243 test loads and primer questions

[bolski]

To start off I am, only a year experienced in reloading. Been having some real good results in other calibers but the 243 is testing me.
Rifle is a tang M77 with 18 lightweight barrel. Loaded 85 gr Sierra BTHP with 34, 35 36 grs IMR 4895. OAL length of 2.60 to start. Cool dry temp of about 58degrees no wind.
All groups are 3 shot groups. Results are, 34 gr 1.233 35 gr 1.361 and 36 gr 1.043. started with a clean bore and a fouling shot. Barrel never got real hot.
My conclusion is it seem s to be shooting better with more charge. The lymen book shows a max load of 38 gr. Still have room to load up but...... all the primers except for maybe 1 per group are not seated flat after the shot and pushed out( sorry for not having the right terms) max is .011 in the 34 gr group, .012 in the 35 and 36 group. This measurement being from the worst of the 3. Now there was no problem extracting and shows no other signs of over pressure. Primer strikes look good with no crater that I can see. What could cause this and should I be worried? I am because I think somethings going on. Wrong powder maybe? Is pressure too high? Maybe not enough pressure for the bolt to reseat the primer? Is .012 acceptable? I doubt but I need some advice before I move ahead.

 

[roninflag]

the primers are backing when fired?? what scope? what brass?

 

[boomtube]

The .243 isn't unique and your high primers have nothinh to do with high pressure, in fact it's the reverse. All primers back out as far as the headspace allows. At normal pressures the bolt face will reseat them as the case stretches back to fit the chamber. Your proud primers are telling you that your pressures are much too LOW or they would be flush with the bolt face!

Primers standing proud by 12 thou says you're setting your shoulders back at least that far and that's far too much! You're setting yourself up for some nasty head seperations ... soon. Back your sizer UP an eighth turn plus a bit more and check to see if the empties chamber properly - refine the case to chamber fit from there with SMALL die changes.

And move your powder charges up too, you're not even getting complete combustion now.

I don't know if a higher grade of scope or better sling swivels would help hold your primers in with really low pressure loads or not. ??

 

[bolski]

Thats funny. What an excuse for the primers. Maybe the wife will go for it. Wait a minute, she pregnant. I can already her the answers now. I was thinking the same thing about the load. Gonna neck size the brass I shot and shoot again and see if that helps.

 

[bolski]

Got a chance to shoot some this week. Loaded 37 and 38 gr of IMR 4895 with 85 gr sierra BTHP. No high primers this time. Guess it was a low pressure problem. .485 group. Not bad