Oops, that was unclear. Before hearing about the GT, I was looking forward to the velocity gain of an improved BR or 6 Creed.
6GT project/range report
- Thread starter NorCalVu
- Start date
Fired first 66 rounds yesterday from barrel I spun up. Will post better detail later.
Overall I'm happy.
6gt, alpha brass, 109Hybrid, cci450 primers, GAP reamer, Hornady dies, 26" Bartline 7.5T heavy palma, tikka action.
1. GAP reamer, headspace gage, Hornady dies seem to fit hand-in-glove with each other.
2. Settled on 34.00gr varget, 2.554" COAL. This is 0.030" jump with the boat tail-shank junction right above the neck-shoulder junction.
3. SD (stdev.s ()) of 8.1 fps for the loads I measured charge weights on my gempro250. Sample size is 18 shots, four different seating depths.
4. Audette ladder test 33.0-35.2gr in 0.2gr increments. 35.2 great varget gave 3040fps 5 shot average, but bolt lift was stiff and I could see slight ejector swipe.
5. Looked at data, decided to back down to 34.0gr as there seems like a slight inflection in the velocity there. Focused remainder of loading there. Hodgdon''s published load for 34.2gr varget, 110Atip, and 24" barrel is 2880, so adding 20fps per inch of barrel I think I'm right in line.
6. Yes, you can reach GAP advertised velocity, but I think it's hard on the brass and my primers were starting to extrude a little bit. I would like to try Staball 6.5 next. A other 100fps at same pressure may be worthwhile. Lengthening the throat for the 109 may also lower pressure.
Overall I'm happy.
6gt, alpha brass, 109Hybrid, cci450 primers, GAP reamer, Hornady dies, 26" Bartline 7.5T heavy palma, tikka action.
1. GAP reamer, headspace gage, Hornady dies seem to fit hand-in-glove with each other.
2. Settled on 34.00gr varget, 2.554" COAL. This is 0.030" jump with the boat tail-shank junction right above the neck-shoulder junction.
3. SD (stdev.s ()) of 8.1 fps for the loads I measured charge weights on my gempro250. Sample size is 18 shots, four different seating depths.
4. Audette ladder test 33.0-35.2gr in 0.2gr increments. 35.2 great varget gave 3040fps 5 shot average, but bolt lift was stiff and I could see slight ejector swipe.
5. Looked at data, decided to back down to 34.0gr as there seems like a slight inflection in the velocity there. Focused remainder of loading there. Hodgdon''s published load for 34.2gr varget, 110Atip, and 24" barrel is 2880, so adding 20fps per inch of barrel I think I'm right in line.
6. Yes, you can reach GAP advertised velocity, but I think it's hard on the brass and my primers were starting to extrude a little bit. I would like to try Staball 6.5 next. A other 100fps at same pressure may be worthwhile. Lengthening the throat for the 109 may also lower pressure.
Last edited:
Shot about 160 rounds so far and still happy. With minimal effort, the 6GT is shooting a lot of small (0.4moa) 5 shot groups, and some 0.6-0.7moa groups with about 10fps SD.
I have been logging velocity with the Magnetospeed, and attached the data for 52 shots of 34.0gr Varget.
After 52 shots, SD rose slightly from origional 8 fps to 10.2fps, average velocity is 2029fps.
Attached is the data from the ladder test, and nearly every shot fired so far. I added in all of the 34.0gr data to see how well the first two shots fit into the curve. I personally think looking for "flat spots" in ladder testing with only 1 shot per charge it not enough data to form a solid picture due to SD. Even with SD's of 5fps, a single shot may be anywhere in a 20fps band.
Also, see the bell curve representing all of the 34.0gr loads.
Shooting all 5 shot groups, some have been in the 0.3's but the group average after 50 shots is closer to 0.7MOA. I need to start using one of the target analysis software packages and averaging all of the mean radial averages to get a better picture of my true accuracy.
I will stick with the 109 hybrids and 34.0gr of Varget for a while, at least until I finish the box of 500.
Room for improvement:
I'm getting fed up with my Gempro250 and Chargemaster 1500. I will have to upgrade my scales to start truly getting to +/- 0.02gr charge consistancy, and believe right now my loads are actually +/- 0.05gr. Based on the linearity of the ladder testing data equation, +/- 0.05 gr around 34.0gr charge only equals +/- 4fps.
The Hornady Die is sizing my necks more than needed. I will either try to lap 0.003" out of the neck, or get a bushing die. It also is not sizing the base enough to allow for a loaded round to drop-in freely. It take some finger pressure to push the round all the way into the chamber gage (I cut an extra chamber from the barrel drop).
I would also like to try a slower powder like H4350 or StaBall 6.5.
I have been logging velocity with the Magnetospeed, and attached the data for 52 shots of 34.0gr Varget.
