View Full Version : Delton AR15 slam fire, Need help!!!

September 6, 2010, 12:10 PM
I just used my Delton AR15 with 16 inch barrel for the first time last night. It sure seemed to me that I was getting double fire with only pulling the trigger once. Maybe I'm totally wrong. I even watched other people shoot it and noticed that It sounded full auto at times. The mags were junk that came with it but I don't think that would cause the problem. The rifle functioned fine otherwise. Is it even possible to get a slam fire or double fire from an AR style rifle? Need some help. I don't have much experience with this style rifle. Hope someone can help. Have a safe holiday.:confused:

September 6, 2010, 12:13 PM
try giving it a good clean and clean out the gas port!!!

September 6, 2010, 12:13 PM
Not sure what to do if it IS happening but it shouldnt be hard to determine that part. Count the number of rounds you have in and how many trigger pulls.

September 6, 2010, 12:29 PM
Or just load two rounds in a mag and shoot once. If two cases fly out, yep, there is a problem.

September 6, 2010, 12:53 PM
It could be that the disconnector is releasing the hammer too early.

Check to make sure the disconnector spring is properly installed.

To check proper function of the disconnector perform the following steps:
1. Remove the upper and set it aside.
2. Hold the lower by the pistol grip with your right hand with the lower across your chest so you can see the hammer, trigger and disconnector.
3. Place your left thumb on the hammer and pull the trigger, easing the hammer to the fired position. Note: DO NOT let the hammer free fall because it can break the bolt catch or crack the receiver!
4. While holding the trigger back, use your left thumb to push the hammer back, cocking it. The hook on the disconnector should catch the hammer. If it doesn't, your problem is identified. You have a bad disconnector or bad disconnector spring.
5. Release the trigger. If everything is working normally, the hammer should be released by the disconnector hook, and will be caught by the trigger nose. If the disconnector is malfunctioning, the hammer will fall to the fired position. (Be sure to use your thumb to keep the hammer from whacking the bolt stop!)

September 6, 2010, 01:17 PM
Try holding trigger back after each shot. it could just be accidental bump firing. I have a 12 ga. semi auto with a smooth light trigger pull that does it , if i don't keep the trigger squeeze back after each round.

Bartholomew Roberts
September 6, 2010, 03:54 PM
Problem is likely wear in the fire control group or something out of spec there. If the trigger nose on your AR is faulty, it will fire once when you pull the trigger and again when you release the trigger. Typically, I see this when guys try to "polish" the stock trigger to get a better pull. They "polish" through the thin case hardening and then the parts wear very fast and the trigger stops catching the hammer after the disconnector lets it go.

To check, unload your rifle and detach the lower from the upper. Using only the lower, cock the hammer with your hand. Place your off hand in front of the hammer to stop it from slamming into the magwell. Flip the selector to fire. Pull the trigger and hold the trigger back with your strong hand. As you catch the hammer with your off hand, cock the hammer again while continuing to hold the trigger back.

If the hammer does not cock; but flies forward while the trigger is still back, then you have a wear issue in your disconnector or hammer. If the hammer catches, release the trigger. If the hammer flies forward, then the wear is in your trigger or hammer. You'll need to replace the worn parts to fix the issue.

September 6, 2010, 07:34 PM
Thanks for all the good replies. This gun is new with only 90 rounds through it. It had problems from the start. I will check the hammer disconnect and spring to see if that is the problem. Will post when I find what the deal is.

September 6, 2010, 07:35 PM
was this a new ar that came complete from the factory or did some one put the lower together. ive seen lowers with the spring installed wrong,beneath the pin do what you describe.

September 6, 2010, 11:31 PM
This was new AR that came from a gun shop. I don't know if it was a parts gun. I had the lower removed, this is what I found. If the hammer was cocked and I put my thumb in front of it and pulled the trigger it would go into the fired position. If I kept the trigger pulled and cocked the hammer it would lock into place. As soon as I let the trigger go the hammer would go into the fired position again. It will go in to be fixed. Physically can't see anything wrong. The rifle is under warranty so Delton can fix it. Thanks for the info.

