Range Report Muzzle Brake and Magnetospeed POI shift

[FFAZ]

Not sure if this is the right section for this question, but heres the situation:

New .308 rifle, no brake. Did the break-in procedure and got a solid 100m zero although I knew I would still be doing a ladder test and some load development.

Once I finished break-in, I attached a muzzle brake since I knew I wouldnt be cleaning as much.

When I did my ladder test with the new brake and a magnetospeed attached, my POI was 6 inches high and 3 inches right. (I know both affect POI)

I started my test at the charge weight I did my break in at, and with the same cases, powder, and bullets.

Can my POI shift be THAT significant or is something else at play here?

 

[XLR308]

That amount of shift sounds pretty extreme.
Did you try it without the MS attached after seeing the issue, the reason I ask is the MS has no impact on groups or position on the two rifles I shoot the most.

 

[FFAZ]

I only loaded enough rounds for my ladder test so I didnt want to take it off and lose data points.

Could it have been the combination of the break-in, brake, and MS? It grouped well, just required an extreme adjustment

 

[XLR308]

Before I put a whole lot of thought into it I would shoot it with the MS off and see were your point of impact is.

 

[FFAZ]

Before I put a whole lot of thought into it I would shoot it with the MS off and see were your point of impact is.

I'm loading up rounds for my refined load development so I'll do some with the MS off and see what happens. I didnt apply the new POI either, just dialed it and left it. I'll post later with results.

 

[Steel head]

Muzzle break will almost surely change POI

They way I do load development I have my Magnetospeed on and am looking at speeds and ES Only and only shoot groups when that stage is done and don’t need the chrony info.

 

[XLR308]

What weight of barrel are using ?
Is a sporter type or more target/varmint barrel ?

 

[FFAZ]

What weight of barrel are using ?
Is a sporter type or more target/varmint barrel ?

It's a heavy Krieger barrel

 

[FFAZ]

Muzzle break will almost surely change POI

They way I do load development I have my Magnetospeed on and am looking at speeds and ES Only and only shoot groups when that stage is done and don’t need the chrony info.

Most charge weights I tested would have amazing ES (between 3-7) and then ONE round would give me 40 FPS low and ruin my ES.

I was particular about everything from seating depth, sorting cases by weight, etc.

But I was lazy on primer depth/uniformity. I hope that's what it was, because if it is, I'm going to have a great gun

 

[Steel head]

Yea
I don’t bother with sorting or primer depth unless it’s proud of the base.
That one anomaly is probably telling you the truth more than the other shots.

 

[tnichols]

Most charge weights I tested would have amazing ES (between 3-7) and then ONE round would give me 40 FPS low and ruin my ES.

I was particular about everything from seating depth, sorting cases by weight, etc.

But I was lazy on primer depth/uniformity. I hope that's what it was, because if it is, I'm going to have a great gun

I would be surprised if primer seating depth would effect velocity that much, but, could be wrong.

 

[FFAZ]

Yea
I don’t bother with sorting or primer depth unless it’s proud of the base.
That one anomaly is probably telling you the truth more than the other shots.

I'm not one of those people who deletes the one flyer and claims that I have some low SD/ES. I'm always realistic and except a margin of error.

I'm just trying to figure out the cause behind those wierd drops in FPS

 

[FFAZ]

looking at speeds and ES Only

I was looking for the velocity flat spots to test those further...

Should I be looking for my lowest SDs instead?

My most consistent load had an ES of 3 but was slower than I want. 2578fps average, with 43.2gr of RL15

My sill was between 2655 and 2657 for 43.8gr and 44gr. BUT NOT the most consistent ES/SD wise

 

[Steel head]

I was looking for the velocity flat spots to test those further...

Should I be looking for my lowest SDs instead?

My most consistent load had an ES of 3 but was slower than I want. 2578fps average, with 43.2gr of RL15

My sill was between 2655 and 2657 for 43.8gr and 44gr. BUT NOT the most consistent ES/SD wise

Your looking for velocity flat spots and/or ES flat spots.

 

[Dthomas3523]

I'm not one of those people who deletes the one flyer and claims that I have some low SD/ES. I'm always realistic and except a margin of error.

I'm just trying to figure out the cause behind those wierd drops in FPS

Your powder charge weight + primer choice is the largest factor with velocity numbers.

It could also be something weird with seating pressure/neck tension if one is substantially tighter than the rest.