SMG Bolt Dimple in the firing pin
- Thread starter rlairdm60
- Start date
Samuel_Hoggson
Well-known member
Cratered. None of mine look that way. Hard primers, suppose. Perforations/gas cutting usually causes pits.
+I agree.
Not saying it can't be done but that's a pretty tricky spot to get into to build up with weld. Re-tempering too would be a challenge.
Several replacements on GB for less than 200$ isn't the best news but....
Not saying it can't be done but that's a pretty tricky spot to get into to build up with weld. Re-tempering too would be a challenge.
Several replacements on GB for less than 200$ isn't the best news but....
I have a MAC-10 bolt that looks like that. I got it used and don't know how it got that way or what ammo was used in it, but it also had some FTFs.
ETA: what kind of ammo are you using? I recently realized that my 9mm reloads using Remington 1-1/2 primers were getting tears/cracks on nearly every round in my Uzi. I hesitate to say "pierced," because it wasn't the typical piercing. When I would deprime them, I noticed a part of the cup almost seemed to be smashed and fused to the tip of the anvil leaving a small tear in the cup. Looking around, I found that there is a notice that you are not supposed to use Remington 1-1/2 primers with "high intensity" cartridges like .40 S&W, .357 magnum, etc. For some reason that warning appears nowhere on the exterior of the box (only on the individual 100 primer packs), and it makes little sense based on pressure ratings.
ETA: what kind of ammo are you using? I recently realized that my 9mm reloads using Remington 1-1/2 primers were getting tears/cracks on nearly every round in my Uzi. I hesitate to say "pierced," because it wasn't the typical piercing. When I would deprime them, I noticed a part of the cup almost seemed to be smashed and fused to the tip of the anvil leaving a small tear in the cup. Looking around, I found that there is a notice that you are not supposed to use Remington 1-1/2 primers with "high intensity" cartridges like .40 S&W, .357 magnum, etc. For some reason that warning appears nowhere on the exterior of the box (only on the individual 100 primer packs), and it makes little sense based on pressure ratings.
Last edited:
Samuel_Hoggson
Well-known member
Slowmo, A better primer for open bolt 9 is the Remington 6-1/2. Technically a SR primer, but it's intended for .22 Hornet. I've loaded it in 9 and .38 Spl. No change in data - lots of info available on the web about this.
People use 6-1/2s in the lower pressure .222 Rem, but they're not recommended for .223. I've tried. Gives perfs in M-16s. The 7-1/2 primer has a thicker cup, as do most other SR primers with the exception of the CCI 400.......also a good choice for open bolt 9s.
People use 6-1/2s in the lower pressure .222 Rem, but they're not recommended for .223. I've tried. Gives perfs in M-16s. The 7-1/2 primer has a thicker cup, as do most other SR primers with the exception of the CCI 400.......also a good choice for open bolt 9s.
Last edited:
Thanks for the advice and helpful chart, but these primers have thoroughly disappointed me. I likely won't buy more Remington primers. I don't care for these poorly publicized limitations on what they are suited for.
I've also had problems with them being undersized. My Dillon pickup tubes will periodically just dump out a dozen or so while trying to load them, and there are some primers simply too small to catch with the tubes that have to be loaded by hand. Unsurprisingly, those primers then fall out of the primer pocket before firing or occasionally blow out of the primer pocket after firing. I had never used Remington primers prior to this and only bought them because my stash of Winchester and S&B primers ran thin during the shortage.
Are there any other small pistol primers that are known to cause issues in an open bolt platform? I've been reloading for about 20 years but am relatively new to the open-bolt applications.
I've also had problems with them being undersized. My Dillon pickup tubes will periodically just dump out a dozen or so while trying to load them, and there are some primers simply too small to catch with the tubes that have to be loaded by hand. Unsurprisingly, those primers then fall out of the primer pocket before firing or occasionally blow out of the primer pocket after firing. I had never used Remington primers prior to this and only bought them because my stash of Winchester and S&B primers ran thin during the shortage.
Are there any other small pistol primers that are known to cause issues in an open bolt platform? I've been reloading for about 20 years but am relatively new to the open-bolt applications.
Samuel_Hoggson
Well-known member
I'd skip Federal 100 and 100M. M in this case stands for match, not magnum. Guys who shoot guns with light hammer strikes love Federals. A sensitive primer is about the last thing you'd want in an open bolt gun. Not just perfs, think OOB.
Since your gun is already perf-ing primers I'd skip SPPs and use SRPs. CCI 400 SR primers are good. WSRs are as well.
