OAL safety, and Load parameters

[Davehb]

Been working on determining OAL for each bullet plan on loading and testing.
With XTP 124gr I’m getting .0005” clearance at 1.063” OAL which just so happens to be the OAL of Hornady factory loaded ammunition. 
 
Current safety recommendations are a set back of .015 which would create an OAL of 1.048 which would require lighter starting load to ladder up.
When Reloading ages ago I would have used a 1.06-1.059” OAL for the 124gr XTP based on my current measurements.  Which would also require lighter starting load.
What are the cons of a .003-.004” set back versus the .015”?
3-4thousandths set back was fairly common among those who helped me learn >30 years ago so just trying to understand updated parameters.


Load data: 😖
How good is VV/Hornady load data?
Hornady load data is over a grain lower for all bullets on both minimum and maximum charge weights than VV for the same powder.
Doesn’t make sense if VV N300 powders aren’t supposed to create as much chamber pressure.
 
I know I’ll have to cautiously work up my own loads, but good grief the more books I get in the more variances in load data. Seeing so many typographical errors in other fields now days makes me nervous.

[Wobbly]

Been working on determining OAL for each bullet plan on loading and testing.
With XTP 124gr I’m getting .0005” clearance at 1.063” OAL which just so happens to be the OAL of Hornady factory loaded ammunition. 
 
Current safety recommendations are a set back of .015 which would create an OAL of 1.048 which would require lighter starting load to ladder up.
When Reloading ages ago I would have used a 1.06-1.059” OAL for the 124gr XTP based on my current measurements.  Which would also require lighter starting load.
What are the cons of a .003-.004” set back versus the .015”?
3-4 thousandths set back was fairly common among those who helped me learn >30 years ago so just trying to understand updated parameters.

• 0.003 to 0.004" will not account for variations in OAL during your manufacturing process. Our standard 0.015" for pistol ammo takes into account variations from multiple sources. There is always variation in manufacturing, and if you tell me all your ammo is +/-0.000 tolerance, then I will say you are lying or that you are spending WAY too much time reloading pistol ammo. 

• Rifle ammo is vastly different. A lot of rifle reloaders can get extra accuracy by closing the ogive-to-rifling gap. 0.003 to 0.004" might work great for deer hunting in your centerfire rifle. But you'll need to ask a rifle reloader.

• Where did the 1.063" OAL come from? The OAL in the manual is part of the Lab Report in the manual. That's all the manual is; it's one big Lab Report. The way the bullet fits the barrel determines any OAL. Since your barrel is different from their barrel, then your OAL will be different.

Load data: 😖
How good is VV/Hornady load data?
Hornady load data is over a grain lower for all bullets on both minimum and maximum charge weights than VV for the same powder.
 
I know I’ll have to cautiously work up my own loads, but good grief the more books I get in the more variances in load data. Seeing so many typographical errors in other fields now days makes me nervous.

Load data is ONLY a general guide. They are shooting from a 16" single-shot "test barrel" that is bolted to the table top. It looks like this...



If you are using their exact same powder, primer, bullet AND your 16" barrel is bolted down, then your results may match theirs. Otherwise, the only believable data, the data I want you to focus on, is the Chamber Pressure. All other data is simply a guide to safe loading. This is why I have previously told you to pick ONE primary reloading manual. And leave the others on the shelf, otherwise you'll only confuse yourself. I have manuals on my shelf that I dearly love... and haven't opened in 10 years !

Doesn’t make sense if VV N300 powders aren’t supposed to create as much chamber pressure.

Who said that? If the bullet is traveling the same speed, then it must have nearly equal Chamber Pressure pushing it. Otherwise it would defy the Laws of Physics. Newton's Second Law says for every force there is an action. If the resulting actions of 2 separate forces are equal, then the forces themselves must be equal.


A Solution
Brother Dave, what I suggest is that we develop this load together, from the very beginning. You tell me all the components you have, the pistol you are using, and what your goal is. We will work through every step together. Step by step. I'll even do the chrono work for you. How's that sound ?

