6BR pressure signs low loads

[Dolomite]

On my second firing of Lapua Brass I'm getting high pressure signs heavy bolt lift, ejector swipes and partially flat primers.

Shooting virgin Lapua Br brass had no pressure signs same load 28.5, resized the brass and started load testing from 25 - 28.5 and every case had ejector swipe and heavy bolt lift. The chamber was dry and the barrel had 39 rounds down the pipe since the last cleaning.

FPS 2575 at 28 grains of varget

Terminus Zeus QC barrel
Bartlien 1:8 twist 6mm HV barrel
.272 neck chamber
.120 Freebore
Varget (25-28.5gr)
CCI BR4
105gr Hornady HPBT
Tested at .020 - .035 off the lands.
Shoulder bump .002
Loaded round is .268 - .269.
Brass neck thickness at .0127 - .013 for a total of around .026.
Lapua Case OAL 1.556
Lapua Case OAL 1.554
Lapua Case OAL trimmed 1.551

I bore scoped the the fired brass in the chamber and it has lots of clearance for OAL.

Neck OD fired case .2705-.271
Neck OD loaded round .268-.269
Chambering empty case new and sized is fine
Chambering a fired case is heavy bolt closure.
Snug fit when trying to insert a bullet into a fired case.

I’m using a Redding type S die (.267 Bushing) and noticed that the base of the neck that is unsized is .2705 and I have a .272 neck.

Does that come into play when measuring loaded rounds vs chamber neck size?

Could the BR4 primers be causing the high pressure?

 

[Bill Norris]

On my second firing of Lapua Brass I'm getting high pressure signs heavy bolt lift, ejector swipes and partially flat primers.

Shooting virgin Lapua Br brass had no pressure signs same load 28.5, resized the brass and started load testing from 25 - 28.5 and every case had ejector swipe and heavy bolt lift. The chamber was dry and the barrel had 39 rounds down the pipe since the last cleaning.

Terminus Zeus QC barrel
Bartlien 1:8 twist 6mm HV barrel
.272 neck chamber
.120 Freebore
Varget (25-28.5gr)
CCI BR4
105gr Hornady HPBT
Tested at .020 - .035 off the lands.
Shoulder bump .002
Loaded round is .268 - .269.
Brass neck thickness at .0127 - .013 for a total of around .026.
Lapua Case OAL 1.556
Lapua Case OAL 1.554
Lapua Case OAL trimmed 1.551

I bore scoped the the fired brass in the chamber and it has lots of clearance for OAL.

OD fired case .2705-.271
OD fired round .268-.269
Chambering empty case new and sized is fine
Chambering a fired case is heavy bolt closure.
Snug fit when trying to insert a bullet into a fired case.

I’m using a Redding type S die (.267 Bushing) and noticed that the base of the neck that is unsized is .2705 and I have a .272 neck.

Does that come into play when measuring loaded rounds vs chamber neck size?

Could the BR4 primers be causing the high pressure?



View attachment 1312321

The Type "S" die will not size the entire neck. The die has a shelf inside and is designed to allow the bushing to rest on it so it cannot possibly size the the neck down to the neck/shoulder junction. I do not see that as an issue.

 

[Bill Norris]

I can't see the BR-4 primer being an issue. I've used many in 2 different 6mmBR rifles and one was a very tight .271 chambered neck. My loaded rounds were @ .268 -.2685 with no issues at all. Sometimes the die will not size the case @ the 200 line enough to have the round chamber freely. It is possible to screw the die in deeper a few thousandths and I have had to take a few thousandths off of a shell holder to get the brass deeper into the die.

 

[Dolomite]

I can't see the BR-4 primer being an issue. I've used many in 2 different 6mmBR rifles and one was a very tight .271 chambered neck. My loaded rounds were @ .268 -.2685 with no issues at all. Sometimes the die will not size the case @ the 200 line enough to have the round chamber freely. It is possible to screw the die in deeper a few thousandths and I have had to take a few thousandths off of a shell holder to get the brass deeper into the die.

