Double....or slam fire?

[highxj]

A while back I was sighting in my 3-gun AR from the bench, and my rifle doubled once. I didn't think too much about it at the time, other than a bit of surprise that it happened with my Wilson TTU trigger which disappointed me a bit. When I got home I checked out the trigger for debris (it seemed to be fine), cleaned it up, and have had no more issues.

It just occurred to me from hearing it mentioned on here that I may have experienced a slam fire rather than a trigger malf......and wondered how a person could actually tell the difference.

My rifle is a 17" with rifle gas, JP LMOS carrier, JP buffer spring, and standard carbine buffer. I use Federal 205's which I do realize are not a tough primer. Do you rifle guru's think it would be wise to go to a lighter firing pin for reduced inertia, or heavier cupped primers? Or was it really a 'slam fire'?

[gose]

More likely bump fire.

[kurtm]

Slam fires are real easy to tell. Look at the brass and if the primer has a little bit of brass sticking back up from the flat primer strike it was a slam fire. Some rifles do, some don't. I have one with all the light stuff and it never has, I have one with an aluminum carrier and it never has. I have one set up like you have and it does it all the time unless I run a Ti firing pin. If it was a bump fire it would be at a determined pace...boom boom, if it was a slam fire it would be more like baboom almost sounding like one. For some real strange reason slam fires happen a lot more on the bench than anywhere else. KurtM

[krdshrk]

Slam fires are real easy to tell. Look at the brass and if the primer has a little bit of brass sticking back up from the flat primer strike it was a slam fire. Some rifles do, some don't. I have one with all the light stuff and it never has, I have one with an aluminum carrier and it never has. I have one set up like you have and it does it all the time unless I run a Ti firing pin. If it was a bump fire it would be at a determined pace...boom boom, if it was a slam fire it would be more like baboom almost sounding like one. For some real strange reason slam fires happen a lot more on the bench than anywhere else. KurtM

Thanks for that - I've accidentally bump fired my AR from the bench before... was afraid it was a slam fire.. Of course, I hadn't cleaned it in a bit

[davel]

I have been having slam fires recently and I was determined to find the cause. I have built my AR with a JP barrel,JP LMOS carrier, JP bolt, JP buffer spring and standard carbine buffer. I load Wolf, Remington BR and Winchester primers and only get the slam fires with Winchester. When chambering a loaded round and ejecting it unfired the dimple is much deeper on the Winchester primers. If I replace the JP LMOS carrier with astandard one the slam fires stop. With the LMOS I get slam fires in every mag with the Winchester LMOS carrier combo. I am sure it is the added speed on the bolt moving forward and the Winchester primers that are known to be a little on the soft side. I am going to stop using Winchesters but I am not real comfortable with the JP carrier as I might be on the edge of a slam fire withit.

[highxj]

Thanks Kurt and everybody else. I'm quite certain it wasn't a bump fire. I agree that the quicker moving LMOS carrier is contributing. My two shots almost sounded like one.

I would think that a Ti firing pin ought to eliminate this gremlin, so that's what I'll try.

[kurtm]

It has cured all the ones I know of!

[Religious Shooter]

I stopped using Federal's and now use CCI, Wolf and Tula. No more slam fires after the change.

[Outsydlooknin75]

I agree with Gose that it was a bump fire and not a slam or double.

I've seen it happen with some triggers. Shot from a bench as you would a precision rifle it would bump fire. Shoot it off the bench and it was fine.

Sent from my PG06100 using Tapatalk

[davel]

How could the LMOS carrier contribute to a bump fire? I thought it would it contribute to a slam fire because of the increased velocity and throwing the firing pin forward harder.

[cas]

Doesn't Federal (err… someone) make a 5.56 primer? I'm assuming a little harder than their normal ones. (or am I thinking of 7.62?)

It's been a bad week for thinking.

[highxj]

Yeah cas, CCI makes the #41 for the 5.56. I used to use them in my 17 Predator shooting 30 gr. bullets at 4100+ fps. That primer would resist cratering with hot hunting loads better than any other primer I tried, including the 7 1/2.

[AlamoShooter]

my Buddie's new build with the JP light stuff and a 16 barrel and carbine buffer. I did the old thing that Zidecker book talked about and put grease on the buffer and spring and the doubles stopped.

The grease is thick and slows the buffer bounce down. that would be IF I remember the book rite

it does make the stock Ping less sound

[MarkCO]

KurtM is right on this one. I had a few slam fires recently and put a standard buffer spring back in. The JP buffer springs work well with standard BCGs, but since they are stronger than stock, have more propensity to slam fire, especially with the lighter lmos carrier. Titanium firing pin does reduce the occurance.

Off the bench, the gun is locked down more so you actually move a little less and absorb a little less energy from the system. That makes the BCG close with slightly more force.

[highxj]

That makes perfect sense Mark...also with so little movement from a locked down bench position, a bump fire would be extremely unlikely. See ya' at a CO 3-gun match sometime I hope! You ever come up to the Weld County matches?