6BR Pressure Found Low Charge

[MikeG08]

Hello I have a 6BR I’m getting pressure at 28.6gr running 2689. Seems really low to be hitting pressure. I did a pressure ladder and felt it at 29 and backed off to 27.5. Then ran up a powder ladder test. 28.0 looks pretty solid. I’m shooting for fun so I don’t need any particular speed. Just seemed really low compared to what many others are getting. Eventually plan to do some comp shooting however I have another barrel different smith cutting that.
The shop that cut the chambered closed so I don’t have reamer specs.
My equip:
Hawk Hill 1:7.5 Alpha and Omega chambered. Barrel has about 1k rds.
Lapua brass
GM205
Varget
103 Vap trail
Here’s a picture of the powder ladder(100yds). Chrono data captured on Garmin.

 

[Dolomite]

At 29 grains what kind of pressure signs? Just Heavy bolt lift? Clickers?

After 1000 rounds you just started having this issue? How many firings on the brass? No neck turn or neck turn.

What does the brass look like? Post a pic of the base and primer and the case neck and mouth.

Brass trim length? Jamming the bullet or jumping?

Barrel length?

Is the base of the bullet above the donut area on the brass?

Lots of good guys here to help you out, just need more info.

 

[MikeG08]

At 29 grains what kind of pressure signs? Just Heavy bolt lift? Clickers?

After 1000 rounds you just started having this issue? How many firings on the brass? No neck turn or neck turn.

What does the brass look like? Post a pic of the base and primer and the case neck and mouth.

Brass trim length? Jamming the bullet or jumping?

Barrel length?

Is the base of the bullet above the donut area on the brass?

Lots of good guys here to help you out, just need more info.

Thanks for the reply. I knew I needed more information but wanted to get the basic question out there and go from there. Lots of information packed into my questions. Was resisting form writing a novel. LOL

This is my first BR, and I am new to reloading. Been doing it about 2 years slowly. Bolt lift is slightly heavy at 28.6gr no extractor marks until about 31gr. The first 900ish rounds were loaded to 29.66gr and ran that with a decently accurate load. The bolt lift isn't always heavy. The brass was virgin to start and I have 3 firings on 300 pieces. I followed Erik Cortina's method to that point. I had my bolt trued by Speedy which changed my ignition so I started load development back at square 1.

I changed my load development process after a conversation with Greg Dykstra, and am now following a OCW style load development. The purpose is to get a more detailed picture of my accuracy window. I have started over using Virgin brass I did test my old brass to see if the pressure signs were there at the same charge and they are. I thought maybe the new brass had something wrong with it, it is a different lot.

I will post a picture of the brass when I get home I have 20 fired pieces still in the fired state.

Brass trim is 1.550 with Giraud Trimmer, Bullet is .040" back of Jam

Barrel 26"

The bullet is past the donut area.

Reloading Equip In the Event its relevant:
Zero Press
SAC BR F/L DIE .265 bushing .241 Mandrel
EC Expander Mandrel which also does the case web area to help clickers
Infinity Seater
AMP Press
AMP Anneal (Every fire)
Giraud Trimmer
Auto V3 Ingenuity Trickler
CPS Seater + Prime Ware (I sort primers by size and separate to the same thousandth number)

 

[G Liles]

Check for a carbon ring.

 

[MikeG08]

Check for a carbon ring.

In the throat? I clean after every firing using a borescope. I get it back to bare metal (or very close) each time. Even when firing 20rds. All of my development stages are done on a clean barrel.
The carbon rings is removed after every firing.

 

[MikeG08]

Here are some pictures of the brass. 3 are the ones that had pressure 3 are not.
I do not turn necks.
Also I am shooting with a suppressor.

 

[G Liles]

Lube on the case, oil in the chamber?

 

[MikeG08]

Lube on the case, oil in the chamber?

It don’t think so.
I use Imperial wax, after sizing I do 6 hour tumble in rice media. If I’m cleaning quick I’ll wipe the lube off with a cloth and use alcohol to ensure it’s all off. Final procedure when cleaning my barrel is to run my chamber rod through with a 9mm iosso brush and a 30cal patch, I turn to ensure it’s dry.
I use PMA bore guide throughout all of the cleaning.

 

[Larry Koch]

I don’t see a sine wave on the neck of the brass. Happy brass. Can you slip a bullet in a fired case. ? I will almost bet you don’t have enough space for good bullet release.
What is a loaded round o.d measured at the neck vs neck dia. You will need to use a 1” digital micrometer. One more case overall length? Are you trimming them ?

 

[MikeG08]

I don’t see a sine wave on the neck of the brass. Happy brass. Can you slip a bullet in a fired case. ? I will almost bet you don’t have enough space for good bullet release.
What is a loaded round o.d measured at the neck vs neck dia. You will need to use a 1” digital micrometer. One more case overall length? Are you trimming them ?

For measuring tools I only have a tube micrometer and a few pairs of Mitutoyo calipers.
All of the case mouths have a dented side, I’m assuming from extraction?
The bullet will fit in the fired case, but there is definite resistance.
The fired mouth is measuring .269” on the low side, then the other 3/4 of the case mouth measure .270-.271”
Loaded unfired round measures .268” all the way around.
So does that mean I’m only working with .001-.003” neck clearance?

