6gt

[John Glidewell]

I am testing N555 with 115 DTACs. Good case fill and some decent speeds. Looks like 2860 is going to be a good place to run them with 37.6 grains of N555. I am not seeing any issues with carbon but I have not run past 150 rounds before cleaning either. We have had good luck with RL16, RL15.5, H4350, N150 and Varget and they all work. The best numbers so far though have been with N555. Recorded 51 rounds with SD of 4.3. I have not been able to accomplish that with any other powders so far.

 

[CK1.0]

I don't believe H4831 will hit the minimum pressure threshold to seal the case before reaching 105% case capacity. I've been using H4350 and am planning on working up Varget due to the carbon issues I've been having with H4350.

"Minimum pressure threshold to seal the case"? WTF lol? That's beyond my expertise, please explain...

 

[Cascade Hemi]

"Minimum pressure threshold to seal the case"? WTF lol? That's beyond my expertise, please explain...

If you don't have enough chamber pressure combustion gasses will leak down the brass. It looks like soot on the shoulder and body.

 

[MilSpecOkie]

I'm wondering what would feel softer: ~33gr of Varget/SWPR versus ~38 of H4831..?

My experience is slower burning powders feel softer, less snappy, than fast burning powders.

This is untested and only GRTs guesstimates for H4831 with my case volume (44.1) and 27” barrel and 112 MB loaded 20K off the lands.

GRT says 38 grains should theoretically yield 2836 fps with 104% case fill and 86% burnt propellant. It would take over 45.1 grains at 120% case fill to get 100% burn.

My experience with anything much less than 90-93% burn and ES starts to suffer. I do believe the numbers would change slightly with actual testing, and would be surprised if it was a winning combo. If you try it report back. I have a jug of it and tried some in my 22 GT without much luck. Now that the barrel is broke in I might look at it again for $h!ts and giggles.

 

[CK1.0]

My experience is slower burning powders feel softer, less snappy, than fast burning powders.

This is untested and only GRTs guesstimates for H4831 with my case volume (44.1) and 27” barrel and 112 MB loaded 20K off the lands.

GRT says 38 grains should theoretically yield 2836 fps with 104% case fill and 86% burnt propellant. It would take over 44 grains at 120% case fill to get 100% burn.

My experience with anything much less than 90-93% burn and ES starts to suffer. I do believe the numbers would change slightly with actual testing, and would be surprised if it was a winning combo. If you try it report back. I have a jug of it and tried some in my 22 GT without much luck. Now that the barrel is broke in I might look at it again for $h!ts and giggles.

I agree that generally slower powder feels softer, but since one needs more of it to match the faster Varget/SWPR stuff (that lets one get away with using lighter charges), IDK what the net recoil "feel" would end up being as compared to each other...

I'm pretty much sold on trying to live in the 2750-2800fps range, that's all the speed I'm looking for. I feel like I might be able to get there with H4831... but what @Cascade Hemi mentioned about the soot and chamber not sealing is a little concerning lol.

Next time I drive by my LGS I might see if I can score a pound for experimentation purposes... I guess if it doesn't work in the 6GT I can use it with my 6CM barrels.

Does the H4831SC "short cut" have any advantages over the regular H4831 or vice versa (does the regular cut provide more case-fill)? I've never used it before.

 

[John Glidewell]

The N555 is very soft on recoil and cool burning. Our rifles are almost identical and my barrel is much cooler after a 10 shot string than hers running 33.4 grains of 15.5. And my 37.6 grain load of N555 is 103% case fill and 100% powder burn. Barrel life calculator estimates accurate barrel life just short of 3k rounds.

 

[CK1.0]

The N555 looks like good stuff for sure too. I've read some things about it and It's interesting stuff in that it's a new formula/compound that offers the power boost of double-base powders without all the unwanted heat, and yeah, supposedly cooler burning than the usual suspects like Varget and H4350.

I guess what I'm wondering is: since I'm not looking for a lot of speed, would I be better off running a slower powder that's better at filling the cases up, versus what I'm doing now, which is maybe teetering on the line before things go to shit, where I'm getting below 80% case-fill?

