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milton
June 13, 2002, 15:02
Further or related questions to StealthyBlagga's previous post on this topic.

I recently took a new build to the range and had two failure to fire incidents. Both times it happened with the first round of a magizine and the primer had a very slight dimple. Again, both times, I rechambered the round, which fired fine the second time. From reading StealthyBlagga's post, was I experenceing the hammer dropping out of battery? Is this experenced more with new rifles? Hopefully!! Anyway to avoid this? Is a forward assist needed? (Threw that in for the AR crowd.) Anything else it could be? Thanks in advance.

Snakeshot
June 13, 2002, 15:32
Before assuming firing out of battery, I would consider weak hammer spring, worn firing pin or crud inside bolt where firing pin resides.

With worn kits being built up these are more likely the cause. Let us know what you find.

Mebsuta
June 13, 2002, 15:33
I experienced the same problem when I swapped in after-market fire control on my STG. The hammer wasn't out of battery; I would squeeze the trigger and hear it fall. The after-market hammer is shaped different and weighs less than the original. I don't think it was striking the firing pin with enough force for hard military primers. I put the original hammer back in the weapon, but I haven't been the range to test fire it. I never had a failure to fire with the Steyr H/T/S.

ratas calientes
June 13, 2002, 17:46
The first round out of a full mag will have the most spring load, and hence the most drag stripping out of the magazine. It sounds to me like the bolt carrier was not all the way forward. The falling hammer used up some of its energy striking the rear of the bolt carrier, and giving you the light strikes.

BTW, how does the head speace measure?

Ratas

milton
June 14, 2002, 09:13
Thanks for the replies.

Snake - This is a well worn R1 built on a new Entreprise receiver, but very, very clean. Prior service + anal retentive = clean weapon. I don't think it's a weak hammer spring or firing pin, because it only happened twice on the first round. However, I'll swap them out with others and see if this happens again.

Nunya - Yes this is FSE fire control parts. Again, seems odd to me that it only happened on the first round each time. I'll weigh the two hammers (fse vs. original) on my reloading scale and see if there is a difference in weight. I have to replace it anyway, because of the recall on the fse hammers.

Ratas - The headspace seems fine. It closes on a Foster's Go and doesn't on a No-Go. Also, the headspace was checked by Entreprise, so I don't think that's it. But I think I see your point, if it's tight it may cause more drag going into battery? Also, I was using new mags, so I think you are right that this was an out of battery strike.

More info, the bolt carrier moves smoothly without any hang-ups. I'm thinking it may be either weak recoil springs or just new tightness. However, I don't like pulling the trigger and not getting a boom. Also, I don't like removing rounds from my weapon with dimpled primers.

Open for more suggestions. Anybody else have this happen with a new build? Does it go away after a little break in? Thanks.

ratas calientes
June 14, 2002, 10:46
New recoil spring couldn't hurt. Also, there has been lots of discussion over the past few months (some if it mine :) ) concerning drag on stripping rounds from the magazine, and how to reduce it. Part of the solution is breaking/polishing the edge on the bottom of the receiver rails just above the magazine. When these are sharp, the put a lot of drag into the round as it is stripped from the mag - especially when the mag is full or near-full. If you do a thorough search, someone even posted some pictures.

Also, since yours is built on an Entreprise "file to fit", also check the "profile" of the lower receiver rails just above the magazine. On my Type 3, the left rail was too "wide", and I had to file it back along the profile at least 0.050 inches to get it to match the profile on my DSA. I did this by inserting a loaded mag in my DSA rifle (receiver cover off and bolt out) and tracing (with a Sharpie) the profile of the receiver rail onto the round in the mag. I then inserted this mag into my Entreprise, and noted that the rail was too wide. So I filed it back until it matched the DSA. This, and breaking the lower edges, fixed my failure-to-feed problems with a full magazine.

Ratas

milton
June 14, 2002, 12:56
Ratas - Call me slow, I didn't connect those dots. Yes, I saw the prior posts and pictures on the brass shavings and was already planning to knock off the rails' sharp edges. I too am getting the shavings and from time to time had trouble chambering a round due to that drag. I've got an Imbel, so I'll also do a comparison of the rail profiles. Great tip, thanks. Now, where's that sandpaper??

gunsmith_tony
June 14, 2002, 14:54
Recoil (return) spring could be weak. Also check for freedom of movement inside return spring tube...grease, crud, dents, etc.;)

Aifwikir
June 15, 2002, 09:15
If your getting gouges or scratches on the brass then your problem is the burrs on the bottom of the mag well. They are causing friction and holding the bolt carrier back enough so that it doesn't quite go all the way into battery. Brand name of receiver makes no difference here as I've heard it on ALL receivers so far, even DSA's.
The reason it's only doing it on the 1st round is because there's more Magazine spring tension on the bottom of the receiver.


http://www.printroom.com/_vti_bin/ViewImage.dll?userid=Aifwikir&album_id=25819&image_id=13&param=30077

Hope this helps out!

:D
Aif

Falfegnügen
June 15, 2002, 09:33
Originally posted by milton

- Yes this is FSE fire control parts. Again, seems odd to me that it only happened on the first round each time. I'll weigh the two hammers (fse vs. original) on my reloading scale and see if there is a difference in weight. I have to replace it anyway, because of the recall on the fse hammers.



Check the hammer height above the receiver rails when it's cocked. I had an FSE HTS set in which the sear's pin-hole was too large, it cause the hammer to sit way too high when cocked, thereby losing a lot of it's energy when released. Had exactly the same effect as a weak hammer spring. This is really easy to see when compared to an in-spec HTS set. Put the originals back in for a comparison.

ratas calientes
June 15, 2002, 12:34
Looks like Aifwikir had those pictures that I was referring to. Let's keep those handy, they seem to be needed every week! :)

Ratas

milton
June 17, 2002, 08:11
Thanks for all the great feedback!!

Tony - No crud, but I'm going to get a new set of recoil springs for each of my FALs. Thanks.

Aifwikir - Yep, that's the picture I remember. Thanks.

Falophile - Something new - hammer height? I was out of town for the weekend, but will be looking at all of these suggestions tonight. I've got a couple of stock lowers to compare with the FSE equipped lower. I'll take a look. Thanks.