msg90 down for a few days

[black_ump]

turns out i had the headspacing about .002 under the low... so i went with +4 rollers and it just got me inside the spec's

so i had to press the barrel out and re-press it in and i put it at dead nutz the hole is drilled and the headspace is still dead nutz so while i wait for the pin iam just working loads up....

iam excited to see if it is gonna print better groups, maybe the headspace was the reason i was so off, not sure....

 

[black_ump]

Re: msg90 down for a few days

DO ANY OF YOU FEEL THE BETTER HEADSPACEING WILL HELP TIGHEN MY GROUPS ?

 

[cubewarrior]

Re: msg90 down for a few days

I think other factors may be at play with the accuracy more than headspace:

1) Need a stable bipod on the front--the HKs don't really cut it.
2) Has your trigger been smoothed out?
3) Is your scope mount solid and are the rings lapped?

When I fired my stock SR9T, I couldn't get it better than MOA accuracy--and it was usually wider than that. That was with a brand new barrel.

After replacing the forearm with a KAC (and Atlas bipod), adjusting the trigger, and mounting an HK Pic Rail mount (lapping rings and shaving the pads), the rifle now shoots half MOA with factory ammo. Worst group I've had with it after making these adjustments has been .75in at 100Y.

I believe that the HK SR9T platform is inherently very accurate due to the floating barrel and the recoil impulse that doesn't disturb the barrel until after the bullet has cleared. That said, most of the "supporting components" (trigger, ergonomics, optics mounting) suck. They definitely will degrade the performance of the shooter if not adjusted. HK 9_ series was the schizzle for its day, but the AR-based platforms have surpassed it.

Steve

 

[ORD]

Re: msg90 down for a few days

It is possible that your groups may improve somewhat. What were your bolt gap measurements before and after the installation of the +4 rollers? Before/after pulling the barrel and reinstalling/repressing it? Getting all these critical dimensions "in spec" certainly won't hurt your accuracy.

Another likely culprit with accuracy issues that I have seen from your other posts is the inconsistent ammo. The best way to determine the accuracy potential of your rifle is to find a standardized commercial match load and shoot several 5-round groups with it (FGMM, BH, Cor-bon, Winchester match loads for example). This gives you ammo that is known to produce accurate results in a wide variety of rifles (although obviously accuracy will vary, it should still be VERY acceptable), thus eliminating one more variable from the equation.

CubeWarrior...the MSG is a different animal from the rack-grade 91 and really shouldn't even be compared to it other than its basic operating principles. It has a fully free-floated barrel. The bipod is a more stabilized design with the integrated accessory rail in the handguard for mounting either a Harris (with adapter) or the MSG90 dedicated bipod. The trigger is the MSG90/PSG1 variety with produces a zero-creep, smooth, polished trigger pull (mine is right at 3.5lbs with little tuning on my part). And the scope mounting is via welded rails on the receiver.

 

[cubewarrior]

Re: msg90 down for a few days

ORD-- I don't think UMP's mount/rings are welded. ARMS rings should probably be lapped--its an easy problem to isolate out.

4" groups with a Douglas Barrel--that just seems to scream that the scope is wobbling.

I agree with you on the ammo--I'd see how Federal 168 match rounds would do off a bench. If the gun can't produce MOA or less with those, then the rifle still needs adjustment. If its shooting MOA with those, then the rifle probably just needs load development work.

 

[ORD]

Re: msg90 down for a few days

black_ump has posted several threads about this project in recent weeks and his efforts to get the gun finalized, broken in, etc., etc. I believe his bases are welded on, but you are correct re: mount/rings and a potential problem there.

 

[black_ump]

Re: msg90 down for a few days

hey guys,

i have 2 1913 tabs welded to the top with an arms 35 qd mount the bases are lock tighted down then the rings on top of the 35 base or mount.

i have never lapped the rings i know this could be a slight issue, my headspace befor this mod was .003 which was .002 under size now it mesures .015, phil at pf custome guns told me to hold this tollarnce for best accuract, .014-.016 so i set it at .015 to be dead nutz

while my rifle was down i bought a torque wrench so i can make sure all my screws are right on.

ORD is right i use an msg90/psg1 forarm and harris style bipod as well as msg90/psg1 trigger with 3.5 pound pull, their is maybe at tops only 5-10% creep i honestly feel almost none it is vary hard to tell when the trigger is gonna break it seems as just when you apply pressure it brakes...

i have also been shooting reloads in which i weight each load's powder, i do not trim as i dont have a trimmer but i do every other step other then trimming the out sides of the necks i do squair the primer pockets clean the burr from the flash hole from the inside also the outside of flash hole ect ect, to sight in the weapon i use regular federal power shock cause it is factory ammo and its cheep, mainly, and i stay away from surplus ammo out side of the federal ammo from walmart every thing else that goes threw the gun are handloads

 

[black_ump]

Re: msg90 down for a few days

bump

 

[harlikwin]

Re: msg90 down for a few days

Actually if you are talking about a real MSG-90 the scope mount is a quick detach type, not really welded on. In his case I he has a welded on mount.

FWIW I have msg90a1 spec and it shoots about .75in with fed gmm at 100. But I have yet to duplicate a handload for that rifle that shoots as well. So you might try some Fed GMM in it and see how it does.

 

[Guest]

Re: msg90 down for a few days

I'm going to be as nice about this as I can, but still try to get my point across.

Let me begin by saying that the HK roller lock system is something that people have tried very hard to copy and perfect. People either spend countless hours and dollars, and with nothing short of infinite patience may succeed. Most who truly know the platform really only trust maybe 4 or 5 guys to do HK builds to any degree of satisfaction. This is no coincidence. And even the "masters" aren't always 100% perfect.

That being said, if you are having the issues stated above, i'm going to assume that this isn't the only thing out of spec on the gun. And as stated above, I think you have a very high standard for accuracy given your choice for the HK/ optic mount dilemma. I was going to ask how you know it's square, but after seeing your "sucked off" thread, it ain't.

And i'm not pointing fingers, but it isn't enough to just be good at welding, machining, and fitting when working with these guns, you need to know the "why" behind what you're going. And given some of the questions I've seen you ask in this area.....

And you keep talking all this mess about load working and increasing accuracy. Are you hoping to match factory accuracy of the real deal? If so, why?

 

[Goot]

Re: msg90 down for a few days

Wow, Cubewarrior seems to be the subject matter expert. Great advice!