Hello all,

I run a Bora Arms BR99 for IPSC shotgun in the UK. It has a AR type fire control group (FCG) and it started misbehaving at a competition this weekend gone, below is a clip (excuse the mild swearing!);

https://youtu.be/8rIFjvmEHRI


You can see the double firing at 0:06, 0:18 and 0:47 and the hammer following the bolt group home (dead) at 0:05 and 0:10.

Could this be caused by a weak disconnector spring? I've had the FCG to pieces now and cannot see any excessive (or virtually any) wear on the sear or hammer, only the anodizing has been slightly rubbed off. The hammer and trigger springs seem fine, however when I tried the disconnector spring against another one, it did feel a bit weaker.

Any help would be appreciated as getting advice on semi-auto AR pattern guns in the UK is pretty hard to come by.

Many thanks

It may not be a weak spring.  It could be that the disconector is not pivoting forward far enough to maintain control of the hammer.  
If it's an AR-15 design, you'll see a foot sticking forward on the disconector that limits how far forward the disconector can rotate.  If you shave some material off the bottom side of that foot, it will allow the disconector to rotate a bit farther forward to give the disconector more engagement on the hammer.

Tony

This. Can you open up that weapon like you can on an AR to manually work the hammer? I've found one brand new fcg that if I held the trigger in exactly the right spot the hammer could go all the way back and all the way forward and not catch the trigger or the disconnector! Now a test I do on all my new fcgs is to very carefully pull the trigger all the way and push the hammer back untill it's on the disconnector, then very carefully release it while taking some pressure off the hammer with the other hand, when the hammer comes off the Disco I lower I make sure to keep the trigger in that same place and see if the hammer catch's on the trigger. If it doesn't you have a problem, obviously. If it does, then I proceed to pull the trigger very slow and carefull, while blocking the hammer with other hand(never let a hammer drop on an unassembled firearm!!!) , To see how much take up there is before it drops. I want a good bit of take up. I found some fcgs that could double even if they seemed ok if they didn't have enough take up after dropping from the disconnector to the trigger.

If parts are available it may be a good idea to get a new Disco spring anyways, or even a whole new fcg.

Thanks for the input gents!

Bfoosh06 - It is an aftermarket trigger, but then its in an aftermarket lower (Firebird Precision TAC-99) - bearing in mind this is a BR99 and not an actual AR-15. The OEM BR99 trigger does not fit in this lower without modification so unfortunately I can’t just swap them over.

TonyRumore - Would a weak disconnector spring not then not push the disconnector far forward enough?

Is the part I’m holding the ‘foot’ part you refer to and it’s the underside that may require filing?

FCG pics

AASG – The gun ahs a split receiver design (although it does not conveneiently just pivot open like an AR!) and I can operate the trigger/hammer manually, I’ll give your procedure a try tonight.

I’ve replaced the disconnector spring with one from another FCG which I’ll hopefully get to test tonight, I’m really hoping it is just that as I have no idea where I’ll get a replacement full FCG from (Firebird Precision no longer send stuff to the UK)

Just for info – I’ve ran this lower/trigger set up in my competition shotgun for 18months-2 years without issue, I can only think the mileage I’m putting on it has weaken something.

Thanks again guys

I've now had two testing sessions 20rds and 140rds and the double firing hasn't occurred again, so looks like it was a weak spring. Its a bit crazy that such a tiny thing can ruin the function of the gun (and potentially send you to prison for 5yrs over here!) Next Brownells order i'll be banging a few spares onto!