Home Forums Hunting & Shooting Gunsmithing Misfires, ideas please.

The rifle is a Rem 700, switch barrel in 250AI. It has a 3 position wing safety and a recently installed Shilen trigger. I am getting misfires in the range of 10 misfires to 1 fire. It worked fine before the trigger install.
Is it possible the trigger is causing this?
The primers show a good strike. I tried increasing the pin protrusion, reprofiles the pin head, and tried a stronger striker spring, I even reset the headspace. It does this with both CCI and Winchester primers. The ammo works fine in a Browning A-bolt in 250AI.

Try increasing your overtravel just a bit. GD

If it worked fine before the new trigger, then yes, that could be the source of the problem. How's the safety working with the new trigger?



How did you do that?

I tried increasing the over travel, no luck.
I increased pin protrusion by chucking the pin in my mill and using a file to cut back the shoulder and remeasure protrusion when installed. The cocking piece remained with clearance from the shroud when the pin was dropped.
I had to cut the cocking piece back more to have the safety work as the new trigger held the pin further forward.

BTW, I just cut down the rear "boss" (the part used to pull the pin back with a shoe lace)on the cocking piece a bit to see if it was interfering with the trigger. Waiting for daylight.
At least my 30-30 scout 94 is up and ready.

Sounds like a great way to start piercing primers.

I've kept an eye on that and also measured the pin protrusion. I am on the outer limit of acceptable as per several published references.

Are you sure that you are not contaminating the primers in some way? miles

I can take the miss-fires and put them in the other 250AI and fire them.
I just ordered a new pin assembly. Mine is lightened. Maybe cutting back the shroud that little bit made it too light and it lacks the impact to do the job?

A lightened firing pin is not a handicap. The total energy delivered to the primer is set by the firing pin spring's stored energy only. A lighter pin merely means that the primer impact velocity is a little higher, a good thing.

RAN

I would guess headspace. Set it tight.

It is tight. Danged odd, this is.

Alright see where the bullet contacts the grooves of the bbl and and load .003 off that measurement.

A light pin does not have the impact of a heavy pin. If the
primer is dented that isn't the problem. Head space can cushion the blow but again if the primer is dented that isn't it.

I have a 338-06 ackley that has excess headspace and will dent primers and not fire upon fireforming cases unless I set the bullet close to the lands. Now after they are fireformed and I just neck size no problems.

Corelokt,

You say the problem started after changing triggers. Based solely on that statement, it sounds like the issue is with the trigger, so focus your attention there. Headspace and firing pin protrusion doesn't change when swapping triggers so I wouldn't be wasting my time looking there. The sole job of the trigger is to release the striker via a sear. If there is any interference with the release of the sear, or the forward momentum of the striker, then that will cause misfires.

The gold standard for trouble shooting such problems dictates, as Greydog mentioned, checking the over travel setting. Too tight of an over travel setting can slow or prevent the sear from dropping fast enough, which can interfere with the momentum of the striker resulting in misfires. Other things like interference between the stock, trigger guard and trigger lever can also result in delayed reaction and misfires. Though these generally manifest themselves as "lighter than normal" primer strikes. Hell, bedding issues that allow the action to be pulled out of alignment when the guard screws are tightened can create interference problems within the trigger resulting in misfires.

I would recommend reattaching the original trigger to make sure that the gun does indeed function well and that the problem only occurs with the new trigger, and then I would methodically examine every inch, or in this case, every thousandths of an inch, of the replacement trigger. If after that you can't solve the problem, scrap the trigger.

Try this. If you have a 7mm expander ball put it on your decapping stem instead of the .250 expander ball. Run several cases over the expander ball (try 3) but do not size. Now reinstall the .250 expander, back out your sizing die a turn or so and size a case. Insert it into the chamber and hopefully the action will not close. Now incrimentally adjust your die down until the bolt just closes with a light crush fit. Now prime the test cases, do not load them, chamber them and see if the primers will fire in the problem rifle. If they fire that would be a good indication that you have excessive headspace.

Sound like the sear on the new trigger is dragging the firing pin and slowing down the force of the strike. If it started with a new trigger then it has to be the trigger.

I'm with Malm and bea. I'll bet something is interfering with teh travel of the pin. It doesn't take much to slow it down enough to still make a dent but not fire.

I've been busy, but will look into it. A little dykem may tell the story. I appreciate the thoughts.