open pistol choking

[P_R]

Hello. I have an open gun that was but by a local gunsmith. It seems to be choking (FTF) on the last few rounds of the magazine lately. It always looks like the picture below. I first thought of a new mag spring but that didn't help. I was then thinking of the extractor as the issue, but I took it to back to the gunsmith and he says the extractor (aftac) tension is just right. His solution was to run more lube on it and buy new brass (38SC). I took it out and ran it real wet and got the same results. My brass isn't that old and it certainly doesn't look so buggered up that it shouldn't run. One thing I find interesting is that when it chokes like this, I can't just give it a little tap on the back of the slide to make it go into battery. It's really stuck there. I have to really give it a hard bump or else ease the slide back just a little bit and let it go forward. I'm now running a 10 pound recoil spring on it with one shock buffer. Which mag in the gun seems to be irrelevant, but it always happens when the mag is almost empty.

So the question is have I overlooked anything? Is the gunsmith BSing me with the buy new brass line?

Thanks for any thoughts you might be willing to share and sorry for the crummy picture.

[Glk21C]

I'd say try the new brass as he suggests

[Pro2AInPA]

Get rid of the shok buff, for one.

[lynn jones]

go to a 11 lb spring.

[ParaGunner]

How old are your mag springs?

[Chris Keen]

I would have to question either your reloading habits (ie.not enough crimp) or possible the chamber is getting a build up of gunk in it. Perhaps it just needs reamed out a little.

Get rid of the shok buff, for one.

You people and your fear of shok buffs kill me ....... go read Brian Enos's book again, and tell me what Brian thinks of shok buffs.

[Dis-1-Shooter]

What is your OAL?? Maybe nose diving? Angle on feed ramp might need tweaking.

[G-ManBart]

I would have to question either your reloading habits (ie.not enough crimp) or possible the chamber is getting a build up of gunk in it. Perhaps it just needs reamed out a little.

Get rid of the shok buff, for one.

You people and your fear of shok buffs kill me ....... go read Brian Enos's book again, and tell me what Brian thinks of shok buffs.

In the picture, the round isn't far enough in the chamber for crimp to come into play (or gunk), and if it were crimp or gunk, it wouldn't only be the last couple of rounds in the mag.

Shok buffs do shorten the slide travel a small amount...no way around that. Even if it's not likely, it is a variable worth changing to see what happens.

I'd actually go to a lighter spring, and remove the shok buff (in two steps) to see if the gun isn't just slightly short-stroking and losing just enough slide travel to cause the feeding issue as the spring/follower changes the amount of upwards pressure for the last few rounds. I'd also chrono the ammo to make sure it's still in the PF range I expected, or what I know has worked previously....could be a combination of a bunch of stuff.

[Flexmoney]

If you can recreate that jam, see if the back of the round has made it up the breech face and is completely under the extractor. If not, it could be hanging up on the firing pin hole, or...more likely...hanging up on getting under the extractor.

Something there is likely marginal...which makes the gun less likely to run with a light spring and/or shock buff.

Check the rim diameter of your used brass. It can flatten outward from repeatedly expanding against the breech face from multiple firings.

[Pro2AInPA]

go to a 11 lb spring.

I realize that 9mm and .38 may be a little different, but in my 9mm open gun, my ammo chambers flawlessly all the way down to a 7 lb spring . . .

[CocoBolo]

If you can consistently run 28 rounds thru the big stick and the last one always hangs, its probably a mag issue. If you put an empty mag in the gun will the slide lock back?

I had issues with running out of ammo and looking in to find one round half fed and loking at me, bad plan to run the stage to mag capacity. Get one mag to work so the slide does not lock back and try it. If that solves the issue you know what the problem is.

A new open gun takes atleast 1000 rounds to break in if it is built tight. I'd stick with the 10# that is what I run in mine, not only does it feel good it runs 100%. Shock buffs are a potential problem so take it out and try it without it. If the problem persists you can put it back in its not the culprit.

I've run Grams and STI followers with good results, the Bolens apparently I'm not smart enough to use. Also make sure the follower allows the last round to be pushed all the way up, especially in SVI tubes the follower won't come up far enough and needs to be trimmed.

Your OAL on 38S or 38SC should be around 1.235 (as recommended by Benny Hill) I've run mine a lot longer but 1.235 is the recommended length.

Edited May 2, 2011 by CocoBolo

[lcs]

Hello. I have an open gun that was but by a local gunsmith. It seems to be choking (FTF) on the last few rounds of the magazine lately. It always looks like the picture below. I first thought of a new mag spring but that didn't help. I was then thinking of the extractor as the issue, but I took it to back to the gunsmith and he says the extractor (aftac) tension is just right. His solution was to run more lube on it and buy new brass (38SC). I took it out and ran it real wet and got the same results. My brass isn't that old and it certainly doesn't look so buggered up that it shouldn't run. One thing I find interesting is that when it chokes like this, I can't just give it a little tap on the back of the slide to make it go into battery. It's really stuck there. I have to really give it a hard bump or else ease the slide back just a little bit and let it go forward. I'm now running a 10 pound recoil spring on it with one shock buffer. Which mag in the gun seems to be irrelevant, but it always happens when the mag is almost empty.

So the question is have I overlooked anything? Is the gunsmith BSing me with the buy new brass line?

Thanks for any thoughts you might be willing to share and sorry for the crummy picture.

I've had (appears) the same problem before. Increasing the recoil spring will just make the jam harder to clear. I run shok buffs in all my open guns, doubt it is the shok buff. The gun should run fine on a 9LB recoil spring.

