Variations in OAL

[chuckshoots]

Hey guys,
Finally got time to reload and its been a few months since I got ym setup. I loaded my first few cartridges and measured the OAL when fulled loaded with primer powder and bullet, and found the measurment to vary from about 2.783-2.794.

Is this tolerable or acceptable or should it be closer? I am using Redding dies for my 308, using hornady brass and 175 SMKs.

Thanks!

[Bill Steele]

Hey guys,
Finally got time to reload and its been a few months since I got ym setup. I loaded my first few cartridges and measured the OAL when fulled loaded with primer powder and bullet, and found the measurment to vary from about 2.783-2.794.

Is this tolerable or acceptable or should it be closer? I am using Redding dies for my 308, using hornady brass and 175 SMKs.

Thanks!

You can't measure using calipers alone. You need a comparator to measure the base to ogive. The meplats are not consistent enough.

Like this: http://www.grafs.com/catalog/product.../7235/inline/1

[BLR81]

Hey guys,
Finally got time to reload and its been a few months since I got ym setup. I loaded my first few cartridges and measured the OAL when fulled loaded with primer powder and bullet, and found the measurment to vary from about 2.783-2.794.

Is this tolerable or acceptable or should it be closer? I am using Redding dies for my 308, using hornady brass and 175 SMKs.

Thanks!

308 is a rimless case which head spaces on the shoulder. If the shoulder isn't resized to the right size the case may not allow the bolt to fully seat the case for proper closer of the breach.

If the cases are formed properly and the cased trimmed to the proper length, then the bullet seating should be adjust by the Ogive and not by the case base to the bullet tip. Soft tip, Hollow point, and polymer tip bullets vary greatly in length. SMK is a HPBT bullet. Measure several and you'll find some variance in length. Rotate them in the calipers and the length will vary.

Bullet seating depth vary per rifle. Find the length needed to reach the lans. That will be when the Ogive is seated at around max length. Then with a Ogive measuring tool, set your seating depth until seating depth seats to your max Ogive seating depth measured by your tool. Then make some test rounds from that length and in .010" shorter for about 4-5 steps short but not less than the min OAL in your data book.

My Lyman Book has 308 175gr HPBT, as needing a 2.80 OAL. So, you may see higher pressures with the seating depth of your loads. If they are anywhere near max powder loads, I'd make up some lessor powder weight loads and try them first. Then work your way up in small increments to your already loaded rounds.

[Ahhnother8]

You can't measure using calipers alone. You need a comparator to measure the base to ogive. The meplats are not consistent enough.

This...

[damndave]

You can't measure using calipers alone. You need a comparator to measure the base to ogive. The meplats are not consistent enough.

Like this: http://www.grafs.com/catalog/product.../7235/inline/1

[Rizzo]

For rifles that use a magazine, that method may keep the cartridges from loading into the magazine since the mag is the limiting factor for the COAL.

I am about to reload some .223 ammo for the first time and have been researching the subject because it is still a little confusing to me.

Given a 2.260 max COAL for a .223, then wouldn't one want to measure from base to the bullet tip to make sure the round would fit the magazine?

With varying lengths of bullets of the same batch, using the ogive method could end up having a cartridge too long for the mag wouldn't it?

[Whiterabbit]

For rifles that use a magazine, that method may keep the cartridges from loading into the magazine since the mag is the limiting factor for the COAL.

I am about to reload some .223 ammo for the first time and have been researching the subject because it is still a little confusing to me.

Given a 2.260 max COAL for a .223, then wouldn't one want to measure from base to the bullet tip to make sure the round would fit the magazine?

With varying lengths of bullets of the same batch, using the ogive method could end up having a cartridge too long for the mag wouldn't it?

Two things:

With respect to OAL consistency I don't care about mag fit or bullet tip. It's the distance from the ogive to the lands when in the chamber that I care about. And the tolerance is NOT in the eye of the beholder, it is in the eye of the robust-ness of the load! Maybe .01" is good enough for the use of the cartridge. I guarantee it for steel shooting offhand at 100 yards! But maybe it's not even close to good enough. All depends on the purpose of the load.

