Nice beautiful build! I’m itching to try the centurion myself was looking for a while in PX than the TCS came up first.
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6mm BRA
- Thread starter cjherrman
- Start date
30 grains of varget is my fireforming load, at 2850 fps, .020 off the lands it shoots lights out.
Went out today and fire formed another 40 rounds. 29 Gr of IMR 4064 with a Hornady 105hpbt jammed .010". Average speed was 2760fps out of 26" PVA barrel.
I’m trying jamming because the chamber seems to be slightly long and I do not have a crush fit on virgin brass.
Few small hiccups on this build so just trying to eliminate a few variables and see if it improves forming.So started some load development the other day. Was mainly just doing a velocity test to see what it would do. All groups were shot with a magneto on barrel so im not sure how dependable they were.
Fireformed Lapua brass
Berger 105 hybrid
Varget
CCI 450
.020" off lands.
I noticed I started to get a little bit of bolt lift at 32gr. Dunno where im going to go from here but looks like might be worth playing around 30.8 or 31.5.
Fireformed Lapua brass
Berger 105 hybrid
Varget
CCI 450
.020" off lands.
I noticed I started to get a little bit of bolt lift at 32gr. Dunno where im going to go from here but looks like might be worth playing around 30.8 or 31.5.
I ran 31.4 in my old BRA barrel and that was a good node for it with 105's and 109's.
It does for sure lol but dunno if it was just luck yet .
Temp of 37 that day so I’m sure things might change a bit when it warms up but trying to get this ready for a club match next weekend.I’m thinking loading up both 30.8 and 30.4 and shoot a cpl groups of each. One for chrono results and another for groups. I’m kinda wishing I had a Labradar right now.
My Varget match load with a 105 Hybrid is 30.6-30.8. I ran in the mid-31 grain range for about half a barrel early on and while it was good initially it eventually got pressurey with bolt lift in dusty/adverse conditions. I would stay well short of 32 grains.
2865-2880 has been a very good node for me over multiple barrels. Current barrel has 2200 rounds, still shoots a ragged hole, was able to win our PRS regional match last weekend with it.
Looking solid!
This is the main reason I bought a labradar. My Magnetospeed never had an issue, but being able to load dev without it being attached is great.
Keep searching, you’ll find one. Definitely worth it.
This is the main reason I bought a labradar. My Magnetospeed never had an issue, but being able to load dev without it being attached is great.
Keep searching, you’ll find one. Definitely worth it.
That's good to hear. Im a little concerned that when the temps warm up another 40 degrees that 30.4 range might be getting a little warm. Its good to see that my numbers are pretty much lining up with most here are seeing for nodes goes to show I am not a complete idiot!
I see the slow shot in the 1st group was 2744 while the other two are 2826 and 2840, I can only imagine it's also the shot on target with the ? beside it. Was this a pulled shot, or was the trigger broken at the same POA as the others?
Your very observant! I have no clue what happen to that one but that was also the cold clean bore. Shot felt good so only thing I can think is either it was because of being the cold clean bore or I fucked up on charge weight.
All these rounds I dumped on a chargemaster light but .2gr under goal than I hand trickled on a beam scale. Tedious for sure but I wanted to get the most accurate weights I could at the time.
I have a barrel that is markedly slow after cleaning. Like 80-100fps as well, but I haven’t noticed that much of a POI shift. It’s also a 1.25” Ø straight. If that is indeed the slow shot that went high, it would be interesting to see if you can force it to do that on command with a charge weight that runs 2740, and if that keeps the same POI. That would just about prove positive compensation is possible.
I know it’s not apples to apples but I was running roughly 2760 forming this brass but with hornady 105s. This was first time shooting the hybrids and I never adjusted scope.
I honestly don’t know what happened I’d like to beleive I wouldn’t shank it that bad but maybe I did.
So do you guys think it would be more beneficial to shoot these groups at 200 versus 100? Brainstorming here
I do not think so, you should see similar results at 100 and 200 when figuring out what seating depth shoots best. Have you checked out the results that mr. Gordon at SAC wrote about with the long bullet jumps?
Thanks for reply. Yes I’ve read it but I should go back and look it over again to freshen up. My plan is to shoot these and if I can keep it sub 1/2” ill be happy. Cutting it close as I’ve got first match this weekend. I can always play with more seating depth later on.
Have a 7.5tw 28" 237 bore hawkhill comp contour 6bra on the way for my Archimedes, chamber is a 274nk 0.140fb. Supplies on hand: 500pcs new alpha ocd 6bra brass, Wilson dasher fl bushing die with 085" cut off bottom. This is the smith's die and I may just get a harrells -3 die. Will just use my SAC "the seater" I have a lot of 8208, 4166, varget and RL15.5. 2k 107smk and 2.5k 108bt bergers. Going to attempt to use my ARC mags vs buying br specific units. I'm usually shooting my 6 or 22 gt in matches so this rifle will likely bear the brunt of the majority my practice sessions and loaning out to friends who want to try a match. This is the smallest cartridge I've ever played with, will be interestig to see how it performs compared to the much larger 6gt. I run a very low node in it, 2900 w/ H4350 in a 28" pipe. No bolt lift till 3120.
