Maybe a bad purchase

[Reverend Duke]

Thanks for the advice ChattanoogaPhil....I find it perfect that the ammo I bought for it today - CCI Mini Mags ( 2 boxes), and1 FED VAL PAK from Walmart(@18.97 ) , match your RX perfectly! Wow, I feel better already! There's a vast amount of knowledge out there - thanks for sharing that tidbit.
Will be posting pics of her "all dressed up" ASAP...

The Rev.

 

[BELT_FED]

As usual.... Belt_Fed cuts through all the noise

Now.... we just gotta get you up to Springfield....

screw that their guns dont hold enough rds friend...... now if fn calls im gone

 

[BELT_FED]

If the bolt is longer, that adds more weight and the spring would have to have less give to it but still be strong enough to push all that weight back to load the next round. I know that it the weight to the bolt wouldn't make too much of a difference.

Im not sure. I was just thinking. I should probably step outside so that the smoke detector doesnt go off

your talkin a 1/10 of an oz. i dont think it will need new srings.... again

 

[BELT_FED]

Hey Rev, welcome.

I have a DTH with around 14k rounds of Fed Value Pack through it. Picked it up last Oct. No problems.

This seems to work for many- Start off with a couple hundred CCI Mini-Mags (They are bit more robust and help to ensure the new rifle cycles). Then switch to Fed Bulk Pack and have a blast.

New rifles seem to fail pretty quick within a few hundred rounds or just keep on ticking for tens of thousands of rounds. If your rifle has ejection problems don't fight it. Either refer to the DIY ejector fix or send the rifle back to S&W.

great advise phil ... i think ive seen that somewhere before

 

[ChattanoogaPhil]

great advise phil ... i think ive seen that somewhere before

Imitation is the highest form of flattery

 

[Brett248Vista]

Chuck,

2.7mm worth of bolt to chamber spacing produced a faint firing pin strike on the rim of the cartridge but no detonation.

 

[BELT_FED]

Chuck,

2.7mm worth of bolt to chamber spacing produced a faint firing pin strike on the rim of the cartridge but no detonation.

See brett told you .. if you made the the bolt 1.5 mm longer then the hammer couldn't get to the firing pin until it was almost closed

 

[Brett248Vista]

See brett told you .. if you made the the bolt 1.5 mm longer then the hammer couldn't get to the firing pin until it was almost closed

Brett,

Even at 2.7mm it's still leaving an impression on the rim of the cartridge, and out of 500 rounds, one of them might detonate at 2.7mm Maybe they should just make the bolt 3.5mm longer and call it a day.

I'll keep shooting mine anyway

 

[BELT_FED]

w

Brett,

Even at 2.7mm it's still leaving an impression on the rim of the cartridge, and out of 500 rounds, one of them might detonate at 2.7mm Maybe they should just make the bolt 3.5mm longer and call it a day.

I'll keep shooting mine anyway

Well that came out wrong I ment see you told them what the distance was.. lol to many bretts in the room and I haven't had enough sleep as usual lol

 

[RON1955]

Just a thought (maybe a dumb one) could the firing pin be just a little to long?

 

[ChattanoogaPhil]

Brett,

Even at 2.7mm it's still leaving an impression on the rim

Right. For discussion purposes of OOB issues... a strike on the rim no matter how light is an issue.

Seems to me that while rapid firing it's quite likely that the hammer will have already engaged the firing pin, and the firing pin is actually chambering the round from a quarter inch out. If the chamber is a little dirty or the round is a little out of spec .... BANG.

 

[chuck s]

Changing the geometry of the rear of the firing pin vs the hammer may help. The firing pin must project beyond the aft end of the bolt or the hammer has nothing to hit, but with the bolt out of battery the hammer is probably striking the lower "corner" of the firing pin, not the full flat.

I can sketch the theory easily, but have no way to pass it on via the computer.

Anyone got a spare firing pin? The theory would be to grind that lower corner off and see at what point the hammer will impact the firing pin out of battery.

-- Chuck

 

[eztarget]

Changing the geometry of the rear of the firing pin vs the hammer may help. The firing pin must project beyond the aft end of the bolt or the hammer has nothing to hit, but with the bolt out of battery the hammer is probably striking the lower "corner" of the firing pin, not the full flat.

I can sketch the theory easily, but have no way to pass it on via the computer.

Anyone got a spare firing pin? The theory would be to grind that lower corner off and see at what point the hammer will impact the firing pin out of battery.

-- Chuck

i can see another belt_fed project...

 

[ChattanoogaPhil]

Chuck,

2.7mm worth of bolt to chamber spacing produced a faint firing pin strike on the rim of the cartridge but no detonation.

Took out the bolt on my rifle. My firing pin must be a lot shorter (or worn down) cuz when I push in the rear of the firing pin all the way the firing pin doesn't quite break the plane of the outer bolt face.. so we're talking about less than 1mm on my rifle. Maybe the hammer can push the pin in further than I can.. but I was applying quite a bit of force and it had a definite "stop". ???

 

[chuck s]

The firing pin may be "floating." Common design. Strikes the primer thru momentum after being hit by he hammer. Like the M1911 pistol, for example.

-- Chuck

 

[HalfSwiss]

Question

So you guys are telling me that the trigger can be pulled and the hammer will fall on the firing pin when the bolt is not fully closed? Sounds consistent with the OOB problems I've been reading about.

I'm used to guns that can't fire until their bolts are fully closed. I'm going to have to change my mind set. Thanks for the info.

 

[chuck s]

OK, at my desk at home.

The M&P15-22 firing pin is not inertial and projects thru the front face of the bolt when the hammer is flush with the aft face of the bolt.

The shape of the rear is tapered, probably for the reasons I theorized in an earlier message. It would need to be completely reshaped to put the impact point by the hammer very high on the back surface, which would require a new design.


Crude sketch of the aft end of the firing pin below. Impact point remains same distance from from front, but is moved higher
_______
............\
............| <-- current impact point
_______/

|<- d ->|
________
............| <-- new impact point
.........../
______/



-- Chuck

 

[avery53]

C'mon Smith, we know you're reading this.
Step up to the plate, and give us a fix.
Don't ignore us!
avery

 

[Brett248Vista]

The bottom side of the bolt that cocks the hammer has a radius to it, so that it can glide over and cock back the bolt using spent gasses. I think there needs to be a more aggressive radius and maybe a flare back on the backside of the bolt below the firing pin, flaring out/upward to the firing pin. This would effectively block the hammer from striking the pin unless the bolt was in full battery and the hammer could hit it square.

Here's my crude drawing of how the bolt is now:

The shaded area is the firing pin.


Here's what was floating around in my head. The only problem with something like this, would be the need for the hammer's profile to be changed to match, when then means no more standard AR hammer.

 

[BELT_FED]

if this was my projsct and i worked for s&w... id add 1.5 mm to he bolt length then make the bolt radious about 4-6 times as large(im talkin 1/5 or better) and shorten the firing pin to the point that its a complete tappet system or very close to it, add in a lighter hammer spring.. the radious and hammer spring would allow for a much heavier bolt return spring and never look back... but what do i know i just build stuff that runs on a belt... these mag fed things are way to simple