6BRA Primers

[mikeeg02]

Resurrecting a good, relevant thread (I think).

I've been trying to get my new 6BRA tuned. Tried Federal GM205M and CCI BR-4 primers running H4895 ladders between 30.0 and 31.0 gr behind 105 Berger Hybrids seated at .010 jam. Lapua brass, fired 4x and induction annealed. Then I tried 450's "because everyone else is doing it". I didn't pierce (blank) any of the 450 primers but about half of them were extruded around the firing pin, some with as low as 30.2 gr. I didn't notice it right away because I had barely any other pressure signs.

If this was a basic factory action I'd assume it's the pin fit and have the bolt bushed. But this is a new action from a longtime custom action builder. Name withheld in case I should go to them for technical support.

So this suggests that out of those three, the 450's are the least tolerant of pressure by a large margin (0.8 grains). That just doesn't seem right. I have not tried 400's but clearly I should avoid them.

I'll admit I'm new to 6BR* game - so I'm looking for ideas of what to check and explore next.

What did your groups look like with 205s? Try going down and starting around 29 grains. Maybe even 28.5. Could be a fast lot of h4895. With the hunter bullet "a" and annealed cases I'm backed off to 29.6 with 205s and h4895. No pressure signs, and it's only going 2920 the one time my buddy chronographed it, but its winning when I can keep all ten on paper.

450s play very well with rl15, but I've found a better load .15 grains lighter than my 450s load switching to 205s. Less vertical at 1k.

 

[Evan]

Resurrecting a good, relevant thread (I think).

I've been trying to get my new 6BRA tuned. Tried Federal GM205M and CCI BR-4 primers running H4895 ladders between 30.0 and 31.0 gr behind 105 Berger Hybrids seated at .010 jam. Lapua brass, fired 4x and induction annealed. Then I tried 450's "because everyone else is doing it". I didn't pierce (blank) any of the 450 primers but about half of them were extruded around the firing pin, some with as low as 30.2 gr. I didn't notice it right away because I had barely any other pressure signs.

If this was a basic factory action I'd assume it's the pin fit and have the bolt bushed. But this is a new action from a longtime custom action builder. Name withheld in case I should go to them for technical support.

So this suggests that out of those three, the 450's are the least tolerant of pressure by a large margin (0.8 grains). That just doesn't seem right. I have not tried 400's but clearly I should avoid them.

I'll admit I'm new to 6BR* game - so I'm looking for ideas of what to check and explore next.

Did you have a chronograph on any of those loads? The 450s may have just given you more pressure and speed. I wouldn't be surprised if that simple switch from 205 over to 450 resulted in an additional 50fps and more pressure. Every primer type ignites differently and you shouldn't swap them without backing down the charge for this reason.

 

[mikeeg02]

Did you have a chronograph on any of those loads? The 450s may have just given you more pressure and speed. I wouldn't be surprised if that simple switch from 205 over to 450 resulted in an additional 50fps and more pressure. Every primer type ignites differently and you shouldn't swap them without backing down the charge for this reason.

Have you chronographed the difference between 450s and 205s with the same powder charge?

I have not, but in three occurances when I switched FROM 450s to 205s(and with two different powders), I had to back off the powder about .10-.15 grains to get it to shoot again. Which makes me think the 205s are hotter than 450s.

 

[dgeesaman]

It's very possible I’m into a hotter lot of this powder, thanks for reminding me. I guess I was expecting a difference on the order of tenths of a grain not a full grain.

I have not set up my chrony yet but I will make sure to set it up next time out.

David

 

[dgeesaman]

Reporting back, I ran a lower ladder and set up my chronograph. I think this lot of powder is a good .5gr hotter, so it’s not necessarily the 450s being soft.

I missed the first two strings with my chrony but got the rest. Looks like I’m in the mid-2900s at 30.6 gr. This time I only saw two extruded primers at 30.3. Bummer is there appears to be a promising node between 30.3 and 30.6. Would I be taking big risks to continue developing there?

 

[Chuckhunter]

Reporting back, I ran a lower ladder and set up my chronograph. I think this lot of powder is a good .5gr hotter, so it’s not necessarily the 450s being soft.

I missed the first two strings with my chrony but got the rest. Looks like I’m in the mid-2900s at 30.6 gr. This time I only saw two extruded primers at 30.3. Bummer is there appears to be a promising node between 30.3 and 30.6. Would I be taking big risks to continue developing there?

