Case Head Expansion?

[BTWalker376]

Hello All,

Recently I was doing some load development for my 22 Creedmoor. I was using load data provided to me by Berger for their 85.5 gr LRHT bullets. I started at the middle of the charge weight table and worked my way up in 0.3 gr increments to the top. I didn't start to see noticeable pressure signs until I started getting close to max charge weight. At the top end of the ladder, there were ejector rings and swipe (also happened to shoot the best group 0.36" at max charge).

After going through the forums trying to learn more about pressure signs and when to back off, I ran into quite a few folks mentioning "case head expansion". So, I measured the case head width on a few pieces of unfired brass from the same box. All measured exactly 0.468". I then measured 15 or so pieces of the fired brass from my recent ladder test and they measured anywhere from 0.469" to 0.471". Seemingly...regardless of the charge weight I am seeing case head expansion ranging from 0.001" to 0.003".

Note: My velocity using 42.9 gr of RE-23 (0.1 gr over max charge provided by Berger) averaged only 3202.6 fps.

Components used in my recent test:

Powder: Alliant RE-23
Primer: CCI 450
Cases: Alpha SRP
Bullet: 85.5 Gr Berger
CBTO: 2.039" (Jam with this bullet in my rifle is 2.079" CBTO)
Starting Charge: 41.1 gr
Ending Charge: 42.9 gr (0.1 gr over Bergers max on the data they provided)


A few questions:
1) Are these pieces of brass that have expanded at the case head "unusable" or "ruined"?
2) is there any amount of "acceptable" case head expansion?
3) If these charge weights are unsafe and therefore unusable, how do I find a safe charge weight for a powder that does not have published data?
4) Anyone have good load recommendations for the Berger 85.5s? I have H4350 and RE-23 currently available

 

[ButterBean]

Your Fine, Let Her Eat

 

[Phil Rizzo]

This isn't simple to explain, would take pages. Do you have a reamer print? Likely available online.

There is always some growth from virgin to 1x fired, you just don't want to exceed the chamber diameter number. Staying below that number .0005-.001" is beyond safe, it promotes longer case life. Mild firing on virgin brass does in fact promote longevity.
Kinda depends on your goal, as to what is acceptable or not….sometimes performance trumps "brass life" for Me. And likely Mr Butterbean too

I wouldn't think Alpha brass is very flexible, likely it will take pressure better than others. I can't wait for them to manufacture it for adult sized non-comp cartridges.

 

[cajun]

Thats a can of worms. Some folks swear by it some say it's voodoo. Either way you need a blade mic
That reads .0001 not a caliper. You also need to measure the right spot at the .200 datum. Either way I think you are fine.

 

[Trnelson]

Case head expansion of a fired case considered by itself doesn't necessarily mean much. It just means that where the case ended up. As mentioned above you'll want to consider it as it relates to the chamber of the rifle, and the sizing die. If you are sizing more than necessary for your chamber it can contribute to case stretching and diminish case life and you can observe what appear as over-safe pressure signs on the brass due to too much headspace. Without getting a solid idea of what the actual chamber size is the other factors are simply measurements, not necessarily indicators of actual pressure.
For instance, say your individual rifles chamber is reamed to the larger end of acceptable Saami headspace. Additionally, if your individual sizing die is reamed to the smaller end of Saami acceptable size. In this instance you will observe pressure signs on the fired case as its headspace is likely to be in excess of what is required for normal function.

 

[BTWalker376]

Case head expansion of a fired case considered by itself doesn't necessarily mean much. It just means that where the case ended up. As mentioned above you'll want to consider it as it relates to the chamber of the rifle, and the sizing die. If you are sizing more than necessary for your chamber it can contribute to case stretching and diminish case life and you can observe what appear as over-safe pressure signs on the brass due to too much headspace. Without getting a solid idea of what the actual chamber size is the other factors are simply measurements, not necessarily indicators of actual pressure.
For instance, say your individual rifles chamber is reamed to the larger end of acceptable Saami headspace. Additionally, if your individual sizing die is reamed to the smaller end of Saami acceptable size. In this instance you will observe pressure signs on the fired case as its headspace is likely to be in excess of what is required for normal function.