Trimming to 1.550” OAL

 

[Larry Koch]

For measuring tools I only have a tube micrometer and a few pairs of Mitutoyo calipers.
All of the case mouths have a dented side, I’m assuming from extraction?
The bullet will fit in the fired case, but there is definite resistance.
The fired mouth is measuring .269” on the low side, then the other 3/4 of the case mouth measure .270-.271”
Loaded unfired round measures .268” all the way around.
So does that mean I’m only working with .001-.003” neck clearance?

Trimming to 1.550” OAL

.268 loaded round neck dia. is going into a .269 - .271 neck chamber? If that what your saying I believe you know what your issue is. But to be sure what is barrel chamber Neck? Annealed brass that has been fired should not shrink much. And if a bullet is tight in a fired case. You might take a few new cases and turn the necks .001 more total and test them and repeat what I have mentioned. You will get a sine wave on your neck on a fired round, when your in the zone. And if you don’t turn a few more necks a little more.
The sine wave will stick out if you look. And once you see that you will always know your good. As far as neck thickness.

 

[Larry Koch]

iGaging 0-1" Digital Electronic Micrometer w/Large Display Inch/Metric

 

[MikeG08]

.268 loaded round neck dia. is going into a .269 - .271 neck chamber? If that what your saying I believe you know what your issue is. But to be sure what is barrel chamber Neck? Annealed brass that has been fired should not shrink much. And if a bullet is tight in a fired case. You might take a few new cases and turn the necks .001 more total and test them and repeat what I have mentioned. You will get a sine wave on your neck on a fired round, when your in the zone. And if you don’t turn the a few more necks a littlemore.

Thanks to all who have jumped in here, sorry if my questions are noob-ish but thats what I am still. I'm trying to get some expierenced perspective and head off some unnecsary time/component expediture. Espeically if the probable outcome looks bleak on my path.

I have never turned necks, I did buy a 21st century neck turner a while back. Would need to get the right components for 6BR.
A couple questions though:

I have a barrel being chambered by Speedy now with a no turn chamber. Is it worth turning the necks if I stay away from pressure in this barrel?

I assume the lack of clearnace will negatvily impact accuracy/precision consistency to some degree. However if I am able to aciheve 3/8-1/2" with consistnecy this barrel will serve a purpose.
Of course I will have to test to know for sure.
But does it seem attainable from an outside perspective, or am I likely going to be chasing my tail?

My thought was go load rounds 27.6gr, 27.8gr, 27.9gr to see what it looks like.

 

[Larry Koch]

Ask Speedy, he has taught me a bunch on reloading, and at the firing line. I’m fortunate to be able to shoot with him at our monthly club matches. Just wished I met him 10 years sooner.

 

[Larry Koch]

Thanks to all who have jumped in here, sorry if my questions are noob-ish but thats what I am still. I'm trying to get some expierenced perspective and head off some unnecsary time/component expediture. Espeically if the probable outcome looks bleak on my path.

I have never turned necks, I did buy a 21st century neck turner a while back. Would need to get the right components for 6BR.
A couple questions though:

I have a barrel being chambered by Speedy now with a no turn chamber. Is it worth turning the necks if I stay away from pressure in this barrel?

I assume the lack of clearnace will negatvily impact accuracy/precision consistency to some degree. However if I am able to aciheve 3/8-1/2" with consistnecy this barrel will serve a purpose.
Of course I will have to test to know for sure.
But does it seem attainable from an outside perspective, or am I likely going to be chasing my tail?

My thought was go load rounds 27.6gr, 27.8gr, 27.9gr to see what it looks like.

I really think your loaded rounds are too tight for the chamber neck. Proceed with caution.

 

[coldboreshot]

This may not have any value, but I'm curious what the actual bore spec is with a pin-gage test. Wouldn't an overly tight bore create excessive drag on the fired round maxxing-out pressures before leaving barrel? By no means am I a barrel maker or metalurgist, just curious to learn.

 

[Dolomite]

Have you shot without the suppressor? If so you do still get the heavy bolt lift?

I’m not familiar with suppressors but I read it blows back carbon into the barrel.

 

[JFrank]

It don’t think so.
I use Imperial wax, after sizing I do 6 hour tumble in rice media. If I’m cleaning quick I’ll wipe the lube off with a cloth and use alcohol to ensure it’s all off. Final procedure when cleaning my barrel is to run my chamber rod through with a 9mm iosso brush and a 30cal patch, I turn to ensure it’s dry.
I use PMA bore guide throughout all of the cleaning.

A couple questions if I may ask;
Have you compared fired case dimensions against sized case dimensions at the .200 line and the case shoulder junction ?
Have you taken the barrel off and cleaned the throat without the bore guide in place ?

 

[MikeG08]

A couple questions if I may ask;
Have you compared fired case dimensions against sized case dimensions at the .200 line and the case shoulder junction ?
Have you taken the barrel off and cleaned the throat without the bore guide in place ?

I have not done these things but I certainly can.

 

[MikeG08]

Have you shot without the suppressor? If so you do still get the heavy bolt lift?

I’m not familiar with suppressors but I read it blows back carbon into the barrel.

No I haven’t shot without the suppressor in a while. I will put this on the troubleshooting steps once I try a few other things. I’m actually thinking about buying a prefit just to test against. My barrel with Speedy is a little while out I’m sure. Patience isn’t a strong suit and it seems like that may yield faster results.