Sniper Country Duty Roster collective wisdom

Semi-auto rifles and slamfires/doubling:

Back to M1A/M14 rifles for a minute.
While shooting last time, I let a buddy shoot my S.A. M1A with cheap UMC ammo. While shooting it, there were times when it would slam-fire. This hasn't happend with match ammo, but it still bothers me that it has done it with other ammo.
Can someone give me the low-down on how to cure this problem?

D. West <>
USA - Wednesday, January 20, 1999 at 09:11:27 (ZULU) 

My M21 slamfires with Fed F210M match primers... it's caused by the heavy weight of the firing pin hitting on its own speed.
CCI makes a hard military spec primer for this problem... one for the .223, and one for the.308... I think the number for .308 is CCI #34. Check with your dealer.
USA - Wednesday, January 20, 1999 at 09:49:42 (ZULU) 
Pablito and D. West,

Are you confusing slamfires and doubling? They are two different things. If you had a real slamfire your rifle would almost certainly have been disabled. And most likely you would have been too. Sounds like you have trigger problems, i.e. hammer hooks, something along this line. This is called doubling.
Ron N.

Ron N. <>
USA - Wednesday, January 20, 1999 at 12:28:28 (ZULU) 

Someone mentioned something about slam-fires or doubling with the M1A. A word to the wise, do not use match grade primers when loading for any semi-auto. They have thinner cups and are more sensitive. Especially Federal match. I use Winchester primers and have had no trouble. I have heard others recommend Remington 9 1/2. CCI makes a hard primer also. The forward inertia of the firing pin on an M1 or M1A can and does leave a slight mark on the primer even if the trigger is not pulled.
Steve <>
S.C.D.H., Ohio, USA - Thursday, January 21, 1999 at 01:25:37 (ZULU) 
Ron N, Pablito,
Ok, doubling. It's firing two rounds off. I've checked the primers of ammo that it does this on and the firing pin is hitting.
Changing the primers of my match ammo now gives me two different loads to use between my M1A and my Rem. 700/ M24
This may not be a big deal to some, but to me it just doesn't cut it.
Anything like this ever happen with the AR-10?
Is there anything that can be done other than changing primers to stop this with my M1A?

D. West <>
Oh, so cold here in, IL., USA - Thursday, January 21, 1999 at 05:16:22 (ZULU) 

Ron N...
"Are you confusing slamfires and doubling? They are two different things. If you had a real slamfire your rifle would almost certainly have been disabled. And most likely you would have been too."

Ron... slamfires are common in heavy auto weapons, if used with primers that have too thin a cup, and/or too sensistive a pellet... and slamfires DON'T result in the disabling of the weapon, or shooter.
Using Fed Match primers in my M21, if I removed a normaly cycled, but unfired round, there was a substantial "dent" in the primer. I switched to CCI #34 Mil-spec primers, and the slamfiring stopped.

As D. West says... "and the firing pin is hitting." This is slamfiring.

I have not found a noticable difference in the group sizes with Fed Match 210M's, and CCI #34's when used in the M21, and in Tactical bolt guns like the PSS's, M70's, etc. If I used the same load in both the bolt gun and M21, I'd use #34's in both, and make one standard load... but I shoot a different load in the M21, so only it gets the #34's.
Pablito <>
USA - Thursday, January 21, 1999 at 10:58:04 (ZULU) 

Slamfires/doubles: One option with a AR-10/SR-25 is that you can go to a titanium firing pin, which will reduce the possibility of a slamfire.
Grasshopper <>
Richmond, CA, USA - Friday, January 22, 1999 at 02:24:02 (ZULU) 
Titanium Firing pins. Don't do it an AR type weapon. One pierced primer and bye bye to pin. Pierced primers are common with this weapon and high presure handloads.

Calif, USA - Friday, January 22, 1999 at 16:34:04 (ZULU) 

On the issue of slam fires in AR 10 rifles. I have an AR-10, and the firing pin has a spring to prevent it hitting the primer until the hammer falls. It is not a free floating pin like the AR-15. I have not found a need to use any type of titanium pin in any rifle. An interesting note on them is an article in the PS annual a couple of years ago. Someone conducted a test and found out that standard deviations increased with the titanium pin. On the use of Fed 210M primers in semi autos, no gas leaking, no slam fires, no problems. That is with reasonable loads however. I try not to Hotrod it much.
Brian <N/A>
ME, USA - Sunday, January 24, 1999 at 18:50:46 (ZULU) 
On slamfires,I donno, it seems to me that if you keep your firing pin and bolt area clean and in good order you don't have rounds going off unwantedly on you.

