Matchgun MG4 load

I just put a dot on my MG4 and I'm trying to work up an "accurate" load. Still at 32 SWL. So far I've got 98gr Missouri coated bullet (.313), 1,4gr N310, mild roll crimp right on the end of the bullet. I have to say that the results are not inspiring - it will just hold the 10 ring at 25 yards from a sandbag. I'm pretty damn sure this is an ammunition issue so - a couple of questions ...

Has anyone slugged an MG4 barrel to see what bullet diameter it would be best with (assuming that would hold true between guns)
Is 1,4gr  N310 a sensible starting point. GRT indicates that would get me somewhere in the 900 fps range which seems high - but I haven't run it with the chrono (too damn cold outdoors still - yeah - I should buy a lab radar)
Is this cartridge particularly load sensitive - e.g. if it's 1.44gr of N310 as opposed to 1.36gr would you expect this to produce a large change at 25yds.
Are there any other high impact 'sensitivities' that I should look out for (bullet seating depth, roll, primer etc) with this cartridge
Is there a known preferred bullet manufacturer that I should be getting on the waiting list for

Edit: Can some kind mod move this to the ammunition section please - which is where I thought I'd posted it. Sigh.

I’ve shot 1.4 gr N310 with swaged Speer plinked bullets and have had good performance at both 25 & 50 yards in my MG4. Ammunition loaded on a Star.
Not easy loading 32 long ammunition ;
Jon

Greetings,

I tested a factory MG4  barrel a while back. If memory serves me well, the groove diameter was 0.314" maybe 0.315".

Here are my test targets fired at 50 yards using bumped Speer HBWC and out of the box Speer Plinker HBWC.

There are two targets using the unobtainable H&N 0.314" I had left over.

The bullet diameter needs to be equal to or slightly larger than the groove diameter.

Cheers,

Dave

Thanks for that Dave. What I'm expecting from the gun is something along the lines of target 2 or 3 (this is 25 yards I'm talking about). What I'm getting is more like 4 & 5. I haven't tried 50 yards yet.
Looks like I need to learn how to slug a barrel and find out what actual diameter is required. Ah well - it would be boring if I had all the answers.

Greetings straybrit,

Unless you cast or swage your own bullets you will be at a disadvantage.

Bear Creek swaged bullets are 0.314" diameter. You might want to try some. My tests showed close to ten-ring accuracy at 50 yards. Examine each base closely prior to seating. Use the rejects for practice.

Loading is a fussy endeavor.

With 0.314" bullets, use Lapua or R-P cases sized to 0.334". With StarLine you may need to size to 0.336".

The bullet should start into the case mouth and with thumb pressure push them further about half way. Cycle the press to complete the seating.

Most "off the shelf" dies are one size fits all. Translation, they size your brass too much.

Sizing the cases beforehand will only need the mouth flared. Most reloading expanders will not touch the inside of the case. This is good.

I taper crimp 0.325", measured at the mouth, only for functioning. I have not seen empirical data to suggest that crimp makes a difference. The old NRA article, written by Col. E H Harrison, revealed that crimp had no effect on groups, provided the crimp was consistent.

Another check is to examine the barrel throat for Lead fouling. Once fouled, groups open up rapidly.

Much testing has shown that velocities in the 700-730 FPS range, at 15 feet, produce good groups.

Yes, you can load "hotter" but remember. This is a blowback pistol and increased velocity = more recoil = more wear and tear.

Buy a spare recoil spring and compare the one in the pistol each time you do a cleaning. If the old spring gets too short it is no longer doing the job it was designed for.

Cheers,

Dave

Well, I got on the Bear Creek waiting list and (re)read the Corbin stuff. I think once I have this barrel sized, i.e. I know what I want, then swaging my own is going to be the way to go. In the meantime I'll see how the .314 groups when it arrives and I'll strip and check the barrel.

Thanks again.

Edited to add - Yes I should have done this sooner - I measured the Missouri Bullet Company .313 bullets - of the 20 I measured (both ends and 2 measurements at 90 degrees at each end) none were larger than .312 and a couple were smaller than .311. So - consistent - but consistently wrong. Probably explains why they are the only people with any available. Ah well - dry firing with a bang I guess.

Also - I checked the barrel and chamber with a scope and no sign of leading. I gave it a good scrub just to be sure.