Winchester subs sonic booming

I have shot these 40gr Winchester subs for quite a while, years but recently they seem to have become noisier and over the last few months I have had a few sonic boom. I have a jw 15 that has an 11" barrel and full over barrel suppressor.
I figure it's happening because of my short barrel, maybe the powder load is calculated for a longer barrel to optimise the speed and my Shorty is letting fly too early, what do you think?
Anyone had their subs sonic boom?
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I had a few in my cci subs packet do it from my 14" cz

I did find that when someone I know shortened one barrel it got quieter as it got shorter then suddenly got louder again. The bang was not the sonic in our case but unburnt powder burning in front of the muzzle. This may not be what you are experiencing but it could be something worth looking into.

Being a jw 15, the soft lead projectile has probably worn the rifling out of the barrel and you are now shooting a smooth bore, this resulting in a higher projectile speed, breaking the sound barrier .........

:shave:

Yep had the same thing when using our little Ruger bolt action.
Pop,pop,pop and then a random BOOM. No pattern to it,just every now and then we got a loud one.

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Shoot some over a chronograph and check the speed vs the noise.

Quote:

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Originally Posted by hotbarrels

Being a jw 15, the soft lead projectile has probably worn the rifling out of the barrel and you are now shooting a smooth bore, this resulting in a higher projectile speed, breaking the sound barrier .........

:shave:

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just checked and the rifling is good

Quote:

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Originally Posted by stug

Shoot some over a chronograph and check the speed vs the noise.

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I'm picking the ones that sonic boom will be faster than the ones that don't :thumbsup:

I get this with the cheap remington subs - 1 in 10 at least goes bang, that is from a 10/22 with a from memory 14" barrel, but with CCI subs I can't remember the last one to go bang.
I think it falls down to quality control, they try and get as close to the sound barrier as possible and some are just a bit too hot.

go to the 42grn load and you wont look back.