My bra cartridges did not feed well out of unmodified arc mags. Hope you have better luck then me.
Both, origin and impact actions. Phantom firearms had a spacer that I bought that helped a lot.
AI mags with Primal Rights kits = money. They have slightly longer feed lips than others. I'm still testing MDTs with the new anti tilt followers.
The low node looks like it’ll work. Didn’t run the magneto on these as didn’t want any interference with groupings but .030”-.040” off looks very good. Looking at my numbers this charge weight was average 2864 with a SD of 4.
First match this weekend so gonna load enough for match as well as 25-30 rounds to run over chrono this week.
First match this weekend so gonna load enough for match as well as 25-30 rounds to run over chrono this week.
I got my 6mm BRA back from the smith this week and did some load testing with it same day. The barrel should speed up another 30 fps, and it puts me right in the 2800 fps area I was wanting.
Winds were variable from 18mph to 30mph, so I was getting some windage spread with my shots. 107s shot ok, especially around 20-30 thou off the lands, berger 105 hybrids shot amazingly.
Lone Peak Fuzion
25.5" Hawk hill 1:7 barrel
Alpha 6 BRA brass
29.7gr Varget
105 hybrids / 107 SMKs (labeled in each picture)
CCI #450s
1.765" base to ogive
(Picture number two has a hole on the left from an adjacent group)
Winds were variable from 18mph to 30mph, so I was getting some windage spread with my shots. 107s shot ok, especially around 20-30 thou off the lands, berger 105 hybrids shot amazingly.
Lone Peak Fuzion
25.5" Hawk hill 1:7 barrel
Alpha 6 BRA brass
29.7gr Varget
105 hybrids / 107 SMKs (labeled in each picture)
CCI #450s
1.765" base to ogive
(Picture number two has a hole on the left from an adjacent group)
If you want faster, you should be able to go significantly more than 2800. I haven't played with Alpha brass, but I'm getting 2940 out of 105s with Lapua.
I have a 6 gt built on a tempest if I want speed. At this point I want time to spot misses/impacts at 300 yds. My Smith got his straight br up to 2930 last summer. The flexibility on these br cases is insane.
Wow! These are great speeds, many well over the 2850 fps max other people have stated. Very impressed. Will need to add a 6 BRA to my collection at some point.
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Curios how you guys are headspacing for bra using br go gauge. Ive read go -4k, alpha recommended go -2 for their 6bra ocd brass. My smith initially cut mine to go -4 today and with alpha brass in the chamber the bolt handle drops shut zero resistance, with a new lapua 6br in chamber, its like a no go, cannot close the bolt. We ended up cutting it go -2 at the recommendation of alpha. Will have to see how much case growth I get upon initial firing.
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Long barrel yes. 26" barrel and a 112 at 2900 will be a high psi load. Optimal conditions you could run it, but wet/dusty will likely be tight bolt lift.
Rifle is finally in my hands. 28" 7.5tw hawkhill heavy comp contour, LPA Fuzion, bna tac pro, manners tcs, ace brake, ats tuner. 1.5" M-brace with zco 527 inside. Took it out yesterday to pop the cherry. 31gr rl16 with 107smk idk how far off lands, just closed the bolt on a long seated round, measured and seated another 15k deeper. Tuner was at factory position foe the first 5 shots ever out the barrel, 1/3 moa group. Moved the tuner to zero and that load opened up. However 29gr rl15.5 shot a couple 10 shot groups that were just over half moa. Zero load development. She'll be a shooter for sure.
My preferred loading:
29.6 gr Varget
105 Hybrids
Alpha Brass
BR-4s
2783 FPS, SD of 4
Some other loads I've been testing with lately:
109 Hybrids
29.6 gr Varget
Alpha Brass
BR-4s
2763 FPS, SD of 3.7. I'm going to see if I can get it up to about 2800. I think I'm hitting two different verticals with this load, should iron out with some extra speed, I think.
105 Hybrids
29 gr 8208 XBR
Alpha Brass
BR-4s
2807 FPS, SD of 4.4. This one shocked me. For dropping out of an RCBS competition powder dropper, the SD was incredibly low. These did a 4 shot group on steel at 600 under 3 inches. I'll probably see if I can do it with 109s but start at a low charge and see if I can get them up to 2785 at least without pressure. 8208 has me excited. Way faster to load up rounds with the dropper.
29.6 gr Varget
105 Hybrids
Alpha Brass
BR-4s
2783 FPS, SD of 4
Some other loads I've been testing with lately:
109 Hybrids
29.6 gr Varget
Alpha Brass
BR-4s
2763 FPS, SD of 3.7. I'm going to see if I can get it up to about 2800. I think I'm hitting two different verticals with this load, should iron out with some extra speed, I think.
