Watched a can get ruined.

[ranb]

The last time I was in Vegas I was at the range shooting with a guy using a 9" form 1 can on his 338 federal bolt gun that sounded rather nice. I was spotting for him and noticed that his last three rounds greatly opened up his group. He took out the bolt and saw that something was misaligned in the can. The blast baffle was greatly misaligned.

At first we thought that it was just a blast baffle problem. But he put the can on his lathe and saw that blast baffle was cocked over enough to bulge the can and make it so that it would no longer align properly. The can appeared to be a total loss. He cut off the end caps and hammered out the baffles. What we saw surprised us. The blast baffle had a strike, but was possibly repairable. The K baffle in back of it looked like this.



He thought he had cut the cone portion of the baffle to be .045" to .050", but he made two mistakes. He removed metal with a large drill bit and fed too far in. He then cut the inside and outside of the cone at different angles making the forward part of the baffle only .022" He managed to put nearly 200 rounds through it before the baffle collapsed.

A hard lesson to learn, but no one got hurt and his barrel was not damaged. I make my K baffles nearly the same way this guy did. In the future I think I will cut my K baffles so that the cone will be thicker in front than in back to ensure I do not have thinner metal where the thickness cannot be easily measured.

Ranb

[Bendersquint]

The last time I was in Vegas I was at the range shooting with a guy using a 9" form 1 can on his 338 federal bolt gun that sounded rather nice. I was spotting for him and noticed that his last three rounds greatly opened up his group. He took out the bolt and saw that something was misaligned in the can. The blast baffle was greatly misaligned.

At first we thought that it was just a blast baffle problem. But he put the can on his lathe and saw that blast baffle was cocked over enough to bulge the can and make it so that it would no longer align properly. The can appeared to be a total loss. He cut off the end caps and hammered out the baffles. What we saw surprised us. The blast baffle had a strike, but was possibly repairable. The K baffle in back of it looked like this.



He thought he had cut the cone portion of the baffle to be .045" to .050", but he made two mistakes. He removed metal with a large drill bit and fed too far in. He then cut the inside and outside of the cone at different angles making the forward part of the baffle only .022" He managed to put nearly 200 rounds through it before the baffle collapsed.

A hard lesson to learn, but no one got hurt and his barrel was not damaged. I make my K baffles nearly the same way this guy did. In the future I will cut my K baffles so that the cone will be thicker in front than in back to ensure I do not have thinner metal where the thickness cannot be easily measured.

Ranb

Sad to hear another Form1 can bites the dust, I hear it far too often though.

That baffle is too thin! Holy cow, wonder what his thought process was on not using the same angles on the skirt.

[ranb]

I made my 308 K baffles about .050" on the skirt. I guess he got sloppy when adjusting his tool holder to 30 degrees to cut inside and outside.

Ranb

[ghostdog662]

Any idea what metal he used? Those walls are really thin, especially for a big round like 338.

[ranb]

It was stainless, I assume it was 304 or 316. He had intended to have the cone portion of the baffle .040" to .050" thick but he obviously cut too much and made it too thin. He is not a member here, but lurks and likes to see what other people are doing. He was kind enough to let me take a photo of the baffle that collapsed after cutting it in half.

Ranb

[mollinst]

Still, it would seem that there was a primary issue of misalignment that would cause a strike that close to the guns muzzle. Was his can loose?

[ranb]

I was not shooting the rifle when the problem happened so I don't know if the can was loose. The blast baffle had a minor strike, but the first K baffle did not have any damage on the front, it just seemed to be collapsed. With the K baffle cocked to the side and bulging the can, the blast baffle was no longer aligned properly either. When I looked through the can before we left the range, the blast baffle was blocking most of the bore.

I suspect that the last round shot through it did the most damage, if it had been shot again the can might have blown up on the muzzle.

Ranb

[kalikraven]

Theres got eo be a way to get a micrometer or something in there to measure it...

[ranb]

I suppose I could use a snap gauge if I found one small enough, but the surface is angled and I'm not sure I would get an accurate measurement by comparing the inside and outside measurements.

Ranb

[Capt. Link.]

I suppose I could use a snap gauge if I found one small enough, but the surface is angled and I'm not sure I would get an accurate measurement by comparing the inside and outside measurements.

Ranb

A tube gauge should work.The baffle may have buckled under pressure and that caused a misalignment.

[Enfield577]

BALLS

Ok to be more polite could you use a couple of steel balls (one inside and one out side) and just use a normal micrometer?

[Capt. Link.]

One ball is all you need. Great idea!!

[epicdoom]

Tiny measuring tips sets are avalible for most Mic's and dials have seen those in Pointed and rounded ball like very tiny even saw caliper type tip set.
Glad no one was hurt


Joe

[PaulNoiseLess]

Hi,

From just one Pic, it’s quite difficult to model the Baffle in 3D to run some FEA on it. I did it but the measurement might not be very accurate.

I’ve seen quite a few (more than few, to be honest) K-Baffles bending. Most of them do from the Base to the back side and usually more or less in a symmetric (little displacement to the port side).

