[status quo]

I want to rebarrel the HK with the best match-grade heavy barrel that's about 20".

I also want to make minimal changes to the rest of the config, like cocking tube, etc.

I have a polygonal now and it's not any more accurate than conventional barrel. I want a little more accuracy as well as velocity, being 2" longer. I also want it optimized for 168grainers and larger, meaning 1/10 twist.

 

[JTinIN]

Did a poll in the old days and about half of the SR9 shooters got better accuracy and half got the same.
What are you running for a trigger, found mine improved with a scope and PSG trigger pack, but there are after market trigger jobs for a lot less.
Myself have tended to find going with bolt guns for half MOA rifles and just sticking to the semi's for a little over a MOA.

Will be interested to see how you come out and what type accuracy you nave now and later.

 

[MOAxp]

Minimal changes... I still have not found that amazing cake with negative calories :440:...
besides what John said above your options are going to be some what limited - RCM doesnt make a hvy barrel, urbach is MIA, you could get a PSG1 type barrel and cut it down for the triple frame. I have tried the minimal changes but always found the PSG1 style builds out shot the G3 tapers - do a quick search on my past posts. The only exception is my G3K DMR build but it is a SBR. all of the deep consistent accuracy game changers require abit more than miminal changes.

 

[status quo]

How about this MSG90 type clone. I am thinking about the following:

20-22" match stainless barrel - polygonal? Lothar Walther USA-Made Polygonal LW-50 Stainless steel. Or Douglas, Wilson, RCM?
Trunnion extension
Stiffening rails
MSG90 forearm - do I need one? I would prefer to keep the wide forearm I have now and the heavy bipod.
Do I need a new cocking tube, can I use the stock one?

I would prefer to keep factory factory BCG and bolt. Also stock claw mount. Or do I need the 1913 rail.

Already have G3/SG1 stock and Williams trigger.

 

[TreySoucie]

TTT im planning a build similar to Status.... If I can find a poly Lothar psg1 profile barrel I will buy it. Unless this happens though, MOA has some conventional psg1 barrels which look really nice.

 

[cv0lv0g0]

Do what I'm doing, unless you don't have access to machines. I'm getting a XX Douglass stainless barrel and having someone cut chamber and flute it for me.

 

[tiger888]

A genuine factory SG1 bbl would be 1st choice, but impossible to find (I have one but it's installed)
Or have Moaxp cut down one of his PSG's?
I'd keep mods to the rifle minimal.