Bartholomew Roberts
September 7, 2010, 08:14 AM
Either the nose of the trigger or the notch in the hammer is out of spec. One or both parts need to be replaced. Since they are new parts and worked for 90 rounds, I'd guess they were not properly case-hardened; but they may just be out of spec to begin with.

It is about a five minute job a monkey could do to replace these parts; if you want to save some turnaround time and have Delton send you replacement parts; but I can understand wanting them to fix their error.

September 7, 2010, 08:42 AM
I hope no one flames me for this. I did bump fire 6 to 8 rounds through it. Hopefully I didn't ruin the parts. Delton says their rifles are milspec so that shouldn't hurt it. Regardless it will go back for them to fix. Thanks for all the good info.

September 7, 2010, 09:37 AM
Slam fires are impossible with an in spec AR15. Typically doubles are caused by out of spec trigger and/or hammers. The second shot will fly when the hammer drops on the let off.

I've had this happen in the past.

September 7, 2010, 10:43 AM
Slam fires are impossible with an in spec AR15.

Not impossible. Get something stuck on the bolt face and it can happen.

September 7, 2010, 10:56 AM
Yes. Or perhaps a high seated primer... I've never heard of it happening, but it would have to be a non weapon related issue.

I've seen a DR200 (DAEWOO) .223 rifle slam fire. I was walking back across the firing line when it happened... scared the [email protected] out of me. :eek:

September 9, 2010, 10:23 AM

Bartholomew Roberts
September 9, 2010, 01:07 PM
My understanding is that you've identified the problem and sent it off to Delton for them to correct. Is there some reason you are bumping the thread?

Bumpfiring won't hurt the trigger group, if that was your concern.

September 9, 2010, 05:04 PM
The topic got a little off post. I bumped it to see if anyone else had any input. I did take it into the shop it was purchased at. They pulled the hammer and spring. The part that the bottom of the hammer hooks on when it is cocked was not ground properly from the factory. Will get it fixed here locally.
Thanks for all the good input.

September 9, 2010, 05:19 PM
Slam fires are impossible with an in spec AR15.

Not true, look at the Fulton Armory FAQ, the article “Slamfire: the M16 story” http://www.fulton-armory.com/

Slamfires happened to the early M16’s because of a heavy firing pin and sensitive primers. If you look in Chapter eight, page 130, of the “Black Rifle” by R. Blake Stevens, there is an entire section on the slamfire problems the Army had with the M16. A number of AR15 slamfire incidents had occurred when cartridges were single loaded and the bolt release pressed.

If you read the report in the book, dated 1963, based on the tests of two rifles with the firing pin configuration available at the time, the energy during bolt closure of one of the test rifles firing pin always was above the “none fire” specifications of the primer. Which meant that statistically some of the primers would ignite at those energy levels. So the Army did two things. The first was to test alternate firing pin configurations, all pictured in the book, and one has a spring undoubtedly like the current AR-10 design, and the second was to change the ammunition specifications to require a harder primer.

more and more accounts of slamfires with AR's are being posted.

AR15 slamfire with Winchester primers.


Occured today while breaking in a new upper ... single round in the mag, pressed the release and ... BANG! A little later on, with three rounds in the mag, pressed the trigger ... round fired. Everything is ok. Pressed the trigger again ... double BANG!

I went back to single loading to finish out the box. Total rounds fired ... 40. Two slam-fires (including the double). Two failures to extract. One failure to feed.

First slam-fire was on the second round fired (while I was still single loading the magazines). The double was on rounds 27, 28 (of 40).

At this point the ammunition is my prime suspect, Winchester "White Box" .223 Rem, 62 grain but I would have to say that ARs do, in fact, slam-fire.

I did inspect for a frozen pin after the first slam fire. I didn't expect one (frozen pin) since I had personally cleaned and inspected the gun last night and it was the second round of the day. I also didn't expect it to foul up too much since it is a piston operated upper (ZM Weapons).