This is good info.

I spoke with my gunsmith and he informed me he reamed my chamber close to SAAMI minimum. With my firing pin and ejector removed, I test fit a piece of my virgin alpha brass and closing the bolt was tight. Thus, at the advice of both Tom Danielson (Alpha brass CEO) and my gunsmith, I bumped the shoulder back 0.002" with my sizing die (short action customs modular die). The bolt was able to freely fall on this shoulder bumped brass.
Not sure that changes your analysis at all.

Appreciate the help!

 

[Beluebow]

At the top end of the ladder, there were ejector rings and swipe (also happened to shoot the best group 0.36" at max charge).

Typically, that is a good indicator of pressure. But it could be new brass and a headspace. What does new vs fired measure at the shoulder?

 

[BTWalker376]

Typically, that is a good indicator of pressure. But it could be new brass and a headspace. What does new vs fired measure at the shoulder?

Right at the shoulder neck junction, I measured around 0.007" of growth between virgin brass (post resizing/shoulder bump) and fired brass. That seems like a lot!

 

[Beluebow]

Right at the shoulder neck junction, I measured around 0.007" of growth between virgin brass (post resizing/shoulder bump) and fired brass. That seems like a lot!

It's probably within SAAMI specs. I would prefer a little tighter on the headspace personally. After the first firing it won't matter.

 

[BTWalker376]

It's probably within SAAMI specs. I would prefer a little tighter on the headspace personally. After the first firing it won't matter.

I miss-typed. that 0.007" growth was at the shoulder & body junction NOT the shoulder neck junction. Not sure if that changes your opinion.

 

[lancetkenyon]

Are you set on using RL23?
I can think of several other powders that should get you more speed...unless you are running a 16" barrel (which I don't remember seeing in your posts). RL17 or H4350.

3202 with a 22CM seems awfully slow.
I am at 3130 from an 85.5LRHT with a 22" 22GT, which has a lot less case capacity than the 22CM. I think I am at 36.0gr Varget.

 

[BTWalker376]

Are you set on using RL23?
I can think of several other powders that should get you more speed...unless you are running a 16" barrel (which I don't remember seeing in your posts). RL17 or H4350.

3202 with a 22CM seems awfully slow.
I am at 3130 from an 85.5LRHT with a 22" 22GT, which has a lot less case capacity than the 22CM. I think I am at 36.0gr Varget.

Certainly not set on RL23. I just bought a pound for load development. Shooting out of a 22" barrel.

It feels slow to me! I'm open to taking any other powder suggestions.

Thanks!

 

[lancetkenyon]

Certainly not set on RL23. I just bought a pound for load development. Shooting out of a 22" barrel.

It feels slow to me! I'm open to taking any other powder suggestions.

Thanks!

Try H4350 or RL17. I think H4350 is THE go-to powder for the CM line of cartridges.

I use it in my 24" 6CM pushing 105s @ 3188fps
Two different 26" 25CMs pushing 133s @ 3008fps or 135s @ 2986fps

I have used it in several 6CM, 25CM, and 6.5CMs as well.
Super stable, easy to find, clean burning, and accurate.

 

[BTWalker376]

Try H4350 or RL17. I think H4350 is THE go-to powder for the CM line of cartridges.

I use it in my 24" 6CM pushing 105s @ 3188fps
Two different 26" 25CMs pushing 133s @ 3008fps or 135s @ 2986fps

I have used it in several 6CM, 25CM, and 6.5CMs as well.
Super stable, easy to find, clean burning, and accurate.

Many thanks for the tip!

As you sound far more experienced in reloading that me, what would you say is a good way to find my max pressure with H4350 (not that the process will differ from powder to powder)?

Hodgdon doesn't have load data for H4350 and the 85.5 gr Berger which surprises me given how many people say its a great CM family powder!