I really shouldn't complain, it's not like the difference between an SD of 3 versus a 6 is holding me back, but since I've decided that slowing things down is working better for me, I'm just wondering if there's a better way to do it.

 

[John Glidewell]

I can't say this with 100% certainty, but it seems the numbers are more consistent and lower with a better case fill. We tested a bunch of powders and bullets due to poor availability and wanted a #2 and #3 set up. The 33.4 of 15.5 is in the 90% case fill area and will get higher single digit SDs for 20 plus rounds compared to the sub 5s I have gotten with the N555 and heavier bullets. (110 Atips and now 115 DTACs). Some of the research we did in other disciplines talked about case fill of 96% or higher, so we went down the rabbit hole and looked at case fill. Again, not saying I can prove it 100% but it sure does seem like there is something to finding a powder with a burn rate that allows for good case fill. In our testing, they all worked and we were able to produce tiny groups and good numbers - but the N555 has provided the best numbers so far and super consistent performance.

 

[CK1.0]

Here's something hopefully someone can help with: when talking case capacity, what/where is considered 100% full?

Is it when/where powder reaches the bottom of the shoulder, the point where powder is compressed, or is it less a percentage of total water capacity?

Does anyone know what the case capacity for 6GT is supposed to be (ballpark, obviously Hornady vs Alpha will differ slightly)?

 

[MilSpecOkie]

CK

GRT calculates it by physical limits. The length of the case, bullet OAL, the COAL. The shorter the COAL the more bullet is in the case. So the 100% fill is dependent upon free bore available and bullet jump. The deeper the bullet the smaller the volume available.

The other part of the equation is the density of the powder being used. I know GRT used to get it from the manufactures before the owner died. It’s also something that can be tweaked in the program but I’ve never messed with it.

I’ve had two 6 GT barrels chambered with Alpha reamers using Alpha brass. 45.1 grains water is what they averaged by my measurements.

 

[John Glidewell]

^^^^ quick load is similar. My Alpha brass holds just over 46 grains of water. By my eye 100% case fill is somewhere around the case body / neck junction, maybe just above. At 103% powder is slightly below neck / shoulder junction.

 

[CK1.0]

CK

GRT calculates it by physical limits. The length of the case, bullet OAL, the COAL. The shorter the COAL the more bullet is in the case. So the 100% fill is dependent upon free bore available and bullet jump. The deeper the bullet the smaller the volume available.

The other part of the equation is the density of the powder being used. I know GRT used to get it from the manufactures before the owner died. It’s also something that can be tweaked in the program but I’ve never messed with it.

I’ve had two 6 GT barrels chambered with Alpha reamers using Alpha brass. 45.1 grains water is what they averaged by my measurements.

Interesting…

This might partly explain why my gun was shooting great even while having the base of the bullet fairly deep into the case… since doing that shrinks available case volume, it may have had the effect of pseudo upping my case-fill.

I think with the next batch of rounds I make for my current barrel I’m going to go back to jumping 50 thou while keeping my lower 32.5gr charge to see what I get… I’m curious to see if my SDs shrink or not, or if the MV changes much…

 

[Niles Coyote]

My barrel trends fast, that said I am jumping .060-.065 on beger 108EH and 109 Hybrid's with 32grains of varget.

freshly cleaned with shot one and two removed, shit last week.

Less clean and July temps.

 

[LR1845]

@Niles Coyote what was the velocities of shots 1 and 2?

 

[Niles Coyote]

@Niles Coyote what was the velocities of shots 1 and 2?

Sorry I'm on the road to the PRS final and don't have access to my log for exact numbers but with the cleaning method used here round one would be around 55-60fps slower than my average and shot two is around 40 fps faster than that and by shot three I'm back into my normal ES range.

Here I cleaned with Patch out and accelerator only and used a bronze between bore treatments.

 

[LR1845]

Sorry I'm on the road to the PRS final and don't have access to my log for exact numbers but with the cleaning method used here round one would be around 55-60fps slower than my average and shot two is around 40 fps faster than that and by shot three I'm back into my normal ES range.

Here I cleaned with Patch out and accelerator only and used a bronze between bore treatments.