The upper was brand new and unfired (except for factory). The lower is a relatively new (about 200 rounds) RRA. Both (upper and lower) were cleaned, inspected and lubricated properly before the trip to the range. The lower has functioned flawlessly for those 200 rounds when mated to a White Oak Armament upper (all Black Hills .223 Rem 77 grain).

I know BR said that the bolt face could cause the slam fire but the two casings did have firing pin strikes with no other dimples or scratches on the primer face.

I am begining to suspect the recoil spring on the ZM upper. It does seem rather robust. This upper might require the harder primers found in 5.56 NATO. Unfortunately I don't know it all yet so I'm still researching.

Watched an AR Slam-Fire Saturday
Posted 20 http://www.usrifleteams.com/forums/index.php?showtopic=13132&view=&hl=slamfire&fromsearch=1 April 2009 - 09:10 AM

I was scoring my firing-point partner Saturday during offhand and he had a slam-fire on about the 5th round. We're talking about an experienced shooter here. Multi-year state HP champion, generally shoots 199-clean offhand, not to mention he's a hell of a nice guy. The bullet hit the dirt about 10 yards in front of the firing line. I was watching him closely trying to learn something from his technique, but didn't expect to learn this. I know his finger was off the trigger for certain but his muzzle was decidedly pointed earthward when he closed the bolt. The area downrange is uninhabited for many miles, so at this range folks are a bit lax about closing the bolt while rifle is pointed toward the impact area. After that, he was pretty careful about keeping it level. He was shooting an AR spacegun. He thought it might have been due to the bolt carrier weight he had just put in for testing before this match. My suspicion is high primer, but he could be right. Another possibility is his loading technique. He places the round through the ejection port, then tips the muzzle down and jiggles the round fully into the chamber prior to closing the bolt. I have always thought it best to leave the cartridge on top of the magazine and let the bolt "strip" and chamber it from it's "natural" position. In any event, let this be a lesson to all of us. Closing the bolt is an inherently risky event. Point yer rifle at the backstop when you push that button. My buddy lost the match as a result of his slam-fire, but next time it could be a lot worse.

Posted 30 May 2009 - 08:09 AM
I am the person Heman referred to having a slam fire on a bolt rifle. The rifle in question is a Stolle BB Panda action with a Kelbly trigger set at 14 oz. The system is two years old and has several thousand live rounds through it as well as countless dry fires. After the match, I re-weighed the trigger and it still breaks at 14 oz. The only thing that was found was a very small piece of dirt on the sear engagement notch, but I doubt that this was the cause of the slam fire. I tried to re-create the condition 8-10 time on the line, without success, then again at home. I KNOW I didn't have my finger on the trigger when I closed the bolt, so that scenario isn't a suspect either. I just returned from a two day Palma style match where I fired over 100 rounds and not a single hick-up with the system. I guess it will just get chalked up to one of life’s great mysteries.
Be safe,

Posted 20 April 2009 - 10:43 AM

I disagree.

It's happened to me.

I've found that dropping the round entirely into the chamber and letting the bolt close with full momentum isn't the best idea.

I now leave the round resting on the magazine and let the bolt "pick it up" as it closes.

Free-floating firing pins and occasionally sensitive primers can lead to this.

Gary brings up a good point about the trigger issue. Another consideration is the primer. I have seen 2 slamfires in an AR15. Both occured during an offhand string, 2 shots in a row. The shooter is a very experienced reloader and highpower shooter. It never happened again to him. He was using WSR primers. Perhaps it was the primer's "sensitivity," a couple of high primers, or a combo of the two.
The occurance sure did shake his nerves though. Both rounds impacted 10-20 yds in front of the firing line.

Posted 20 April 2009 - 12:02 PM
I had it a few years ago practicing off hand with winchester white box in my service rifle.

Second shot of the night, shot went into the ground in front of me. I put the rifle down and tracked down my 2 ejected brass. Looking at the primer strikes, one had metal flow out into the firing pin hole in the front of the bolt. So, instead of a primer srike like an innie belly button, one of the brass had an outie. No damage to the rifle.

Whats most amazing about your post PamF is the 199 to 200 part!


