[320pf]

Originally Posted by Flewis

I hate to start another thread, but didn't want to hijack anyone else's either.

I just got a new M1S upper (a week or so ago):

A3 Upper, 16" 1:8 twist with a chrome bolt and carrier (based on people's recommendations that the chrome bolt cycles easier... seems to work). Gas port is at the carbine position.

I cleaned the upper and lubed the bolt well.

Also, I'm using standard GI 20 round mags and a 6 position carbine stock with the stock spring and plunger.

Oh, also the gas port is .125. Strangely enough when I called M1S and asked if their .300 Fireball upper would cycle sub-sonics they said no. Then I asked what size the gas port was and after checking she said .125. I can't image it would be much good to shoot a super-sonic load with that size port and no adjustable gas system, but...

I'm setting this up for strictly sub-sonic 220 SMK loads.

Ran five rounds of H-110 w/9.2gns and the first two shots cycled completely, the remaining three ejected but did not strip the next round. They were all running slow at around 950 fps.

The next five rounds was 13gns of Reloader 7. All cycled properly and the bolt locked back after the last round. Ran about 1200+ fps. A little fast. I had one or two pierced primers, but no other pressure signs.

Last was five rounds with 11.5gns of 1680. Ran about 1050 fps on average and all rounds cycled properly. Also had a couple of pierced primers, but no other pressure signs.

I'm using Winchester small rifle (WSR) primers. I've read that they're a little soft (never had any trouble with my .223 loads though). I'm going to try some CCI-41 milspec primers next time.

Also, COAL was around 2.160

So far I'm very pleased. Today I'm loading up some more and am going to see how the accuracy is. I also picked up some PMags since everyone seems to like them.

If anyone's interested, I can post my spreadsheet with the trim to, COALs, brass and primer types, velocity's, etc.

Flewis,

Here is some load data from the Sierra manual for 220 gr MK. These are the starting loads, so you should not be getting any pierced primers. Even with the Winchester primers. (I use Winchester primers and have not pierced any primers. Even with the max loads that I have worked up to.)

I suspect that there is something wrong with the firing pin and/or the bolt/carrier. I would call M1 and ask them to send you another bolt/carrier and firing pin.

AA#9--9.4 1000 fps
2300--10.0 1000 fps
VN110--9.4 1000 fps
H110--9.9 1000 fps
W296--9.8 1000 fps
VN120--11.5 1000 fps
AA1680--11.7 1000 fps

320pf

P.S. Check out the pride fowler scopes. The 22LR has nearly identical ballistic trajectories and the 330-221 fireball sub-sonics.