New ACR Slam fires .223 rounds

[IXLR8]

I sent the following email to Bushmaster a week ago and they have not responded. If you have an ACR I would not shoot it, and if you do, be aware that it may fire any time the bolt is closed with live ammo.

Email:
I was very very happy to receive my new Bushmaster ACR Enhanced this week, I waited a year to get it. Today I took it to the range to sight in the weapon. I loaded 1 round of Parvizan 5.56 and shot it, no problem. A precaution I take with all new firearms. I then loaded a full clip of the PRVI Parvizan 5.56 BT ammo and shot the full clip without incident. I changed stations from the 50 to 100yd benches. It setup and fired 4 more boxes of PRVI 5.56 ammo without incident.

The problem started when I loaded Hornaday .223 ammo. I released the bolt from the open position using the release button. The rifle fired from an open bolt. After releasing the bolt with the button, the bolt chambered a round and fired it in a single action. I was very surprised by this and immediately unloaded the rifle. I then removed the bolt and examined it to see if there was a stuck firing pin, or some other malfunction. Everything seemed to operate freely and properly. There was almost no gunpowder residue on the bolt, and I examined the locking rings in the barrel and they were clean and clear. I thought that this may have been a single unusual event. I loaded another single round and tried it, and it loaded and fired as expected. I loaded up 15 rounds of Hornaday .223 ammo and l loaded a round into the chamber using the bolt release button. No problem. I fired 6 rounds and no problem was detected. On the 7th round, I pulled the trigger and 3 rounds fired in quick succession. I was very surprised to fire 3 rounds with 1 trigger pull. I immediately unloaded the weapon and again disassembled the bolt assembly and did not find anything unusual. I was curious about the ammo being a problem so I loaded first a single round, then 3 clips of 10 rounds of the PVRI 5.56 ammo. There was not any malfunction or misfire through the 31 rounds.

I have the 3 spent cases from slam fire, the original ammo boxes for the Hornaday, and some examples of PRVI cases fired. Upon examining the slam fired cases, there is an indention from the firing pin, but it is not crisp and deep like the 5.56 cases, or the .223. In addition I have 3 unused .223 Hornaday rounds from the box I was shooting from.

I will wait for your reply before touching this firearm again. Please let me know what action you would like to undertake? I am very disappointed that I received a firearm with an obvious defect, after all of the fine articles I have read about the ACR. I actively blog on a number of online gun forums. I will give Bushmaster a chance to respond, before I start posting this information online. I am a fair individual, and it is possible that something I did caused the slam fire, since it is a brand new weapon to me, and the first time that I shot it. I have used both types of ammo in my Bushmaster Varminter for the 2 years that I have owned it without a single problem.

 

[IXLR8]

I know that the previous post was kind of wordy.

If you Google the Bushmaster ACR and slam fire, you can read about a guy who shot his big toe off with a 15 round burst, and the safety was on!

If I would have heard about these things, I would not have purchased it.

 

[Texas1911]

Sounds like the gun is sensitive to soft primers. It also could have been a batch of high primers from Hornady. I would write both and see what happens.

 

[IXLR8]

Sounds like the gun is sensitive to soft primers. It also could have been a batch of high primers from Hornady. I would write both and see what happens.

The manual says 5.56 or .223 ammo without any qualifications. The Hornaday is a premium ammo. I can post pictures of the slam fired rounds, they did not have high primers. They did however have a distinctive pin mark on them, about half the depth of the fired ammo.

Bushmaster must know this because they added a return spring to keep it from happening. Maybe I should just apply for a Class 3 for it... ;(

 

[Texas1911]

M1s can have this issue, I would give the manufacturer some time to address the issue.

 

[AresV]

Hmm, I've got a 6XX serial # gun and don't have this problem.

What serial # range is your rifle?

 

[Bullseye Shooter]

M1s can have this issue, I would give the manufacturer some time to address the issue.

99.9% of slam fires with an M1 are from either high primers or a stuck firing pin. Neither of these seem to be the problem. Hopefully the mfg can shed some light on the problem. The next step would be to ship it to them for repair or replacement.

 

[codygjohnson]

The bad thing is, when you get the rifle back, you'll probably have a 14# trigger and light primer strikes on every other shot.