Not a big deal I was just curious, Thanks

 

[MilSpecOkie]

Here I cleaned with Patch out and accelerator only and used a bronze between bore treatments.

Bore treatments, are you using HBN?

 

[CK1.0]

My barrel trends fast, that said I am jumping .060-.065 on beger 108EH and 109 Hybrid's with 32grains of varget.

freshly cleaned with shot one and two removed, shit last week.
View attachment 8262535
Less clean and July temps.
View attachment 8262541

2850fps from 32gr is pretty sweet.

Is the bearing surface of your 108/109s below the shoulder/neck junction running a 60-65 thou jump?

I’m wondering if my bullets are just long (112 Match Burners) or is my chamber short too (SAAMI/Proof prefit)? Because 60-65 thou off would probably put the base of my bullets below the start/bottom of the shoulder (though I’m not necessarily convinced that matters lol).

Ideally more jump usually work better for me in 6CM, so I’d like to jump as much as 100 thou if I could, but that’d put a whole bunch of bullet deep into the case (which again, might not matter).

 

[LR1845]

2850fps from 32gr is pretty sweet.

Is the bearing surface of your 108/109s below the shoulder/neck junction running a 60-65 thou jump?

I’m wondering if my bullets are just long (112 Match Burners) or is my chamber short too (SAAMI/Proof prefit)? Because 60-65 thou off would probably put the base of my bullets below the start/bottom of the shoulder (though I’m not necessarily convinced that matters lol).

Ideally more jump usually work better for me in 6CM, so I’d like to jump as much as 100 thou if I could, but that’d put a whole bunch of bullet deep into the case (which again, might not matter).

If your smith is local he can add free bore to your barrel and shouldn't need to put it into the lathe or even remove the barrel from the action...this is something you can do yourself as well...if you trust yourself to do it.

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[MilSpecOkie]

2850fps from 32gr is pretty sweet.

Is the bearing surface of your 108/109s below the shoulder/neck junction running a 60-65 thou jump?

I’m wondering if my bullets are just long (112 Match Burners) or is my chamber short too (SAAMI/Proof prefit)? Because 60-65 thou off would probably put the base of my bullets below the start/bottom of the shoulder (though I’m not necessarily convinced that matters lol).

Ideally more jump usually work better for me in 6CM, so I’d like to jump as much as 100 thou if I could, but that’d put a whole bunch of bullet deep into the case (which again, might not matter).

IME I’ve found that is you have sufficient neck clearance, like 5-6K, you can run the bearing surface below the neck/shoulder junction without a problem. If you only have 2-3K I find I may start to get doughnuts at the neck/shoulder junction after a few firings.

 

[4O6shootist]

2850fps from 32gr is pretty sweet.

Is the bearing surface of your 108/109s below the shoulder/neck junction running a 60-65 thou jump?

I’m wondering if my bullets are just long (112 Match Burners) or is my chamber short too (SAAMI/Proof prefit)? Because 60-65 thou off would probably put the base of my bullets below the start/bottom of the shoulder (though I’m not necessarily convinced that matters lol).

Ideally more jump usually work better for me in 6CM, so I’d like to jump as much as 100 thou if I could, but that’d put a whole bunch of bullet deep into the case (which again, might not matter).

112s in a 120fb chamber are going below neck shoulder by the time you get maybe 25-30k off lands. I much prefer the 169fb chambers.

 

[CK1.0]

If your smith is local he can add free bore to your barrel and shouldn't need to put it into the lathe or even remove the barrel from the action...this is something you can do yourself as well...if you trust yourself to do it.

Premium Uni-Throater Kit - Pacific Tool and Gauge

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pacifictoolandgauge.com

This isn’t a bad idea, though I’ve always felt it’s best to stay fairly vanilla as far as chambers go so one can piggyback off others’ data/experience… but it seems like the 6GT SAAMI chamber’s freebore is kinda short.

I might end up with that reamer though… I’ll try seating the bullets deeper first, but that might be where I end up.

I’m wondering what bullet George and Tom designed the GT around (thinking 105 hybrids)?

