Heavy bullets in .223, harmful to semi-autos?

[His lordship.]

I was reading a post about a guy who was having receiver problems with his mini-14 and he was using NATO spec. SS 109 62 grain ammo, a responder said it was too hotly loaded and the heavy bullet added trouble.  I know that the early tests done with the M-1 Garand in 30-06 found that the heavy bullets were beating the rifle too hard and they went with the 150 gr. FMJ to prevent problems.

I have mostly used a bolt action .223 over the years, did not think of any problems with the heavy bullets, but with my fairly new Mini-14 in .223 I am worried about using 62, 69, 75, or even heavier bullets in it for wear issues?  I also might get an AR-15 down the road.  Should I stick with the 55 grainers in semi-autos and the heavy bullets in my bolt gun, or are the 62-69 grs. ok for limited use in a Mini or AR?  

Thanks.

[billy_56081]

The problem is not with the bullets but the pressure they are loaded to. Mil spec ammo in 5.56 is not the same as 223 I am told. But I believe the mini 14is speced for both 223 and 5.56.

[84Jim]

I don't know much about mini 14's, but the standard AR-15 highpower round for 600 yds. is 80 grain Sierra, Bergers, and Noslers.  I've heard of 90 gr. bullets (Bergers?) but have never tried them, or known anyone who has.  In fact, many shooters are using 77 MK's loaded to mag length for the shorter ranges.  That being said, properly loaded heavy bullets ain't gonna do nuthin' to your AR

[shvlhead.45]

Chris D.

 Billy_56081 is correct, if your Ruger is marked .223 don't shoot the 5.56 marked ammo in it.  I've never seen a catostrophic failure from shooting 5.56 in a gun/barrel marked .223 but I've seen a whole bunch of failure to extract and eject issues as well as accuracies issues.  Don't think frame stretch on a Mini 14 would be near the issue as the pounding of the bolt would put on the receiver, which I believe would crack a receiver before stretching it (no expertise meturology but cast seems to crack before stretching).

As to your bullet weight question; bullet weight is only an issue if it won't chamber properly, it won't fit in the magazine, and heavy bullets like fast twist barrels like the 1:7 to be accurate.  Hand loads loaded over book will cause problems as well.  Semi-autos gas systems will be more tempermental than a manually operated action.

Shvlhead.45

[TargetTerror]

I was reading a post about a guy who was having receiver problems with his mini-14 and he was using NATO spec. SS 109 62 grain ammo, a responder said it was too hotly loaded and the heavy bullet added trouble.  I know that the early tests done with the M-1 Garand in 30-06 found that the heavy bullets were beating the rifle too hard and they went with the 150 gr. FMJ to prevent problems.

I have mostly used a bolt action .223 over the years, did not think of any problems with the heavy bullets, but with my fairly new Mini-14 in .223 I am worried about using 62, 69, 75, or even heavier bullets in it for wear issues?  I also might get an AR-15 down the road.  Should I stick with the 55 grainers in semi-autos and the heavy bullets in my bolt gun, or are the 62-69 grs. ok for limited use in a Mini or AR?  

Thanks.

The issue with the Garand and M14 is that they use an operating rod to cycle the action.  When the bullet passes the gas port, the gas pushes on the operating rod which slides along the side of the barrel/receiver and actuates the action.  When the pressure at the gas port is too high (which happens with heavy bullets and/or slow burning powder) the operating rod slams back HARD which is all sorts of bad for the rifle.  The AR series is direct impingement, meaning the gas vented from the barrel gets dumped directly on the bolt.  I don't know whether certain loads may be more or less violent and damaging for the AR, but I do know that, as mentioned, standard highpower match loads are max loads with 77 grain bullets.  I've never heard of these loads causing any issues whatsoever.

So, in short, a heavy bullet is not, in and of itself, an issue in an AR.