How much fudge factor allowed in OAL?

[Lucky Strike]

So i loaded up my first batch of ammo yesterday. First off thanks to those on here who have helped me get to this point.

I just did a small batch (50) of 9mm on my 550B. I used Berry's plated 115 DS RN bullets. Cases were all once fired Remington.

I went on Hogdon's reloading site to get info (I have a Lyman book but it didn't get a load for 115 RN) and found one for what I was doing and it gave an OAL of 1.100". I used the recommended starting powder weight.

when i stared loading, the first ones were coming out too long..first couple were 1.108..lowered the seating die..next few were 1.105...lowered again some more and got 1.102...lowered some more got some 1.098...raised some and got either 1.101 or 1.100 for the last 35 in the batch.

My question is are those first ones where I was fine tuning the seating die ok to shoot? I'll be shooting these in an XD subcompact. I know OAL is important but just wondering how tightly you need to stick to it and still be safe.

 

[30Cal]

+/- 0.010" is usually fine. I have no idea why manuals print OALs out to three digits--it really doesn't make any sense.

 

[The Bushmaster]

I can usually keep mine with in +/- .002". I did some experimenting with loads that were .025" over OAL and had weak loads. Those that were .025" under OAL tended to be a bit hot. 30cal said +/- .010" will probably be OK, but with practice you should be able to get them to a better tolerance.

 

[NCsmitty]

If they function through the gun ok, you'll never notice any difference in accuracy with those minor changes.

NCsmitty

 

[shadowalker]

Most load OAL's are minimum, you can load longer but going shorter can cause problems.

I typically configure my dies for .005 longer than the load to allow for variance. Factory ammunition also has variance between rounds.

Anything more than .005 under minimum OAL I set aside and pull, they are probably fine but I'm not in a hurry.

 

[5knives]

Going shorter or a weak crimp allowing bullet set back in the magazine, will raise pressures, sometimes a surprising amount.

FWIW,

Usually a tad longer is okay as long as every thing feeds properly.

9mm headspaces on the case mouth, so watch your CASE length before reloading.

If you're sticking to moderate loads, shouldn't be an issue for a LONG time.

Regards,

 

[1SOW]

I believe 9mm max OAL is 1.169

I measured Win value-pak 115fmj @ 1.162 Feeds great in a CZ
I'm just starting to load 124gr, fmj and will try to keep the OAL the same or a little longer than the Win oal for reliable feeding.

5knives +1

Different powders give different pressures and the prescribed OALs will change.

The CZForum has a very good explaination of all this in the reloading section. Author is 'FEG'.