OK, some advice needed. I have been developing some loads for my 308 with Remington cases, with some promising results. I recently bought some brand new Sellier & Bellot brass and the loads that worked fine with the Remington brass immediately showed pressure signs (flattened primers) with this new brass. I stopped shooting these loads and when I pulled the bullets, the powder had become compressed and was hard to remove. I checked the case capacity and lo and behold the S&B had a smaller capacity (3.434cc vs 3.545cc). So I thought, no problem, I'll just over and build up again from start loads but then dang! Even at start loads the primers are still flattening out! So where to from here? Has anyone else experienced this and how did you approach the problem? I guess the only way to go is down, but by how much? The start load according to my Lee reloading manual was 42gr Varget with 165gr Nosler ABs. Any recommendations would be appreciated.
Pressure Signs with New Brass
- Thread starter Tommo64
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Mikecr
Well-Known Member
Doesn't sound like a pressure problem. Flattening primers can occur with high headspace until new brass is fire formed.
What happens; On firing the primer slams back against the bolt face, proud of it's pocket support and flattening a bit. Then as load pressure builds the case stretches back to the bolt face, reseating the flattened primer.
Don't plan anything serious with new brass until it's fire formed to fit your chamber, and sized per your plan -from there..
What happens; On firing the primer slams back against the bolt face, proud of it's pocket support and flattening a bit. Then as load pressure builds the case stretches back to the bolt face, reseating the flattened primer.
Don't plan anything serious with new brass until it's fire formed to fit your chamber, and sized per your plan -from there..
DUSTY NOGGIN
Well-Known Member
bolt action or semi ??
over sizing can cause early signs... once the brass is fire formed , it can alleviate some of the signs you are seeing
compare your fire formed with one of the new cases , measure case base to shoulder on both .. using a universal depriming tool get the primer out without changing the shape of the brass , while insuring that you do not measure the ejector opening mark on the back of the case
forget the .002 less shoulder bump for a minute and focus on the bolt closing feel while removing the firing pin and spring loaded ejector plunger , what ever that measurement is, is what i would size to during your this workup
your case volume measurement is certainly going to affect the pressure. but, i dont think it would push the pressure all the way to a starting load? do you know someone with quickload that can run both of those water differences , using your remington safe load as a base measurement
i would
remeasure lands , seat next batch at least 15 to 20 off if your bullet allows (verify jam isn't causing pressure)
clean thoroughly ( maybe your Remington trim length left carbon at the gap and your sb brass is longer ) ,
keep note of primer feel at next install ,
remove pin and plunger from bolt and get exact measurement of chamber ,using a once fired case
verify your scale is accurate, with check weights
see if a 308 bullet will drop right in a once fired brass
measure once fired neck measurement , record measurement and compare next seated bullet of next batch
maybe use a lighter bullet to finish fire forming the new brass
and try again at starting load
over sizing can cause early signs... once the brass is fire formed , it can alleviate some of the signs you are seeing
compare your fire formed with one of the new cases , measure case base to shoulder on both .. using a universal depriming tool get the primer out without changing the shape of the brass , while insuring that you do not measure the ejector opening mark on the back of the case
forget the .002 less shoulder bump for a minute and focus on the bolt closing feel while removing the firing pin and spring loaded ejector plunger , what ever that measurement is, is what i would size to during your this workup
your case volume measurement is certainly going to affect the pressure. but, i dont think it would push the pressure all the way to a starting load? do you know someone with quickload that can run both of those water differences , using your remington safe load as a base measurement
i would
remeasure lands , seat next batch at least 15 to 20 off if your bullet allows (verify jam isn't causing pressure)
clean thoroughly ( maybe your Remington trim length left carbon at the gap and your sb brass is longer ) ,
keep note of primer feel at next install ,
remove pin and plunger from bolt and get exact measurement of chamber ,using a once fired case
verify your scale is accurate, with check weights
see if a 308 bullet will drop right in a once fired brass
measure once fired neck measurement , record measurement and compare next seated bullet of next batch
maybe use a lighter bullet to finish fire forming the new brass
and try again at starting load
Last edited:
Thanks guys, that's interesting. I hadn't thought about the headspace issue. Apart from the flattened primers there have been no other pressure indications to speak of, e.g., stiff bolt lift, etc. For info, yes it is a bolt action. Brass has had a couple of firings, so not entirely virgin but probably not fully fire formed either. I have been FL resizing but only just enough to push the shoulders back a couple of thou. That said, if the brass is not quite fully fire formed this may be too much? Maybe I should just neck size for the next few firings? Seating wise I am nowhere near the lands as this rifle has heaps of freebore and as I'm trying to develop loads for hunting I have been seating to SAAMI COAL to fit the mag. Anyways, thanks for your advice. I think I will do the above and persevere with the light loads and see how things go.
How are you checking your headspace as to whether the shoulder needs to be bumped back? You are possibly bumping the shoulder back when you do not even need to at this point? If the brass is new, it is likely undersized, and by bumping shoulder back you are just putting it back to original smaller size.
Just a thought, I'm new to reloading so far from an expert.
Good luck!
Steve
Just a thought, I'm new to reloading so far from an expert.
Good luck!
Steve
Thanks Steve, no I think you are probably right. I think I should probably just neck size only until the brass is definitely fire formed. I'm still on the learning curve with this reloading thing too.
planetwaves
Well-Known Member
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Different brands of brass have different capacity. You need to back off the powder charge and work up again. A while back I put the same 270 win load into 5 different brands of once fired, FL sized and fully prepped brass with the following fps (6 rounds each):
Nosler 3009 s=1
Hornady 3019 s=11
Win 3060 s=16
Barnes 3129 s=11
Rem 3133 s=26
So I'd suggest backing off the charge a few grains and working up.
new2mud
Well-Known Member
Wow--what a great test. 120+ fps difference just on brass.
Flintlock shooter
Well-Known Member
Maybe slightly off topic, but here is something to consider. I feel like the first firing on new brass is by far the hardest on the case. That being said, I develop a load the is approximately 1.5gr lower than the loads I shoot in competition. These loads are still accurate, just slower. I use them for practice or in one-day matches that aren't overly important. In my experience, the primer pockets seem to go first and this helps them to live longer. I strive to get 20+ firings on my cases.
new2mud
Well-Known Member
Out of curiosity how which brand cases/caliber? And have you noticed significant longevity differences vs. other brands?
Flintlock shooter
Well-Known Member
If taken care of and not over-revved, I think any good quality brass with last thru many firings. I shoot 6XC and use Alpha Munitions brass. Mostly because I'm anal about my ammo, I anneal after each firing.
