Do groups open up or get tighter with fired brass?

[AM_Hunter]

I began reloading for my Seekins Element 308. Its my first time doing serious reloading so I am definitely a newbie and could use any insight. Loaded up 25 rounds of Barnes 168gr TTSX in hornady brass with Federal 210 primers and Varget powder. After attempting to load to 0.020" off the lands and realizing I cant fit them in my magazine, I decided to load to maximum cartridge length of 2.200" CBTO and went from there. Loaded 5 rounds ea at 41.5 - 43.5gr and was able to get a very happy group of .56MOA with the 43gr. This is better than I can shoot and im extremely happy with this group, but im wondering if it will open up or get better once I re-use the brass.

Im hoping the group sizing stays the same after I reload with the fired brass as I am hoping I dont have to do further load development. Does anyone have any experience with this?

On another note, I did not know I should chamfer the new brass before loading so the first 25 were loaded this way and I also loaded another 50 at 43grs for 2x 10 shot groups and some dope development. Definitely had some bullet shavings after seating the rounds but after the group I got I thought nothing of it. Will chamfering the cases possibly open the group up or could it only help?

Appreciate the help!

 

[pbroski]

The short answer is that the groups will stay the same. It's one of those things with handloading ammo that would take hundreds of shots with large sample size groups to prove either way.

Chamfering will not hurt, but with that level of precision I doubt you will see an improvement.

 

[northernalpine]

Groupings won’t change, just keep an eye on the length of brass over firings. Soft brass will stretch enough after 1-3 firings you may need to trim, Hornady is one of the brands with softer materials from my experiences.

 

[AM_Hunter]

Groupings won’t change, just keep an eye on the length of brass over firings. Soft brass will stretch enough after 1-3 firings you may need to trim, Hornady is one of the brands with softer materials from my experiences.

I usually trim to SAMI specs during case prep on reloads every time, should I not do that?

 

[northernalpine]

I usually trim to SAMI specs during case prep on reloads every time, should I not do that?

If it needs to be trimmed, trim it, if it’s within spec and chambers in your rifle, load and shoot it. I measure mine after every firing, but usually end up trimming every other just to keep everything consistent. If your process is to trim every time, go with it, there’s no adverse effects.

 

[sdupontjr]

Shouldn't change 1 lick. This is 130 ttsx in my Tikka 308 after about 5 firings of the same load. I do anneal every time. 49g varget, CCI200, 130ttsx loaded at 2.825"

Also, Barnes shoot better at .050" and more off the lands in my gun. Never shot well chasing the lands. If I remember correctly, Barnes even states to start at .050" off lands, but could be wrong. haven't looked at it in a while.

 

[AM_Hunter]

Shouldn't change 1 lick. This is 130 ttsx in my Tikka 308 after about 5 firings of the same load. I do anneal every time. 49g varget, CCI200, 130ttsx loaded at 2.825"

Also, Barnes shoot better at .050" and more off the lands in my gun. Never shot well chasing the lands. If I remember correctly, Barnes even states to start at .050" off lands, but could be wrong. haven't looked at it in a while.


View attachment 734447

Thats good to know, I think I am around .038-.043" off the lands.

On a side note, how fast are your rounds running 130ttsx with 49gr???

 

[sdupontjr]

I don't know but want to check. I'm definitely on the hotter side but that's where My tikka liked it. All were good, but opened up at 49.5. They have 49.2 (max) according to the chart should be 3100 plus. Tikka barrels are usually slower but I figured I'd have to be close to that. At 49.5 I still had no pressure signs, but as you see, groups opened up. And these 130's hit like lightening strikes. at those speeds.

 

[northernalpine]

I don't know but want to check. I'm definitely on the hotter side but that's where My tikka liked it. All were good, but opened up at 49.5. They have 49.2 (max) according to the chart should be 3100 plus. Tikka barrels are usually slower but I figured I'd have to be close to that. At 49.5 I still had no pressure signs, but as you see, groups opened up. And these 130's hit like lightening strikes. at those speeds.

View attachment 734911View attachment 734912

Looks like you're right on the money anywhere in the 47.5-49gr range, the difference in those groups is just likely to be shooter-related as it is powder charge.

 

[sdupontjr]

exactly. The gun and load will shoot better than me, thats for sure.