I have the same issue with the redding die not getting to the base but I use a forster press so no shell holders to adjust.

It doesn't feel like I have clickers its a heavy bolt lift from start to finish.


Do you think not sizing the base enough is cause the pressure issues of ejector swipe?

 

[Bill Norris]

I have the same issue with the redding die not getting to the base but I use a forster press so no shell holders to adjust.

Do you think not sizing the base enough is cause the pressure issues of ejector swipe?

Well from your numbers above I'm am all out of answers Bro. Hopefully some others will chime in and offer you some help. It would be hard to relate that to pressure in my opinion.

 

[Dolomite]

Well from your numbers above I'm am all out of answers Bro. Hopefully some others will chime in and offer you some help. It would be hard to relate that to pressure in my opinion.

Thanks for the info. Someone mentioned in another post that it could be the humidity in the powder. I reload at around 70% humidity, not sure if that is causing pressure issues.

 

[Bill Norris]

Thanks for the info. Someone mentioned in another post that it could be the humidity in the powder. I reload at around 70% humidity, not sure if that is causing pressure issues.

Absolutely wish I could be more helpful. That don't seem like an unreasonable humidity level to me.

 

[243winxb]

I don't see any ejector swipes. Bolt will be a little stiffer after brass has been fire formed. Primers look ok. No flow.

The unsized neck is normal & after more firings will not spring back. Then it should measure very close to .272"

Bullets not fitting into fired brass can happen with my 243 win using slow powder & starting loads, factory neck diameter.

I am not seeing any problems.

 

[Dolomite]

I don't see any ejector swipes. Bolt will be a little stiffer after brass has been fire formed. Primers look ok. No flow.

The unsized neck is normal & after more firings will not spring back. Then it should measure very close to .272"

Bullets not fitting into fired brass can happen with my 243 win using slow powder & starting loads, factory neck diameter.

I am not seeing any problems.

maybe this is a better picture.

 

[243winxb]

What action/bolt?

 

[Dolomite]

This is 2x fired brass… no issues with fire forming the brass

 

[Dolomite]

What action/bolt?

Terminus Zeus QC action 6br bartlien 1:8 barrel

 

[243winxb]

I dont know. Something going on i guess. Wonder what in the pin indent? Seems odd.

 

[JFrank]

I have the same issue with the redding die not getting to the base but I use a forster press so no shell holders to adjust.

It doesn't feel like I have clickers its a heavy bolt lift from start to finish.


Do you think not sizing the base enough is cause the pressure issues of ejector swipe?

Maybe

 

[Dolomite]

I dont know. Something going on i guess. Wonder what in the pin indent? Seems odd. View attachment 1312347

interesting I didn't notice that....

 

[Dolomite]

I dont know. Something going on i guess. Wonder what in the pin indent? Seems odd. View attachment 1312347

ok I went back and checked the primers and there is a stamp that says B on it which looks like why there is that weird mark.

I dont know. Something going on i guess. Wonder what in the pin indent? Seems odd. View attachment 1312347

This could be that odd mark there is a B stamped on the BR4 primer

 

[243winxb]

Maybe a fast lot of powder? Have you checked the velocity with a chronograph and compared to load data.

 

[Dolomite]

Maybe a fast lot of powder? Have you checked the velocity with a chronograph and compared to load data.

yes I chronoed.. 28.5 gr of varget im getting 2575 FPS out of a 24" barrel, which seems really slow.

 

[pdhntr]

With the amount of swipe that is showing on the case head, I would think the primers would show more pressure.

I know primers aren't a definitive measure of pressure, but those aren't showing any pressure at all. Nice round edges.

A .272 should allow a bullet to fall through a fired case neck. Unturned brass also.

Jim

 

[Dolomite]

With the amount of swipe that is showing on the case head, I would think the primers would show more pressure.

I know primers aren't a definitive measure of pressure, but those aren't showing any pressure at all. Nice round edges.

A .272 should allow a bullet to fall through a fired case neck. Unturned brass also.

Jim

what does it mean if my bullet won't drop into a fired case freely?