Posted 20 April 2009 - 12:46 PM
I've had two slam fires and both of them scared the beejiminees outta me. One of the more experienced shooters in my club made the observation that slams seem to happen more often when the muzzle is depresseed as the bolt goes forward. He postulated that the firing pin is already lying forward from gravity almost as if it was preloaded. He figured that as the bolt rode forward with the pin already out, if the primer was gonna go that just gave it the extra opportunity to do so. Since that time I've never let the bolt go forward with the muzzle depressed. I have no idea whether his idea has any merit but it makes me feel safer. For what that's worth. LOL

Posted 22 April 2009 - 11:06 AM
We had at least 2 MIA's over the years at New Holland that had rounds go off when the bolt was closed.
The reason I am able to think of at least 2 is the severe damage to the rifles. In the 2 listed instances the rifles were damaged to the point the receivers were cracked and or broken.
We have an AR-15 do the same thing a time or 2 a year. We have not had rifle damage from the AR-15 slam fires.
My finding at the end of the M1A era and start of the AR-15 era was to completely ensure an AR-15 will not slam fire is to install a light weight firing pin.

Posted 22 April 2009 - 12:31 PM
I had a slam fire several months ago. I was just at my regular local club's range doing slow fire standing practice. Put the round in the ejection port, sort of tipped my rifle forward very quickly to let inertia start the round in the chamber and dropped the bolt. Round went off about 10 feet in front of me. I make an effort to keep the rifle parallel to the ground when dropping the bolt, but get lax about it sometimes.

I was using handloads. Hornady 75gr HPBT, 24.0gr RL15, Remington 7-1/2, LC03 brass. I'm betting the primer was a bit high, because it was once fired brass from military source and I used a Dillon Super Swage tool to just barely swage the pockets (keeping them tight as possible, but still accept a primer).

Posted 23 April 2009 - 01:58 PM
I g=had a slam fire with a Garand in the first highpower match I EVER shot. Really unnerved my. I was a reloading greenhorn, but others found some issue with the dies a friend had loaned me. learned a lot that day. I've always remembered that.

Posted 03 May 2009 - 08:52 AM
We've had only one instance in the 11 years I've ran local matches. AR15, handload. The same gun has been used many times since w/o any problems. The round impacted the ground 15 feet in front of the line - not a big problem with me compared to having the muzzle raised and the bullet leaving the range.
Me, guess like most, load with the muzzle slightly depressed, drop it in, and hit the bolt release. Bent several rounds trying to drop 'em on the follower. Haven't lost 10 points to slamfire yet, although I have employ many other methods of losing points !

Posted 29 May 2009 - 11:46 AM
I saw two slam fires by the same shooter in the same offhand string.
He was a good shooter who posted a poor score for the day because of this.
I never found out what caused this in his rifle that day but it reinforced the absolute importance of having the muzzle ALWAYS pointed in a safe direction when closing the bolt on live ammunition. (in any firearm)
Both rounds impacted the ground a few yards ahead of him but later, in the same match, I witnessed him closing his bolt with the muzzle well above the horizon. ????????
Bullets impacting the ground will tumble and have a limited flight distance but ones angled above the horizon can pose a much more serious hazard.
Trying to close the bolt with the rifle aimed at the backstop is, in my opinion, asking for trouble. I always keep my muzzle down when closing the bolt and have never experienced a slam fire in my own firearms.
Most folks close their bolts sky high during their rapids and I wish that they wouldn't

Posted 29 May 2009 - 12:33 PM
I had mine to slamfire monday while chronographing some loads. It was completely horozontile on a front rest when I loaded and closed the bolt. I'm just glad it was pointed downrange and wasn't pointed at the chronograph when I closed the bolt. Scared the crap out of me though.
Slamfire, how is it scored?
Posted 21 July 2009 - 12:05 PM
How do you score or count a slamfire? Is it considered as a miss or are you allowed to fire over with another round and disreguard the slamfire? I am referring to having a slamfire while shooting slow fire 200 or 600. The reason I'm asking I have had 2 slamfires one was recorded as a miss at one range and the other one was disreguarded and I was allowed to fire another round in it's place at a different range. Just wanting to know the proper procedure. Tim

