Hi!
This is my first time posting on this forum, so I hope I’m in the right sub !
I assembled a Rebel-9 using DIY components and during the test firing I experienced misfire. The round chamber and eject normally but there is no ignition.
It looks like the firing pin I made is not impacting to the primer hard enough, or possibly that the firing pin is too short.
However I don’t thinks this is a firing-pin length issue, as protrusion from the breech block exceeds 1.2 mm.
The issue may be related to the hammer spring, although I followed the printed jig to make the springs with 1 mm piano wire.
If anyone has insights or suggestions that could help me correct the issue, I would greatly appreciate it! :)
Weak hammer spring or hammer binding and loosing energy are possibilities. Too much headspace (either due to a build problem or the bolt not going all the way into battery) can also cause this.
If it’s a spring issue, does that mean I should use thicker wire? I’m not sure it would be compatible with the hammer.
I didn’t notice any obvious friction at the hammer, but I can always lightly sand the edges more.
I hadn’t considered headspace, but now that you mention it, I do feel like there’s some play with the barrel and the barrel retainer. Will print it again to see.
Thanks for the tips !
Perhaps not thicker wire, just wire made from a higher quality steel. DIY springs are rarely as good as commercial because most people don’t have the ability to anneal and heat treat them like commercial factories do. However, the fact that you do have a clear firing pin imprint on the primer leads me to think your hammer and hammer spring are probably ok.
Play in the barrel retainer could certainly account for this problem. It’s possible to check headspace on a completed build. Remove the bolt and place a dummy round in the chamber. Hold the dummy round firmly seated in the chamber and place a wood dowel in the barrel from the muzzle end until it contacts the round. Scribe the dowel at the end of the muzzle. Now reassemble the firearm and chamber a dummy round using the bolt. Put the marked dowel in the barrel again making sure to press the round against the bolt face and pull the barrel forward to take up any slack in the retainer. If the previous mark on the dowel is now more than 0.15mm short of the end of the barrel, you have a headspace problem.
I’m glad I decided to read through this post! IDK why but i never thought about this method to take a rudimentary measurement on headspace but damn this is creative!! I will forever keep this method in my pocket lol
Thanks for the method, I’ll measure everything next weekend !
Does it make any difference if I use a live round for the measurement (with the firing pin removed of course)? I find that dummy rounds don’t have very accurate dimensions.
I also think I may need to reprint the upper and lower, as there is a gap between them that could potentially affect this issue in a way I don’t understand.
I didn’t understand why the barrel needs to be pulled forward to take up the slack in the retainer when marking it.
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The headspace measurement method I describe will work with anything – even an empty case. Please don’t do the headspace measurement with a live round. It’s bad practice to be muzzling yourself and putting things down the barrel with a live round in the chamber. It’s really more of a no-go indicator than a precision measurement, so a slightly out of spec dummy round isn’t really a deal-breaker.
The reason to pull the barrel forward is because you’re trying to determine the maximum space between the bolt face and the case head. That means you want the chambered cartridge as far from the bolt as it can get. Tugging on the barrel to take out any front/rear “slop” gets you the maximum measurement.
This is a 3d printed firearm, yes? I suppose it’s possible the spring and firing in are ok, but there is too much friction that’s robbing the pin of the energy to fire?
Did this happen multiple times? You could also try a box of ammo from a different batch, to be sure it wasn’t just some bad bullets? Idk, never assembled a printed firearm, but figment for things that slide I’ve had plenty of trouble with printing.
Yes, it is.
If it’s a friction issue, would it be more likely coming from the hammer then ?
Yes, it happened several times with other cartridges from the same batch, but it seems very unlikely to me that the issue comes from the ammunition. They are factory ammo, not reloads or anything like that, so I find it hard to believe that an entire box could be defective 😅. The problem is definitely on my end.
When you say sliding parts, do you mean the breech block in the upper? I don’t have any issues there it moves freely and chambers the round correctly every time.
