7 SAUM HELP!!

[mtnhunter22]

Bare with me..long post. Looking for opinions on some odd groups/patterns I am seeing with a new 7SAUM. Below are rifle specs. Pictures below.

Bighorn TL3
24” proof barreled by local gunsmith who I’ve had good luck with
Manner LRH pillar bedded
MK 3-18
Chamber is cut to SAAMI
Loading to Mag length shooting 180 Berger hybrid

Did a ladder test and found two loads I wanted to try. 60.7 RL26 & 60.2 RL26. Here are my ladder velocities. Keep in mind I do not believe that the barrel has broken in yet.

RL26 Ladder
58.4 - 2753
58.6 - 2757
58.8 - 2759
59 - 2732
59.2 - 2728
59.4 - 2786
59.6 - 2779
59.8 - 2804
60 - 2811
60.2 - 2822
60.4 - 2824
60.6 - 2840
60.8 - 2838

Loaded at 60.7 & 60.2 and shot groups. Middle two targets (top and bottom) are 60.7. Right targets (top and bottom) are 60.2. This is where the fun starts.

First shot on ALL groups matched the ladder (~2840 respectively and ~2820). The following 4 rounds dropped 20-30 FPS and settled in. First shot on all but the first is approx 1 MIL high. Second shot about and inch high, and following 3 all close to eachother. I’ve circled all groups below and numbered the shots. I’ve also included the pic of groups shot during the ladder. First shot high, adjusted, second shot still high, adjusted, 3-11 good.

Any thoughts here on what could be causing such a big POI shift as well as velocity changes?

Trying different stock tomorrow, as well as shooting groups at distance with and without magnetospeed attached.

 

[nn8734]

1) Barrel not broken in yet (ideally put a hundred rounds on it before load development and testing)

2) differing barrel harmonics at different charge weights

3) ladders themselves arent real reliable indicators of long run behaviors/ performance

 

[mtnhunter22]

1) 130 rounds down the tube

2) I agree just looking for reason for the same pattern on two separate loads

3) also don’t disagree here. Again just looking at the pattern and causes.

When I do ladders I’m generally looking for a place to start. From there I find loads, shoot groups, and look for a good match up between group size and SD/ES. It’s worked well for me in the past with my rifles and have never had this issue. Same process used on 4 different rifles.

 

[nn8734]

Gotcha, Pick two close charge weights (.3-.5 grain spacing) at whichever velocity you want to run and shoot a 3-5 round group and see if the point of impact is the same at 100m and it groups tight, you should be good to go. Load up an additional 30-40 rounds and do your drop validation at 50/100m increments and see how the load does.

 

[mtnhunter22]

That is what I did here. The two charge weights are .5 gr apart. Both shot decent three shot groups, once the first two flyers were out of the way. But that is what I’m trying to figure out is why and where those two flyers are coming from. Shot 1 is way high, shot 2 is better but still a touch high. Shots 3-5 are good. Almost like there is stress somewhere in the system that is being relieved as the barrel warms.

 

[nn8734]

Were all these shot with that magnetispeed attached? Just noticed that at the end of your post. If so id strongly consider that to be the problem.

Otherwise, check the barrel/stock relationship maybe contact is being made somewhere? Also anything feel “odd” when seating your rounds, like a few that had noticably higher or lower seat pressure? Scale ok, throwing consistent charges - do you verify using another scale?

Just throwing out possible causes.

 

[mtnhunter22]

Yeah I appreciate the reply’s. I’ll try no magnetospeed tonight as well as a different stock. I’ll report back

 

[nn8734]

Yeah I appreciate the reply’s. I’ll try no magnetospeed tonight as well as a different stock. I’ll report back

Your’re welcome. Magnetospeed is a good tool but you don’t want it on the barrel when doing any substantive load testing as it will change the barrel harmonics and throw rounds, at least in my experience.

 

[Steel head]

Your’re welcome. Magnetospeed is a good tool but you don’t want it on the barrel when doing any substantive load testing as it will change the barrel harmonics and throw rounds, at least in my experience.

 

[Adam B]

I had a 7 saum that shot like this. It was a bad barrel or a bad chambering. Took it off put on a new barrel and it hammered. I don’t buy the barrel isn’t broken in. If you use a good barrel maker and a good smith it should shoot great, especially with reloads.

 

[mtnhunter22]

Went back out and shot without the magnetospeed so have no idea my SDs or ES but groups were much better. I’ll attach pics below. First group good, Second group still had a bit of a first round flier but something like that could very well be the shooter, and third group was a 7 shot group with the first being about and inch high and then the 4th being a little high as well. So again, probably shooter error more than rifle. Still shows a bit of a pattern but I may not be loading into the rifle on my first shot. Probably need to go throw it in a lead sled. But shooting a distance later this week and we’ll see if it holds up. But still night and day difference from what was happening this morning.

 

[Shoots 700's]

What distance are the last groups at?

 

[nn8734]

@mtnhunter22 Good to hear its more consistent and doing better sans magnetospeed.

Id forget the lead sled, just focus on fundamentals.

If possible take a video or two of yourself shooting and watch it, looking for things you would do differently. Watch for subtle reticle drift as you are breaking the shot (something that i occasionally let happen to me and the results look like i have fliers).

Lastly, SD/ES aren’t super critical unless this is something you will be shooting regularly at 1200m plus (perhaps to a mile) and you as the shooter can shoot to the potential of the rifle and a single digit SD load. If you’re production process is well managed and everything is consistent (good brass, neck tension, powder charge, etc) then muzzle velocity consistency will reflect that positively.

 

[mtnhunter22]

What distance are the last groups at?

100 yards . So a couple decent. One rough one