Groups reduced from 1.5 to 0.5 MOA with correct bedding and clearance!!

Just wanted to share short success story with a 0.243 Mauser M12 which had started out as <0.5 MOA when purchased but opened out to 1.5 MOA after a few years.
Initially I thought the change in Ammunition batch was the cause the change, but I wanted to be sure so started to check out a few things...
Some key points to note at the start:

• The the M12 has a silver Cerakote finish all over the action.
• The action has a recoil Lug welded to the barrel.
• The synthetic stock has another free floating metal lug which engages the Action Lug.

What I found was interesting... I noticed one side of the Action Lug which engages with a free floating metal Lug had the Cerekote worn down, to be specific the left hand side was worn down but the right side was unworn. On closer inspection it turns out the free floating lug measured 0.2mm thicker on the left side!!!
So first fix was to file it down to make it square, once happy with dimensional accuracy I blue coated it once again. To compensate for the slightly narrower Lug I added layer of aluminium tape to the back of the free floated lug so it fitted snugly into the stock again.

Initial Results:
Firing at 50m (using my near zero point) the groups definitely improved from > 1.5 MOA to <0.5 MOA on the horizontal plane but I still had Vertical Stringing at about 1.5 MOA.

Back to the workshop, next up was to examine forend clearance:
Measured clearance was 0.8mm.
Google AI told me that a 0.243 needed sufficient clearance to withstand up to 5 to7Lbs of pressure...
So using a bench vice to hold the stock forend and placing a 7Lbs drum of water on the barrel closed the gap to Zero!! WOW, this definitely needed fixing!
Clearance was easy, the stock was making contact at extreme end closest to the mussel, so a little sharp blade work soon opened it to 3mm. A retest with the 7Lbs weight showed 1.5mm clearance even with the weight, so the 0.8mm was not enough.

Final results:
Testing at 50m again, the group was a 'clover leaf' at 0.5mm diameter which is <0.5 MOA at 50m.
Happy days!
I shot another group at 150m and measured 0.6 MOA so again so really happy with that!

So lessons learnt...
1. Synthetic stocks do flex over time, keep an eye on them.
2. Check your Lugs for uneven wear
3. The Batch theory was not valid, glad to say.

Happy hunting all.

Any uneven contact with the recoil lug rear surface will cause the action to flex - leading to erratic accuracy

Well done on the fix

All proper riflemen do this. Well done.

Cheers lads, I'm over the moon with the outcome.

And correcting a silly typo error...
"Final results:
Testing at 50m again, the group was a 'clover leaf' at 0.5centimeters diameter which is <0.5 MOA at 50m.!"

I had similar with a tikka t3x in 243 shot 75 vmax perfectly but switched to nosler and had comtant double grouping investigated and found recoil lug only making contact on 1 side relived bedded with jb and shot bug holes

Scottb123 said:

I had similar with a tikka t3x in 243 shot 75 vmax perfectly but switched to nosler and had comtant double grouping investigated and found recoil lug only making contact on 1 side relived bedded with jb and shot bug holes

Click to expand...

Nice one. I will have to retest some ammo I previously discounted because it wasn't grouping well, especially the more powerful ones which were probably worse due to the misalignment issues.