 

[IXLR8]

Hmm, I've got a 6XX serial # gun and don't have this problem.

What serial # range is your rifle?

The serial is BL029xx

3 failures in 27 rounds is a problem. Two types of .223 were used with the same result. I will post the picture of the primers in the failed rounds. There is a very distinct indentation, about half as deep as the fired rounds.

 

[IXLR8]

Pictures of the actual ammunition used


3 Rounds of .223 that were slam fired without using trigger, note indents from primer.


Unfired .223 rounds from the same box that were slam fired, nice level primers.


5.56 rounds that were fired before and after without any problems.

What do you think?

 

[Spiff]

View attachment 5001

What do you think?

I think when you use clips instead of magazines you're bound to have problems.



But it does sound like a serious problem. I'm curious if you did give Bushmaster a chance to respond, before posting this information online, as you stated in your original post.

I wouldn't shoot that thing anymore until it's fixed, regardless.

 

[IXLR8]

I think when you use clips instead of magazines you're bound to have problems.



But it does sound like a serious problem. I'm curious if you did give Bushmaster a chance to respond, before posting this information online, as you stated in your original post.

I wouldn't shoot that thing anymore until it's fixed, regardless.

I gave them a week to respond, it happened last Saturday. I was just trying save someone else the same problem this weekend.

I heard that my post was forwarded to the ACR Product manager, but I have not received any response.

This weekend I will disassemble the BCG and look for any anomalies. Perhaps they just forgot to insert the firing pin return spring, which is supposed to prevent this type of mishap.

When a solution is found, my posts will be updated. I really like Bushmaster rifles. The Varminter I bought 2 years ago has had thousands of rounds through it without a feed problem or any problem, regardless of the ammo used. I had purchased the Hornaday ammo for it on several occasions, and never had a problem. It is just too darn expensive for plinking. I was trying to get some nice tight groups to show off, so I splurged for the expensive ammo.

 

[cuate]

Send it back to the factory by all means for testing and repair. There may be a manufacturing glitch and other rifles may have similiar problem and would be capable of killing or injuring shooter or others. Play it safe...Good rifle like that is worth waiting for.

 

[IXLR8]

I removed and inspected the BCG. I am not an armorer or a gunsmith and do not proclaim to be one. The ACR is one of the easiest guns I have ever worked on. The parts can be removed without tools, as long an you have something resembling a bullet tip to push out pins.

The Bolt does not appear to have any damage or wear. The bolt face moves smoothly in and out of the bolt. When in the retracted position, the firing pin is fully retracted (by a spring). I removed the firing pin and inspected it. It had a little bit of gunpowder residue on it and a little rem oil that sprayed on the action before firing it, but wiped clean without anything but a clean rag. The spring was intact and very clean. There were not any nicks or abrasions on any parts that were inspected. All parts moved freely. Before and after assembly I checked the operation of the firing pin by pressing the back of it while in the BCG. It moved freely and returned to position without assistance. The recoil spring was clean, and moved freely along the axis of compression. The was not any visible grease on any parts. The locking ring on the barrel was clean and free of debris.

By all appearances everything is as it should be. Since I do not have the specifications for the springs, I could not test to see if they had the proper compression force. When the action was reassembled, I cycled the action several times and it appeared to operate correctly. The action has a positive feel and the trigger has an amazingly crisp breakover. I recall being amazed at the lack of play in the trigger, it has truly an awesome feel.

If requested I will photobucket the pictures of the BCG in various states of diassembly. I am sure you will want the high resolution pics to verify my observations. Unless someone has a better way to post a 800meg picture.

At this point I am not sure what Bushmaster can do. The weapon appears to meet the operational design.

I have not tried removing the barrel yet, but it looks like fun. A click and a twist, on off she comes.

Any questions?

 

[IXLR8]

I tried to call Bushmaster today about the problem. I was in a call queue for 20 minutes, then it asked to leave my name and number, but told me that I could not leave a name and number, because the mailbox is full...

So much for calling.

