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6BRA pressure signs and looking for input.

K

Ks_Coyote

Private
Minuteman
Sep 4, 2019
44
20
I'm looking for input on how to produce a brass friendly and accurate round.

Ingredients:
Hornady 105 BTHP
Peterson BR brass
CCI 400 primers (they are what I have readily available)
H4895

I started playing with fire formed BRA brass. Started at 29 grains powder 2 thou off the lands.
29 grains, I was reaching 2975 fps, which I am more than satisfied with and would have stopped there, but you don't know what you don't know...
My loads progressively worked up in .2 grain increments and I didn't see any issues or progress until 30 grains.

At 30 grains, I experienced cratered primers. but no ejector marks. My last loading was 30.2 grains and I had very severe cratering of the primers and ejector marks with heavy bolt lift. If I had a 30.4 I wouldn't of shot them. I honestly didn't expect to be so hard on the brass and the cratering at 30 grains should have been more than enough for me to call it quits.

(FPS at 30.2 was 3175fps and it produced the best group 1 ragged hole at 100 yards.)


I honestly want to stick around 3000 fps and I'd like to try and make my BR brass last a lil longer than my Valkyrie brass lol
-My idea is to stick around 29.2 grains and play with seating depth until I find what works best. 29.2 put me around 3045 and it seems very manageable like the initial fire forming.
If needed, I can switch to Varget and play with that a bit (I've got a little bit)

The weather was 92, and very humid.

I honestly did not expect this round to spike in pressure so quickly, I learned the Peterson brass has a bit less case volume than the Lapua that everyone uses, and if I'm able to get the same results with less powder.. thats ok too.

Has anyone experienced this, or have any input?
 
Last edited:
I use Lapua and am at 30.8 to get pressure signs, 30.6-.7 is a good node and I get ~2940 in cool weather and 2965 in hot.

Less case volume is fine until you need it (e.g. with 109s).
 
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barrel and length? because 30.2g of 4895 at 3175 is SMOKEN fast unless you left your ammo laying in the sun.
 
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Yeah that is way fast. I am in the low 2900s with 30.0

Are you throwing accurate powder charges?
 
26 inch Bartlien 7.5 twist 4R

My loads were in the sun while getting set up, I honestly try to keep heat soak to a minimum.
My powder charges are with in tolerance, I use the inexpensive Frankford Arsenal auto trickler. I do calibrate it after its warmed up for an hour or so and I verify and spot check my charges periodically on a separate calibrated scale.


I'm still relatively new to handloads. I'm always concerned about making a mistake and blowing my fingers off because of an oversight/negligence
 
so im running a 26" bartlein 7.5 and ran up to 30.8 4895 and i think i just broke 3000 4895 did not shoot that great and was to temp sensitive for me.

that said if your going to run 4895 you need to turn that load down to about 2975ish...my suggestion would be to switch to varget now and be done....start at 30g and work up to 31.5 with a 105...look at that little tiny case...2950-2975 is plenty fast....i had 16 loads on my last 110 pcs of brass with 105s at 2975 and 109s at 2940-2950...if it dont shoot close to the lands jump them .060 plus off the lands...and/or switch to better bullets.
 
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Doom said:
You might try changing primers to those with thicker cups like Rem 7-1/2, CCI BR4 or 450.
Click to expand...
THIS.
Chart is old but it shows how the 400s are thin low pressure primer. Get something more capable and your premature primer pressure signs will go away.
1591714846340.png


The heavy bolt lift is another concern though.
 
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Ks_Coyote said:
I honestly want to stick around 3000 fps
Click to expand...

While it may not be a popular opinion, I believe it correct none the less. If you want 3000fps with a 105 in a BRA... you need a longer barrel than 26". A 30" BRA might do it... but even a 26" dasher doesn't belong beyond about 3020fps at most, and that's the top end. I'm running the low node on my present dasher barrel at 2950'ish.

People tend to run these little cartridges much too hot, with much too fast of powders. They give up brass life and consistency across conditions and round count by doing so. With heavy 6mm's in the BR-based cartridges, something in the category of burn characteristics exhibited by H4350 is much more desirable.

If a 3150fps 105gr 6mm is the goal, then you need to start with a 6mm creedmoor, and even that gets complicated... but we're talking about a whole other animal than BRA here.
 
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Doom said:
You might try changing primers to those with thicker cups like Rem 7-1/2, CCI BR4 or 450.
Click to expand...

why would he want to run a harder primer when he is already at 3175 with a BRA? again thats way to fast for that little cartridge.
 
47guy said:
why would he want to run a harder primer when he is already at 3175 with a BRA? again thats way to fast for that little cartridge.
Click to expand...

Yeah... like broken chronograph or wrong powder kind of fast. Definitely warning signs. I wouldn’t try to hide them with a thicker primer.
 
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My goal was not to run 3175 or anywhere near that,
I didn't think 30.2 grains was going to be that hot.

The chrono might be off, it's a magneto sportster. I believe that it is set up correctly but maybe not.

I've attached a pic of one of the primers. Looks like the moon
 

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I'm sorry did I read this correctly... 0.002" off the lands?

