Need Advice on Seating Depth Results

[Philys21]

First time reloader here and I'm starting to develop a load for my 6.5 Creedmoor. This morning I completed 5 shot groups in .005 jumps from -.040 to -.075. All shots were at 100 yards, and I shot each group without waiting between shots. I did wait until the barrel was cool to the touch before shooting the next group (10-15 minutes).

I used a magneto speed to record all the shots, (attached to arca rail) and I noticed the 4th shot in 5 of the 8 series was the slowest, think that's coincidental or could there be a reason for this?

I'm not sure if should I should pick one of these jumps and move onto OCW or do some seating depth testing. Any advice is appreciated.

Action: 737r
Chamber: 6.5 Creed
Barrel: 26" 1:8 twist Brass:
New Lapua SRP
Case Prep: No sizing, No trimming/chamfer, Mandrel 0.2625, Imperial Dry Neck Lube
Bullet: 140 ELDM
Primer: CCI BR4
Powder: H4350 41.5 Grains

 

[nn8734]

Why didn’t you run an OCW first? What is your minimum velocity requirement for the rifle/bullet combo?

Also, if/when you do your OCW (assuming your not currently satisfied with the above results using 41.5g), do NOT shoot it with the magnetospeed attached (disregard this - overlooked the fact it’s attached to your rail not your barrel).

I don’t see much, if any obvious variation in your groups so I’d jump them more towards .075 to keep pressure down, as your load shouldn’t be compressed using Lapua brass.

 

[Baron23]

First time reloader here and I'm starting to develop a load for my 6.5 Creedmoor. This morning I completed 5 shot groups in .005 jumps from -.040 to -.075. All shots were at 100 yards, and I shot each group without waiting between shots. I did wait until the barrel was cool to the touch before shooting the next group (10-15 minutes).

I used a magneto speed to record all the shots, (attached to arca rail) and I noticed the 4th shot in 5 of the 8 series was the slowest, think that's coincidental or could there be a reason for this?

I'm not sure if should I should pick one of these jumps and move onto OCW or do some seating depth testing. Any advice is appreciated.

Action: 737r
Chamber: 6.5 Creed
Barrel: 26" 1:8 twist Brass:
New Lapua SRP
Case Prep: No sizing, No trimming/chamfer, Mandrel 0.2625, Imperial Dry Neck Lube
Primer: CCI BR4
Powder: H4350 41.5 Grains

What bullet?

 

[nn8734]

What bullet?

The second pic says 140 eldm

 

[ShtrRdy]

I like the results from the 60 thou

 

[Philys21]

The second pic says 140 eldm

Ha forgot most important part, Yes the 140 ELDM.

I choose to do seating depth tests first after reading the articles on Precision Rifle Blog, listening to RADD podcasts, videos and podcasts with Scott Satterlee, etc.

 

[spife7980]

Those look fine but I’d still go from .015 off to .035 off in the search for best accuracy.

 

[nn8734]

Ha forgot most important part, Yes the 140 ELDM.

I choose to do seating depth tests first after reading the articles on Precision Rifle Blog, listening to RADD podcasts, videos and podcasts with Scott Satterlee, etc.

Ok. At this point id do a brief 3-5 shot OCW starting at 41g in .3g increments to 41.9g to see if your POi is stable through that range, assuming your MV is satisfactory to you

 

[spife7980]

Ok. At this point id do a brief 3-5 shot OCW starting at 41g in .3g increments to 41.9g to see if your POi is stable through that range, assuming your MV is satisfactory to you - do NOT attach the magnetospeed for this. seating depth is your call.

Since you repeated it, again, it’s on an arca rail, not barrel mounted.

I used a magneto speed to record all the shots, (attached to arca rail)

 

[nn8734]

Since you repeated it, again, it’s on an arca rail, not barrel mounted.

Thanks, I definitely overlooked that.

 

[KnowNothing256]

I experimented with an off-barrel mount with the MS and still observed POI shift. A prior study illustrates that the sonic boom off the bullet will reflect off a nearby surface and impinge upon the bullet, causing yaw. I wasn’t able to get the MS far enough off the line of bore to avoid this without getting inconsistent and unreliable readings, even after playing with sensitivity.

