ejector imprints

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fat but funky

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Hi Folks,

Have a question regarding ejector imprints.

I have developed a load for my 6.5x55 T3

140 gn Sierra Game King
46.0 grn H4350
win LR primer
muzzle vel. 2750-2780 fps - measured with chrony
3.070" COAL
Cases full length resized and trimmed to length
all charges weighed on RCBS chargemaster combo

In the development of the load, I had pushed all the way up to 47.0 grains - but was seeing pressure signs - significant ejector imprints, cratered primer, gas leakage around primer, and sticky bolt lift. Backed off to 46.0 grains, getting 3-shot groups around 1", maybe better on a good day.

Between sighting and practice I have shot maybe 60-70 rounds of this load through the gun with no problems. Mostly in the winter (about 0C), a little in the summer (20+C).

Today I was looking over the spent brass, and maybe 10-20% have very faint ejector imprints on the case head. You have to tilt the case head to just the perfect angle with the light to see it. No primer cratering, no staining, and I haven't been having any particular difficulty with the bolt. Just an ever so slight round outline on the case head.

Should I be worried about this? I know the load is on the warm side - but I would have thought safe in a modern firearm.

I have a little less than 150 rnds of this load left and would like to shoot it up if possible.

Thanks

Fat
 
fat but funky said:
Hi Folks,

Have a question regarding ejector imprints.

I have developed a load for my 6.5x55 T3

140 gn Sierra Game King
46.0 grn H4350
win LR primer
muzzle vel. 2750-2780 fps - measured with chrony
3.070" COAL
Cases full length resized and trimmed to length
all charges weighed on RCBS chargemaster combo

In the development of the load, I had pushed all the way up to 47.0 grains - but was seeing pressure signs - significant ejector imprints, cratered primer, gas leakage around primer, and sticky bolt lift. Backed off to 46.0 grains, getting 3-shot groups around 1", maybe better on a good day.

Between sighting and practice I have shot maybe 60-70 rounds of this load through the gun with no problems. Mostly in the winter (about 0C), a little in the summer (20+C).

Today I was looking over the spent brass, and maybe 10-20% have very faint ejector imprints on the case head. You have to tilt the case head to just the perfect angle with the light to see it. No primer cratering, no staining, and I haven't been having any particular difficulty with the bolt. Just an ever so slight round outline on the case head.

Should I be worried about this? I know the load is on the warm side - but I would have thought safe in a modern firearm.

I have a little less than 150 rnds of this load left and would like to shoot it up if possible.

Thanks

Fat
Click to expand...

Back off your loads another 0.5 grains and you should be OK.
 
What the fellows have said about 1 grain being too small a safety margin, from a too hot load, is correct. However, the ultimate test of whether your present loads are too hot, is if the primer pockets enlarged. If they enlarged enough to be detectable after only one firing, your present load is still too hot.
 
It sounds like you need to back off the powder charge by at least another grain.Shooting a few very slightly hot loads won't cause an action to fail,but the effects are cumulative.
 
The #14 Speer reloading manual has listing for 6.5x55 Military actions.
140 grain bullet max load 36 grains of H4350

And also Strong Commercial Actions in 6.5x55
140 grain bullet max load 40 grains of H4350

Hodgdons manual
140 grain bullet max load 44 grains of H4350

The loads listed above are in the 58,000 psi range and American made SAAMI cases are at their design limits at this pressure. European made cases are designed for up to 65,000 psi limit so Lupua cases might be able to take the pressures you are striving for.

For now back off at "LEAST" two grains from your 46 grain load, your brass is telling you a story.

Read the link below, none of the 140 grain bullets for these 6.5 cartridges used over 42 grains of H4350

http://demigodllc.com/articles/6.5-shootout-260-6.5x47-6.5-creedmoor/?p=1

http://demigodllc.com/articles/6.5-creedmoor-260-done-right/

The 6.5 is a very old cartridge that has always been extremely popular in Europe, and for good reason. It has been an excellent long range competition cartridge with excellent 6.5 bullets available. There have also been companies such as Lapua and Norma that have always loaded superb match grade ammo for it. Over the years I have become a fan of this cartridge based off of its history, pleasant shooting qualities, and great long range accuracy. Unfortunately, the 6.5x55 has never really been considered for much long range shooting in the USA, although to serious long range shooters and European shooters its no real surprise at how well this cartridge does. In the USA there was a brief bit of interest in this cartridge a few years ago but the thing that has hurt it recently is the introduction of the short action 6.5 cartridges such as the 260 Remington, 6.5x47 Lapua and 6.5 creedmore. These all produce performance on par with the USA loaded 6.5x55 ammo, but in a short action. But, you see, the 6.5x55 actually has more case capacity than the others but because there are so many very old rifles built and chambered for this cartridge, most of the USA manufacturers are not willing to load this cartridge to its potential. Instead of labeling the ammo "modern firearm use only" they have decided to handicap everyone using the 6.5x55. In Europe, this is not a problem so Lapua, Norma and others load it to much higher velocities. HSM here in the USA is also working on a hot version of the 6.5x55 with the sierra 142 SMK as well and that should be out very soon and readily available for the USA shooters.


http://www.snipercentral.com/65swed.htm


YOU NEED BETTER 6.5x55 BRASS IF YOU WANT TO SHOOT HIGHER PRESSURES. ;)
 
46.0 grs of H4350 with a 140 gr AMAX is the exact load I use in my Mauser, except its OAL is longer (3.250") so in my case the pressure would be lower than yours. That load is used by many target shooters, and is up near 60K psi, so it's safe in modern actions, and nowhere near "Proof" loads.

