Question on M-1 carbine misfires

[irishjack]

I have been having occasional misfires with my handloaded ammunition, maybe 10% requiring a second strike to fire the round. I am using Winchester standard small rifle primers and a load of 14.0 gr. IMR 4227 with a 115 gr. lead bullet. Could this be caused by a weak firing pin spring requiring replacement? Or should I try another brand of primers, ie Remington? Or maybe switch to magnum small rifle primers? Any advice would be appreciated.

[Doug Douglass]

It's the rifle unless the primers are oil damaged.

[Tuna]

It's not the rifle if 90% of your reloads are firing first time. There is no firing pin spring in a USGI carbine. If your primers are just a little bit high then that can account for the misfires. The primers have to be seated deep in the case with the carbine. If the primers were oil damaged they would not go off the second time. Also make sure your cases are trimmed to the proper length. If a case now and then is just a little bit too long then it will not allow the firing pin to hit the primer the first time but when put in for a second time the case moves and it's just short enough to allow the hammer to hit the primer. A small dent in the primer is from the firing pin when the case is chambered and not from the hammer hitting the firing pin. Case length is critical in the carbine. Cases should not be over 1.90 in length. They must be checked each and every time the case is sized. Trim cases to 1.80 but no more then that. Factory cases are around the 1.85 length.

[kcw]

I would second Tuna's comment regarding case length. It's a common issue with the 30 carbine, especially if the brass has been fired multiple times. The problem is that the over length brass doesn't allow the bolt to turn enough to obtain "battery" position. Take note of what a bolt that's closed on an empty chamber looks like relative to the receiver lugs. Then, the next time you have a misfire, stop and make the same bolt lug to receiver lugs comparison. What you're likely to observe is that the bolt turn stopped a number of degree short of where the bolt over the empty chamber stopped. For reasons related to safety, the bolt must rotate a minimum number of degrees before the firing pin is clear to move forward under hammer pressure to hit the primer. Mind you, the bolt need not be fully closed in order to achieve "
battery" position. but it must be closed (turned) "enough".

[joem]

Second Tuns's recommendation on trim length. I trim mine to 1.80 and they go bang every time with CCI, Federal ro Winchester. You might dismantle the bolt (get the right tool) and give it a good cleaning.

[phil441]

Just for grins, you might want to measure the firing pin protrusion from the bolt face. As I recall it should measure from .048 to .065 inch or so. Grunge in the bolt can give variable readings there.

[emmagee1917]

Two reasons not to use magnum primers in a .30 carbine.
First , there is not enough grains of powder nor any slow enough powders to justify or warrant their recommendation for magnums.
Second , magnums have thicker cups , making your problem greater , not smaller.

[da gimp]

silly question.......... but has he made sure the hammer is locked back after every shot? have one that had this problem. swapped trigger groups.

[Sunray]

Never had to trim .30 Carbine, but as with any semi-auto OAL and case length matters. 14.0 of IMR4227 is .5 under max for a 110 grain jacketed bullet. You may want to look at that too. What brass are you using?
Magnum primers are not necessary. Thicker cups they ain't though.

[joem]

I check every carbine case for length. Any over 1.85 get trimed to 1.80. I use AA9 in my carbine loads.