question: Those of you shooting the 6.5x6.8 and the Nosler 123gr Custom Competition bullet, what is your barrel twist rate, what is your measurement to the lands and what is your loaded OAL? I'm having performance issues with this bullet using 8208 and everyone else seems to be enjoying success with it. I guess maybe include your velocity notes on your most accurate as well, although I think I'm in the ballpark on this aspect. If the 8208 combination is not giving you the results your looking for, try a different powder. CFE223 has worked well for me. It's a dense ball powder and will give some excellent velocities. I have also read that H335 is working well for this application.
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Post by mosigdude on Jun 10, 2015 19:08:40 GMT -8
Ok, I'll post up my whole process and let everyone theorize...
I just received a 22" BHW 6.5x6.8 1:9 Twist, Standard Profile, Target Crown barrel. I built this into a pretty basic upper. The receiver has been lapped true at the barrel threads and the barrel was "bedded" into the upper with the usual blue locktite routine. The upper is fitted with a BTE adjustable gas block and a free-float handguard. I have the upper assembled with a M16 carrier and a standard 6.8 bolt. I set this onto a fixed-stock A2 Lower with standard Buffer, buffer spring and it is fit with a 2lb Jard Trigger. For load-development, I always use a high-magnification target scope and this one, for this purpose was fit with a Mueller 8-36x target scope in a solid 1-piece mount (I don't recall the brand, but I just leave this scope in the mount and have used it on bunches of AR's for load development). So that is the setup...
Before putting loads together, I fired a few known-safe loads and made a modified case for my Hornady OAL measurement tool. I also used the Hornady Headspace tool to measure and set my sizing die to bump the shoulder back .004 over a fired case. All cases were prepared together and processed the same. I started with new Federal pull-downs, sacrificed the primer that they came with, removed the crimp and uniformed the flash hole. All were trimmed to minimum length spec for 6.8SPC All were sized to provide somewhere between .002 and .003” neck tension with the appropriate bushing.
The bullets I'll talk about have the following measurements to the lands in my barrel (checked 10 different bullets in each, all measured .001 plus-or-minus in each):
Hornady 95gr Vmax 2.335"
Nosler 123gr Custom Competition 2.360"
Nosler 120gr Ballistic Tip 2.380"
Sierra 120gr Pro Hunter 2.285"
I used the 95gr Vmax to work up a known-safe load for break-in and to do rough adjustments to get the scope on paper and also to get a general setting on the Adjustable Gas Block. These are flying in the low 2600FPS, I did not do a ladder test on these since I didn't intend to use these for anything other than above.
The remaining I loaded as ladder tests stopping at 28.5gr of 8208XBR
I loaded all except the Sierra Pro Hunter to 2.300" I loaded the Pro Hunter with a .010" Jump to the lands.
Prior to shooting all rounds, I verified that none of the bullets were seated with the bullet ogive into the case at the loaded length.
Yesterday was 85 degrees F and calm wind. I set out to do my barrel break-in and first round of load development.
Barrel break-in and gas adjustment went well, as a bonus, the load I randomly picked for the Vmax grouped at about 1-1/4" at 200 yds
For the remaining testing, I cleaned before each test group and fired a few 'fouling loads' before each load test.
First up was the 120 Ballistic tip, I ended up with one group just a touch under 1/2" @ 200 and the largest of the remaining in the ladder test was just over 1-1/4", so on a positive note, I have a load already that will shoot out of this barrel!
Next was the 120 Pro-Hunter. This was very unimpressive, groups ranged in the 3-1/2” to 4” range also at 200.