After 52 shots, SD rose slightly from origional 8 fps to 10.2fps, average velocity is 2029fps.
Attached is the data from the ladder test, and nearly every shot fired so far. I added in all of the 34.0gr data to see how well the first two shots fit into the curve. I personally think looking for "flat spots" in ladder testing with only 1 shot per charge it not enough data to form a solid picture due to SD. Even with SD's of 5fps, a single shot may be anywhere in a 20fps band.
Also, see the bell curve representing all of the 34.0gr loads.
Shooting all 5 shot groups, some have been in the 0.3's but the group average after 50 shots is closer to 0.7MOA. I need to start using one of the target analysis software packages and averaging all of the mean radial averages to get a better picture of my true accuracy.
I will stick with the 109 hybrids and 34.0gr of Varget for a while, at least until I finish the box of 500.
Room for improvement:
I'm getting fed up with my Gempro250 and Chargemaster 1500. I will have to upgrade my scales to start truly getting to +/- 0.02gr charge consistancy, and believe right now my loads are actually +/- 0.05gr. Based on the linearity of the ladder testing data equation, +/- 0.05 gr around 34.0gr charge only equals +/- 4fps.
The Hornady Die is sizing my necks more than needed. I will either try to lap 0.003" out of the neck, or get a bushing die. It also is not sizing the base enough to allow for a loaded round to drop-in freely. It take some finger pressure to push the round all the way into the chamber gage (I cut an extra chamber from the barrel drop).
I would also like to try a slower powder like H4350 or StaBall 6.5.
Attachments
Also, feeding and ejection have been perfect so far from my tikka t3 and unmodified AI mags.
If a already had a 6x47L, this wouldn't make sense for me, but as an entry point to a competition focused 6mm cartridge, its been easy.
I want a slow twist barrel to shoot the lighter flat based varmint bullets for all of the 100yd and XTC practice I do. No sense in shooting $0.45 high BC bullets and burning up my comp barrel at 100yd when a $0.14 varmint bullet is very accurate.
If a already had a 6x47L, this wouldn't make sense for me, but as an entry point to a competition focused 6mm cartridge, its been easy.
I want a slow twist barrel to shoot the lighter flat based varmint bullets for all of the 100yd and XTC practice I do. No sense in shooting $0.45 high BC bullets and burning up my comp barrel at 100yd when a $0.14 varmint bullet is very accurate.
rwj
Gold $$ Contributor
The beginning of a great YouTube channel for shooters!
MikeMcCasland
Team Texas F-T/R
whatwind?
Silver $$ Contributor
That's my channel.
Glad you like it.
great job Mike, keep it up
Very cool video
Tried Winchester 6.5 StaBall powder with same primers, COAL as Varget, very happy and will make the switch. topped out at 3120fps, primers has small raised ring around the FP hole, so i will back down a bit. No sticky bolt or extraction issues. I will do another ladder between 39.8-40.5 grains in 0.1 grain increments to see if my data is repeatable, and get some 3-shot groups to check accuracy. The attached target is all 30 rounds shot at the same aiming point. 24 rounds in the same ragged hole!
Attachments
MikeMcCasland
Team Texas F-T/R
Anyone run N-150 in theirs?
You are
kindabitey
Gold $$ Contributor
I did. Hit pressure at around the 2870 mark w/ Alpha brass, 450s, and 105 hybrids. Fairly low case fill. I'd have to check my notes to be sure.
N555 seems to be showing some promise with 105s and 115 Dtacs.
It's quite funny you said that about the 40 degree shoulder ,I have been running what I call I 6 / 47 40 degree shoulder .100 thousands short since about 2012 in 600 and 1000yd benchrest.
I make my case's out of 6.5x47 lapua brass.
Attachments
TAJ45
Silver $$ Contributor
115s You say? What is your tw rate? Any promise showing up in the groups? Velocity w them?
kindabitey
Gold $$ Contributor
I only did 5 shots, at .5 gr increments, to find a pressure point. I'll check later today, and pass the findings on. I do remember that all five end up right around 1/2" and somewhere in the upper 2800 range.
26" 7.5 twist Bartlein from Stuteville.
I'm using up the 105 Hybrids I have on hand to finish up my current barrel, and plan to use Dtacs and N555 in the next.
kindabitey
Gold $$ Contributor
Finally found my notes. It won't be long before I can hide my own Easter eggs
This was with VV N555/ 115 Dtacs at -.030
34.5- 2808
35.0- 2810
35.5- 2831
36.0- 2831
36.5- 2854
And this is the 5 shots.
This was with VV N555/ 115 Dtacs at -.030
34.5- 2808
35.0- 2810
35.5- 2831
36.0- 2831
36.5- 2854
And this is the 5 shots.
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