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soulboy1957

One for the experts-Subsonic 12g not enough inertia

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I have a Laporte o/U 12g fully moderated, this gun is a fabarm. 

Unfortunately it does not fire the second barrel due to insufficient recoil to set the inertia block. 

A thump on the recoil pad does it, I'm thinking maybe a heavier shot load, have been loading 1oz,would increasing this to 1 1/4 oz increase recoil? 

Any ideas, bit stuck on this one. 

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8 hours ago, soulboy1957 said:

I have a Laporte o/U 12g fully moderated, this gun is a fabarm. 

Unfortunately it does not fire the second barrel due to insufficient recoil to set the inertia block. 

A thump on the recoil pad does it, I'm thinking maybe a heavier shot load, have been loading 1oz,would increasing this to 1 1/4 oz increase recoil? 

Any ideas, bit stuck on this one. 

A heavier load would probably do it. Whether the extra 1/4 oz would be sufficient remains to be seen. 

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You have a gun that has been modified beyond the makers spec . You could try heavier loads but whether you need to go up to 1&1/4 remains to be seen . Have you spoken to the people who did the modifications as I would have thought it was there responsibility to see the gun worked or gave recommended loads .

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Hi, it's based upon the Fabarm Gamma, sold as a LA Porte swing trap fully moderated. 

I wonder if it's possible to decrease the spring tension on the inertia block, thereby allowing it to fall back and engage the 2nd sear with subsonic loads. 

Seems strange as it was marketed as such. 

The original design is very good, a high quality action, barrels and stock with well made moderator, however not that quiet compared to my 20g o/U hushpower, the reason being the barrels were not ported, this has now been done and is now fairly quiet. 

Before porting

Screenshot_20200630_180641_com.whatsapp.jpg

After porting

Screenshot_20200630_180651_com.whatsapp.jpg

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I had a Laporte swing trap and i used many different subsonic loads including some with fast burning red dot powder, and i never had a single issue with the trigger inertia tripping. Try loading a heavier load, but it could be the mechanism is short of some maintenance and cleaning. .

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The question was about the inertia block working, but especially for the gun police, yes its been re proofed. 

I'll try upping the shot charge and powder (maxam CSB5) 

Thanks for all the replies so far. 

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Not an x- spurt but I would suggest that the spring needs changing to a lighter one just like you have to do if you use .410 tubes in a 12 bore to shoot nssa skeet (1/2 ounce load)- common problem with non mechanical triggers . A proper gunsmith ( not gun seller )would soon help you.

I have shot the type of gun you have - nearly bought one - I must say they look some good size holes you have put in those  barrels would be interested to know how it all works out.

Good luck with it .

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On 01/07/2020 at 15:40, soulboy1957 said:

The question was about the inertia block working, but especially for the gun police, yes its been re proofed. 

I'll try upping the shot charge and powder (maxam CSB5) 

Thanks for all the replies so far. 

Wow.

Dont up the powder charge ! Not with fast powders. Itll just end up loud

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Thanks guys, it seems LA Porte almost got it right, full length moderator, 8 inches of baffling at the end, just didn't port the barrels to lessen the powder blast, having looked at my 20g o/U hushpower and my mates 12g mossberg, the hole  size is 6mm with 50mm spacing. 

Anyway it's done the trick and is now fairly quiet, the inertia system now works with 16.5 grains of Maxam CSB5 and 1/1/8 of no 5's, chronographed at 1020 fps tonight. 

Thanks 

Mark

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