I have a Flemming sear.

A trigger box to mount your sear has to be a semi auto, meaning either a factory semi box drilled for installing your auto sear, or a factory auto box first modified to eliminate the factory auto sear position.  Simply cutting a clearance into a factory burst pack would make it an unregistered conversion trigger box, hence the need to eliminate the factory auto sear location before redrilling it to mount your conversion sear.

If you want a burst pack, you'll have to order and mod the factory burst pack to semi, then drill for and install your conversion sear, or send it out to have someone do it for you.

It's possible to drill your existing semi host trigger box to install burst internals, but that would be even more involved than modifying and repurposing the trigger box of a factory burst pack.

Depending on how good you are with tools, and what tools you have access to, you might well be able to order a factory burst pack, modify the trigger box to semi, and drill for and install your conversion sear to the "semi" burst trigger box yourself.

 

I've 3 sear packs including a registered trigger pack, sear, etc.
The burst pack looks good on my MP5 but I rarely use it.
Maybe good for training a novice user or that cool factor.  

It's very important that you need to sell or get rid of your existing sear ready pack if you decided to get a new burst pack.
ATF only let you have one sear per modified pack.  

I don't have any lore regarding the HK specialist smiths out there, so couldn't tell you with regards to Donn Quinell, sorry.

How you go about getting your sear moved to a burst pack depends on how long you can stand to be without it.  The most usual way would be to ship your current pack and sear off to be relocated to a modified burst pack - that way you never have more than one trigger box in your possession, and the HK smith has everything there to time your sear with the new pack if needed.

If you didn't want to be quite as long without your sear, you might have an HK smith mod a burst pack for you with you providing lots of pictures and measurements, and let you know when it's ready, only then shipping your pack and sear off to have the sear moved to its new home and tweaked.

Or you might be able to get a smith to modify a factory burst pack for your sear and ship it to you, for you to do the sear installation and dispose of your old trigger box yourself.

I'd just send it to a smith. Have you played with a sear in a burst pack chas? It's like a damn Swiss watch.

 

You will also need a special burst hammer to work with your reg sear as the factory hammer wont engage the sear in a burst pack.  Michaels Machine makes a single piece hammer for burst pack conversions and/or whomever is converting the pack can weld an extension on the factory hammer to engage the sear.

The other option if you just want the Pictograms is to get a 0-1-A ambi  pack.  They are much easier to convert, cost less, and all you are missing out on is the 3rd burst and the three extra little bullet icons between the semi (1) and Auto (7) bullet markings.

Oh, don't get me wrong, the picto is cool. I had one. Now I've only got SEF. I'll get a burst again some day, just to have, but sold the burst because a guy wanted a burst and made me an offer I couldn't refuse. Actually almost tripled my money on it.

Ok thanks guys.

heard about them and seen them, but not shot them personally.

never heard good or bad about them functionality-wise, definitely no legal issues.

long as they fit your trigger box and safety, and fit your host gun(s) and make you happy, it's all good