The major piece of information you did not list was your OAL and bullet. I switched bullets not to long ago and forgot to check my OAL. I was loading to short. The angle the bullet was going in the chamber was causing the jam. I changed the OAL and never had the problem again. OAL should be around 1.232 or longer depending on the bullet. The bullet might be hitting the ramp to low which can slow the slide down also. Look at the ramp, you should see where the bullets are hitting when the gun is a little dirty.

[kmca]

Go-Manbart,

I don't understand how a buff shortens the stroke, unless you' re getting spring stacking?

[2alpha]

Shokbuff shortens stroke because it takes up slide travel except for the amount it can compress. You can run into recoil spring coil bind also depending on the combination.

I would play with different OAL load up some dummy rounds and try longer and shorter but I bet you end up going shorter. Dummy rounds because if you shorten the OAL you will probably need to back off on the powder a little to maintain the same PF.

[Hi-Power Jack]

Get rid of the shok buff, for one.

+1. That could cause the problem by itself.

Real easy to test the hypothesis - take it out

and see if problem goes away, hopefully.

[P_R]

Wow! Thanks for all the fast replies.

I checked my OAL - 1.265 with MG 124JHP's. So I might run a few a bit shorter to see if that helps.

I also checked the crimp on the ammo. It seems like the the brass my be about a half a thousandth wider at the mouth than it is a 1/4" lower. So I might make an adjustment there.

I also managed to recreate the problem by just hand cycling the slide. I noticed that when it happens the case head always seems stuck on the bottom corner of the extractor hook. I'm thinking hard of just giving that hook a tiny bit more of a radius. I really think that that looks like the problem. I was pretty zeroed in on looking at the inside of the extractor for the problem, but now that I look at it again, that low corner of the claw looks real suspicious.

I'm going to do a search on extractor tuning now, but if you have any thoughts on the matter, please let me know.

Thanks again for the help.

[Dis-1-Shooter]

Wow! Thanks for all the fast replies.

I checked my OAL - 1.265 with MG 124JHP's. So I might run a few a bit shorter to see if that helps.

I also checked the crimp on the ammo. It seems like the the brass my be about a half a thousandth wider at the mouth than it is a 1/4" lower. So I might make an adjustment there.

I also managed to recreate the problem by just hand cycling the slide. I noticed that when it happens the case head always seems stuck on the bottom corner of the extractor hook. I'm thinking hard of just giving that hook a tiny bit more of a radius. I really think that that looks like the problem. I was pretty zeroed in on looking at the inside of the extractor for the problem, but now that I look at it again, that low corner of the claw looks real suspicious.

I'm going to do a search on extractor tuning now, but if you have any thoughts on the matter, please let me know.

Thanks again for the help.

From my understanding, max OAL for STI mags are 1.250". Your OAL is too long. Try loading some dummy rounds to 1.235" to see if the problem gets better before tunning the extractor.

[Freddie the Swede]

With that lenght it can be the bullets dragging on the inside of the magazine.

Make 'em shorter and see if that makes it better.

//Freddie

[eric nielsen]

You're probably on the right track looking at the bump in cycling as the round goes under the extractor. All the great gunsmiths on here will recommend a radius & slight polish on the extractor groove. Tension is worth a look too: I have an Aftec extractor and it positively needs to have a combination of one strong and one weak extractor spring. If both Aftec springs are new, it won't feed.

Also, the last round in the magazine has the least amount of push from the mags spring & so the slide/breechface smacks into the round to feed it just a little bit later in the firing cycle. Couple 0.001 seconds can make a difference. Ammo with longer OAL than needed will be more prone to hiccup on the feed ramp in that situation.

BE has a fabulous post early in the forums (2002?) on the best way to polish a 1911/2011 feed ramp.

[eric nielsen]

Topic is SV 40cal mags but a golden oldie: http://www.brianenos.com/forums/index.php?act=ST&f=3&t=5188&st=0#entry65267

Also, a snip from another post, didn't find the original:

benos:

Here's one more super-trick mod. Get some 600 grit wet/dry sandpaper. Then you have to find something with the same radius as your feedramp - a 40 case works perfect for me. Wrap a single layer of the sandpaper around the case, or whatever, clamp the barrel in a bench vise, and polish the ramp, moving the sandpaper up and down the ramp in the direction the bullet feeds. Keep polishing forever, until you can see from inspection that the entire ramp has been polished. This can make a big difference, much bigger than you might think. <br>Before you do it, hold the barrel in one hand and a loaded round in the other. Hold the round parallel with the barrel and press the nose on the feedramp and push it up the ramp - feeling the resistance. (It kind of feels like phonograph record.) Then do it after the polish job - you should notice a big difference. (All the spinning type polishers actually polish the ramp in the wrong direction.)

be

Variations of the above start with 600 grit wet/dry and move on to 800 and then 1000 grit, using gun oil each time.

[2alpha]

HP's hit the feed ramp in a different place than FMJ's loaded to the same OAL. Shorten them to 1.235 and see what happens.

[Glockcomma]

Both of my open guns run 100% with both Aftec springs, but a lot of people need to run only one. That should make it easier for the rim to get under the extractor. Be careful with heat on the Aftec they are really hard and need to stay that way. I think the OAL and the Shok Buff are your biggest problems.

[P_R]

Okay, I thought I'd post an update on this.

I took the a little bit of the corner off the aftec and polished it up real nice. I haven't had any issues with it since. I did reduce the OAL on my ammo to 1.236 (from 1.265) but it feeds both of them now. I intend to do the ramp polishing procedure described a few posts above.

Thanks much for the help.