Finally was the Nosler 123 Custom Competition. My first group of 3 had exactly one bullet near the center of the target backer… and no other holes (my backer is approximately 24” wide x 18” tall). I assumed I had dropped the reticule out of the scope and the scope was now probably FUBAR. In an effort to verify this, I fired the next group at a target at 100 Yds. All 3 were on the target backer but in a group a little over 8”. I then fired a group of 3 with my Vmax sighters, expecting them to be no better but to my surprise, a tiny cloverleaf! I fired the remainder of my ladder test with the 123gr Custom Comps and none were better than the second. Velocity readings with the 120 Ballistic Tip and 120 Pro Hunter were predictable, increasing as I moved up the ladder test. Velocities with the 123 were surprisingly high (not high overall, just high for the lower charge volume) with the lower ladder tests and all over the place higher and lower as the test loads increased. There was no significant average velocity change across 2-1/2 grains of powder difference. All powder charges were weighed and I started and stopped with the same charge weights for all 2 bullets, None showed any indication of excessive pressures. In looking at the targets for the 123 Custom Comp, I see no evidence of keyholing.
One other thing I noticed with this round of tests that I haven’t seen as much with other rifles is a very significant shift in point of impact with different bullets. For example, the 95 Vmax load was pretty much centered in the bullseye. The 120 Ballistic tips were about 8” higher (@200) and a little to the right, the 120 Pro-hunters were almost an equal distance below the POI of the Vmaxes. The 123 Custom Comps were all over the place so I can’t really say how they compared. Anyhow, I’m not sure that the POI shift matters as they seemed to group well once adjusted (with the bullets that worked well anyhow) but I just haven’t seen this much difference in other rifles.
Everything on the rifle seems snug and function, other than accuracy, is flawless.
Finally, I guess I should add, I used this same lot of bullets a few days prior in a 264LBC workup using the same barrel twist and a slightly slower velocity and got good results with this bullet in that test.
Ok, so pick apart my process. While I’m glad I have a load that works (the 120 Ballistic Tip), I’m very confused of the huge difference in success with the 123 Custom Comp between my rifle and everyone else’s that seems to shoot lights-out with it. I would like to be able to shoot this high BC bullet out of this rifle and I know the AMAX isn’t an option in this cartridge. Ideas?
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Post by mosigdude on Jun 10, 2015 19:12:07 GMT -8
Before I get into details, and I will but I just don't want to lead anyone, I want to ask a question: Those of you shooting the 6.5x6.8 and the Nosler 123gr Custom Competition bullet, what is your barrel twist rate, what is your measurement to the lands and what is your loaded OAL? I'm having performance issues with this bullet using 8208 and everyone else seems to be enjoying success with it. I guess maybe include your velocity notes on your most accurate as well, although I think I'm in the ballpark on this aspect. If the 8208 combination is not giving you the results your looking for, try a different powder. CFE223 has worked well for me. It's a dense ball powder and will give some excellent velocities. I have also read that H335 is working well for this application. I read this about an hour before I went to work and quickly put together a few middle-of-the-rung loads with CFE223 and the 123 Custom Comp. I didn't have time to set up a chrony so I don't know what speeds are but accuracy was not measurably better. I do very much like the powder but I don't think that's the issue in this set of tests.
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Post by GLSHOOTER on Jun 11, 2015 5:01:50 GMT -8
Good data report. This looks like a tough one. By chance after the CC's were going all over the place did you go back and shoot the known good ammunition?
Greg
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Post by mosigdude on Jun 11, 2015 7:23:55 GMT -8
I did, the Vmax "sighter" load was just a bit over an inch at 200 prior to the ladder tests, I didn't shoot it again at 200 after the ladder tests because I had already moved my target backer to 100 while attempting to diagnose the issue with the 123 Custom Competition load. As a final diagnosis I shot a 3 shot group with the sighters at 100 and it was a tiny cloverleaf, very likely the same or maybe even slightly better than the load had been earlier in the day. I'm kind of stumped on this one, obviously rifles often show a preference but this is a huge variance in accuracy!