And/or at least give Rem 6-1/2s a try before dismissing because the 1-1/2s didn't work well. They are definitely not loose in our 9mm pockets. Quite the opposite, I can't get them to seat below flush in Norma .38 Spl brass, so run them down with a RCBS ram prime. Sick of doing that, so I discard Norma brass. Anyway, 6-1/2s have never loosened in 9 for us, and we loaded a variety of headstamps.
ETA: our Glocks have no trouble with 6-1/2s. Interestingly, have several thou Adcom Nato 9mm. Stuff misfires regularly in Glocks, but runs an Uzi like a sewing machine.
I've never used any primers other than CCI. I've had good luck with them for years. I use various ammo, Winchester NATO 125 White Box performs the best, Sellier & Bellot 155 works well, and my loads are 147 gn Extreme bullets copper plated AAC number 7. All work well, when I first got the gun in 2018 it ran anything you wanted to put in it until last year. Then intermittently it will run great and have FTF with no rhyme or reason. The dimple has been there as long as I have had the gun, it makes a unique primer strike. I've done everything imaginable, mag test, bolt slide freely test, top cover adjustment, magazine height, top cover adjustment, checked trunion weld, restrictor ring, etc.
"ETA: our Glocks have no trouble with 6-1/2s. Interestingly, have several thou Adcom Nato 9mm. Stuff misfires regularly in Glocks, but runs an Uzi like a sewing machine." Agree with NATO 100% best results for me as well before I had issues.
brenbuilds
UZI Talk Supporter
I've had good success with Zinc Point (Servicios y Adventuras). They are manufactured in Argentine, and importation largely spawned from the shortage here in the U.S. The primer cups are slightly thicker ( I don't have the dimensions on hand, but in line with SR primers) so they do not always perform well in striker fired handguns with lighter springs, but for subguns they run fine. I've gone through at least 4k in multiple open bolt 9mm subguns without issue.
Samuel_Hoggson
Well-known member
Worth fixing for sure. Cratering, of itself, may not be the cause of your FTFires. One of my M-16 pins cratered at some point, but went on working for another 10k or so. It finally broke back at the flange, or I'd still be using it.
Maybe best to send bolt with the host gun so your smith can assess what's happening.
delta-10
Well-known member
I have heard of gunsmiths just drilling the bolt out like a semi-auto bolt is and then putting a new fining pin in. They usually just modify a semi-auto firing pin so that it stays in the bolt. It is a hell of a job because of how hard the bolt it. They may have to "soften" the metal, drill it out then re harden it. Hopefully someone more knowledgeable will see this thread and provide you with the contact info of a gunsmith who can help you out.
9mmsubgun-m11
UZI Talk Life Member
Could have been mine you saw.My registered bolt as a triangular look with a flat point.
mike
UZI Talk Life Member
Who is the manufacturer of the bolt? Is it a B&G or a group industries, or someone else?
navgunner
UZI Talk Life Member
@rlairdm60
I read through your post again trying to think about similar issues that I’ve personally seen and the things that I’ve done trying to correct them.
I’ve realized that I made an assumption that I should confirm. Does your FTF mean “failure to fire” or “failure to feed”?
We’ve been focusing on the cratered firing pin (integral) so it leads me to believe that it’s a failure to fire issue and the UZI is cycling relatively normal otherwise. If this is correct, I’m gonna go out on a limb and recommend that you next try a different barrel. Ideally, you would measure the headspace, but if you don’t have access to gauges, hopefully you have a spare barrel laying around that you can use as an alternative (something that’s new(ish) and hopefully has tighter headspace).
My hypothesis for this is that it’s possible that the barrel’s headspace opened up over time. I don’t know how long you’ve had your registered bolt or how many rounds you have down that barrel so I’m making a lot more assumptions here but It’s definitely plausible.
Respectfully,
Nav
I read through your post again trying to think about similar issues that I’ve personally seen and the things that I’ve done trying to correct them.
I’ve realized that I made an assumption that I should confirm. Does your FTF mean “failure to fire” or “failure to feed”?
We’ve been focusing on the cratered firing pin (integral) so it leads me to believe that it’s a failure to fire issue and the UZI is cycling relatively normal otherwise. If this is correct, I’m gonna go out on a limb and recommend that you next try a different barrel. Ideally, you would measure the headspace, but if you don’t have access to gauges, hopefully you have a spare barrel laying around that you can use as an alternative (something that’s new(ish) and hopefully has tighter headspace).
My hypothesis for this is that it’s possible that the barrel’s headspace opened up over time. I don’t know how long you’ve had your registered bolt or how many rounds you have down that barrel so I’m making a lot more assumptions here but It’s definitely plausible.
Respectfully,
Nav
Please Visit our Sister Sites Below
Please consider becoming an UZI Talk Supporter