Regards

[flyingbrass]

One big factor I rarely see mentioned when determining max OAL for pistol cartridges is the length of the case being used for the test.

Since 9mm headspaces on the case mouth, throat clearance is determined by the amount of bullet sticking out of the case, not the OAL.  OAL is only a proxy for this.  At a given OAL, the shorter the case, the more bullet protrudes in front of the mouth.

My recommendation is to sort through your fired cases and find a few of your shortest.  Size them and measure again.  Use these shorter ones to determine your max OAL.  Record the max OAL you arrived at along with the case length for future reference.  Repeat this test multiple times.  Use longer cases if you like, just be sure to record their lengths before checking max OAL to compare.  Notice the trend of your max OAL changing along with case length.

My method of determining max OAL is to fully load a cartridge with the bullet deliberately seated out too long.  By fully load, I mean be sure to crimp.  Crimping should only straighten out the mouth flare, not drive the mouth into the bullet.  Then I seat deeper incrementally while testing for plunk and spin.  This goes quicker if working in relatively large increments to begin with (.005" - .010").  Then, after zeroing in to a smaller range with the first try, you have a better idea where to begin with a new round (again with a known sized case length) to work down in .001"ish increments until you just barely have plunk and free spin.

Repeat this test another time or several.  Even when using cases of about the same length there will be some variations for multiple reasons.  One is your estimate of where clearance actually begins.  Another is bullet variation.  In loading rifle cartridges, OAL often varies considerably, even when base to ogive distance is consistent.  The same likely holds true for handgun bullets.

SAAMI spec for 9mm case length is .744" to .754".  In the real world you will find that case lengths are all over the place.  I have some new 9mm cases from RMR (my first brand new 9mm cases ever), and they vary somewhere around .005" in extreme spread of length.  My mixed range brass consisting of probably well over 100 different headstamps and ages ranges from the few low oddballs at around .738" up to .753ish after sizing.  That's a .015" spread, and there may be some shorter ones I haven't caught.  I've only measured samples, not all of my cases.  BTW, the shortest ones I've found have been of all different headstamps, many being Winchester, Remington, Federal, etc., not only the more questionable headstamped stuff.  I suspect the shortest ones have been fired more times.  Unlike rifle brass, auto pistol brass shortens with use.  I'm sure some of these cases have been fired teens or tens of times.

For max OAL, if you can plunk and spin with short cases, IMO there isn't any necessity to seat WAY deeper to allow for short cases because you've already checked with some short cases.  Go a little deeper though because you don't want to be on the hairy edge.  There is some variation in depth from the equipment alone when seating bullets.  Progressive presses tend to be worst about this.

In an ideal world I'd prefer to have plenty of clearance.  Extra is better than not enough.  However, CZ and some others make stupidly short throats so we're often left seating shorter than we would prefer but trying to not go shorter than necessary.  Case length makes a significant difference in max OAL results and affects how much you may want to subtract for allowing extra room.

I recently got a P-09 that has a short throat.  It's about .040" shorter than my previously shortest throated pistol, a CZ-75 SA (which has a relatively long throat for a CZ - factory, not reamed).

My usual generic practice 9mm loads are RMR 115 FMJ.  With these bullets max OAL in my CZ-75 with a case that measured .7475" after sizing was 1.162".  The same bullet in a case measuring .7465" after sizing plunked and spun at 1.122" in the P-09.  This comparison is relatively apples to apples because the case lengths were only .001" apart.

Remember, I'm using cases of different lengths (so are you, though maybe not quite as varied), and max OAL depends on case length.  I checked more of the rounds I had previously loaded at 1.130"ish in the P-09's barrel.

These overall lengths plunked and spun in the P-09:
1.1285”
1.127”
1.127”
1.132”
1.128”
1.130”
1.1275” almost - slight rub in a spot

These didn't until reseated to the latter length:
1.1275”  1.121”
1.130”    1.125
1.130”    1.123”
1.127”    1.122”

See any pattern there?  Me either.  The difference is the case lengths.  At a given OAL, more bullet sticks out of a shorter case.