 

[CK1.0]

IME I’ve found that is you have sufficient neck clearance, like 5-6K, you can run the bearing surface below the neck/shoulder junction without a problem. If you only have 2-3K I find I start to get doughnuts at the neck/shoulder junction after a few firings.

Any idea how I can figure how much clearance I’ve got besides trial and error lol..?

(SAAMI looks like .274 and without measuring/off the top off my head I think my loaded rounds/necks are ~.272 or so… I can measure them later.)

 

[LR1845]

This isn’t a bad idea, though I’ve always felt it’s best to stay fairly vanilla as far as chambers go so one can piggyback off others’ data/experience… but it seems like the 6GT SAAMI chamber’s freebore is kinda short.

I might end up with that reamer though… I’ll try seating the bullets deeper first, but that might be where I end up.

I’m wondering what bullet George and Tom designed the GT around (thinking 105 hybrids)?

Most all SAAMI free bore's are short...I shot a 6BRA for a few years and after a bunch of adjusting free bore I had a reamer made with a .275 neck and .145 free bore....4 barrels and every one shot at 50 to 70 off both 105s and 109s...also shot several different calibers and I always had the best luck with big jumps.

 

[Malum Prohibitum]

This isn’t a bad idea, though I’ve always felt it’s best to stay fairly vanilla as far as chambers go so one can piggyback off others’ data/experience… but it seems like the 6GT SAAMI chamber’s freebore is kinda short.

I might end up with that reamer though… I’ll try seating the bullets deeper first, but that might be where I end up.

I’m wondering what bullet George and Tom designed the GT around (thinking 105 hybrids)?

I don't know the answer, but Tom's bullet is 103 grains.

 

[CK1.0]

I was looking here: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

…and looks like the bullet I’m using, 112MB, is 1.331” in length, as compared to a 105MB at 1.199” Hornady 105BTHP at 1.220”, 110 A-Tip at 1.307”, and a 105 hybrid at 1.282”…

So looks like the bullets I’m using are kind of long, and depending on ogive, the SAAMI freebore might play nicer with the shorter 105s, a Hornady 105BTHP would give me another 111 thou to play with, even a 110 A-Tip would give me another 24 thou (again, depending on ogive)…

 

[MilSpecOkie]

Any idea how I can figure how much clearance I’ve got besides trial and error lol..?

(SAAMI looks like .274 and without measuring/off the top off my head I think my loaded rounds/necks are ~.272 or so… I can measure them later.)

Measure the necks of loaded and fired cases and subtract the loaded from fired. If you have a powerful ejector spring make sure the neck isn’t dents from that or hitting the ground. Measure a few just to me sure.

 

[4O6shootist]

Any idea how I can figure how much clearance I’ve got besides trial and error lol..?

(SAAMI looks like .274 and without measuring/off the top off my head I think my loaded rounds/necks are ~.272 or so… I can measure them later.)

Alpha reamers are 274 neck. New loaded neck diameter is 269. After 6 firings it's 270 on the lower half my necks now due to some brass flow. Still no issues. 22gt is the problem child on neck clearance. Alpha finally went to a bigger necked reamer a month ago, I told them there was a problem in January of last year.

 

[Niles Coyote]

Bore treatments, are you using HBN?

No, just referring to my applications of patchout and accelerator between brushing.

Is the bearing surface of your 108/109s below the shoulder/neck junction running a 60-65 thou jump?

Not in this .0170 alpha chamber, I forget how the Alpha .120 chambers lined up but if it was, it didn't cause problems.

 

[CK1.0]

I forget how the Alpha .120 chambers lined up but if it was, it didn't cause problems.

I didn't notice that I had my bearing surface below the shoulder/neck junction for like 900, maybe 1200 rounds lol. I loaded the first 300 to whatever the average SAAMI COAL is on virgin brass and shot them (low charge, baseline MV, stabilize barrel speed). Cleaned it, measured the distance to the lands, learned they were .050" off, they shot great so I just left it there... didn't even consider the bearing surface, base of the bullet, blah blah blah.

Then one day I was reading something about reloading somewhere and it was mentioned (along with donuts forming) and I was like "oh shit, oh yeah, that" lol.

Still not sure it matters. I've got 150 loaded now that are 10 off that I may just seat deeper to see what I get.

