The results of excess OAL?


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MoreIsLess
October 7, 2011, 11:52 AM
I just started loading 9mm 115 gr FMJ after spending most of my previous time loading .45acp. I have been loading to an OAL of 1.155 to 1.159 with 4.3 gr of Win 231 to try and emulate the factory ammo I had been using which was running around 1.162. I guess the ma OAL according to SAAMI is 1.169 for 9mm FMJ. I have noticed that a lot of people here are using an OAL of 1.125 -- 1.135.

Last night I had a bullet get lodged in the barrel of my Sig 226 while testing these. I have several questions:

Could the OAL have been the cause of this or is likely to have been caused by something else. I don't think it was to much flareing because the bullets would barely stay upright in the case when I was seating them.
What happens when the OAL is too long

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bds
October 7, 2011, 12:12 PM
Not all bullets (even FMJ round nose) have the same nose profile (ogive) and different barrels will have varying length of leade (space bullet jumps from the case neck/chamber to the start of rifling) and rifling type. For these reasons, reloaders must determine both MAX and IDEAL OAL for each bullet type and pistol/barrel to reload for.

For most commercial FMJ RN bullet nose profiles, 1.125"-1.135" OAL will work for most pistols/barrels. But some bullet manufacturers have increased the length of bearing surface (part of the bullet that rides the rifling) to better stabilize the bullet. This changed the bullet nose profile and the typical OAL will not work for them, especially in barrels with shorter leade.

Why determine the MAX OAL? So your bullet nose/bearing surface won't hit the rifling when chambered. The closer you get to the start of rifling without hitting will reduce high pressure gas leakage and produce more consistent chamber pressure for more accurate loads. IDEAL OAL needs to be determined from MAX OAL so you can identify the OAL that will reliably feed/chamber from your magazine. Often both are the same and sometimes IDEAL OAL is shorter.

Vec
October 7, 2011, 12:21 PM
I have Sig 226 as well and just about the same load except with a 125gr bullet round-nose bullet.

I did the ghetto way of measuring the throat of the barrel by taking a fired case with a bullet somewhat loose in it and pushed it in, carefully pulled it out and measured half a dozen times. You could try that to see that could be the problem. If it isn't then the OAL can't the the problem.

In my case I could seat the bullets well beyond SAAMI spec and still not touch the rifling. I had an extra 0.1" if memory serves me right.

I'm guessing here, but maybe lighter bullet (less case to hold onto it) might have jumped the crimp upon chambering? I've had that happen to me once it felt like a squib but I found a small pile of unburnt powder in the gun. I just eased the crimp a bit tighter (a few thousandths more crimp) and it's not happened since.

squarles67
October 7, 2011, 02:44 PM
When you say lodged in the barrel are you talking about a squib that fired but didn't make it all the way out or one that stuck in the rifling and pulled out of the case when you cycled the pistol by hand?

A squib is from too light of a charge and your 4.3 is awfully light for a jacketed bullet.

bds
October 7, 2011, 02:54 PM
squarles67, probably stuck in the barrel when barrel drop/function check testing.
Last night I had a bullet get lodged in the barrel of my Sig 226 while testing these.

Could the OAL have been the cause of this or is likely to have been caused by something else. I don't think it was to much flareing because the bullets would barely stay upright in the case when I was seating them.
More than likely the bullet got pressed into the rifling and got stuck.

What happens when the OAL is too long
You will probably have feeding issues and your finished rounds won't chamber fully. Or the bullet will get pressed into the rifling when the slide slams against the case. If the bullet nose is pressed against the rifling when the powder ignites, it will further increase the chamber pressure. You want the bullet to slide across the start of rifling instead of being jammed against it like a wheel chock. If you are using max load data, this increase in chamber pressure may become an issue depending on how much of pressure spike you may end up with.

Vec
October 7, 2011, 03:50 PM
A squib is from too light of a charge and your 4.3 is awfully light for a jacketed bullet.

In my particular case it sounded and felt like a squib, but there was powder in the case as evidenced by what was left over in the gun after clearing it. The primer went bang but the powder wasn't contained in the case any more and didn't seem to ignite. In my specific case (a year or so back) I was shooting lead 9mm with 4.4gr of HP38. I wouldn't really call it a squib in the conventional sense though. I've made a few squibs in the past and the it was enough to engrave the bullet into the rifling; in this case it was more just "wedged" in without really engaging at all.

As a side note with my testing even 4.0gr would cycle my gun most of the time (P226-X5 9mm). Your mileage may vary though.

I guess the real question I have is when you say "lodged in the barrel," how far down the barrel was the bullet? 1mm? Ha;f way down? Somewhere in between?

243winxb
October 7, 2011, 05:11 PM
I had a bullet get lodged in the barrel No powder or a to light charge.

rfwobbly
October 7, 2011, 11:01 PM
I too started out at 1.160" because after measuring I knew the chamber would accept it. But now I've come to comprehend that a short bullet like a 115gr needs more support from the case. Load some up at 1.150, 1.140 and 1.130". I think you'll see the difference on paper.

zeke
October 9, 2011, 04:20 PM
Win 115 hollow base bullets have a longer bearing surface, and a nose profile that facilitate seating out longer.

Tough to comment without knowing the specific bullets and brass you are using

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