Yesterday I loaded 200 rounds after adjusting my seating die down to provide around 1.120" average OAL (spread roughly between 1.118" - 1.122").  I checked every round in the P-09 chamber.  All passed plunk and spin, though maybe 2 or 3 out of the 200 were just barely there (slight hint of rubbing when spinning).  I'll probably go down another couple thousandths next time to provide a little more wiggle room.

I chronographed 20 rounds of this batch from each pistol today.  Their average velocities were the same, which is surprising but has nothing to do with what I'm writing about here.  Given the wide variety of brass I don't think the spreads are bad at all.  Loads are 4.8 grains WSF.  Temp about 82 F.  ProChrono chronograph at about 15'.

P-09
20 rounds
Average 1133
ES 61
SD 20

CZ-75
20 rounds
Average 1134
ES 78
SD 20

I'm including the chrono results because I found them interesting.  While nothing conclusive, it's a data point showing no difference in SD with one load between a pistol with minimal bullet clearance to the throat (but all rounds clearing) and one with considerably more clearance.

[Davehb]

A Solution
Brother Dave, what I suggest is that we develop this load together, from the very beginning. You tell me all the components you have, the pistol you are using, and what your goal is. We will work through every step together. Step by step. I'll even do the chrono work for you. How's that sound ?

Regards

Berrys 124gr HHP
Starline brass
Primer: federal #GM100M small pistol

Sierra V crown 124gr
Star line brass
Primer Federal #GM100M

Hornady XTP 124gr 
Star line brass
Primer Federal #GM100M 
 
Currently have
VV N340 which I’m most interested in.
AA#7
And if I have to VV 3n38

Hornady data lists an N350 data with
max load of
5.2gr
1050fps 

CZ75B Omega

Using Lyman manual it shows a generic 124gr jhp load data using N340
OAL 1.060 (which makes me think it is data for Hornady XTP
Max load 4.6 gr
Velocity 1071fps psi 32700

VV load data
Closet seems to be
Laupa 124 fmj
OAL 1.142
N340
Max load 5.1gr
Velocity 1181fps
 
124gr XTP:
tested OAL with .0005 clearance is 1.063
-.015=OAL of 1.048

124gr V Crown.
Tested OAL: with .0005 clearance 1.103
-.015=OAL of 1.088.

Berry’s HHP 124gr
Working on OAL 1.061 -.015=1.046
Same primer and cases.
VV does show load data for the Berrys HHP
N340
OAL 1.126
Max load of 4.9gr
Velocity 1115fps
 
My OAL is .08 shorter.
For varmint control, and hunting. Wanting to match as close as possible federal HST 124gr.
I know an HST running 1150 will drop a tough battle hardened wild cat, or bobcat (wife called me 2 weeks ago cause one our dogs had bobcat bayed up in middle of driveway 20 yards from house. 🤷🏼  Coming after our fowl I guess. She Wasn’t able to get it cause I was concerned about pass through with what she had. It’s Been prowling around at night ever since.) in its tracks on a shoulder->shoulder without worry of a pass through. Which I like for safety reasons.
 
From what I’ve seen of Berrys it may be good one for what we need.
Just been practicing with the jhp before working on the plated Berrys.

[Wobbly]

I don't need the book loads or the book OAL... we will develop that information for ourselves.

What I need is the average of multiple telescoping chamber length tests using each bullet mentioned.

I have the Berry 124gr HHP and may have the 124gr XTP on hand.

[Wobbly]

One big factor I rarely see mentioned when determining max OAL for pistol cartridges is the length of the case being used for the test.

In practice, I believe the 0.015" set back takes care of this. Mathematically you can prove if all the tolerances lean one way you can get in trouble with case length. That has not been my experience with any of my mixed brass shooting. Additionally, in the nearly 2 decades I've had this method posted here and training novice reloaders, to my knowledge it has never caused an issue. It works.

