Firstly I've really struggled with the MP10 to get consistent groups using same recipes.

My worst group was around 3" @ 100m
My best was under 0.5" @ 100m

My good recipe is as follows...
2.000" OAL cases. Sorted into weight lots.
Slight crimp on seating to the max P-Mag will allow
RCBS AR10 dies on Forster Coax press
A-Max 168gr
39-40 of AR2208 (I think this is Varget in USA)
CCI Large Rifle primers

I've shot sweet groups...
as stock rifle (.78" group)
with Muzzle Brake (0.5" group)
with MB and polished stock trigger (0.8" group)
with MB and Timney trigger (0.6" group) - nice trigger BTW.

These groups shot from 20th round to around the 700th.
Barrel was broken in (4 x 5 rounds groups with JB paste and Boretech cleaning between each string).

Rifle bore cleaned after each days sessions till no blue CU fouling.

HOWEVER - I notice that with exact same reload parameters that grouping can significantly vary (from said 0.5" to 2.4" groups) depending on how you "grip/load" the fore end.

I'm picking that the free-float will sort this for my rifle. My M4 16" does the same (non-free float) - POI changes depending on off-hand, sitting or prone. Our NZ Army Styers (also non-free float) do the same change of POI when changing shooting position.
My sniper and hunting rifles are all free-float and do not change POI at all (atmospherics notwithstanding).

MP10 (811310) Setup:
Product: Model M&P10 .308 WIN/ 7.62x51 (Compliant)

3-9 Schmidt & Bender PMII with custom MBrake and Timney trigger off bench rest and rear support.
Airsoft rubber AR10 stock (cost $30 from Hobbyking and fits like a glove - absolutely no wobble and slides/adjusts smoothly). I went this route as exporting from USA difficult.
Dytac VLT Style MOD stock (Black)

I also found the stock magazine to FTF multiple times (fails more often than not on 'naked' gun). The PMag is faultless even when using the brass catcher. I no longer use the stock MP10 mag. I tried filing the MP10 magazine feed tabs to no avail.

The trick was to find a free-float tube under $100USD. Damned USA export limits will make this very hard.

So time to look as trading in on Sig 716, as I need a consistent 1" or better accuracy for competitions.

Hope some might find my experience and recipe helpful.

I believe there are no free-float tubes for the M&P10 available in the USA for under $100. Most are well over $200. Thanks for sharing.

PM me as I may part mine out!

Update:
Freefloat arrived and installed, along with said parts.

Different scope installed (S&B 3-12) and range test completed today.

Was going very well (consistent 1" groups @ 100m) using 42gr AR2208 with Amax 168gr. OAL of 3.196" using the Hornady .308 comparator (which is 1" long), so 2.196" is to the ogive.
Handloads use a smidge of crimp.

A friend let me try 5 shots of Australian Outback 168gr ammo - also just under 1" group.

Being thorough I removed the crimp and reset AOL. WOW 2.5" group.

Now I've got to find my crimp factor and retest, seems 1" is it - still not bad. Guess I was over hopeful to get 0.5"

I've also now polished the ramp fed as I noticed scratching on the projectiles. I've removed the extractor and cycled and now only get extraction marks. Some judicious tweaking of lugs should remove these.

My completely stock M&P10 shoots .5 moa groups with 168 grain AMAX, .75 with Aussie 168 grn match. 2-3 inch groups with anything lighter.

Hey up lad, good to hear from you. Well at least you are getting consistent 1" groups from the skinny thing! Funny that relieving the crimp caused them to go off? That seems counter to me?


I am still plodding along. Seems there may still be hope as it seems I actually got down to a 1.5 group with the 168 Fed GMM open tip bullet, and the standard American Eagle 168 OTM was not far behind. The only Amax I had was the Superformance in 150gr and it did not fare as well.

I now have some 168 amax from a couple different reloading sources to try, as well as some of the Aussie Outback 165 game stuff. We shall see?

Oh,BTW, I gotta keep telling myself it aint no bolt gun!!!!!!!!

Update.

I had an entire day at range and tried out BM2 powder (38gns), consistently around or under 1" so quiet happy.

I've also heard 8208 is VERY good too.

In did spend considerabe time polishing the feed ramps (several nights using 1000grit and rouge paste).

Understood re no bolt gun. I too are a bit guilty of trying to get .5" groups. Will leave that for my TRG.

Good luck with the outbacks.

Well lad, after reading up a bit due to a post from another fellow on another forum who is currently a spotter in Afgan running a M110 rig, it seems to me the M110 is speked at 1.5 MOA or less, with 1-.5 being within norm with the good issue ammo.

Therefore, I do believe you are in the zone!

And them guys only get a 10x scope! You are cheating!

Have not heard from 2cants in a while. Whats up lad?

Wonder if anyone have tried the 175 range bullets yet.

Been shooting weekend before last and what a load.

As above on old NRA range (300 feet). 2 sighters then 10'shots. 4V Bulls, 4 bulls and 2 4 pointers.

Happy

Good to hear from you, but I have no idea how this is scored, but it sounds good!

Thanks to your sorry ***, and the fact I have not been able to hit anything much with my gun, I have drug my reloading press out of its 25-30 years of storage!

I got things going, got a few new bits to go with it all including a digital powder scale and a new powder measure for rifle.

I had run a few batches of 9mm to feed my hungry CZ pistols(if you do not have a P07 or 09, you want one!) in the prior weeks, then got the .308 full length resize setup going and I chose commercial brass to start because I did not have a primer pocket ream at the time.

I had previously purchased some 168 Sierra 168 HP match bullets, but my tests with the Federal factory ammo and the gold metal match using that bullet were not grand, at 1.5-2.0 in range(moa) and I had done somewhat better it seemed with the reman 168 Amax I had purchased, so I bought a box of them bullets. And this is where I began.

I loaded 15 rounds in groups of 5, starting low, yet a fairly large spread, using Reloader 15 and the Amax 168. No crimp. 2.8 oal.

39gr
41gr
43gr

Took the other reman ammo from 2 others to compare.

It was late in the day and I only had about 45 min. to setup and test. Mosquitos coming out!

Ran the reman stuff first for a warm-up, 5 ea., no surprises, at 2 in groups or possibly a bit better with one.

In with the 39gr and it did as well as the others, possibly more.

In with the 41gr and the first two were side by side. On the third round I hade a mosquito bite me on the neck as I made the pull, and I do not know where that round went into the already shot target I was using for tests, forget it!

Ok, back to it, round 4 and 5 left me with a 4 leaf clover into an inch. WoW!

The 43 was no more or less impressive than the 39. So I will work from there it seems.

40
40.5
41
41.5
42 this will be my next test group to possibly find the node!

I had not previously measured case length(dummy) as was first run brass, but I did after the test and these things are running really long at 2.060-2.075 as compared to the 2.015 spec. Case trimmer ordered!

Why are you trimming to 2.0? Is there a reason for that?

Mind you, I am not going for 1000 meter perfection here, but I would like to hit something at 2-300, as them long range guys get too carried away with things in my practical range!

The other question I have for you is just how sensitive are things are the brass? I know I need to reduce from max loads in mil brass, yet do lower charges run the same or do I need to run them less as well to achieve the same result? (which meand a whole nuther workup on the loads) ????

Any idea?

Changing internal volume can give you completely different results

Hi Coppermech

Great to hear your got those tight groups.

My testing was similar, very sensitive sweet spot.

I was well impressed with my results. Finally happy camper