You should be fine there, I have shot up to 31.3 gr's with three different lots of H-4895 using either Br4's or 450's with no pressure problems. Current load @ 30.8 Gr's gives me an avg. velocity of 3007 fps. from a 28.5 inch Krieger with 103 Gr. V.T. With my current lot of 4895, 105 Hybrids run at 3000 fps with the 30.6 Gr. load and CCI Br4's

 

[mikeeg02]

Reporting back, I ran a lower ladder and set up my chronograph. I think this lot of powder is a good .5gr hotter, so it’s not necessarily the 450s being soft.

I missed the first two strings with my chrony but got the rest. Looks like I’m in the mid-2900s at 30.6 gr. This time I only saw two extruded primers at 30.3. Bummer is there appears to be a promising node between 30.3 and 30.6. Would I be taking big risks to continue developing there?

Wheres the target ? I dont care what your chronograph said.......

 

[JFrank]

I suspect one could build and tweak a load around any of the major players.
I don’t believe this is unique to BRA .
As Mikee says is all about the target.
Just my 2c

 

[dgeesaman]

Wheres the target ? I dont care what your chronograph said.......

 

[Evan]

Would I be taking big risks to continue developing there?

Safety is probably fine as long as you aren't extruding enough to risk primer failure if it gets hotter. I'd imagine all it will cost you over time is brass and barrel life. I always go low cause any pressure excursion on a high node, max load means you can start breaking stuff. I prefer to play it safe and leave the headroom.

 

[Rich S]

Resurrecting a good, relevant thread (I think).

I've been trying to get my new 6BRA tuned. Tried Federal GM205M and CCI BR-4 primers running H4895 ladders between 30.0 and 31.0 gr behind 105 Berger Hybrids seated at .010 jam. Lapua brass, fired 4x and induction annealed. Then I tried 450's "because everyone else is doing it". I didn't pierce (blank) any of the 450 primers but about half of them were extruded around the firing pin, some with as low as 30.2 gr. I didn't notice it right away because I had barely any other pressure signs.

If this was a basic factory action I'd assume it's the pin fit and have the bolt bushed. But this is a new action from a longtime custom action builder. Name withheld in case I should go to them for technical support.

So this suggests that out of those three, the 450's are the least tolerant of pressure by a large margin (0.8 grains). That just doesn't seem right. I have not tried 400's but clearly I should avoid them.

I'll admit I'm new to 6BR* game - so I'm looking for ideas of what to check and explore next.

My understandind is the BR4 and 400 have the same charge. The difference is the BR4 has a thicker cup.

Below is a response I got from a question I sent to CCI.


Actually BR4s contain the same amount of priming mix as a CCI 400 so they are not a magnum primer. BR4s do have a thicker cup and are more consistent than the 400s which makes them our benchrest primer. CCI 450s have a magnum priming mix and a thicker cup like the BR4s but with a magnum priming mix rather than a standard.

 

[mikeeg02]

Looking at that target. Without knowing how close together the strings were for condition changes. I like 28.8, 29.4 and 30.3. But I would like to see you shoot them at 300 yards next. 29.4 may blow up.

 

[mikeeg02]

At what distance where these shot?

Going from the lack of vertical dispersion across 2 grains of powder, I would say 100 yards. There's a very small chance its 200, but I'm not that lucky.

 

[Poor Shot 65]

A question. To determine which load shoots best - why (at 100 yards) would the target be more important to see than that of the chronograph ? If you are shooting strings using different loads of powder -- isn't it more important (at first) to look at SD and ES etc ?

Thanks

Adam

 

[mikeeg02]

A question. To determine which load shoots best - why (at 100 yards) would the target be more important to see than that of the chronograph ? If you are shooting strings using different loads of powder -- isn't it more important (at first) to look at SD and ES etc ?

Thanks

Adam

The shape and size of the group tells more of the story than the chronograph in my experience. The further out you go, the more clear the shapes and patterns appear. Assuming you know the conditions when you shot.

I've only used a chronograph a handful of times (when I borrowed one) and didnt find that it told me anything, that the paper with the holes in it wasnt more clear about what was going on. The paper doesnt care how fast they went through it, nor the speed difference between shots.

 

[Poor Shot 65]

The reason for my question is that i have shot many groups that looked incredible on paper, but their SD / ES was total crap (when compared to other groups shot using different loads). I always found it difficult to figure out how to get both a good grouping and good SD/ES. It hard to understand how the grouping could be good, but yet have a bad SD/ES (and vise versa).

I am about to do load development on a 6BR and I am trying to figure out which direction to go in.

It still confuses me.

Thanks

Adam

 

[newbieshooter]

A question. To determine which load shoots best - why (at 100 yards) would the target be more important to see than that of the chronograph ? If you are shooting strings using different loads of powder -- isn't it more important (at first) to look at SD and ES etc ?