That's likely your problem if true. Any amount of ogive variance and/or seating variance and/or fouling will have you jamming (spiking pressure) in no time.

Another thing to consider is that most of the time you see pressure signs on the outside of the case/primer well above 65ksi. Like 70-75ksi. So maybe try a different powder, or less of it, and re-adjust your expectations.
 
Less powder and more gap.

29 grains seemed alright, what would be the recommended jump for the 105s? Jammed slugs seems like a likely culprit.
 
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if you have varget try it...
06E64503-5F34-4E9F-A99A-97EDB8B4C85D.jpeg

I shot A-2 for 1680 rounds...started at .005 off at 1680 I was .015 off...I’m at 31.5g varget now still .015 off at 2975...#4 5 rounds

4B01FB73-51BF-46F2-A4F1-8E1708A56789.jpeg
 
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Good lord, I see the issue now.

Need to gap the piss outta my loads.

Thank you! I'll do some work on Saturday!
 
Not necessarily...lotta guys run close I’m one...most times...like I say I started at .005 off the lands and stayed there for 1680 rounds so the first 800-1000 rounds I was .005 off the lands.

I ran those long jumps just to see how they shot because I have a buddy running a bra with a 105 hybrid at .075 off and it shoots...my next barrel has .180 freebore I’m going to run long jumps and see how it goes.
 
That’s better speed then I’m getting with my 6creed and that things definitely no slouch at 3150 and my dasher at 2940. That being said you’re either on the razors edge of pressure or found the holy grail of BRA recipes but either ways it’s a scary place to be.
 
I just put 2500 rounds on a 26” gain twist Bartlein. I started out with 30.4 grains of H4895 at 2930fps. it’s at 2917 now with 31.4 of Varget. Reading primers is difficult. Speed comes with pressure.
 
jhunter said:
I just put 2500 rounds on a 26” gain twist Bartlein. I started out with 30.4 grains of H4895 at 2930fps. it’s at 2917 now with 31.4 of Varget. Reading primers is difficult. Speed comes with pressure.
Click to expand...

so you got 2500 rounds out of a 6BRA? good accurate rounds?
 
47guy said:
so you got 2500 rounds out of a 6BRA? good accurate rounds?
Click to expand...
Yes it’s still shooting at 100yd. I noticed it starting to open up at distance. But not by much closer to 1 MOA at 700 yards and further. Borescoped the barrel and the throat is rough. It’s starting to firecrack but nothing like a Creedmoor at 1000 rounds. I’m thinking that is creating a wide ES on the BC of the bullet. This is an 8 shot group at 2400 rounds.
 

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jhunter said:
Yes it’s still shooting at 100yd. I noticed it starting to open up at distance. But not by much closer to 1 MOA at 700 yards and further. Borescoped the barrel and the throat is rough. It’s starting to firecrack but nothing like a Creedmoor at 1000 rounds. I’m thinking that is creating a wide ES on the BC of the bullet. This is an 8 shot group at 2400 rounds.
Click to expand...

“I SUCK” LMAO!!!

well that gun was still shooting great at 2400 that’s encouraging....I’m at 1750 now and if I get 2000-2200 I’ll be real happy with that...and as good as this barrel has shot if it goes sooner I’ll still be real happy
 
I am at 2400 right now... still shooting great. Have another barrel waiting but there is no need to swap yet.
 
IMO with the 6BRA 2950 is the "hot" node and the safer place to be is 2880-2920 fps with a 105. I know from experience that 2950 is not rain safe, and can even get pressure if your shooting in tough dusty conditions.

I'm loaded up for a match this weekend, picked a nicer low node, 29.9 H4895 105 Hybrid, 2865 fps, 27.5" barrel. This one has 1800 rounds on it and is shooting good but not quite as one-hole as it was originally. My first 6BRA barrel is at 2500 rounds and has lost a bit of velocity but is still a hammer, solid 1/4 MOA.
 
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Sheldon N said:
IMO with the 6BRA 2950 is the "hot" node and the safer place to be is 2880-2920 fps with a 105. I know from experience that 2950 is not rain safe, and can even get pressure if your shooting in tough dusty conditions.

I'm loaded up for a match this weekend, picked a nicer low node, 29.9 H4895 105 Hybrid, 2865 fps, 27.5" barrel. This one has 1800 rounds on it and is shooting good but not quite as one-hole as it was originally. My first 6BRA barrel is at 2500 rounds and has lost a bit of velocity but is still a hammer, solid 1/4 MOA.
Click to expand...
H4350 to the point of hearing the crunch when seating... can produce some really excellent results in the low node. Most of the time you can't get enough of it in there to even find the high node easily. ;)
 
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orkan said:
H4350 to the point of hearing the crunch when seating... can produce some really excellent results in the low node. Most of the time you can't get enough of it in there to even find the high node easily. ;)
Click to expand...
Definitely no fear of over changing with H4350
 
Sheldon N said:
IMO with the 6BRA 2950 is the "hot" node and the safer place to be is 2880-2920 fps with a 105. I know from experience that 2950 is not rain safe, and can even get pressure if your shooting in tough dusty conditions.

