Need some insight on loads with light ejector marks/swipe on hotter days.

[dlouie87]

Hello,

I'm still new to reloading but I have a quick question concerning case swipe. When I did my OCW a few weeks back, there were no ejector marks or any indication of high pressure on the Lapua brass that day. I went back to shoot the best load from the OCW and a few of the brass fired that day had some ejector swipes on there. It was about 30 degrees warmer on this range trip than the day I did the OCW on. It was about 65 degrees the day I did the OCW and it was about 95-100 a few days ago. I understand that with increase temperature, there can be an increase in cartridge pressure but should I tune it down so there are no case swipe at all?

Should I be concerned with this load since it has some ejector swipe from the hotter days?

I attached a few pictures.

The gun is a bolt action in a .308. Barrel is a 23'' bartlien cut with a Bisley reamer. The brass was FL sized with a forster die and bumped back .002-.003''.

The load is:
44.1 gr of Varget with 175 SMK, new Lapua brass trimmed to 2.005, COAL 2.777, BR2 primers, and it's shooting at 2780fps with a SD of 6 and ES of 14.

The marks are faint and I hope you can tell from the pictures. If it's not a big deal, I'll keep on shooting this load but I just wanted to make sure.





Thanks,

DL

 

[dauntedfuture]

What weight bullet? What rifle? I cant see the pics, it this is a gas gun then you can get extractor marks if your not quite sizing the brass enough. Check to see that you can easily close bolt on a stick of sized brass and open without any difficulty. 30 deg will raise pressure a little if ammo was sitting in the sun now and last time it was not. A change in humidity can spike pressure too.

 

[Seandradamus]

Was the ocw done with new brass or fired , were your next loads fl sized or neck sized only.
Your loads dont look too hot to me, the primers are nice and round on most .is the bolt lifting nice and easy

 

[dlouie87]

I updated the first post with more info.

The loads were with 175 smk and were shot out of a bolt action. The brass were all virgin Lapua resized through a Forster FL die and shoulder was bumped back .002-.003. I bumped it back .002-.003 according to the measurement of the FGMM brass that I used before I started the OCW. The measurement was taken with a Hornady headspace gauge.

The bolt is lifting smoothly and it's loads are grouping well. Everything seems fine besides these faint marks. I was thinking about adjusting the seating depth or backing off the load .1-.2 grains; but wanted to see see what you guys think first.

 

[Ballistic308]

Move your COAL out to 2.800 - 2.805". You are increasing pressure by running them that short. If you do this you may find you charge needing to increase .2-.3gr.

Most people run in the area of 44.5 with the components you have listed.

I'm trying to figure out how you're getting 2780fps out of a 23" barrel with that charge weight. Elevation maybe?

 

[dlouie87]

Move your COAL out to 2.800 - 2.805". You are increasing pressure by running them that short. If you do this you may find you charge needing to increase .2-.3gr.

Most people run in the area of 44.5 with the components you have listed.

I'm trying to figure out how you're getting 2780fps out of a 23" barrel with that charge weight. Elevation maybe?

It would be "jammed" into the lands if I loaded them to 2.800-2.805. Marc @ Spartan Rifles built this rifle and used a Bisley reamer. I had a older thread asking about the shorter COAL / BTOG and found some answers. I wanted to confirm my findings with Marc so I called him. He confirmed that the Bisley reamer does cut the throat short.

As for the base to ogive measurement, I used the Hornady comparator and it measured an average of 2.195'' with the 175s touching the lands. I loaded my OCW loads to 2.190 base to ogive to get a COAL of 2.777. So I'm about .005 off the lands right now and if I load to 2.800, I'd be .023 jammed into the lands.

As for the velocity, it was taken from a Magnetospeed v2 at 93 feet elevation from sea level.

Thank you all for the replies so far.

 

[djskit]

Dan - I don't think there is a compelling reason to drive 175's faster the 2700-2725 FPS. How you are doing that out of a 23" bbl and 44+ grains of Varget is a mystery to me as well.

Dial you load down to the low 2700's and see how that groups. You will not gain anything going faster and, as you can see, your brass is being stressed due to over-pressure.

My 308 is 26" and gets 2725 with 44.5 grains of Varget.

 

[dlouie87]

Will do. I'll try to find another accuracy node. I'll start at 42.8 and work up and report back.

 

[haroldwilson]

Maybe I read this wrong, but did you bump the shoulders on virgin Lapua brass? If so, would it not chamber in its virgin state? This would be odd. I don't shoulder bump new brass.

 

[dlouie87]

It would chamber with virgin brass. I just did it anyways. I didn't know that you weren't suppose to. Like I said, I'm still new to this stuff and I don't remember seeing in the manuals that bumping virgin brass will be bad. If it is, then a new tip learned today.

 

[haroldwilson]

It would chamber with virgin brass. I just did it anyways. I didn't know that you weren't suppose to. Like I said, I'm still new to this stuff and I don't remember seeing in the manuals that bumping virgin brass will be bad. If it is, then a new tip learned today.

It is just creating more head space which isn't needed and isn't a good thing. You don't want to size your brass and move your shoulders .005". Moving them .001" - .002" is better.

I sometimes body size new brass, but usually I don't even do that. I trim it, chamfer it inside and out, load it and shoot it. You are fire forming it when you fire it the first time.

After that, measure the shoulder dimension. But before you bump it, see if it will chamber. It is possible that the first firing didn't move the shoulders out all the way. If it will chamber, you can body size it and shoot it again without moving the shoulders. You may see that it moves out further on the second firing. If it does, base your bump back dimension .001" - .002" from that shoulder.

Another tactic is to set your sizing die at the same shoulder dimension as the shoulder of your once fired brass. Assuming the shoulders didn't move all the way out, it is likely within a few thousandths of the chamber and will likely be fine.

 

[dauntedfuture]

The Bisley reamer was made for the Palma matches in the UK. Over there they check your chamber and throat to make sure tis within spec when you brink your rifle over. I don't have the dimension's here, but I recall that some of the dimension's are generous and its designed to shoot a sierra 2155 (possibly a 2156). The end result is that your not going to have to neck turn and your bullets will be quite deep in the case. Try some 155's (2155 or 2156) I think they will shoot well too.

Shooting in Bisley is a hoot BTW, you have a few beers at lunch and its encouraged, very European!