Posted 21 July 2009 - 04:05 PM
I never had this happen until I bought some CCI400 primers. The rem. 7.5 never slamfired on me. I'll be glad when the CCI's are gone.
Posted 25 July 2009 - 06:12 PM
I had it happen to me twice in the same stage of a match, standing slow fire, with the newer Winchester SR primers. I was able to borrow a friends extra amo and finish the match. I now only use Rem 71/2's at matches and have never had a problem since. The old Win SR's were harder. I have used CCI mil spec primers on my practice loads with no issues also

Bartholomew Roberts
September 9, 2010, 06:33 PM
I think demigod may have been thinking "firing out of battery" when he said "slamfire" given the high seated primer comment. An AR15 can slam fire; but if it is in spec, it should not fire out of battery absent a defective/high-seated primer because the firing pin does not protrude from the bolt face until the bolt has locked.

September 9, 2010, 09:40 PM
it should not fire out of battery absent a defective/high-seated primer because the firing pin does not protrude from the bolt face until the bolt has locked.

I will agree with that, I have not heard of an out of battery slamfire in a AR action.

Heard of lots of out of battery slamfires in Garands, and a few in M1a's.

February 15, 2011, 10:47 AM
I've had one slamfire a few weeks ago while I was clearing a jam from steel cased ammo. They give the warning card for a reason, and I felt the need to test it out. Run brass only, and mine works as good as any I've ever owned!

June 19, 2011, 09:58 PM
My AR-15, with a Delton lower and .22lr upper, was having a similar problem. It'd double or triple fire and it's happening more and more frequently. At first I thought I had found a sweet spot in being able to shoot rapidly and figured it was the perfect point of where the semi-auto feature reset without having to completely release the trigger but when trying to shoot a single round and a surprise round goes out, that's a safety issue and a serious concern. I've tried the steps listed here of using my thumb on the hammer trying to recreate the issue but I can't. I've tried probably a dozen times to see if the hammer isn't catching...now it's not very smooth when the disconnector lets the hammer go to be caught by the primary sear, but it wouldn't happen when testing at all. Nothing looks worn or damaged and I cleaned it all up nicely. Any thoughts what could be causing this? To be safe, I ordered new trigger parts and springs so I can rebuild it to be safe and legal.

I would love those spare parts to be just that and get my rifle working fine again but I want it to be safe. It's messing with my head that the gun does it with life fire but in testing the lower I see nothing. It's a .22lr so it can't be bump firing...the recoil is almost non-existent.

June 20, 2011, 06:13 AM
>>Not true, look at the Fulton Armory FAQ, the article “Slamfire: the M16 story” http://www.fulton-armory.com/

Ah... yes the experts at Fulton. I've purchased two rifles from them.

When I bought my first AR I asked them "why should I buy from you guys?"

"Because we literally, wrote the book and I can guarantee the gun is built right."

Of course there are tons of good AR builders out there now.

A buddy of mine had the exact same problem with a DEL-TON carbine doubling that he purchased right after the Obama gun surge. DEL-TON was extremely difficult to get through to on the phone, due to call volume. He ended up replacing the trigger group with a 2-stage Rock River and it fixed the problem. A few weeks later he received a replacement trigger group from DEL-TON in the mail.

June 20, 2011, 10:39 AM
I had the same problem with a delton that I built. I replaced the trigger group and that cleared it up. I read somewhere that it is the disconnector being out of spec. Just get a new trigger group, and replace it yourself (or at least make sure that the person fixing it locally replaces the parts, rather than modifying the out of spec part to work). But, replacing a trigger group is easy, there are videos out there to show you how, and you should learn to take the rifle apart and put it back together, that is one of the advantages of the AR.

June 21, 2011, 05:07 PM
I had the local smith replace the bad parts with a used trigger kit. It was one that was used a few times then changed out for a competition trigger kit. It hasn't been used since. I did check to make sure that is would reset correctly and for proper function.