Shorten or lengthen OAL to improve feeding?

[lucky strike]

Is there a general rule on adjusting OAL to improve feeding.....I think I should shorten (not going below minimum OAL for pressure concerns) but am just checking here first.

I shot some MG 124gr JHP's with 4.0 Titegroup @ 1.100 for the first time this weekend and every 20th or so round wouldn't feed right.

Edited May 18, 2010 by lucky strike

[Will_M]

It depends on the gun. Some guns (STI/SV's) like the rounds loaded longer than SAAMI spec.

If you can give me more details on the gun, and the caliber (I'm assuming 9mm or .38 super), I can help you out more.

[Will_M]

Also, could you describe the jam for me?

[briansea2]

sounds a bit short, mine are 1.180 using the MG 124.Not quite sure what SAAMI is.

[Sarge]

Seems too short to me as well. Most of what I researched told me longer is better as long as it fits the mag.

[orangeman711]

I'm loading an oal of 1.175 for 9major in an STI Trubor. Fits in the SV mags with no problem and feeds well.

[BMartens]

Depends on the gun. I've loaded the 124 JHP anywhere from 1.090 to 1.25 for several production guns and out to 1.175 for a 9 major gun.

Need to know the max OAL length for your gun determined by what the chamber and the magazine can handle.

[rooster]

As a general rule longer is usually better. The first two rounds off a mag have the most pressure applied by the mag spring which makes those rounds want to hit the feed ramp lower. If the rounds are on the long side then they contact the ramp a little higher which will result in smoother feeding.

[lucky strike]

Also, could you describe the jam for me?

Gun is a 9mm XD service, I can't really describe the jam completely because I was shooting an IPSC match at the time so I only was able to see it for a second or so before I just did a malfunction drill. In the brief moment that I was able to see it it looked like the round was getting caught up on the feed ramp. I had these happen about 5 times throughout the match.

This is my first time loading JHP, before I've just used RN and have loaded it between 1.125 to 1.145 and never had any feeding issues but I know you can't just translate that over since RN and JHP have different shapes.

Maybe I'll load another batch at 1.120

I can find the chamber depth with my caliper I guess and then add the rim thickness and that'll give me the max OAL for my particular gun right?

[GForceLizard]

I measured factory Remington Golden Sabre 124gr JHP at 1.125

[Sarge]

Though most problems can be worked out some guns are just finicky especially with HP's. You could laso maybe take some flitz to the ramp.

[fltbed]

This is my first time loading JHP, before I've just used RN and have loaded it between 1.125 to 1.145 and never had any feeding issues but I know you can't just translate that over since RN and JHP have different shapes.

Maybe I'll load another batch at 1.120

I can find the chamber depth with my caliper I guess and then add the rim thickness and that'll give me the max OAL for my particular gun right?

The first thing I do when loading a new bullet is determine what the OAL should be. Then I work up the powder charge.

In my experience, -.010 off the Max OAL for the chamber has always proven to be the most reliable for me.

I copied this method out of an old book I found in the high school library, oh so many years ago. It’s always worked for me.

Finding your OAL

Things you’ll need:

1. Dowel rod that fits down your bore. (cleaning rod will work in a pinch)

2. Exacto knife, razor blade or scribe.

3. Dial calipers

With the action closed, insert the dowel rod through the muzzle till it’s resting against the breach face and scribe a line on the rod at the muzzle.

Now insert the bullet you plan on loading into the chamber and hold it against the rifling with something. (another piece of dowel rod, cleaning rod, etc.)

Reinsert the dowel rod till it’s resting against the nose of the bullet and scribe another line on it at the muzzle.

Measure the distance between the two lines and you now have the maximum OAL for that bullet in your chamber. I normally back off my OAL another .010 or, if it's real long, to the max OAL that will function through the magazine.

I know there are other ways of determining OAL that are more precise and more expensive, but I’ve always found this method more than adequate for my needs.

Hope this helps.

Jeff

[blind bat]

fltbed - That's a pretty stellar tip.

lucky strike - Do you chamber gauge all your rounds? The chamber on my XD9 is really tight and I used to have extraction problems because cases were getting stuck in the chamber. Using a Dillon case gauge and a EGW/Lee U die solved my problem. It doesn't sound like the same type of jam but still might be something to keep in mind.

[Outsydlooknin75]

My method for finding OAL is to take an empty unprimed case, seat a bullet in it LONG. Remove the barrel from the gun and drop the bullet in and see if it goes completely into the chamber ... if it doesn take it out and seat just a little deeper, and try it again. Keep seating slightly deeper until the dummy round will drop into the chamber and when the barrel is tipped upside down the dummy round freely falls out. When it freely falls out, check to see if it fits in the magazine. If it fits in the mag at that point, I will load some up at that length and test them. When you are playing with the seating depth dont worry about crimping the bullet ... just seat it.