6BRA load data

[BartsBullets]

Bart according to hogdon website H4895 is 89 and IMR is 91 on burn rate chart. So how’s IMR 4895 too slow?

James
The powder is in large chunks. You can’t get enough in the case. At least with the 8 pounds I bought.

Bart

 

[TroyG]

I started with H4895. 30.6grs with 450 primer and 105 Hybrid. It was giving me 2965 with ES of 15 and SD of 7. Found it hard to keep in tune with humidity and temperature swings on the days I tested loads.

I switched to VV150 because I had 8lbs sitting around as a Varget substitute. I settled on 32.3 grs for 2964 fps average with ES of 6 SD of 4. Seems to stay in tune a little better than the H4895 I have.

6BRA 1/7.5 Bartlein barrel.

 

[JohnMill]

I started with H4895. 30.6grs with 450 primer and 105 Hybrid. It was giving me 2965 with ES of 15 and SD of 7. Found it hard to keep in tune with humidity and temperature swings on the days I tested loads.

I switched to VV150 because I had 8lbs sitting around as a Varget substitute. I settled on 32.3 grs for 2964 fps average with ES of 6 SD of 4. Seems to stay in tune a little better than the H4895 I have.

6BRA 1/7.5 Bartlein barrel.

I found the 6BRA tempermental but maybe it was just the H4895 (lot that I got). I will try the Viht powders 140 & 150 and Varg of course. Can't wait to get my own cartridge in the field. Barts forever as it stands now.
John

 

[TroyG]

I sure would like to get my hands on some of the custom 6mm bullets from the States.

 

[JohnMill]

I sure would like to get my hands on some of the custom 6mm bullets from the States.

Well, what's stopping you? All them guys got some method of exportin important stuff.

 

[Nellej12]

I have my 6BRA shooting very well with varget. Just shot a 200-13x and 200-17x (my personal best score) in a match today at 600 yards. Relay 3 was cancelled due to heavy rain.
32.2 grs varget, Berger 105 Hybrid, 2990 for velocity with a 30 inch barrel.

 

[Terry]

I have my 6BRA shooting very well with varget. Just shot a 200-13x and 200-17x (my personal best score) in a match today at 600 yards. Relay 3 was cancelled due to heavy rain.
32.2 grs varget, Berger 105 Hybrid, 2990 for velocity with a 30 inch barrel.

Congratulations!

Nice shooting!

 

[B Allen]

I have shot 4 barrels that have all been very similar loads in each reamer based on wheeler print

28" Krieger/237 bore/4 groove/7.5 twist x 3
28" Bartlein/237 bore/5R/ 7.5 twist

H4895 30.2 gr - 2925 FPS
F205M/450s
105 hybrid @ 17 K jump


Varget 31.4 gr- 2940FPS
F205M/ 450s
105 Hybrid @ 10 K jump

Varget 31.5 gr - 2910 FPS
F205M / 450s
Berget 108 HPBT @ 5 K jump

How did the 28" Bartlein/237 bore/5R/ 7.5 twist shoot compared to the four grove?

 

[Falfan2017]

Getting pressure with 30.6 h4895 with a 105 seated 5k in the lands. Stiff bolt and ejector marks. Not sure what’s causing that. Groups aren’t bad.

Also had pressure fireforming with 29.5 h4895.

Any ideas?

Edit: ejector mark not extractor

 

[shoot4fun]

Getting pressure with 30.6 h4895 with a 105 seated 5k in the lands. Stiff bolt and extractor marks. Not sure what’s causing that. Groups aren’t bad.

Also had pressure fireforming with 29.5 h4895.

Any ideas?

I hit 30.9 H4895 with Bart's Gungnirs with zero pressure signs one day and blew primers out with it the next.
I think H4895 is the devil.
The Gungnir is, according to Bart, bigger and builds more pressure. I backed down to 30.5 and things are looking better. Think I'll try some Varget though.

 

[Falfan2017]

I hit 30.9 H4895 with Bart's Gungnirs with zero pressure signs one day and blew primers out with it the next.
I think H4895 is the devil.
The Gungnir is, according to Bart, bigger and builds more pressure. I backed down to 30.5 and things are looking better. Think I'll try some Varget though.

these are hammers but I had similar pressure with the same load of vapor trail. I’ll try 30.5 or 30.4. I’ve tried varget and the pressure signs don’t happen but the groups aren’t as good.

 

[Jet]

Getting pressure with 30.6 h4895 with a 105 seated 5k in the lands. Stiff bolt and ejector marks. Not sure what’s causing that. Groups aren’t bad.

Also had pressure fireforming with 29.5 h4895.

Any ideas?

Edit: ejector mark not extractor

Do you have enough neck clearance? Carbon ring?

 

[DHuffman]

Getting pressure with 30.6 h4895 with a 105 seated 5k in the lands. Stiff bolt and ejector marks. Not sure what’s causing that. Groups aren’t bad.

Also had pressure fireforming with 29.5 h4895.

Any ideas?

Edit: ejector mark not extractor

When I'm getting ejector marks it seems like it's usually a wet chamber or too much headspace type of thing. Stiff bolt can come from both also as well as lube left on the cases.

@Jet brings up a good point about the carbon ring also.

 

[Falfan2017]

Do you have enough neck clearance? Carbon ring?

I should have the neck clearance. 265 loaded round with a 268 chamber. I don’t know about a carbon ring. Is there a good way to check?

 

[Falfan2017]

When I'm getting ejector marks it seems like it's usually a wet chamber or too much headspace type of thing. Stiff bolt can come from both also as well as lube left on the cases.

@Jet brings up a good point about the carbon ring also.

I don’t think it’s too much headspace when I was fireforming the virgin lapua brass had the nice snug fit. I don’t know about lube on the cases I wipe em off with alcohol and clean out the chamber with a large patch on a brush.

 

[BartsBullets]

I don’t think it’s too much headspace when I was fireforming the virgin lapua brass had the nice snug fit. I don’t know about lube on the cases I wipe em off with alcohol and clean out the chamber with a large patch on a brush.

Did you change powder lots? I have a batch of H4895 that is significantly hotter then my old stuff.

Bart

 

[Nature Boy]

When I'm getting ejector marks it seems like it's usually a wet chamber or too much headspace type of thing.

So far, I see that when the brass is new

 

[Falfan2017]

Did you change powder lots? I have a batch of H4895 that is significantly hotter then my old stuff.

Bart

Tried three lots all doing roughly the same thing.

 

[DBLNUT]

Tried three lots all doing roughly the same thing.

A chronograph is your friend. My new lot of h4895 takes about a half grain less powder to reach the same velocity as my old lot!

 

[BartsBullets]

Tried three lots all doing roughly the same thing.

Weak or too heavy of a firing pin spring can do that also.

Bart