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Post by GLSHOOTER on Jun 11, 2015 8:32:54 GMT -8
I did, the Vmax "sighter" load was just a bit over an inch at 200 prior to the ladder tests, I didn't shoot it again at 200 after the ladder tests because I had already moved my target backer to 100 while attempting to diagnose the issue with the 123 Custom Competition load. As a final diagnosis I shot a 3 shot group with the sighters at 100 and it was a tiny cloverleaf, very likely the same or maybe even slightly better than the load had been earlier in the day. I'm kind of stumped on this one, obviously rifles often show a preference but this is a huge variance in accuracy! You verified the scope was GTG and that's a major step. I guess I'd be off to the powder shelf and possibly looking at some seating depth. Sometimes it's like noodling for catfish. You get bit a lot before the big one gets pulled out of the hole. Greg
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Post by mosigdude on Jun 11, 2015 9:09:17 GMT -8
I may have to play with powders just a bit more but I don't think I have a lot of option on seating depth, any deeper into the case and I'll be putting the ogive below the case mouth, any longer and I won't be able to feed from the magazine. Are my measurements to the lands close to everyone else's?
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Post by GLSHOOTER on Jun 11, 2015 11:33:03 GMT -8
It seems like your numbers are about right. I'll see what I have in my records. I think I recall Ritch telling me yours were close to his but that is just my memory working.
Greg
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Post by mosigdude on Jun 11, 2015 15:10:31 GMT -8
The variety of 100 grain pills seem to measure out quite a bit better in my chamber. None of these give me the high BC of the 123 Custom Comp but I'm going to try about 3 workups to get a baseline. I have the 100 Ballistic Tip, the 100 Amax and a 100 grain Hornady Interlock SP on hand, I'll begin with those I believe.
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Post by mosigdude on Jun 12, 2015 15:26:27 GMT -8
Last night I took some more measurements and decided to explore some of the 100 grain projectiles to see if that was the magic in my particular chamber. I had the Nosler 100 gr Ballistic Tip, 100 gr Hornady Interlock SP (Flat Base) and 100 gr Hornady AMAX on hand. All 3 can be seated at magazine length without seating into the ogive of the bullet. At magazine length the Ballistic Tip has about a 0.080" jump to the lands and both of the Hornady bullets are mid 0.040's. I loaded all at 2.300" and used IMR 8208 XBR in 0.3 gr increments from 29.9 - 30.8gr. I had previously done a quick batch of loads looking for pressure signs only and found 30.8 to be the first load I was seeing indications of pressure so I opted to go no higher in ladder tests. 30.8 is 0.1 gr over Hodgdon's max listing for the 100 gr Ballistic Tip in the 6.5 Grendel. At the conclusion of today's testing (80degree F) I saw beginning indications of pressure with all 3 projectiles with this charge weight so if I use this powder further I will not load this hot again. On to the results... MAGIC!!!! Everything today was at 200 yards and I had no need to back anything up. Not a single group today was over 1.5" (3/4MOA) and several were well under an inch. The best average went to the Nosler Ballistic Tip which clocked in in the mid 2700's - low 2800. The best group of the day was 0.41" with the Hornady Interlock with 30.5gr @ 2782fps avg. (@10ft) The 100gr projectiles all behaved like I am used to seeing, a slight shift in POI from projectile to projectile but nothing extreme like the 120-123gr tests I did. During velocity testing at the end of my day I fired all projectiles into a single point of aim, 3 different bullets, 4 different powder charges on each and 3 of each loading, so 36 projectiles total and all were in a group roughly 2" @ 100, not too bad for absorbing all the load variables of the day! I'm planning to revisit this test with at least one other powder but at least I have some loads that will shoot and I can continue my praises of the BHW name!
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Post by GLSHOOTER on Jun 12, 2015 16:20:53 GMT -8
You have the magic on those for sure.
Greg
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Post by mosigdude on Jun 12, 2015 19:05:49 GMT -8
I put this one together with the idea of it being a reasonable-length-weight rifle for hunting deer/pig class critters, so one of the goals was/is to get as much speed out of it as possible within safe pressure limits. I'm liking that the two hunting-class bullets that have turned out to be the most accurate are also most accurate at or near their max load!
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Post by mosigdude on Jun 16, 2015 8:45:10 GMT -8
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Post by GLSHOOTER on Jun 16, 2015 10:57:33 GMT -8
That is a sweet thread. Thanks for the results. I need to go buy some more varied 6.5 bullets. I have a couple groups I'll post up later from a down and dirty quick test. Geg
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