I'm loaded up for a match this weekend, picked a nicer low node, 29.9 H4895 105 Hybrid, 2865 fps, 27.5" barrel. This one has 1800 rounds on it and is shooting good but not quite as one-hole as it was originally. My first 6BRA barrel is at 2500 rounds and has lost a bit of velocity but is still a hammer, solid 1/4 MOA.
Click to expand...
I have found Varget to be more rain safe. H4895 is a good choice for perfect conditions.
 
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orkan said:
H4350 to the point of hearing the crunch when seating... can produce some really excellent results in the low node. Most of the time you can't get enough of it in there to even find the high node easily.
Click to expand...

My buddy has had good results with H4350 and a 115gr bullet, the 105's seem like they'd be a bit light for that slow of a powder but we haven't tried them.
 
Sheldon N said:
My buddy has had good results with H4350 and a 115gr bullet, the 105's seem like they'd be a bit light for that slow of a powder but we haven't tried them.
Click to expand...
They aren't. For me... H4350 has been nothing short of magical in 6BR, 6BRA, 6Dasher, and 22BR(with 80's). Granted, I'm not looking to make my 6BR run velocities barely achievable by a 6 creedmoor either. Slow and stable nodes, that shoot with extreme precision, accuracy, and predictability is what I'm going for. Obviously when you get down in the 87'gr category, I wouldn't use H4350 there... but for 100gr and upward, it's the perfect fit in my opinion. 100% case fill, doesn't burn out throats, nice gentle pressure curve, etc. It's just awesome in these little cartridges. Most under-rated powder for them, I think.
 
orkan said:
They aren't. For me... H4350 has been nothing short of magical in 6BR, 6BRA, 6Dasher, and 22BR. Granted, I'm not looking to make my 6BR run velocities barely achievable by a 6 creedmoor either. Slow and stable nodes, that shoot with extreme precision, accuracy, and predictability is what I'm going for. Obviously when you get down in the 87'gr category, I wouldn't use H4350 there... but for 100gr and upward, it's the perfect fit in my opinion. 100% case fill, doesn't burn out throats, nice gentle pressure curve, etc. It's just awesome in these little cartridges. Most under-rated powder for them, I think.
Click to expand...

I might have to try some in my dasher project, plus it would be nice to only need one powder for both comp calibers I’ve got.
 
King_beardsly said:
I might have to try some in my dasher project, plus it would be nice to only need one powder for both comp calibers I’ve got.
Click to expand...
That's another thing I like about it... I use H4350 in a TON of other things. The entire creedmoor family of cartridges for starters. 308's... etc. It's just a great powder to have around in large quantity.
 
orkan said:
That's another thing I like about it... I use H4350 in a TON of other things. The entire creedmoor family of cartridges for starters. 308's... etc. It's just a great powder to have around in large quantity.
Click to expand...
I’ve got the dasher, 6creed, 270 win and the trusty 308. So streamlined powder will be very helpful, and a time saver
 
Sheldon N said:
IMO with the 6BRA 2950 is the "hot" node and the safer place to be is 2880-2920 fps with a 105. I know from experience that 2950 is not rain safe, and can even get pressure if your shooting in tough dusty conditions.

I'm loaded up for a match this weekend, picked a nicer low node, 29.9 H4895 105 Hybrid, 2865 fps, 27.5" barrel. This one has 1800 rounds on it and is shooting good but not quite as one-hole as it was originally. My first 6BRA barrel is at 2500 rounds and has lost a bit of velocity but is still a hammer, solid 1/4 MOA.
Click to expand...

im not arguing or saying this is not possible but ive shot my BRA at 2975 in the snow(wet ammo....not soaked like rain but wet)with no issues also my load was developed in the winter and ive shot the same load from 25deg to 90deg.
 
orkan said:
They aren't. For me... H4350 has been nothing short of magical in 6BR, 6BRA, 6Dasher, and 22BR(with 80's). Granted, I'm not looking to make my 6BR run velocities barely achievable by a 6 creedmoor either. Slow and stable nodes, that shoot with extreme precision, accuracy, and predictability is what I'm going for. Obviously when you get down in the 87'gr category, I wouldn't use H4350 there... but for 100gr and upward, it's the perfect fit in my opinion. 100% case fill, doesn't burn out throats, nice gentle pressure curve, etc. It's just awesome in these little cartridges. Most under-rated powder for them, I think.
Click to expand...

ill have to look back but ive compressed H4350 in my BRA and i dont think i broke 2800.
 
47guy said:
im not arguing or saying this is not possible but ive shot my BRA at 2975 in the snow(wet ammo....not soaked like rain but wet)with no issues also my load was developed in the winter and ive shot the same load from 25deg to 90deg.
Click to expand...

This match was hardcore Pacific Northwest sideways rain all day. Wettest I've ever been.
 
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Sheldon N said:
This match was hardcore Pacific Northwest sideways rain all day. Wettest I've ever been.
Click to expand...

gotcha we don’t get those kinda rains in Nevada...well gully washers couple times a year but other than some light rain or a little snow that’s all I’ve shot in
 
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