 

[OLDVET]

I have a Springfield Armory M1A rifle. This type of rifle is prone to the same "slam fire" problems you discussed. Springfield even warns you in their literature to use only quality military ammo. The problem is with the the bolt. It has a floating firing pin. The inertia of the bolt closing causes the firing pin to emerge from the bolt and strike [dent] the primer, setting the round off. I shoot only reloads in my M1A and use whatever primers I can find. I have never had a "slam fire" in my rifle, but I have read about others who have. Civilian primers are generally made with a softer metal than is used for the military. Recently I purchased some Winchester primers that were so soft the firing pin on my Rock River AR actually pierced the metal on the primers. I suspect your rifle has a "floating firing pin" and you may be having a similar problem. Last Saturday I shot next to a guy who just received his new Bushmaster ACR. He fired some imported ammo as well as some reloads his friend had loaded. The rifle shot all the ammo okay. One thing I did notice and found peculiar was that the imported ammo ejected towards the rear of the rifle and the reloads ejected towards the front of the rifle. After the bolt had returned to battery after each reloaded shell was fired, a small amount of white smoke escaped from the front of the ejection port. The guy claimed he thoroughly cleaned the rifle prior to bringing it to the range, so I assume the smoke must have been oil burning off.

 

[IXLR8]

I have a Springfield Armory M1A rifle. This type of rifle is prone to the same "slam fire" problems you discussed. Springfield even warns you in their literature to use only quality military ammo. The problem is with the the bolt. It has a floating firing pin. The inertia of the bolt closing causes the firing pin to emerge from the bolt and strike [dent] the primer, setting the round off. I shoot only reloads in my M1A and use whatever primers I can find. I have never had a "slam fire" in my rifle, but I have read about others who have. Civilian primers are generally made with a softer metal than is used for the military. Recently I purchased some Winchester primers that were so soft the firing pin on my Rock River AR actually pierced the metal on the primers. I suspect your rifle has a "floating firing pin" and you may be having a similar problem. Last Saturday I shot next to a guy who just received his new Bushmaster ACR. He fired some imported ammo as well as some reloads his friend had loaded. The rifle shot all the ammo okay. One thing I did notice and found peculiar was that the imported ammo ejected towards the rear of the rifle and the reloads ejected towards the front of the rifle. After the bolt had returned to battery after each reloaded shell was fired, a small amount of white smoke escaped from the front of the ejection port. The guy claimed he thoroughly cleaned the rifle prior to bringing it to the range, so I assume the smoke must have been oil burning off.

The firing pin does have a substantial spring return. It is about .5" x 3" spring and provides a stiff return, but the pin still free floats, and is not blocked in any way. It may be the very strong buffer spring that pushes the bolt into battery. When you push the bolt release, it really quickly moves the bolt forward. It is much harder than my AR.

Bushmaster has had my rifle for a week, I am sure that whatever the problem, it will be taken care of. I will post any info that BM provides.

 

[M. Sage]

Haven't been paying attention to this thread, but the pics you posted earlier make me think this is an ammo problem. Those "strikes" on the slam fires are way too light. And the primer on at least one of those looks high to me.

Those aren't reloads, are they?

I have a Springfield Armory M1A rifle. This type of rifle is prone to the same "slam fire" problems you discussed. Springfield even warns you in their literature to use only quality military ammo.

This is to ensure you don't use some target ammo that has light primers. Semi autos (generally) need hard primers.

 

[IXLR8]

Here is the official reply from Bushmaster directly from the ticket. It took 2 weeks to get an RMA# and exactly 2 weeks to send, and receive back my rifle from repair.

Repair Notes:
D101.1
D140
ADJUSTED FIRE CONTROL GROUP. BOLT HAD A SMALL CHIP BY CAM PIN. EXCHANGED BOLT ASSEMBLY AS WELL. TEST FIRED OK 90 ROUNDS WITH NO MALFUNCTION.

I have not fired it since receiving it today. I will give a range report this weekend.

 

[AusTex]

A little off topic but I can tell you that in one of my ar15s with youngMF national match expensive ass BOLT when I charge and load the weapon if I eject the shell I can see a pretty deep primer dimple and they are reinforced primers. I have not had one slam fire but it is kinda dis heartening to say the least.
I have had 2 ar-15s slam fire on me over the years and one Galil sporter do it.