105 Hybrids
29 gr 8208 XBR
Alpha Brass
BR-4s
2807 FPS, SD of 4.4. This one shocked me. For dropping out of an RCBS competition powder dropper, the SD was incredibly low. These did a 4 shot group on steel at 600 under 3 inches. I'll probably see if I can do it with 109s but start at a low charge and see if I can get them up to 2785 at least without pressure. 8208 has me excited. Way faster to load up rounds with the dropper.
For further reference as I could not find a ton of info with 7.5tw barrels and 87gr vmaxs...
27" 7.5tw Bartlein Mod400 barrel
30.4 gr varget with a 87gr vmax
Thunderbeast ultra 9
AVG speed across 30 rounds, 2960ish. Shot the best jammed 5thou and right at the lands.
Hole at the bottom is from my 204ruger.
Ignore the center and the 4 round group on the right target. Center was 108 bergers and the 4rd group is from my 204. Top right of the left target is at the lands with the 87's. All 3 round groups.
Going to load some more jammed and at the lands to confirm. While kind of slow, it will do the trick for coyotes and prairie dogs I reckon.
27" 7.5tw Bartlein Mod400 barrel
30.4 gr varget with a 87gr vmax
Thunderbeast ultra 9
AVG speed across 30 rounds, 2960ish. Shot the best jammed 5thou and right at the lands.
Hole at the bottom is from my 204ruger.
Ignore the center and the 4 round group on the right target. Center was 108 bergers and the 4rd group is from my 204. Top right of the left target is at the lands with the 87's. All 3 round groups.
Going to load some more jammed and at the lands to confirm. While kind of slow, it will do the trick for coyotes and prairie dogs I reckon.
I purchased a 6mm BRA Stuteville prefit barrel in early October and thought I would share my results after 3 different powders.
CCI450 Mag primers, New Alpha 6BRA brass, Barnes 105 bullets, all shots .020” jump
Never could get enough powder in the case to make velocity with H4350. Lots of powder crunch after 31.5 grains. I would only run this powder if it was all I had.
Varget was disappointing to me from a velocity standpoint. I stopped at 30.6 grains and 2851fps with heavy bolt lift and slightly difficult extraction. I was surprised by the abruptness of which pressure signs showed up. Perhaps I should try smaller powder interments. I suspect I can run this powder at 29.9 – 30.2 grains running 2800fps and will likely develop a load there.
I settled on VV N540 at 30.8 grains which gets me 2915 fps with ES 14 and SD 4.5. Put 5 shots in a 4” group at 883 yards. I love this load and imagine it will be hard to beat with any other powder but I'm open to suggestions.
Given that Varget made pressure at a lower velocity than N540 and Varget is faster burning than N540, Should I expect H4895 will burn too fast to make better than 2900fps?
CCI450 Mag primers, New Alpha 6BRA brass, Barnes 105 bullets, all shots .020” jump
Never could get enough powder in the case to make velocity with H4350. Lots of powder crunch after 31.5 grains. I would only run this powder if it was all I had.
Varget was disappointing to me from a velocity standpoint. I stopped at 30.6 grains and 2851fps with heavy bolt lift and slightly difficult extraction. I was surprised by the abruptness of which pressure signs showed up. Perhaps I should try smaller powder interments. I suspect I can run this powder at 29.9 – 30.2 grains running 2800fps and will likely develop a load there.
I settled on VV N540 at 30.8 grains which gets me 2915 fps with ES 14 and SD 4.5. Put 5 shots in a 4” group at 883 yards. I love this load and imagine it will be hard to beat with any other powder but I'm open to suggestions.
Given that Varget made pressure at a lower velocity than N540 and Varget is faster burning than N540, Should I expect H4895 will burn too fast to make better than 2900fps?
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H4850? Is that new? Or you mean H4895? Thats faster than varget. Will likely psi out sooner. Vastly different results than I found with Varget and H4350. I was able to safely say that run 2900-2950 with both powders in my rifle, granted I do have a 28" pipe.
2900 node is def the high node in a bra, similar to the 2930-2950 node in the dasher. However you should be able to run it, guess not safe in all rifles. This is why I usually run longer barrels, free velocity. If N540 shoots well run it. I have found most the N5 series usually burn pretty dirty, hot and are hard on throats, be my only concerns. N150 is a good cool clean burner for the BRA. I run 33.4-33.7gr H4350 depending on which lot of powder for 2950fps. With a drop tube and 140k freebore, I observe zero powder crunch with 105 bergers.
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Thank you for sharing. To be fair to H4350 I never did make pressure. I just quit when I felt like the case was getting full. I think I will go back and try 33 ish grains and see what speeds I get. Apprciate you input.
how long is your barrel and is it past 200 rounds down the barrel?
Thanks for asking, the barrel is a 28" 1:7.5" and i have put 97 rounds downrange.
