Hi guys, Newbie here, I have been loading now for 3 years and I just recently picked up the M&P 10.

First question: are people that are loading for accuracy here for M&P 10 have there barrel free floated? (I only have the stock M&P 10, that is why I ask) Should I even develop a load for it because its not free floated?

Second question: This will be the first time I would be loading for a .308 thats a semi-auto ( I do load .308 for my Rem 700). Does everyone use a small base die or can I get away with just using a full length sizer die? are the users in here that are loading for accuracy use a small base die or only full length resize die? Thank you in advance!

Welcome to the forum! My 10 is not free floated and I handload to find the most accurate rounds the rifle will fire. I only use IMR-4064 powder (both .308 and .30-06 for commonality) but work up different loads for various bullets. Ladder loads are part of the fun of handloading. If you plan to free float your barrel in the near future, might not be worth your time to develop loads now. Of course free float is more accurate just like your bolt action. The M&P 10 isn't a target gun but can do mighty well if reworked for it.

I switched to the small base die but am not totally sold it's really needed. It's just insurance for me as I use LC brass. However, the answer is yes for the regular die - just be sure the shoulder setback is correct. Good luck!

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Webfarmer

It depends on what you mean by developing a load. As long as you stick within the limits of published data, I don't see a problem and it's the best way to discover what your rifle likes best.

If you are talking about going outside published data, tread carefully and I hope you have a lot of knowledge and experience behind you for there "be monsters".

Free floating the rifle will help with accuracy but out of the box, people have been able to reach out to 700 yards plus with it not being free floated.

Thank you all for the great feedback! I think I'll start the ladder to see what my M&P 10 likes. I shot some pmc 147 gr and it seems good at 25 yards but once I got to 100 yards it was everywhere. I appreciate the feed back!

Hi Webfarmer, can you tell me what groups you are getting at 100 yards? And what load you are using? I currently have 175 gr SMK bullets that I will be using and thinking about using PMC brass for now with federal match primers.

I share these with this caveat - you should work up to them and I hold no responsibility if you try them.

LC case 42.0 IMR-4064 WLR Sierra 165 HPBT: 20 rounds - 5 shot groups at 100 yards = 0.625" smallest 1.250" largest (I'm impressed by this load and will be trying it again)

LC case 41.6 IMR-4064 WLR Hornady 150 FMJBT: 5 shot group at 100 yards = 0.562" <<< having a good day?

LC case 38.0 IMR-4064 WLR Hornady 178 A-Max: 5 shot group at 50 yards = 0.562" Haven't tried at 100 yet.

These measurements are center to center and done with a tape measure. So when you see two with the same groups? They're rough measurements - not done with a caliper and converted to thousandths. 0.562" = 9/16". I ladder test at 50 yards followed at 100 with whatever won. I'm sometimes surprised at either how badly I shoot the next time OR something in the load simply sucked further out. Good luck and trust your reloading manuals more than some guy on the internet

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Webfarmer

Thank you for the input webfarmer (For sure I will not hold you responsible for any action I do! lol). I was going to use this as a starter from the Hodgdon website:
Poweder: IMR 4064
Bullet Diam .308"
C.O.L. "2.800"
Starting load Grs. 41.5 (ft/s) 2,500 45,200 PSI
Max load Grs: 45.6C (ft/s) 2,728 59,500 PSI

might be a slower because this was from a 24" barrel on there site.

When I get loading I'll post the shots I make at 100 yards!

Hmm, those seem pretty stout to me. I checked the site and what you typed is exactly what they show. Here's what my Hornady manual says for 178 A-Max: 34.0 (2,000) to 41.3 (2,400). For M-14's (service rifle) 33.6 (1,900) to 39.0 (2,300). I included that just because it's semi-auto data and peculiar to the M-14.

My Sierra manual says for your 175 bullet: 35.7 (2,200) to 42.8 (2,600).

The loads above are commercial brass. Thicker base Mil brass generally means to use 1-2 grains less powder due to less available volume. Generally. Lots of arguments about that on the net by caliber. On the low end, watch for ejection patterns. Higher up, watch for pressure signs. Somewhere in-between is the magic load for your rifle with that bullet. Your shell holder should touch the die for basic shoulder setback (follow their directions) when resizing. Good luck!

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Webfarmer

Will do, I might pick up a copy of the sierra manual and see. thanks for the heads up!

On a good day in the woods I might develop a couple new good loads. I never looked closely for ejection patterns. Then again I am not a perfectionist.