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6BRA load data

wkdickinson said:
I am having a problem getting the velocities everyone else seems to be getting in the BRA. In order to get over 2,900 (actually 2,920) I am at 32.3 gr of Varget with 107SMK, CCI 450 and new (fire-formed and reloaded twice) Peterson brass. I am not getting any pressure signs with this load and it shoots really well. But I am concerned about why I need an extra 1.0gr to get there. Kelbly Atlas, 28" Brux 8 twist (3,500+ rds.), Garmin XERO, AutoTrickler V4. Anyone's thoughts would be appreciated.
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3,500 rounds might have something to do with it. You have to add powder when your barrel begins to wear out to keep the same velocity.

Also, you may just have a slower lot of Varget.
 
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In addition to my more serious tight neck 6BRA, on a whim I decided to put together a fun gun from some available components using a varmint contour Urban Rifleman barrel with a no turn chamber, with zero freebore and eight inch twist. A friend did me a favor and sighted it in for me and fire formed some cases, during a recent range session, as a fill in, while waiting for his rifle's barrel to cool. It is hot in Fresno right now. Anyway, the plan is to set up the rifle for anyone who is less experienced that I take to the range. The rifle has a benchrest stock, light trigger and 36X scope. My friend has an excellent rest, and has been coming along very nicely with his bench shooting, that I have been working with him on a bit. The loads were made up using some short range benchrest bullets, all with the same guesstimate load. As he started to shoot the rifle, which were its first shots, he could see that it had potential, so he put up another target wit a pair of aiming points and shot this three shot group. He chickened out on adding more, not wanting to spoil it. I thought that you might be interested. It certainly made me smile. The reason that I had some confidence in the potential of light bullets with an 8" twist barrel was because of a post in this thread. I have a lot of short range odds and ends, with usable quantities of several, and plenty of this powder, so I think that the project is GTG. Looks like a low to mid one to me.
 

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BoydAllen said:
In addition to my more serious tight neck 6BRA, on a whim I decided to put together a fun gun from some available components using a varmint contour Urban Rifleman barrel with a no turn chamber, with zero freebore and eight inch twist. A friend did me a favor and sighted it in for me and fire formed some cases, during a recent range session, as a fill in, while waiting for his rifle's barrel to cool. It is hot in Fresno right now. Anyway, the plan is to set up the rifle for anyone who is less experienced that I take to the range. The rifle has a benchrest stock, light trigger and 36X scope. My friend has an excellent rest, and has been coming along very nicely with his bench shooting, that I have been working with him on a bit. The loads were made up using some short range benchrest bullets, all with the same guesstimate load. As he started to shoot the rifle, which were its first shots, he could see that it had potential, so he put up another target wit a pair of aiming points and shot this three shot group. He chickened out on adding more, not wanting to spoil it. I thought that you might be interested. It certainly made me smile. The reason that I had some confidence in the potential of light bullets with an 8" twist barrel was because of a post in this thread. I have a lot of short range odds and ends, with usable quantities of several, and plenty of this powder, so I think that the project is GTG. Looks like a low to mid one to me.
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I would assume you approaching 3400 fps with light bullets perhaps faster. In an 8 twist have you borescoped? How many rounds down the bbl? Is there a lot of copper showing in the throat area? Curious.
 
6BRA said:
I would assume you approaching 3400 fps with light bullets perhaps faster. In an 8 twist have you borescoped? How many rounds down the bbl? Is there a lot of copper showing in the throat area? Curious.
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This is going to be a bit of an experiment. No break in, or cleaning for the first 50 rounds through this rifle. On the velocity, these are fire forming rounds so I cannot predict the velocity. I am going to call him this morning and ask him to chronograph a few of the loads. It will be interesting to see if the accuracy has fallen off by the end of 50 rounds, and how the barrel cleans up. We both have Teslong bore scopes. I will probably do a couple of wet patches and a couple of strokes with solvent on a bore brush, dry it, and take a look for copper. The issue in the throat is usually powder fouling and possibly some hard carbon. Jacket fouling is usually an issue farther down the barrel. I looked the barrel over inside when I got it and it is a lot better than a factory barrel. One thing that I have learned is that you cannot predict accuracy with a bore scope.
 
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My friend did a pressure test for me. 748, Tucker #3 65 gr., 205, .005 NT, around touch, one shot per charge, half grain interval from 33 to 37.5 grains. First shot the chrono. did not register. 33.5 was 3,349 fps. 37.5 was 3,771 fps. Looking at the bullet holes proximity to each other 36.0 (3,625) and 36.5 (3,655) overlapped at the same elevation. The temp. was about 85. There were no pressure signs as far as bolt lift, with slight cratering of the primer of the hottest load. I will probably do a neck tension experiment at 36.3. at the same ambient temp. All powder charges were done at home, using a Chargemaster. Every load came out right on the money. When he brings the rifle back, I will do a light cleaning and take a look to see what the jacket fouling situation is. After the fire forming, I had some copper, but not bad, then I cleaned it spotless.
 
Tomiboy said:
Dime size group at 500!! Nice! What some guys would give to shoot that at 100! HAHA!! Good shooting!
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Tom, you’re shooting pretty darn good yourself’ this barrel seemed finicky with H4895 so I kinda got lucky with the Varget.
 
Stan Taylor said:
Well I tried a load yesterday at 600yd at Whitehorse a test for my 6mm Bra-less LOL I shot 31.1 of H4895 105 Berger primer I used was 205M federal it shot very well.PS velocities is about 2950ish I shot smallest group of the day.wasn't anywhere close to Barts record I would like to grow up an be just like him someday LOL.PS Alex I don't know that chamber is a true BRA it's right at 1.135 long at the shoulder but it's 40degree shoulder.
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It would be a respectable group if it wasnt for that flier. :) :)
 
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