Muzzle blast pattern on Crown

[LTRDavid]

I thought I’d share these pics. I found the pattern quite interesting. This is a 11° degree crown on a 6 BRA barrel. The outer ring is a PMA Tuner. Some barrel jobs I provide the service of fire forming some cases, in this case 3 cases each fired 4 times, to send to Harrell’s for one of their F/L dies. I use a barrel trap in the shop so the task is pretty easy to accomplish. Questions and comments welcomed. Thanks for letting me share.

 

[dnellans]

Do those corrispond to either the lands or grooves in terms of clocking? 4 groove barrel?

 

[GenePoole]

I think that the pattern becomes more pronounced when there is a hindrance to the gas flow like a dished crown, or in your case, a tuner. There are some interesting patterns that fluid flow engineers might appreciate. Here's a flat dished sharp-edged crown on a cut-rifled 5R; notice the mushroom-top pattern where the gas runs into the side of the dish:

Here's a 6 groove button-rifled 11° crown with a thread protector. Interesting here is the twisting of some of the "spokes" probably caused by the spanner notches in the thread protector:

 

[Fast14riot]

11° crown on a gas gun.

 

[LTRDavid]

Do those corrispond to either the lands or grooves in terms of clocking? 4 groove barrel?

Yes, 4 groove Krieger…

 

[cb186]

Totally normal. If you don't have a nice, even rosette pattern, your crown may not be centered.

 

[butchlambert]

Tuner appears off center.

 

[LTRDavid]

Tuner appears off center.

Handheld camera shot.

 

[jackieschmidt]

I’m not real sure exactly what all of this is supposed to mean, aside from making interesting conversation.
At the very least it shows that shooters are thinking.

I think the best looking of all is the crown in Post #4.

 

[Fast14riot]

I’m not real sure exactly what all of this is supposed to mean, aside from making interesting conversation.
At the very least it shows that shooters are thinking.

I think the best looking of all is the crown in Post #4.

As an interesting topic, the ironic thing to me, my barrel (post #4) is actually an E.R. Shaw discount barrel I paid $120 for, lol! Its a 6.8spcII I rechambered (from 6.8spc to 6.8spcII) and 1.075" diameter, 24" long with rifle length gas. Coppered up bad for the first 300ish rounds, but kept up with it and its averaged 3/4 MOA inside of 500m (all I shoot it at) with nearly 1600 rounds on it now. Its a 1:10 twist that i shoot Hornady 110bthp over 29.6gr of H335.

 

[misser]

this all reminds me of something that was happening with my encore 209-50 . there is a e-z load at the muzzle I noticed a track at one point on the e-z bore .it had been machined off-center

 

[MasterYoda]

All are a little different

 

[dryhumor]

I think they are pretty cool…

 

[cb186]

Looking at the different patterns makes me happy.

 

[Dimner]

Rorschach testing starts now!

 

[LVLAaron]

Here's a fun one.

 

[Skeet69]

My Obermeyer Palma barrel
Mike B

 

[dryhumor]

4 leaf clover?

 

[cb186]

My Obermeyer Palma barrel
Mike BView attachment 1548296

Crown doesn't appear concentric to bore.