What I’ve never seen before is the base bending and also the side of the cones. There are several reasons for this to happen:

1) The end of the Cone is not faced flat (and/or the base of the next Baffle). It’s got some sort of angle.
2) The OD of the Base and the OD of the Baffle are not the same.
3) The Baffle does not have a true center. That means asymmetric: r1 <> r2 but r1+r2=d.

For any (or all) of the 3 reasons above to archive this kind of deformations, the Can must be loosen and the Blast has hit the Baffle.

So, my bet:

1) Thin walls in a critical place (0.02 inches)
2) 1 and/or 2 and/or 3
3) High pressure plus the Blast hitting the Baffle

I have already run a quick FEA on the Baffle and reproduce exactly what happened except for the Cone side to bend that I need to know what and where to put the constraints to force the side to bend.

I you have any ideas, I’ll work the model little more.

Paul

[Bendersquint]

Hi,

From just one Pic, it’s quite difficult to model the Baffle in 3D to run some FEA on it. I did it but the measurement might not be very accurate.

I’ve seen quite a few (more than few, to be honest) K-Baffles bending. Most of them do from the Base to the back side and usually more or less in a symmetric (little displacement to the port side).

What I’ve never seen before is the base bending and also the side of the cones. There are several reasons for this to happen:

1) The end of the Cone is not faced flat (and/or the base of the next Baffle). It’s got some sort of angle.
2) The OD of the Base and the OD of the Baffle are not the same.
3) The Baffle does not have a true center. That means asymmetric: r1 <> r2 but r1+r2=d.

For any (or all) of the 3 reasons above to archive this kind of deformations, the Can must be loosen and the Blast has hit the Baffle.

So, my bet:

1) Thin walls in a critical place (0.02 inches)
2) 1 and/or 2 and/or 3
3) High pressure plus the Blast hitting the Baffle

I have already run a quick FEA on the Baffle and reproduce exactly what happened except for the Cone side to bend that I need to know what and where to put the constraints to force the side to bend.

I you have any ideas, I’ll work the model little more.

Paul

The OD of the baffle and the base do not have to be the same, they can be quite different and still not suffer this fate.

The problem was the varying thickness of the skirt/cone.

[delta9mda]

Hi,

From just one Pic, it’s quite difficult to model the Baffle in 3D to run some FEA on it. I did it but the measurement might not be very accurate.

I’ve seen quite a few (more than few, to be honest) K-Baffles bending. Most of them do from the Base to the back side and usually more or less in a symmetric (little displacement to the port side).

What I’ve never seen before is the base bending and also the side of the cones. There are several reasons for this to happen:

1) The end of the Cone is not faced flat (and/or the base of the next Baffle). It’s got some sort of angle.
2) The OD of the Base and the OD of the Baffle are not the same.
3) The Baffle does not have a true center. That means asymmetric: r1 <> r2 but r1+r2=d.

For any (or all) of the 3 reasons above to archive this kind of deformations, the Can must be loosen and the Blast has hit the Baffle.

So, my bet:

1) Thin walls in a critical place (0.02 inches)
2) 1 and/or 2 and/or 3
3) High pressure plus the Blast hitting the Baffle

I have already run a quick FEA on the Baffle and reproduce exactly what happened except for the Cone side to bend that I need to know what and where to put the constraints to force the side to bend.

I you have any ideas, I’ll work the model little more.

Paul

The OD of the baffle and the base do not have to be the same, they can be quite different and still not suffer this fate.

The problem was the varying thickness of the skirt/cone.

owned again. tirant/ element (and a few others) have a base/ baffle of different dimensions/ diameters. obviously not the issue. as bender said, wall thk of the cone was the problem.

[ChimeraPrecision]

___

[Bendersquint]

When I do my form 1, I intend on sawing the first baffle in half and then doing an inspection and then destroying the parts. a mic with ball tips is probably your best bet

You know that is a illegal, we have had this discussion before. ATF does not allow for replacement of parts by Form1 builders, you know this.

There are PLENTY of legal ways to inspect your work.

[PaulNoiseLess]

Hi,

Yes, I agree wall thickness is the main issue on this one (0.022 is just too thin). What I’m trying to say is that there are more issues.

Some of the other issues described (let’s say they are "potential" issues by now due to the lack of accurate dimensions) can also force the Baffle to bend even with thicker walls, like 0.045.

Paul

[Bendersquint]

Hi,

Yes, I agree wall thickness is the main issue on this one (0.022 is just too thin). What I’m trying to say is that there are more issues.

Some of the other issues described (let’s say they are "potential" issues by now due to the lack of accurate dimensions) can also force the Baffle to bend even with thicker walls, like 0.045.

Paul

Not like this is a new design with bugs to work out on it, and is most definitely not one of your designs. The problem was the wall thickness was way to thin, it shouldn't have been a varied thickness.

The rest of the baffle doesn't appear out of design so.....Case solved within 1 minute of seeing the picture.

[PaulNoiseLess]

Hi,

Yes, and I agree: Wall thickness is an issue in this one. This Baffle Pic was a nice opportunity to dig deeper into the world of “hidden walls” that causes 90% of K-Baffles failures. Wall thickness is one but not alone …

Anyway, Mr. Bender-HCaine; OK, I got it !, case is closed now !, you are the boss …

Paul