That is not to say I am not paranoid of this happening to me. When I shoot my Chinese SKS that is notorius for someone getting killed by a slamfire sometime ago, I do three things.
1. I am fairly secure in the knowlage that its in working order and clean before the first shot.

2. With the SKS, at least maybe others, the bolt stays open after the last shot has cycled it. Making it easy to run my little finger across bolt face and check to see if the firing pin is stuck out or even crud on the face.

3. The one I use religiously is single feeding the fowler, Hey, allready stated I am paranoid about accidents at the range. With the bolt locked back its easy to single feed a top feeding semi.

I have never yet (knock on wood) had a slamfire with any semi. Not even the first M-16s (do probably to the fact of a thorough cleaning
after each session). You keep your equiptment in good shape and chances are it won't screw up on you.

bill <>
Central , Ny, USA - Sunday, January 24, 1999 at 20:42:46 (ZULU) 

Regarding primers: The M1A has a reputation for slam fires cased by the free floating firing pin striking the primer when the bolt slams shut. I'm not sure that I agree with this or not (I have my own theory), but it is recommended that you seek out CCI's new Mil Spec primers, which are supposedly less susceptable to this problem.

If you are interested in Highpower competition, you may want to aquire the above book (PS has a website for contacting them), or others which might give the best advice on reloading for the service rifles.

Hope this helps,

Andre Peterson <>
Minneapolis , MN, USA - Thursday, January 28, 1999 at 18:15:17 (ZULU) 

Andre in Minnesota: I'd be interested in hearing your theory re: primers and M1A slam fires. I've loaded and shot hundreds of rounds with Fed 210M primers, and I've never had a problem with my M1A (knock on wood). I always check for high primers and am careful about every other step in the reloading process. Am I missing something?
Bach Melick <>
New Orleans, LA, USA - Thursday, January 28, 1999 at 21:21:25 (ZULU) 
Bach Melick,

My theory re: Primers & slamfires in the M-14 is that it is not really the cause. It appears to be the general consensus among M-14 users that a (the?) major cause of slamfires in the m-14 is the primers, either high or too sensitive (caused by the slamming of the bolt, or the floating firing pin, respectively).

I don't think this is the whole story. First of all, nobody should be shooting rounds with high primers, and if they are loading that way, then they deserve what they get. I don't think the generally resposible peope who own and care for a match M-14 are doing that. Regarding the floating firing pin, well I just don't think it's a real problem, or it would be much more common than it is (and Springfield probably would have been forced to correct it). These things CAN cause slamfires, but I don't think it's the major culprit.

What I think is happening, based on my own experiences with this rifle, is that when the first round goes off, the rifle is jammed back into your shoulder and the trigger hand is able to slide foward on the not overly gripping (frictious?, is that a word!?) stock, far enough so that the trigger is able to "reset" (if it in fact even needs that). Then when the gun slides forward again after recoil, the trigger finger, still in proper follow through, sets off the next shot just like it would if you had intended it.

(NOTE: I may be misusing the term slamfire, and am really talking about a "double," but most writers do not make this distinction when they talk about it. There is apparently a much more harmfull accident that happens with the bolt still partially open, but I have never seen this personally.)

When the Corps taught me to shoot, follow through was an important part of real marksmanship (M16A1), but the shooting techniques which I used on the M-16 has caused numerous slamfires or doubles in M-14 which I have shot using the same techniques. I have found that shooters who use less follow through tend to have less problems with this, and that I rarely have the problem when I jam the rifle into my shoulder and grip it with excessive force.

In other words, I think that the relatively harmless version of slamfires are caused by a combination of shooting technique, a stiff trigger finger, and a lighter match trigger.

Sorry about the length here folks.

Semper Fi,
Andre Peterson <>
Minneapois, MN, USA - Friday, January 29, 1999 at 02:45:57 (ZULU) 

Slammfire Vodoo !

There that did it, took my Norinco M305, with M14 NM Bolt to the range and Poof, Slamfire !