Thanks

Adam

The reason for my question is that i have shot many groups that looked incredible on paper, but their SD / ES was total crap (when compared to other groups shot using different loads). I always found it difficult to figure out how to get both a good grouping and good SD/ES. It hard to understand how the grouping could be good, but yet have a bad SD/ES (and vise versa).

I am about to do load development on a 6BR and I am trying to figure out which direction to go in.

It still confuses me.

Thanks

Adam

Related question in this post:
http://forum.accurateshooter.com/threads/so-whats-the-real-deal-with-all-this-es-sd-bs.3985516/

Another load development point of view:
http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/

 

[dgeesaman]

^^^
The difference between 300 and 550 yards can be quite revealing, at least it was for me.
I think there is a point where you could test your barrel away.
I made a choice and stuck to it.
J

I don’t shoot competitively (yet) so on some level I will test my barrel away. I had this rifle built to shoot for shootings sake, if that makes any sense. It is very well built for long range shooting, but not built to compete.

If I get into competition I will probably pick up a good used action/stock and put a fresh barrel on it using my chamber reamer. In that sense, what I'm doing here could prepare for competition.

Looking at that target. Without knowing how close together the strings were for condition changes. I like 28.8, 29.4 and 30.3. But I would like to see you shoot them at 300 yards next. 29.4 may blow up.

I shot my strings consecutively not round-robin. I get 25 rounds down in about a half hour and I go early when the sun is low to minimize wind and mirage. Conditions were very good for both of these targets and conditions hardly changed.

The longest range I have easy access to goes to 200, so I loaded a seating depth ladder and brought my chrony. This target is the result. Previous target was 100y.

Good news: the velocity of my touch and jammed groups was ES of 7 or less, which is the resolution of this chronograph. I attribute that to using dry neck lube for the first time with the 6BRA. Maybe this shifted the optimal charge weight, maybe it did not.

Neutral news: about one in four extruded around the firing pin. No pierced primers but I'm not going to stay at 30.3 unless I can find a primer that handles is (205M? BR-4?, I expected 450s to be plenty tough)

Bad news: the results on target were all over. Either it was one hole or 1.5”. Maybe the change in neck tension has changed the ideal charge weight. I might go back and retest the charge ladder using the better seating length and dry neck lube.

General comment: I'm 300 rounds into this barrel and nothing yet that resembles a useful tune. On one hand, a 4 shot ragged hole group at 200y is rare from a 1moa barrel. On the other hand, .003 of seating depth should not completely blow the tune as you see here. For you experienced guys, that would be cause to junk it or rechamber. It could be me though - so possibly the next step is to put it in the hands of a reputed shooter and see if they agree.

 

[X-Caveman]

I don’t shoot competitively (yet) so on some level I will test my barrel away. I had this rifle built to shoot for shootings sake, if that makes any sense. It is very well built for long range shooting, but not built to compete.

If I get into competition I will probably pick up a good used action/stock and put a fresh barrel on it using my chamber reamer. In that sense, what I'm doing here could prepare for competition.



I shot my strings consecutively not round-robin. I get 25 rounds down in about a half hour and I go early when the sun is low to minimize wind and mirage. Conditions were very good for both of these targets and conditions hardly changed.

The longest range I have easy access to goes to 200, so I loaded a seating depth ladder and brought my chrony. This target is the result. Previous target was 100y.

Good news: the velocity of my touch and jammed groups was ES of 7 or less, which is the resolution of this chronograph. I attribute that to using dry neck lube for the first time with the 6BRA. Maybe this shifted the optimal charge weight, maybe it did not.

Neutral news: about one in four extruded around the firing pin. No pierced primers but I'm not going to stay at 30.3 unless I can find a primer that handles is (205M? BR-4?, I expected 450s to be plenty tough)

Bad news: the results on target were all over. Either it was one hole or 1.5”. Maybe the change in neck tension has changed the ideal charge weight. I might go back and retest the charge ladder using the better seating length and dry neck lube.

General comment: I'm 300 rounds into this barrel and nothing yet that resembles a useful tune. On one hand, a 4 shot ragged hole group at 200y is rare from a 1moa barrel. On the other hand, .003 of seating depth should not completely blow the tune as you see here. For you experienced guys, that would be cause to junk it or rechamber. It could be me though - so possibly the next step is to put it in the hands of a reputed shooter and see if they agree.

Do you know your scope is holding POA?

 

[dgeesaman]

Do you know your scope is holding POA?

The rings and scope passed a box test recently on another rifle. I rechecked the clamp screws are tight (Burris Signature Zee) but I have not checked the pic rail screws to the action.