Reloading is a big tent. All are welcome. It's a fun and fantastic mixture of Science and Art which allows one to explore many details. There are multiple ways to do it "correctly". If this is your version of "correctly", then that's wonderful.

Now back to our regularly scheduled thread.

[Wobbly]

Dave -
Here's the steps in order...

• Berry recommends a velocity of 1050 to 1150fps for this bullet. This data is from the bullet maker's web site. That means we are searching for a specific velocity in order to make the bullet work optimally.

• Next do the "push test" to determine the Max OAL for this bullet in your barrel. Yours and mine came out just under 1.050", so that is a useable number. Not too short; not too long; very easy to measure.

• Next we look at the Max Velocity for the HHP in the VihtaVuori online data. We see the Max Velocity listed as 1115fps. Thus we know we cannot use any N340 load that generates more than that velocity. To do so would also generate the maximum Chamber Pressure, which is a no-no. We are always watching the Chamber Pressure !!

• We can also see that the Vit recommended loads are 4.2 to 4.9gr, but this is at a much longer OAL of 1.126". So we can't use any of these loads. We must find our own, and the way to do that is by using Velocity.

• The only thing to do is try some (1, maybe 2) shots across the chrono, while we keep working the load up toward the "magic" velocity of 1100fps. We'd be using gross incremental steps of (maybe) 0.3gr as we work our way up.
(Note: At this point we are changing ONLY 1 variable: the amount of N340. The primer, powder choice, bullet, OAL, etc are all firmly fixed and unchanging.)

• I have this data already recorded in my notebook
Using N340 @ OAL 1.050" with Federal primers
As fired in a P10c

Average of 8 rounds over a chrono
4.9gr    1086fps
5.0       1101
5.1       1121
5.2       1135
5.5       1178

• Based on these results, your choice MUST BE 4.9 or 5.0gr because anything higher violates Vit's Max Velocity finding.

• So in the end, the load was defined by a combination of Berry's and VihaVuori's recommended velocities.

Hope this helps.

[Davehb]

Dave -
Here's the steps in order...

• Berry recommends a velocity of 1050 to 1150fps for this bullet. This data is from the bullet maker's web site. That means we are searching for a specific velocity in order to make the bullet work optimally.

• Next do the "push test" to determine the Max OAL for this bullet in your barrel. Yours and mine came out just under 1.050", so that is a useable number. Not too short; not too long; very easy to measure.

• Next we look at the Max Velocity for the HHP in the VihtaVuori online data. We see the Max Velocity listed as 1115fps. Thus we know we cannot use any N340 load that generates more than that velocity. To do so would also generate the maximum Chamber Pressure, which is a no-no. We are always watching the Chamber Pressure !!

• We can also see that the Vit recommended loads are 4.2 to 4.9gr, but this is at a much longer OAL of 1.126". So we can't use any of these loads. We must find our own, and the way to do that is by using Velocity.

• The only thing to do is try some (1, maybe 2) shots across the chrono, while we keep working the load up toward the "magic" velocity of 1100fps. We'd be using gross incremental steps of (maybe) 0.3gr as we work our way up.
(Note: At this point we are changing ONLY 1 variable: the amount of N340. The primer, powder choice, bullet, OAL, etc are all firmly fixed and unchanging.)

• I have this data already recorded in my notebook
Using N340 @ OAL 1.050" with Federal primers
As fired in a P10c

Average of 8 rounds over a chrono
4.9gr    1086fps
5.0       1101
5.1       1121
5.2       1135
5.5       1178

• Based on these results, your choice MUST BE 4.9 or 5.0gr because anything higher violates Vit's Max Velocity finding.

• So in the end, the load was defined by a combination of Berry's and VihaVuori's recommended velocities.

Hope this helps.

What’s the determining factor for starting load?

