Well, this could just as well go into gunsmithing - but hey, I'm here now...

I went out to the range the other day to plink a bit with my AR15. DPMS upper, heavy bbl. Anyway I started getting a LOT of light strikes on primers. Not every time, about 40% of the time though.

Of the rounds that fired, the primers have a nice, solid indentation as expected. Light strikes almost look like they barely tapped the primer at all.

any thoughts here guys? it's basically a brand new rifle with barely 150 rounds put through it.

Winchester small rifle primers are being used.

Is it possible that the bolt isn't quite going into battery? Since it's a new gun and things are still tight I'd clean and lube the bolt and carrier and then try watching the carrier position in the ejection port as you fire each shot.

quote:

Originally posted by Rick R:
Is it possible that the bolt isn't quite going into battery? Since it's a new gun and things are still tight I'd clean and lube the bolt and carrier and then try watching the carrier position in the ejection port as you fire each shot.

That's a good thought - but I think I covered this one. On some of the later shots I was pushing the forward assist down all the way to make sure the bolt was fully close before pulling the trigger. Nope, still got a light strike.

Which begs the question (based on the other auto's I've fired) - how can an AR fire if the bolt isn't 100% in battery?

Final question: it's entirely possible that my load was a little light. BUT, if the load was light and the rifle didn't fully cycle - then wouldn't it be the case that either the trigger was reset or the bolt wasn't in battery?

IIRC (since I'm on the road today) that the load I used was 1/2 a grain under max. H322, 23.5gr.

clean out the inside of the bolt, don't grease, either leave dry or use breakfree or the like

It sounds to me that your load is a little light and the recoil process is not completed to cock the hammer always such that the hammer follows the carrier down after case ejection marking the case from the mag with slight primer marking because the bolt does in fact lock up.

Remove the bolt check the firing pin it may be in half !.

Shoot Straight Know Your Target . ...

1. Look for a mechanical reason for light strikes. Perhaps one "leg" of the hammer spring broke.
2. This sometimes happens when components aren't balanced. A super light firing pin added as an afterthought has been known to produce such symptoms.
3. Good old fashioned carbon will also cause this phenomena. Some powders produce more soot/carbon than others, and with the gas tube venting directly into the action, soot/carbon accumulation will produce light strikes too.

1/2 grain under is not really a light load! I would look to disassemble and clean the bolt and carrier throughly, and lube well with CLP or breakfree. If the rounds were not cycling the action to the extent that the last round would not hold the bolt open position... what bullet weight did you say was over the 23.5 H322?

quote:

Originally posted by 308Sako:
1/2 grain under is not really a light load! I would look to disassemble and clean the bolt and carrier throughly, and lube well with CLP or breakfree. If the rounds were not cycling the action to the extent that the last round would not hold the bolt open position... what bullet weight did you say was over the 23.5 H322?

I think it was a 55 gr. bullet (maybe a 50, pretty sure a 55. I can't check my notes just yet.) I pulled the load from my Speer manual.

OH, almost forgot. I also tried a full manual cycle on rounds as well. IE: Light Strike: pull the bolt back and let fly, ejecting the round and fully chambering a fresh round: check the forward assist: squeeze the tigger and...

"Click."

Happened a couple of times.

Step 1: fully clean the dickens out of the rifle.

Step #2: buy a box of "factory" ammo - preferably military grade (aka, Wolf, Black Hills, etc.)

Step #3: head back to the range and try to isolate the issue.

even with the assist your rifle will not go fully into battery if your loads are to long. had this problem with a customers dpms and if it is the very slightest bit out the pin will fall but be in effect too short. full length size and trim your brass. just my .02

Check for these potential problem areas.
1. Deep seated primer
2. Overly resized cases(too short, head to datum line). Also possible is a slightly under resized case.
3. A slightly deep chamber(headspace issue).
4. A dry bolt/ bolt carrier(AR's need to run "wet").
The above singly or more likely in some combination can cause intermitant problems you have described.

As was already alluded to, this problem may have a mechanical cause.
Broken or out of spec. firing pin, hammer spring, or the hammer itself.
A mismatched upper receiver/lower receiver.
Start with the simple things. Eliminate them one at a time.

muck

Check the firing pin and the firing pin hole to make sure everything is OK. Sounds like you may have a burr or powder in the flash hole or a broken or short pin. A weak hammer spring would cause all of the rounds to have light hits.

