Reloading for the M&P45

mmattockx

mmattockx

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I tried this in the reloading forum and got nothing, so here we are...

I took my new to me M&P last friday for the first time. It shot BDX 230gr FMJ just fine, grouping OK and right on POA at 7-10yds.

I also tried a couple different reloads consisting of two different cast 200gr SWC bullets. One was the venerable H&G #68 and the other unknown (shorter, fatter ogive than the #68). Both are from Ben Hunchak, cast in his medium alloy and sized to 0.452". The #68 was loaded over 4.9gr of WW231 and the other bullet over 4.5gr of Red Dot. These loads cycle my Norc 1911 100% (though the Norc doesn't feed the #68 worth a damn) and shoot groups that are just slightly larger than the BDX 230gr.

The M&P functioned 100% with everything I tried but it shot the cast bullets like crap. At 7yds the H&G #68 loads would string 8+" vertically with minimal horizontal dispersion. The other load was a bit better, but still grouped over twice the size of the BDX loads. Not nearly as much vertical stringing, though. The M&P uses conventional rifling, not polygonal so that shouldn't be a factor. A post-shooting cleaning and inspection showed that there was very minimal leading, just a couple light marks, so it wasn't smearing the bullets horribly and they don't look to be undersized for the bore, either.

Any ideas on why it hated the cast bullets so much and what I should try next to sort this out?


Thanks,
Mark
 
What sort of rifling does the M&P use? Some modern styles such as the Marlin microgroove with the minimal bore to groove difference are known to be hard to get good results from with cast. Perhaps the M&P uses something similar?

A common thing with using cast bullets is also to slug the bore and then ensure that your bullet is sized such that it's at or a thou over the groove diameter. Perhaps your barrel's groove diameter is larger than the bullet diameter.

Or it could be as simple a matter as what 'ranger mentioned and you're crimping too much.
 
1riot1ranger said:
Check your crimp. Over crimping can deform the bullet enough to cause inaccuracies.

Only crimp enough to get the cartridge to pass a chamber check/gauge.
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I don't crimp at all, the dies are set to just barely straighten out the flare needed to get a cast bullet to seat and allow the round to drop cleanly into the chamber. I will have another look at the remaining ammo and make sure a crimp didn't slip in over time on my die settings.


BCRider said:
What sort of rifling does the M&P use? Some modern styles such as the Marlin microgroove with the minimal bore to groove difference are known to be hard to get good results from with cast. Perhaps the M&P uses something similar?
Click to expand...

Good question. It looks like standard rifling to me with 5 or 6 lands (from a quick peek in the bore).


enefgee said:
I had an M&P 45 and I used a slightly heavier load of W231 (5.2 gr) and the H&G 68 and it was very accurate. Try going up and down by the tenth.
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All of this ammo was loaded for my Norc 1911 and I was just testing it out in the M&P to see. I will definitely try some hotter loads, especially if that worked for you. It shot very soft, with noticeably less recoil and muzzle flip than the 1911 so there is lots of room to up the load some.


Mark
 
mmattockx said:
I don't crimp at all, the dies are set to just barely straighten out the flare needed to get a cast bullet to seat and allow the round to drop cleanly into the chamber. I will have another look at the remaining ammo and make sure a crimp didn't slip in over time on my die settings.
Click to expand...

Consider if you have enough flare. I didn't have enough and the projectiles were deforming slightly on seating (I was basically trying to force them into a case). I increased the flare and controlled the crimp and all my (ammo related) accuracy issues went away.
 
How do you not crimp an autoloader? Bullets could be pushed in to varying degree just from recoil and being pushed up the feedramp. You could be experiencing verticals because the oal of chambered rounds varies from your loads. Pushed in boolits make for bad juju at the range.

The 45acp also headspaces on the casemouth so ensure you trim them all to length. A gentle taper crimp is all that is needed..
 
curseyou said:
How do you not crimp an autoloader? Bullets could be pushed in to varying degree just from recoil and being pushed up the feedramp. You could be experiencing verticals because the oal of chambered rounds varies from your loads. Pushed in boolits make for bad juju at the range.

The 45acp also headspaces on the casemouth so ensure you trim them all to length. A gentle taper crimp is all that is needed..
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There is no crimp, the sides of the case are simply straightened back to their original sized shape. The headspacing is part of why I have been careful to not over crimp in the past. I have never seen bullets pushed in on a hand gun. It can be an issue on tube mag rifles with heavy loads, but I can't see it on these mild .45 loads. I have shot a couple thousand of these loads through my Norc 1911 and never had a problem to date, which is part of why I was surprised at how poorly they did in the M&P. I will have to shoot half a mag next time and then check the remaining rounds for signs of the bullets being pushed in or getting ogive damage.


Mark
 
One way to test for sure is to fire one and eject the other for a decent sized sample. Say 2 mags worth. Use a micrometer to measure length and confirm.

all my rounds where the action pushes up a feedramp get a genlte crimp. even bolt actions except when my round is meant to be single fed by hand.But Ill admit Im overly cautious on most things.
 
enefgee said:
Try a lee factory crimp die - it works amazingly well, allows a good crimp, good shoulder at the mouth for head space, and post sizes the round.
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It works ok on the tapered case? I use one for .44 mag and it works great for that, but never thought of it for tapered case semi-auto cartridges.


Mark
 
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