Did you start with the lightest load even with shortening of OAL?
Edit:
Or Reduce by certain percentage?

Reloading in 1990’s I didn’t have to worry about a shorter OAL cause every OAL could be lengthened as long as staying in max parameters for the caliber.

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[Wobbly]

What’s the determining factor for starting load?

Did you start with the lightest load even with shortening of OAL?
Edit:
Or Reduce by certain percentage?

Reloading in 1990’s I didn’t have to worry about a shorter OAL cause every OAL could be lengthened as long as staying in max parameters for the caliber.

Sorry for skipping that.

We're working in Vit data, so I would have stayed with Vit data. I proabably began with the Vit Starting Load of 4.2gr, then immediately realized after 2 shots that it wasn't even in the ballpark. This despite the shorter OAL. Loads don't always work out like you think they will. You have to go where the data leads you.

Then loaded upward in coarse increments of ~0.3gr to 4.8gr. Loading 4.8gr would have shown enough promise that I reduced the increments to 0.1gr

The P10c barrel is about 1/2" shorter than the 75. I will try the ammo in an SP01 for a velocity check tomorrow.

[Davehb]

Loaded 2 Berrys 124gr HHP with 4.2 grains VV N340 @1.050 just to test.
Clocked at average 1035fps. 10fps difference between the 2 rounds.
There is a difference in type recoil with the VV powder. 
I think I gonna like it.

[Wobbly]

The P10c barrel is about 1/2" shorter than the 75. I will try the ammo in an SP01 for a velocity check tomorrow.

It's been too overcast to get a reading here.

[Wobbly]

Loaded 2 Berry's 124gr HHP with 4.2 grains VV N340 @1.050 just to test.
Clocked at average 1035fps. 10fps difference between the 2 rounds.

So your results are roughly matching my data. 4.2gr is way too low. We need to be up around 1100fps.

So we are working toward higher velocity loads, and also getting better "case fill" as a free side benefit.

Still no sun down here.

[Davehb]

Loaded 2 Berry's 124gr HHP with 4.2 grains VV N340 @1.050 just to test.
Clocked at average 1035fps. 10fps difference between the 2 rounds.

So your results are roughly matching my data. 4.2gr is way too low. We need to be up around 1100fps.

So we are working toward higher velocity loads, and also getting better "case fill" as a free side benefit.

Still no sun down here.

Since it’s supposed to be a while before we have any days with Sun, after today, I sat out with chrono and waited for break between clouds today. [emoji23]

I loaded 2 rounds each trying to get a ball park.
Same components as before.
W/4.5gr VV n340
1st shot:  1067
2nd shot: 1097

W/4.7gr VV n340
1st shot:  1092
2nd shot: 1137.
 
Couple shots didn’t feel right, especially the last one at 4.7gr, (harder recoil, and louder report), sign of slightly higher pressure, so went through everything with fine tooth comb trying to figure out why.
I think it’s inconsistent bullet length and swaging.

After setting up die, for OAL of 1.05, and loading @4.7gr, noticed some bullets on the table stood out looking short, tall, fat on ogive.
Went back and checked OAL of everyone I had loaded, after that for my attention.

One had length of .540 other was .532. 

Which shouldn’t affect OAL of cartridge, but some look to have less of a tapered (fatter) ogive.

1/3 of my loaded batch was .004-.006 short.  some seem to have less tapered ogive because some of same length will seat deeper. All from same Lot#. [emoji848] I had checked quite a few bullets for consistency, but guess I didn’t check enough.

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[Wobbly]

Are you using mixed brass for your testing ? If so, fish through your collection and dig out 25 that are the same brand. Use those matching for your testing.

[Davehb]

Are you using mixed brass for your testing ? If so, fish through your collection and dig out 25 that are the same brand. Use those matching for your testing.

I’m Using All new Starline brass. 
 
Thinking I had to have gotten one of longer bullets in the mix resulting in couple seated deeper eating up a few thousandths of cartridge space.


 
 
 


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