YMMV, but I will only use the MS for speeds going forward, nothing where group size matters.

 

[nn8734]

I experimented with an off-barrel mount with the MS and still observed POI shift. A prior study illustrates that the sonic boom off the bullet will reflect off a nearby surface and impinge upon the bullet, causing yaw. I wasn’t able to get the MS far enough off the line of bore to avoid this without getting inconsistent and unreliable readings, even after playing with sensitivity.

YMMV, but I will only use the MS for speeds going forward, nothing where group size matters.

That’s interesting, and im not surprised to be honest. Im a LabRadar guy, can’t stand MS though I know a lot of folks use / like them for their smaller size and convenience factor.

 

[Philys21]

I experimented with an off-barrel mount with the MS and still observed POI shift. A prior study illustrates that the sonic boom off the bullet will reflect off a nearby surface and impinge upon the bullet, causing yaw. I wasn’t able to get the MS far enough off the line of bore to avoid this without getting inconsistent and unreliable readings, even after playing with sensitivity.

YMMV, but I will only use the MS for speeds going forward, nothing where group size matters.

I've read about exactly this and I listened to a podcast or youtube video of David Tubb confirming what you're saying. Going off memory I think Tubb said it was a slight impact or only noticeable at ELR, but don't quote me.

Iabradar is 2nd on my list, I'm buying a tbac bipod first.

 

[nn8734]

I've read about exactly this and I listened to a podcast or youtube video of David Tubb confirming what you're saying. Going off memory I think Tubb said it was a slight impact or only noticeable at ELR, but don't quote me.

Iabradar is 2nd on my list, I'm buying a tbac bipod first.

So with everything said, I’d still keep the magnetospeed off of the rifle or at least do a quick POI shift test to confirm/deny its presence influences your point of impact before going to the OCW.

 

[Philys21]

So with everything said, I’d still keep the magnetospeed off of the rifle or at least do a quick POI shift test to confirm/deny its presence influences your point of impact before going to the OCW.

Sounds good, I’ll let you know how I make out.

 

[Dthomas3523]

I've read about exactly this and I listened to a podcast or youtube video of David Tubb confirming what you're saying. Going off memory I think Tubb said it was a slight impact or only noticeable at ELR, but don't quote me.

Iabradar is 2nd on my list, I'm buying a tbac bipod first.

Tubb now mounts his a certain distance away(can’t remember how much) and turns the sensitivity up. Says the POI shift goes away.

But with it mounted at the specified from magneto distance, you’ll usually notice a poi change away from the bayonet (wherever you decide to orient it). Sometimes the groups size stays same and sometimes it doesn’t.

 

[6.5SH]

2x the diameter of the bullet away from the bottom of the bore.

 

[KnowNothing256]

2x the diameter of the bullet away from the bottom of the bore.

Thanks for filling in the blanks, folks! I wonder if he’s still able to get good readings because the larger ELR calibers give a stronger response for the MS to pick up? It didn’t give me acceptable results on 100gr 6.5mm bullets, and I was aiming for 2x caliber free space too (the original study called out 1.7x I believe).

 

[6.5SH]

He did state that the bullet composition and density can affect it, was more of a rule of thumb.

 

[Philys21]

I did my OCW testing this weekend (100 yards) and am happy with the results, but came away with some questions. My biggest question is what takes priority, mean radius or the SD/ES of the velocity node? My lowest ES was from 41.4 to 41.6 but my smallest mean radius was from 41.8 to 42.0. I attached the grouping and ladder results of both groups.

How would you guys proceed?

 

[nn8734]

I did my OCW testing this weekend (100 yards) and am happy with the results, but came away with some questions. My biggest question is what takes priority, mean radius or the SD/ES of the velocity node? My lowest ES was from 41.4 to 41.6 but my smallest mean radius was from 41.8 to 42.0. I attached the grouping and ladder results of both groups.

How would you guys proceed?

How many rounds for each charge weight? If less than 20 then ignore SD/ES. 20 is the bare min I’d need for that info to be useful.