What are the pressure signs for 6BR Lapua cases?

[johnsopa]

I installed my Shilen 1:8 6BR barrel,chambered for no-turn necks) on my Savage last week.

I am now working a ladder and am surprised that I am not seeing any pressure signs yet. I am up to 31.6 gr of Varget and 32.0 gr of RL-15 using 87 gr V-Maxes seated to 2.220" COL. My cases are showing 39.1 gr of water capacity once fired.

My bolt is still easy to lift and there are no ejector or extractor marks on the cases.

I am getting between 3010,Varget) and 3058 fps,RL-15) in my 24" barrel.

Does it seem right that I am not seeing any pressure signs yet or do the Lapua cases show pressure differently than the run-of-the-mill Winchester 204, 223 and 308 cases I am used to?

Thanks,

John

 

[Forum Boss]

Just feel like I have to add that different barrels respond differently to loads, and there are slow and fast lots of Varget. Many 6BR shooters will find that even 30.5 grains of Varget is at,or close to) max.

Just don't want anybody loading 31+ grains of Varget with a 107 right out of the gate.

That said, I agree with Lynn that your load is not necessarily at max with the 87s. The first thing I usually notice with pressure signs is the ejector mark--a round spot where the brass is actually flowing into the ejector hole. But there are many other signs. You should look at the edge of the primers, measure the growth of the case, and check for loosening of the primers cups.

 

[johnsopa]

This is gonna sound like a stupid request, but could someone post or point me to a picture of a case that shows ejector marks? I have never gotten this far, I guess, with my newbie loading for my Savages.

Thanks,

John

 

[tammons]

I have the exact same setup. Savage model 12 and a shelin 6mmBR 8 twist barrel. I am mostly shooting 105 gr senecars jammed over 30 grains of varget br4 primers with no pressure signs.

I have loaded it higher, but felt I could probably not reach the next node safely so I backed off. RL15 is next.

Shot 80 gr bergers from 30.5 up to 32.5. Best group was at 31 grains jumped. Very tight. Got some slight erratic pressure signs at 32.5.

As far as ejector marks, I have my ejector removed. I tried to photo a ring mark. Not easy. This is 6.5x47 lapua which is basically the same case just extended, with 123 gr senecars and 42 gr of H4530. I started getting these types of marks, but no heavy bolt. Jumped and moly bullets I probably could have gone a bit higher, but I decided I like 22 caliber and 6mmbR better.

I am building a 22x47 lapua if I ever get it together.

Ejector mark. I had to lighten the area to make it more clear.
I alway thought lapua cases were a work of art until I shot this macro. The round spot is a slight raised area.

 

[johnsopa]

Thanks Tres. Looking forward to seeing them.

 

[dreever]

I mic new brass just above the extractor groove on the web.
I re-mic once fired brass and prefer not to see any expansion over .001. On the second firing if it adds .0005 that's acceptable, but that's it. Regardless of firings I don't want to see any expansion over .0015 ever.
For example when I was playing with Reloader 15 working up loads trying to get a cleaner burn at 31.2 grains I had very slight bolt lift, no sticking cases, or marks on the case, but the first firing web expansion was .003! That was probably 80,000+ PSI. Not good. I gave up on the Reloader 15 and went to Varget where expansion was under .001 on the first firing. A much safer and saner load, and way easier on the brass.

Danny

 

[Forum Boss]

I used the same basic standard as Danny. It seem that, even with a mild load,i.e. 28.5 Varget with 105s in a 6BR) I'll get .001 expansion, but I don't want to see more than about .0017 ever.

For example, I have a box of Factory-loaded 6BR ammo. New, unfired, this measures 0.4685 at the top of the extractor groove where it meets the case body. The fired factory brass expands just about .001 to 0.4695.

