Poor Groups - What to check next time out?

[EastCOYotes]

I have a savage model 12 6.5 creed that normally shoots 1/2" groups for me with factory hornady 140 gr ELDMs. During my range time yesterday the gun didn't shoot as tight (maybe .75 - 1 inch ish on the few groups I shot... However, a few variable come into play at this range session vs the ones prior when I was shooting 1/2" groups.

I recently had the barreled action sent off and had a brake mounted. After getting the barreled action back I put it back in with 50in/lbs torque on the action screws (HS precision stock with aluminum bedding block).

during my worse than normal groups I had a magnetospeed mounted to the end of the barrel (velocity SD was fairly high but maybe this was because I started with a clean barrel).

My question is, what should I tweak or look at to try to get back to shooting 1/2" or smaller groups with this gun. I'm thinking that shooting with the magneto speed mounted can mess with groupings? Maybe starting with a clean barrel affected accuracy/velocity spread and it didn't get enough carbon fouling worked up to be consistent? Or maybe I need to tweak action screw torque?

Any insight appreciated.

 

[Olen_4504]

1) magnetospeed mounted to your barrel can for sure have an effect. some people experience BETTER groups, some experience worse.

you can buy a mount like Wiser or MKM and that keeps the chrono off your barrel.

2) your first few shots through a squeeky clean barrel will be definitely slower. in my experience - up to 70fps slower. i usually shoot 3-5 rounds before i start recording data.

but since i handload and know where my load should go. i still shoot over the chrono and just delete the shots that are no where near my expected speed.


also - when re-installing your action and torquing - there's a general rule of thumb of how to do it. something along the lines of

"get them barely snug, then bounce the rifle on the buttstock to get the action/recoil lug set. snug up the front action screw, then back. then alternate back and forth until you reach the required torque."

i'm doing that from memory.

but i HAVE half-assed thrown my barreled action in a stock and not torqued it properly and saw the consequences down range.

 

[EastCOYotes]

Next time I shoot I'll see how the velocities look, since the barrel should be fouled enough now.

I basically did the procedure you described when putting my action back in, but I may back the screws out a touch and re-check their torque.

I also didn't shoot any groups on paper last time with the magneto speed off, so I'll do that as well to see how it reacts vs grouping with it on.

 

[EastCOYotes]

Well I made it back out today, and with a fouled bore the gun shot great (with MagnetoSpeed on) and velocities were also much tighter. I feel much better now.