The start-6bra Load development

[MDM]

So I've got my first 6 bra going. 170 rounds on the barrel. Brass is fired in and ready for load development. 28" bartlien, .105fb. This is a bit of a different animal for me as I'm coming from years of shooting a 6.5x47 and know where to load it. Let's start of with establishing a "jam" number. My touch point is 2.810 with a 105 hvld, however, my jam number is 2.860. (.002 neck tension) This seems a bit excessive to me as it's actually .050 in the lands before the bullet is nudged back when chambering. Is that excessive?

I was thinking about trying Eric Cortina's method for this round of load development, so I'd be starting that with the bullets .030 in the lands to find an initial charge weight. I can say that I'm starting to see some pressure at 30.8 H4895 and 31.8 Varget. Those both seen to top out at 2930-2950ish for velocity.

If I wanted to try the method that Tim Singleton has posted a lot about - testing a high, middle, low load and seating depth all at once, where should my 3 charge weights be with this little guy?

I guess I'm looking for some tips on where to start if I want to do an initial charge weight with 4895 and what jam length. Fyi, this is a prs type build, no bench stuff. Open to suggestions on how to kick this load development off.

 

[Performance Shooting]

Mine likes 29.6 and 31.0 H4895 jammed .010....with 105 VLD's.....both shoot very well, I'm shooting five shot groups at 300, in the .7's & .8's with those two loads, it seems to be a little better with the 29.6 load, more .7's and a few .6's

 

[MDM]

Does this look like a decent range to try? .24g increments

H4895

29.68

29.92

30.16

30.40

30.64


Varget

30.56

30.80

31.04

31.28

31.52

 

[Falfan2017]

One idea is to measure in grams and go up in .01 gram increments. This is equivalent to .15 grains. I just find 1.94 1.95 1.96 1.97 1.98 easier to remember and think about than
30.56
30.8
31.04 etc.

 

[MDM]

So here is what I did today using a version of Eric Cortina's method. I'm just trying to find the powder charge, so nothing spectacular with the crosswind I had. All I'm worried about is the vertical center of the groups. I have my thoughts on where I should go for the charge when I test seating depth next, but let me hear your thoughts please. I tested Varget and H4895

105 Hybrid
.005 in the lands
150yds
3-7 mph crosswind

H4895


Varget

 

[LitLBoy]

H-4895 try 30.8 and 31
Varget 31.5 work with seating depth
LitLBoy

 

[MDM]

H-4895 try 30.8 and 31
Varget 31.5 work with seating depth
LitLBoy

31.6 Varget is top end in 88 and humid- 2 out of 3 started to get sticky. Same with H4895, don't think I want to go much higher in these temps.

 

[Link]

I can understand the Varget. Where do you get the 30.8 and 31 H4895 from.
trying to learn Don

 

[MDM]

I can understand the Varget. Where do you get the 30.8 and 31 H4895 from.
trying to learn Don

Pretty sure he meant I should have tried 30.8 and 31 in my initial H4895 test.

Nothing promising in my 4895 loads then?

 

[KenOath]

30.2 4895, 31.4 Varget..

 

[MDM]

That’s what I was thinking based on the vertical center of each group in relation to the horizontal line. Not worried about the windage really because the wind was up and down from left to right.

31.4 has shot consistently well leading up to this test. The barrel has picked up 40 fps across the board from when it was new. This is the first time looking at 4895. I’d like to run it because I’ve got more of it but I’m gonna test the seating on both.

 

[Curious]

So here is what I did today using a version of Eric Cortina's method. I'm just trying to find the powder charge, so nothing spectacular with the crosswind I had. All I'm worried about is the vertical center of the groups. I have my thoughts on where I should go for the charge when I test seating depth next, but let me hear your thoughts please. I tested Varget and H4895

105 Hybrid
.005 in the lands
150yds
3-7 mph crosswind

H4895
View attachment 1057052

Varget
View attachment 1057055

Let me throw a banana skin out there for you - why dismiss the windage element when it could well be telling you things?

The conditions you shot the tests in are not extreme enough in my opinion for you to dismiss the horizontal and more importantly the POI stability information available in those results.

H4895 has a better POI stability than Varget but having previously struggled with these two powders in my own 6BRA I would go as far as to say I think neither will give you the highest level of accuracy you are looking for based on what I can see on those targets, assuming of course your shooting and gun handling skills are good enough to make the results valid?

I say this from experience, dont be lulled into thinking H4895 is the right powder or be influenced because you have lots of it and it has worked for others. Feed the barrel what it wants as opposed to what you want it to eat - my advice would be to try a different powder with your Hybrids seated 20 thou off to start.

 

[MDM]

I'll be the first to admit, my bench skills are sorely lacking compared to those that do it regularly. Actually, I haven't shot off a bench in probably 8 years. I'm usually prone and rear bag, but decided to go the bench route to get up a little an out of the mirage, and free recoil it since that is how I tackle the positional stuff nowadays. If I'm off of a bench, I think I can hold my own pretty well, and I'm confident in the results posted. I'm out on a limb here even trying H4895, lol. I'm Varget and H4350 all the way coming from 6 and 6.5x47. No double based powders do to the extreme temps and conditions I can shoot in, 15 degrees to 95 and rain, sun or snow. That said, I'll heed your advice and run my seating test out to 20 off when I settle on a solid charge to try.

 

[Curious]

I'll be the first to admit, my bench skills are sorely lacking compared to those that do it regularly. Actually, I haven't shot off a bench in probably 8 years. I'm usually prone and rear bag, but decided to go the bench route to get up a little an out of the mirage, and free recoil it since that is how I tackle the positional stuff nowadays. If I'm off of a bench, I think I can hold my own pretty well, and I'm confident in the results posted. I'm out on a limb here even trying H4895, lol. I'm Varget and H4350 all the way coming from 6 and 6.5x47. No double based powders do to the extreme temps and conditions I can shoot in, 15 degrees to 95 and rain, sun or snow. That said, I'll heed your advice and run my seating test out to 20 off when I settle on a solid charge to try.

My suggestion was to run the Hybrids at 20 thou off during powder charge testing as you have to start somewhere and its always worked well for me. What seating depth you end up at will come from the target.

Personally I dont like the look of either powder if your shooting is on point.

 

[Rope2horns]

30.2 4895, 31.4 Varget..

This^^^ or split the difference and go 30.3 H4895 or 31.5 Varget then shoot a seating depth ladder.

 

[Link]

This^^^ or split the difference and go 30.3 H4895 or 31.5 Varget then shoot a seating depth ladder.

What range does the seating depth usually end up with 105 VLDs?
thanks

 

[LitLBoy]

30.8 or 31 of H 4895 are usually good velocity nodes in a lot of guns, just not yours I guess.
LitLBoy

 

[Rope2horns]

What range does the seating depth usually end up with 105 VLDs?
thanks

No idea..it's just something you will have to check...you know the ole saying every barrel is different..test it it will tell ya what it likes.

 

[Sheldon N]

I like 31.4 Varget. That's basically the load I'm running in my 6BRA as well.

 

[KenOath]

What range does the seating depth usually end up with 105 VLDs?
thanks

5 to 8 jam is common but test from 30jump to 15jam..