I now have a .308 case that could take a .45 Bullet. This thing launched before it was even seated.

I have not taken the rifle appart, but it has taken a beating to the Op-rod for sure.

Torsten <>
Germany - Friday, January 29, 1999 at 06:58:04 (ZULU) 

Torsten; glad to see your OK! I'm sorry boys but that M-1/M-14 etc class of weapons is a scary curse to me! I've spoken against them many times at great expense to reputation, my father's scorn and even my Loyalty to America but I never had such a surprise as the first time I fired one of those "things" and then looked inside it. Bad Ju Ju! I'll take the HK-93/G3 over those things sorry! Even FAL.Or them
Valmets or other Kalesh's if I have to pop .308s in a semiauto.
B.Rogers <>
USA - Friday, January 29, 1999 at 14:45:10 (ZULU) 
I would be interested to know what OTHER auto loading rifles are prone to slam fires, besides the Voodoo-hexed M-14/M1A? And whether those "slamfires" were bolt-open, or bolt closed occurances?

I know one person here mentioned the AR-15. Are all auto loaders subject to this problem, or does it seem to be confined within a certain rifle or caliber?

I've NEVER seen or heard about this happening in an auto loading pistol.

BTW, lest I be deemed disrespectful of the M-14, I am not. I like that rifle a lot, it just bugs a bit me when one shot out of thirty will tend to double. Thank god I've never had one blow with the bolt open. I'm happy that Torsten's OK. I consider it a reminder to use extra care when handling that gun loaded.

Andre Peterson <>
Minneapolis , MN, USA - Friday, January 29, 1999 at 19:23:25 (ZULU) 

On slam fires I have 3 kinds of M-14 M1A. A springfield a new one with about 460 rounds throw it. An Arm Corps about 1 year old about 1260 founds throw it. And a Fed Ord. very old I've put about 11,000 throw it in the last 10 years and bought it used for about $350. I shoot box and hand loads with match primers in them and not had a slam fire in any of them over the years. I do know that if you do not set the primers in all the way it will slam fire thow. My friend has done it for fun. LeMay OUT
LeMay <>
Michigan, USA - Friday, January 29, 1999 at 19:35:53 (ZULU) 

thanks for your kind thoughtfulness.

I was stupid enough to do it twice !

I was shooting on a Hunting range were no magazine is allowed, had to place the ammo in the chamber, let go of the slide and "bam" 1st one in the dirt.

Checked the bolt, Ammo and barrel and shot two more without a problem, fourth one went "Poof" and the dragon breath hit me smack in the face, but due to Scope Mount and Glasses I was not cut up to bad.
The empty is without neck, full dia. base to mouth.

Torsten <gone until the 8th of feb.>
almost in, Atlanta, USA - Friday, January 29, 1999 at 19:59:32 (ZULU) 

Slam-fires seem to most commonly occur in rifles that have free-floating firing pins, like the M1, M14/M1A, and M16 variants. That's part of what's going on. I personally also think that it's probably not coincidence that that the slamfires often occur in rifles which are used very frequently by thousands of match shooters, many of which handload their ammo.

Fulton Armory has a good article on this. They also have M16-specific slam-fire articles here and here. (I don't agree with the lead-in to trying to get you to buy a titanium firing pin on those last two articles though!)

I've never experienced a slamfire in my M1A, but then again it has never malfunctioned in any way whatsoever. Can't say that about most of my guns!!!

Time to head to the range.

Dave <>
San Jose, CA, USA - Friday, January 29, 1999 at 20:03:18 (ZULU) 


You may want to entirely reconsider your single shot loading method. Regardless of whether it may have contributed to a slam fire or not, letting an M1A bolt ride home with no resistance is not a good idea. It was designed to DRAG a round off the magazine. Too little resistance on closing is not really a good thing. (in fact, maybe it slam fired so dangerously because the bolt didn't lock shut properly) You may want to talk this over with whomever enforces the no magazine rule in your hunting area, or perhaps see if you can legally hunt with a modified magazine that will only hold one round.

It's interesting that it became full sized all the way up the case. The bolt must not have even been close to locking home when that happened.