"Pressure Signs" are all subjective, and even when you measure case head expansion, it only means something if done accurately and against a baseline for the particular brass you are using. IMO, the only sure pressure sign is loose primer pockets, and even that's bit subjective - is "loose" when they feel looser, when you can push them in with your thumb? If they are "loose" after five or fewer firings your pressure is high and brass life will suffer. However if the load is accurate, it's well worth it. If the primers are loose after 1-2 firings, I'd back off by at least 2 grs.
 
46.0 grs of H4350 with a 140 gr AMAX is the exact load I use in my Mauser, except its OAL is longer (3.250") so in my case the pressure would be lower than yours.
Click to expand...

If the COL is longer,the bullet is likely seated closer to the lands,which usually causes an increase in chamber pressure.
 
stubblejumper said:
If the COL is longer,the bullet is likely seated closer to the lands,which usually causes an increase in chamber pressure.
Click to expand...

It depends on your throat of course, and how close or far you are from the rifling. Closer to the lands (longer OAL) gives more effective case capacity and lowers pressure, but when close to or against the rifling, pressure rises. In between, all kinds of things happen.

Those who say "just go by the loading manuals, they have the pressures to the closest ten psi" need to understand that it's just not that simple. Brass varies, chambers vary, primers and powder lots vary, barrels vary, etc. Fortunately receivers are overbuilt and there are plenty of warning signs short of damage.
 
It depends on your throat of course, and how close or far you are from the rifling. Closer to the lands (longer OAL) gives more effective case capacity and lowers pressure,
Click to expand...

The effective case capacity would be the volume with the bullet against the lands,since it takes very little effort to push the bullet out of the case neck.As such,the pressure is nowhere close to maximum before the bullet strikes the lands,and the resistance of the bullet into the lands comes into play.
 
fat but funky said:
Mostly in the winter (about 0C), a little in the summer (20+C).

Today I was looking over the spent brass, and maybe 10-20% have very faint ejector imprints on the case head.
Click to expand...


Perhaps the 10-20% that are showing ejector marks are the ones you shot when it was 20+C and the rest were shot when it was cooler? How much does your muzzle velocity vary between cold and warm weather? From my experience, probably about 100fps, which is enough of a difference to exceed max pressures.
 
I would conduct an experiment. I would drop the charge several grains, load up test lots in one grain increments back to my top level and shoot them. I would find out where the "indicator" starts to show. It might show in all of them, in which case I would ignore it. It might show only on the top load, in which case I would drop my charge.

As a general rule, if I am asking myself (or anyone else) if something is indicating too much pressure, I do some actual testing. If I still feel uncertain after testing all the variables I can, I back off until I am convinced beyond any doubt that I am safe. It's my gun, my loads, my procedures. How can anyone else know for sure what is happening?

I would never want to shoot loads for which I had doubts every time I pulled the trigger.
 
Kinda bringing this thread back from the dead

did a few things to investigate:

1.) Looked through some of my other cases from other guns. Could find similar, very faint, ejector marks on a few cases from most of these guns. This includes 204 ruger Sav mod 12, 303 brit SMLE, 308 win - Norinco M14. These loads are at or below max. But, again, only a few of the cases were affected from each gun.

2.) Took my suspect cases to a guy at work who has been reloading for more years than I have been on this earth. He took a look and dismissed them as being fine.

So then I remembered something I heard about testing Lee Enfields back in the 'old days'. I seem to remember something about using greased up cartridges to increase the backthrust on the bolt. Making sure, I guess, that the bolt doesn't fly out when the trigger is pulled.

So, I'm thinking that maybe these cases are the first ones I fire after I clean the barrel and run a little G96 down it. I pull a dry patch down after the G96 - but I bet there is a little lube left in the chamber. I wonder if that little bit of lube is enough to prevent the brass from 'grabbing' the chamber walls as much as usual - putting more force on the bolt head (and therefore the ejector).

Anyway, that's my best explanation for why it occurs so sporadically but in more than one gun at below max levels.

I'm going to shoot what I have left of these current loads, then start with new brass on a new load - maybe try some RL 17 and some SST's

Thanks for all the input

Fat
 
sticky bolt

I have been reloading for 20+ years now. In my opinion when you get to the "sticky bolt" pressures you are usually a fair bit over max pressure. In this situation I don't think backing off one grain is enough. If your at 47gr with a sticky bolt, I would be trying to 44-45 grains as your max. For accuracy purposes I would be shooting from 40-45 grains in increments, accuracy is way more important than velocity.
 
If the ejector mark is very faint I would continue to shoot them. I've shot many that way. Your only real risk is that you will enlarge the primer pockets too much and have to discard the brass. Fortunately you have a powder that is quite temperature insensitive, so the pressure should not go up too much in warmer weather, but you should watch it. I've heard that while H4350 is an extreme powder it may still be a little temperature dependent. For future loads I would back off in 0.5 grain increments and take note of when the ejector mark goes away.

I think I would also go to a touch slower powder like the H4831. You may be able to hold that velocity without running the high pressures.
 
46.0 grains of H4350 is 2 grains over max. You need a manual if you don't have one already. If you do, you need to follow it religiously.
 
sunray said:
46.0 grains of H4350 is 2 grains over max. You need a manual if you don't have one already. If you do, you need to follow it religiously.
Click to expand...

But, to be fair the published loads for the 6.5x55 Swede are light to protect the older military actions. Hodgdon max data is based on 45,000 CUP. A modern gun load is usually based on about 50,000 CUP.

Assuming the OP has a modern action gun then I don't think two grains over 44 is unreasonable. But, every gun can be different, and one has to respond to the signs.
 
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