 

[combatgrunt84]

Does the Berger book have any factory data for the 109s in 6GT?

 

[mdram]

Does the Berger book have any factory data for the 109s in 6GT?

no, i called and got this

 

[357Max]

Does the Berger book have any factory data for the 109s in 6GT?

Not on their list, but N555 was the first powder I tried.
38.6 = 2920 with 109 LRHT @ 2.588". Shot so well I've never tried another powder.

 

[combatgrunt84]

no, i called and got this

Awesome thanks.

 

[Malum Prohibitum]

Does the Berger book have any factory data for the 109s in 6GT?

no, i called and got this

That only matters when they start producing 109s again.

 

[combatgrunt84]

I got 2k in the last week from various venders

 

[4O6shootist]

That only matters when they start producing 109s again.

They just ran 105s, 109s be hitting now.

 

[MDof2]

curious if anyone is running varget with 105's. what your load and speed are?
im currently running 34gr under a 108bt for 2880 from a 24", but may try some 105's

33.6 of Varget pushing a 105 Hybrid 2850ish. I was jumping them .040 or so when I started 2100 rounds ago and haven't looked back.
Still hammers.

 

[combatgrunt84]

Anyone have the Berger Load sheet for 6GT with the 108's before I call them tomorrow afternoon?

 

[Landon4]

What powder are you using

 

[combatgrunt84]

Varget or h4350

 

[Landon4]

I’m shooting the 108’s at 2880 with 33.7 of varget out of a 26” hawk hill 7.5 twist with cci 450’s, just for a reference if your interested

 

[NiteQwill]

Anyone have the Berger Load sheet for 6GT with the 108's before I call them tomorrow afternoon?

Load it with 31.5 to 33.5 gr of Varget and it will shoot bugholes.

 

[mdram]

Anyone have the Berger Load sheet for 6GT with the 108's before I call them tomorrow afternoon?

berger said it uses the same data as the 109s i post up the page
but i am using 34gr of varget

 

[Bigd7378]

 

[Malum Prohibitum]

So for Varget there is a three grain variance from short load to max. And max velocity is 2857.

I wonder what powder Hornady is putting in their Match cartridges that is driving the 109 Hornady bullet to 2950 or so.

 

[mdram]

So for Varget there is a three grain variance from short load to max. And max velocity is 2857.

I wonder what powder Hornady is putting in their Match cartridges that is driving the 109 Hornady bullet to 2950 or so.

this is what i got from a 24" barrel
108bt and varget

 

[Malum Prohibitum]

this is what i got from a 24" barrel
108bt and varget View attachment 8285602

Wow, that is very different from what is published. And your bullet is only one grain different.

 

[mdram]

Wow, that is very different from what is published. And your bullet is only one grain different.

but its more inline with what hodgdon has

 

[combatgrunt84]

Need's ya'll .02 on this matter.

I just got my MPA Matrix Pro 6GT on Friday did some loading at found out it liked this load of Varget with 109's the best. I'm not an expert shot by any means the one small group was a shear fluke lol I average the other two maybe a little smaller with my other rifles. My Velocity was from inconsistent across a few strings and my SD's were like 15 for each string. But these are my groups I shot 5 at 200yards (Max range) and they all stacked into a nice SUB-MOA group without any issues. I'm not a pro PRS Guy just regional matches. I'm thinking it might be the primers maybe? I was going to load same load with my CCI BR-4 and Federal AR Match that I have to see if that helps. My Labrador though was kicking mud butt still working on getting used to using it would not pickup a lot of the shots was only getting like data on 2 or 3 of the 5 if that so I think it was moving because of my muzzle brake or rocking on the bench. All shots were at 100yards with bipod and rear bag today its 54f little wind, but misty.

I measure the OAL of the bullets today they are from 1.270 to 1.289 big difference from Bergers
Load:
Varget 34.0 (Auto Trickler v4)
Berger 109 (Meplat Trimmed)
COAL: 2.605
Lands: 2.620
Jump: .15
Alpha OCD Virgin Brass ( resized it before loading)
Remt 7 1/2 BR Primer
Lab Radar