I have never been a big fan of the stock assault rifles.
If I had some skill with modeling I would change them, but unfortunately all I can manage right now is cobbling together bits and pieces from other models in nifskope to make things I like, while at the same time aligning them to use Ironsights.

Recently I bashed together a weapon I really like, using that stupid scoped-but-no-stock abortion from the Pitt.
I hacked off the scope and silencer and added a AKMS style folding stock, picatinny rail and reddot sight.
I ended up with something that I think looks practical and handles very well with Ironsights.
Here are a few shots:
http://i237.photobucket.com/albums/ff292/VonGrantoven/HKG37-1.jpg
http://i237.photobucket.com/albums/ff292/VonGrantoven/HKG37-2.jpg
http://i237.photobucket.com/albums/ff292/VonGrantoven/HKG37-3.jpg
http://i237.photobucket.com/albums/ff292/VonGrantoven/HKG37-4.jpg

I was planning to use it as a replacement for the stock assault rifle, but unfortunately, it seems to like to CTD if I load a save where it is drawn. I have to put it away before saving, then later open the save and draw the weapon, or it is crash city.
Once it is up and running though I don't have any further crash problems (well, no more than usual anyway)

From the stock model, I deleted 3 objects and added 5.
Does the number of objects affect the memory load or something?
I have had similar problems in the past with the GECK crashing while trying to load such models.

What is the problem and how might I fix it?

Slight update;
It seems that most of the crashes happen if the save is outdoors.
Indoor saves seem to be much more stable.

Whats up with that?

maybe a corrupt index in the nif, probably from all the copy/paste. I would rebuild the nif, or better, import(if it lets you) into a 3d app, set it up and reexport a clean nif.

Thanks for the tip.
I'm afraid I dont have any ability with 3D apps, so how would I go about rebuilding the nif in nifskope?

Strangely after a bit of trial and error it seemed like the folding AK stock was causing the problem. Replacing it with a different one seems to remove the problem.

I have found similar issues a few times though. One with substituting (and resizing) a silencer for the 10mm and another with trying to replicate an aperture style sight (ala the Canadian C1A1) for the FAL. In all cases is seems to be a single part that causes the CTDs and inability to view in the GECK.

One common aspect though is that in all cases I had overlapped the meshes. Is this likely to be the problem?

Doubtful. geometry is pretty versatile, just about anything can be done to it. It's probably the hex numbers being mismatched from copy/pasting. sometimes stuff doesn't get added to the the index correctly.

to rebuild the nif do it exactly how you did in the first place. you can do some things to try minimizing your impact. So pick a donor nif. you say you deleted 3 objects. don't. try pasting over the top of those nodes trishapedata/tristripdata blocks < that will leave those nodes indexed correctly.

then paste in the rest of you blocks. If straight forward still messes up- you could try copying and pasting the last node in the donor nif back into itself(a few times). then replace the trishapedata block with your blocks data. :shrug:

It might not even be a corrupted nif- the random crashes are a pretty sure sign of that. it could be something else.

Yeah, its the random factor that is most worrying!
Still, by trial and error (this game can sure be a time vacuum!) I am pretty sure it is the .nifs that have been the issue.
Thanks for the tips. I will surely make use of them
Cheers

If you ever get this working I'd really love to hear it from you, if you're willing I might be able to use it one of my mods. PM me later.