Confused... (Update!)

[Magnum Mike]

Ok, here's a new one on me!

My gun and loads:

Core15 9.5" 1-8" barrel, spikes upper/lower/bolt carrier group, pistol gas, no clue the gas port size(everything is rockset or lock tight'd so I won't be checking anytime soon), SpecWar flash hider(that's torqued on), no clearance issues with bore/can.

Accurate Mold 240, 2.125" oal, LC reform, 10.0 - I4198, wsr, .002" crimp

Lee 230, 2.250" oal, LC reform, 10.0 - I4198, wsr, .002" crimp

Both the above run 100%, feed & lock the bolt back on last round with or without the can.

Left is AM240, top is without can, bottom is with. Right is Lee, top is without can, bottom is with.



Target at 10 yards, standing, using Magpul mbus. As you can see, it appears the load becomes unstable when the can is attached?!?!? Since the loads seemed fine (shot top groups without can first), I put 3 rounds each through the can. After reviewing the target, I check my SpecWar and find this!



Looking at the baffles, there's no evidence of a strike, just the end cap of the can. I checked orientation, screwed the can off and on a half dozen times and it always comes up with the mark at 12 o'clock.

So, I am quite confused. Most times I see velocity go up when a can is attached which should increase stability, not decrease it. This load is mild, less than .001" case head expansion, so I can bump it up. It is subsonic and very quiet but, obviously, unacceptable as is.

Anyone seen anything like this?

[Magnum Mike]

Pic of the complete pistol:

[rpk47]

I'm not familiar with the design of the can but my initial guess is that it is creating cross bore turbulence. That aids in suppression but according to Novesky it can cause the bullet to become unstable. At least thats why they say not to use k baffled suppressors with their 300blk barrels.

[kroeker]

My first form one can was built for a 9mm and I clipped the baffles. On my 700 groups were worse than yours subsonic or supersonic there was no consistency at 100 yrds groups were over 8"

I built a new form 1 can exactly the same as the first one except I didn't clip the baffles. Supersonic groups were less than 1/2 moa at 100 yrds subsonic never measured but they were respectable.

Only thing I could come up with was I was getting to much cross jetting from the clipped baffles and it was causing the bullets to become unstable. Not saying its the same problem but might be something to look into.

[dellet]

You might check for stability without the can at a closer distance and instead of shooting for groups shoot distinct separate spots so one hole does not interfere with another.

It would also be worth checking to make sure that the threads are concentric with the bore.

[Magnum Mike]

Did Core15 have a problem with bore concentricity?

[dellet]

Did Core15 have a problem with bore concentricity?

Not that I know of, but it is certainly a possibility. I have heard of enough other barrels in general with the problem.

I also haven't heard of a SpecWar can causing a bullet to become unstable.

[svh]

You might check for stability without the can at a closer distance and instead of shooting for groups shoot distinct separate spots so one hole does not interfere with another.

It would also be worth checking to make sure that the threads are concentric with the bore.

What kinda distance would one check for stability ?

[dellet]

You might check for stability without the can at a closer distance and instead of shooting for groups shoot distinct separate spots so one hole does not interfere with another.

It would also be worth checking to make sure that the threads are concentric with the bore.

What kinda distance would one check for stability ?

As close as you can without having the muzzle blast destroy your backing.

Here is a simulation Berger bullets did that shows the yaw of a bullet from 0-200 yards.

https://www.youtube.com/watch?feature=p ... pF8W5liSRc

[Magnum Mike]

Ok, got out today and and tried a half grain heavier load. The results:



Left: AM240, top is no can, bottom with.
Right: Lee 230, top is no can, bottom one whole shot is without.

The Accurate Molds 240 grain is stabilizing and seems to shoot well. I'm going to load some more and continue testing. Happy I've got something to move forward with.

The Lee on the other hand isn't even close. I'm still getting less than .001" case head expansion so I'm going to bump the load another half grain. I really want this bullet to work but it's not looking good. As you can see, I shot one round and quit since it went thru the target almost sideways.

All loads, once again, fully cycled and locked open on the last shot.