With respect to magazine fit, if I have a load that could accidentally be seated .01" too long and suddenly it didn't fit in the mag anymore, my load has already lost the definition of being "robust".

[ptmn]

Chuckshoots, you are getting a lot of good advice from the forum posters, but I think some of it might be a little to technical. The simple answer to your question about a .01 variance is that it is ok, but I myself like to cut that variance in half for match loads. Either way, your .01 is just fine for a 308. If you get a chance, measure some factory ammo and you will see that their variance is sometimes more than your .01 Hope I was able to answer your question. Have fun reloading and have a Merry Christmas.

[elhefe50ss]

Shoot ive measured factory ammo and they have been more variance then that lol

[chuckshoots]

Hey guys, so I got my comparator finally and am able to now try it out. I am getting consistent 2.207" measurements to the O-give with the 5 cartridges I loaded up.

My question is now how do I correlate these number to the OAL? The load book only gives the OAL value to be at 2.8", is there a source for measurements to the O-Give?


thanks

[Ahhnother8]

My question is now how do I correlate these number to the OAL? The load book only gives the OAL value to be at 2.8", is there a source for measurements to the O-Give?

It does not matter. Do the rounds fit/function in YOUR magazines?

[Bill Steele]

Hey guys, so I got my comparator finally and am able to now try it out. I am getting consistent 2.207" measurements to the O-give with the 5 cartridges I loaded up.

My question is now how do I correlate these number to the OAL? The load book only gives the OAL value to be at 2.8", is there a source for measurements to the O-Give?


thanks

Good progress.

With rifle loading, the OAL data is really unimportant, other than a guidepost to what the tester was using.

If you are loading for a gun with a magazine, then you only need to correlate the comparator number (which tells you if your seating depth is consistent), to an OAL that will allow your rounds to fit in the magazine and feed. This dimension is where the bare caliper is useful.

If you are loading for maximum accuracy, then knowing the corellation of the comparator dimension to where the ogive contacts the lands will be helpful. Most guns for a given load, prefer a certain amount of jump (that is the distance the bullet moves before the ogive/bearing surface contact the lands). The comparator is REALLY useful with this task. To determine what jump your gun likes is a trail and error thing, similar to working up loads.

For instance, in most of my rfiles I have two comparator dimensions I use for setting my bullet seat depths. The first is my hunting load, which is a load where the bullet is seated deep enough to assure my magazine will feed. The second is a bullet seating depth that optimizes my groups, this is usually larger comparator dimension (less deep seating depth) but also usually means I am single feeding the rounds as they will not fit in my magazine. I do everything with the comparator, except when I am starting with a new bullet and developing my hunting load (if I use it for hunting, for instance I don't have hunting loads for my SMK's, AMAX's, VLD targets, etc., so these have one comparator dimension I use for seating depth (written on the box)).

I hope that all made sense.

PS - For handgun the OAL matters, don't go below the load data OAL.

[Whiterabbit]

aaaaaaand you might want to know your gun max OAL, the point where the ogive does start to contact the lands. Easy to measure. make a dummy round, chamber it, and push a cleaning rod against the tip and mark the muzzle on the rod. Then put JUST a bullet into the chamber and use something like a dowel or pencil to push the bullet into the lands, and measure again with the rod. Add the difference at the muzzle with the OAL (from the ogive) of the dummy and you have your max OAL (measuring the ogive) before the bullet contacts the lands.

Good info to know.

[chuckshoots]

thanks for the help guys. I adjusted my die to be right at 2.800 and loaded 5 cartridges each at increments of .5 grains starting at 34gr and working up to 37.5 grains for now.

I was going to do more but a corded drill fell off the top shelf and landed on my head and sort of ruined the vibe.

These are my first loads and I must say I am quite nervous about shooting them. Even with multiple checks for double charges and such.

Is it odd when you seat the bullet to see some copper from the jacket scratched up off the bullet? I am thinking it is from grime on the inside of the case neck, as it only happened on a few.

thanks guys

[Whiterabbit]

I've seen it before. They'll still go bang. Not that you should tolerate it, but you dont need to go pulling down everything.

The bigger problem is the opposite one, where you dont have ENOUGH neck tension. Sounds like you have more than enough.