[bbbean]

My .40 SVI/Caspian limited gun running 180 and 200 gr loads with an OAL of 1.205 has developed an occasional ammo nose dive that used to show up once every few hundred rounds, but showed up on 8 out of 10 stages at last weekend's match. Suffice it to say that giving up at least 30 seconds to yanking stuck mags out of the gun, reloading where I didn't intend to, and then making mental mistakes because I was distracted and blew by targets didn't do my score or standing any favors.

On the plus side, I'm getting lots of practice on my reloads and mid-stage slide rack. Never know when those skills will come in handy.

I've had several recommendations from other shooters for a fix that range from re-tuning mag lips to replacing the extractor to taking up another sport, but in the interest of expediency I'm going to experiment with my OAL first. The problem is that I've had equally credible shooters advise going much shorter and going much longer.

I'm inclined to load a a test batch at 1.25, based on the notion that if rounds are nose diving at 1.20, then 1.15 is going to be worse. I'm also fairly sure that working up the load for a new OAL will have fewer pressure issues at 1.25 than at 1.15. But I'd sure appreciate any suggestions or references.

BB

This post has been edited by bbbean: 13 October 2009 - 02:17 PM

[Matt Cheely]

How old are your mag springs?

[bbbean]

Matt Cheely, on Oct 13 2009, 04:17 PM, said:

How old are your mag springs?

I replaced the springs and followers in two mags this summer, the other 3 were new this winter. How often do you replace yours?

[G-ManBart]

The fact that the problem was already there every couple of hundred rounds (way too frequent to start with) and now has gotten worse says it may be a developing condition. Most folks replace mag springs about once a year, but if the problem was already happening, it doesn't sound like that is the problem. Have you checked that the extractor doesn't have a burr on it and that the tunnel isn't gunked up? R,

[Matt Cheely]

Replace them at least once a year.

An intermittent problem that is getting worse, I wouldn't change your ammo, it's something with the mags/gun.

[CocoBolo]

I'm going to agree with Matt on this one. It could be as simple as tuning the springs properly do they cant to the right slighlty when you look at the backside of the follower.

I have three S_I 40's I load out to 1.20 and have shot factory ammo as well, none of them seem to be affected by OAL. I have six mags and the newest ones need the spring retuned every time I stuff 21 rounds in them the other 4 only hold 20. I only do this when it might make a difference. I also prefer the Dawson followers for 40 and use grams for 38 Super. I have had lots of issues with STI followers and 40, but they work fine in 9 mm and 38 supers.

I clean the extractor tunnel about every 3000 rounds these keeps them running.

The easy thing since its now a predominant problem is to borrow a mag from another shooter and see what happens. If it runs mystery solved, the process is known as trial and error.

[calishootr]

lets go the other way with this??? maybe the rounds are too long??? and catching/binding in the mag thus causing the nosedive???? I'm running an OAL of 1.195ish to 1.200 and they seem to feed fine in both the 2 SV's and 4 STI's i run w/ my .40 limited....

also I have an original gunracer hicap, that has the original springs in those mags from '92, rumor had it back then, that replacments were gonna be wolf beretta 92 springs, got an umopened package ofthose layin around here somwhere....

[G-ManBart]

Since it had the problem when the mag springs were new (even if it was only every couple of hundred rounds) it makes me think it's not the springs, but the feed lips could be just out of spec enough that they work most of the time with fresh springs and get significantly worse as the springs soften up a bit. I've run some pretty soft springs in untuned tubes that had the proper feed lip dimensions and they ran perfectly.

It probably shouldn't make a difference, but what weight recoil spring are you running and has it been changed recently? Sometimes recoil springs will run forever, sometimes they gradually soften and other times they die seemingly immediately. If the slide doesn't have enough oomph to really solidly strip the round it might be slowing down enough as it does so that you get the nose dive.

Proper feed lip dimensions are .385-.395". R,

This post has been edited by G-ManBart: 13 October 2009 - 07:10 PM

[bbbean]

Thanks for the suggestions, guys.

I'm going to try a few simple fixes first - I've loaded up some longer rounds, will check feed lips, and am going to give the extractor a thorough cleaning and examination. If that doesn't clear up the problem (it'll take a few practices and a match or two to be sure), then its time for an annual tweaking and spring check anyhow, so I'll let the smith take a look.

BB

[bbbean]

G-ManBart, on Oct 13 2009, 06:33 PM, said:

Have you checked that the extractor doesn't have a burr on it and that the tunnel isn't gunked up? R,

Sometimes it's the simple things that throw you off. I've just been cleaning the breechface with a toothbrush and a cloth every thousand rounds or so and haven't actually pulled the extractor on this gun. But after seeing the wad of gunk I just pulled out of the extractor tunnel and doing a thorough cleaning of the slide, I'm amazed it was working at all! The slide's probably a half ounce lighter!

I think I'm going to keep the longer OAL as well - The extra .05 doesn't seem like a lot, but its hard to see how a round could nosedive at 1.25. I'll run a few hundred rounds with the newly clean extractor and longer OAL and see how things work, but I'm 90% certain the combination of OAL and gunk were more than adequate to cause the occasional jam.

BB

This post has been edited by bbbean: 15 October 2009 - 12:48 PM

[bkeeler]

Just as a suggestion only change 1 thing at a time. If you start changing more than 1 thing at a time you could create other problems that were not there before.

BK

[bbbean]

bkeeler, on Oct 15 2009, 03:24 PM, said:

Just as a suggestion only change 1 thing at a time. If you start changing more than 1 thing at a time you could create other problems that were not there before.

BK

So far the only "change" has been the OAL. De-gunking the extractor was simply much overdue maintenance I'd overlooked. The first couple of mags worth of the new OAL ran without a hitch, but the old ammo ran without a hitch, too - until you hit a hitch!

BB