This is measured with calipers not a mic, so YMMV. Also a very slight difference in the placement of your brass in the jaws will affect the reading, but the point is you can get nearly .001 expansion with a "safe load"

 

[johnsopa]

Wow, thanks. That is a great picture. I have never seen anything like that,albeit a probably smaller mark given the smaller ejector) on my Savages.

What is the trapezoid shape around the "WSM"? Is that the extractor marking?

I guess I'll have to get a micrometer to start measuring case head expansion.

You are measuring the expansion of FL sized brass, not neck sized brass, for the case head expansion, right?

 

[Forum Boss]

John,

Measure the expansion AFTER firing but BEFORE sizing of any kind. Some people like to measure .020" above the extractor cutout because that's where a pressure ring is located. However, I've found it's easier to measure right where the extractor groove meets the case body.

When you've really "toasted" your cases, the groove itself and the rim will grow--sometimes enough you can't get the case in a shell-holder.

 

[johnsopa]

Sorry, what I meant was this...

Is case head expansion something that should be measured after a round that is FL sized has been fired or can it be measured after a round is neck sized and then fired?

I typically FL size once, then fire and reload until rounds start chambering hard, at which point I FL size them.

Can case head expansion happen after each of these firings or is the +0.001 - +0.0015 measurement range good only after the first firing?

Thanks,

John

 

[Coleridge]

Gun...

A freind of mine bought the first 300WSM,a-bolt) we came across. We stopped shooting the factory box of bullets 3 rounds in after seeing similar results. Winchester had the first 300WSM offerings WAY hot. He ended up pulling 3 boxes of factory bullet to reload. When he first got his brass wasn't even available,It was about another month before Midway had it).

The only other time I have seen that stong of ejector mark was in a 270WSM loaded at max LOAD from the Sierra book,I've found that Sierra is usually conservative).

 

[Lane]

I installed my Shilen 1:8 6BR barrel,chambered for no-turn necks) on my Savage last week.

I am now working a ladder and am surprised that I am not seeing any pressure signs yet. I am up to 31.6 gr of Varget and 32.0 gr of RL-15 using 87 gr V-Maxes seated to 2.220" COL. My cases are showing 39.1 gr of water capacity once fired.

My bolt is still easy to lift and there are no ejector or extractor marks on the cases.

I am getting between 3010,Varget) and 3058 fps,RL-15) in my 24" barrel.

Does it seem right that I am not seeing any pressure signs yet or do the Lapua cases show pressure differently than the run-of-the-mill Winchester 204, 223 and 308 cases I am used to?

Thanks,

John

Absolutely! All brass is not equal in hardness, all chambers are not equal in dimensions and tolerances. Traditional pressure signs like described previously can be misleading. Case expansion based on what for reference? Case expansion at the case web of .004 as opposed to what? Pressure indicator like flattens primers is it over the top pressure or a case head-space issue? Pressure indicator like hard bolt lift is it over the top pressure or rough chamber,rough bolt lugs that are not smooth and polished. Brass hardens every time we fire it or re-size it I think we would all agree. Through firing and resizing the hardness of the brass increases and at some point the case head hardness will increase and show less expansion, and primer pockets still produce a tight fit with seated primers. Is this condition brass hardness or lack of pressure in the specific load? As a pressure indicator the hardness of the brass in the case web or,primer pocket) may mask any expansion in the primer pocket, case web. The best pressure indicator tool is a chronograph. Factory ammunition as reference ammunition and using the specific components listed in a loading guide,primer,powder,case, bullet). If you are going to use traditional pressure methods to judge pressure in your loads experience has educated me to have some very accurate measurements before fired, after fired and before and after any resizing? Case measurements, expansion ) taken when, in reference to what, and taken at what point on the case? We all know to get velocity we need pressure a chronograph tells us something about the pressure in our loads in my view however we still need something to use as a baseline to compare our loads to. Fired brass changes. Fired brass and re sized brass one time changes. Fired brass and re sized brass twice changes. Personal point of view. Lane