John

Well, now that I have managed to recover from the Flu I find that I can spend a bit more time working on the rifle and trying to isolate the problem.

Actually, I think I did...but that's to come a little later.

First, I stripped the rifle and cleaned it heavily. I've only put around 125 rounds through it - I was quite surprised how dirty it already was. Scrubbed, swabbed, patched. Pulled the bolt apart and!

Nope, firing pin and bolt worked just fine. Nothing broken here...

Damn. That would have been too easy.

Time to check the ammo: and HERE is where I truly think I had a problem.

1. The sizing die: my sizing die for .223 are old and fairly tired. I bought them back in the late 80's when I was first starting to reload. In all honesty, I didn't take that good a care of them back then. What I noticed is that it didn't seem to quite snug the neck down enough. I could, using finger pressure, push a bullet into the case.

2. My answer to #1 was to use my Lee factory crimp die. I kept snugging it down just a little bit more...and more...and more until the bullets caught more heavily and didn't shift around.

And THAT is where the problem I think lies. I'm fairly sure that what was happening was that in the process of Crimping I was somehow pushing the shoulder back ever so slightly.

With the shoulder back, the round could seat marginally deeper into the chamber - which in turn meant that the primer wasn't being struck quite properly.

Light-Strike!


Just for giggles I ordered a new Hornady FL die and loaded a couple of dummy rounds: the neck was very snug and there was virtually zero need to use a crimp die at all.

I'm betting this solved the problem.

I'll be headed to the range this weekend. Wish me luck!

Autos and semi autos need SB Dies to insure proper case fitting in the chamber .

Shoot Straight Know Your Target . ...

I just read about this last night. I think it was at... http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm
Anyway, sounds like a headspace, OAL, or brass problem to me. Something is too long causing the fireing pin to hit the primer on battery. Do you notice the 'light stike' on a missfire or just when the bolt cycles?

quote:

Originally posted by Dr.K:
Autos and semi autos need SB Dies to insure proper case fitting in the chamber .

Shoot Straight Know Your Target . ...

No they don't.

Unless they were built by some gunsmith that still thinks 1in12 is still the perfect twist rate for an AR15 in .223.

Covey16

quote:

Originally posted by highpower223:
I just read about this last night. I think it was at... http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm
Anyway, sounds like a headspace, OAL, or brass problem to me. Something is too long causing the fireing pin to hit the primer on battery. Do you notice the 'light stike' on a missfire or just when the bolt cycles?

Actually, I've figured out PART of the light strike issue. I used a dummy round with a primer in it for this test.

Much to my shock, the firing pin in my AR is completely FREE FLOATING. Yep, that's right - there's no spring to keep the pin to the rear of the bolt. So whenever a round is inserted into the rifle, the firing pin can move forward just enough to put the smallest of marks into the back of the primer.

This is just a tad disconcerting - and I'll have to check if there is supposed to be a spring there or not.

BTW, the Upper is a DPMS 20" heavy bbl upper straight from the factory. Bolt was pre-installed. So given that, I'd imagine that the firing pin was designed to operate without a spring...

Anyway, yes, I'm pretty convinced this is all about OAL and somehow I was compressing the rounds a bit. I'll be at the range tommorow and will definitely find out.

Hello,
There is no spring regarding the firing pin in the AR15/16 firearm system. There is a specification on protrusion, but not likely that is your problem. If you are resizing your brass, full length that is, and crushing the shoulder so far back that it provides space/room in the chamber for the round to move forward could be part of your problem. Doubt you are using the rifle for service type work, but rather for sport/target/hunting purposes and would suggest you obtain the dimension of your chamber, fired round w/ use of Stoney Point system, Moe's gauge, etc. and resize your brass to something 2-4 thousands less than your chamber. Have you employed Go and NO GO gauges on the rifle?? Any competent 15/16 "gunsmith,mechanic,etc." should be able to inspect and determine problem rather quickly. I know very few folks using SB dies for reloading the 223 round for it is a very easy round to load for and extremely versatile depending on the twist of your barrel. Hopefully it is a 9 and 8 or 7 would be even better for wide range of bullet weights to use. Seek out someone in your area that shoots the 15 in Service Rifle matches and they will most likely be glad to assist you any way they can.

Well, a day at the range and a day of answers.

First, the light strikes was definitely a reload problem. My fresh reloads had no problems cycling at all and ignition was spot on. No light strikes!

Second, one of my magazines is quite prone to jamming. Great.

Oh well, I call it a success anyway!