Dave in San Jose,

I think I've read that article at the Fulton site (if it's the same one that Springfield now packages with their new M1As). I didn't agree with their emphasis on primers and floating firing pins. I also find it difficult to believe that such a huge percentage of handloaders for this rifle, don't seat their primers properly, or are missing some sort of secret. I suspect that most match-conscious handloaders do a much more careful job that any factory loads. All of my slam fires happen to have been with factory ammo (Remington). I honestly think that the trigger is somehow tripping prematurely. Either improperly (with the bolt still open) or properly (shooter's error). I'll have to check out that Fulton article.

BTW, I never saw a slam fire in an M-16A1, and I don't honestly recall ever being warned about one.

Andre Peterson <>
Minneapolis, MN, USA - Friday, January 29, 1999 at 21:03:48 (ZULU) 

RE; Slamfires. It appears there is some confusion regarding slamfires. Semi-automatic weapons were designed to be fed from a clip, or a magazine. The bolt is slowed considerably when it has to pick up a cartridge from a clip or magazine. The firing pins in the M1, M1A, and AR15 weapons are all floating pins; there is no spring to retard the forward movement. Just check a cartridge you have closed the bolt on in the normal way; you will find a "dimple" in the primer. However, military primers are harder than commercial ones, that is why you rarely have a slamfire when using military ammo. If you single load, using reloaded ammo,you should let your bolt half-way home, then release it. This approximates the force of the bolt if it were slowed up in picking up a cartridge from a clip, or magazine. This is a "must" when using commercial primers. I had an AR15 which slamfired after picking up a cartridge from the magazine, which was unusual, but can happen. As you know, the bolt locks into the rear end of the barrel, It blew before locking up. Result? Upper receiver sides blown outward, extractor blown off bolt, gas then blew downward thru magazine, destroying it. Fortunately, cartridges in the magazine did not explode. After spending $200 to fix it, I sold the AR15; I consider it a piece of crap. Spent the money on rebuilding my DCM Garand into a match rifle. I do not appreciate having anything blow up in my face. Very disconcerting, to say the least. Hope this helps. Semper Fi; Leatherneck
Leatherneck <>
Avon, Ma., USA - Friday, January 29, 1999 at 22:00:49 (ZULU) 
Slamfires: SR-25s have a floating firing pin, but I've never had a slamfire. I use WLR primers, so that may be a reason, I understand the Federal primers are more sensitive.

Grasshopper <>
Richmond, CA, USA - Sunday, January 31, 1999 at 06:09:11 (ZULU)

Andrae; Your right about the double stuff! That even happens on AR-15s when they aren't held correctly. I've been there and done that. Course when the case is messed up it's definitely something else.
B.Rogers <>
USA - Friday, January 29, 1999 at 14:45:10 (ZULU) 
As for slam fires on M-14s, I've shot M-14s, M-21s and everything close to an M-14 since 1967 and I have NEVER, REPEAT, NEVER, had a slam fire. I use hand loads and military ammo and have NEVER had a problem. The ame goes for my AR-15s and M-16s, NEVER! I have had some IMI match blow out through the side and mess up my glasses but that was not a slam fire.
Gramps <>
USA - Tuesday, February 02, 1999 at 07:52:17 (ZULU) 
M14/M305: I looked at my personal "slam fire" and here is what happend. I have a NM TRW bolt in a Norinco M305, I shot realoads that were made for and previously shot out of my G-3, the local hunting clubs range I shoot at does not allow magazines, or slings,(go figure) to be used.
My conclusion: headspace is really on the tight side after lapping the bolt in, the realoads even though full sized still had the H&K flutes on them and may not have seated all the way in the chamber, I used thin CCI Bench rest primers in tight PMC brass pockets that were seated real flat, and I had to load the round into the chamber and then close the bolt onto it which causes a higher bolt speed forward that if it would feed a round out of the mag. BAM, Slammfire ! Clearly not the Guns fault, but operator failure. The only damage that I found so far is a small deformation in the OP rod cam were the bolts giudewheel runs. I´ll take her to the range again and fire some factory FMJ out of a Magazine to see if the little deburring I did solved the problem.

The straight wall, no neck .308 case is in a special glass case I reserved for little reminders. This case also includes a 1" truck wheel nut and bolt that I stripped. It was stamped L for left hand thread, but in the heat of battle, what do I know.

Torsten <>
Germany - Thursday, February 11, 1999 at 08:50:34 (ZULU) 

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