Where on Wednesday forty four: Size matters

in The Pew: Guns & more2 years ago

Size really does matter...Who wants something that's too small or big? Mostly people want to make sure things fit right, comfortably, and can operate as intended and desired. Come on, you know I'm right.

This Wednesday, I've been in my workshop messing about with some gun things because in the not too distant future shooting will resume after shutdowns due to the flu. So today's #whereonwednesday post comes to you from my workshop.

This post will cover a few concepts around size when applied to making ammunition for long range shooting purposes. As you may know, I make my own and this is one of the steps required to be able to make precise hand-loaded ammunition; It's the process of determining the overall length of a completed rifle round. I will refer to it as OAL from this point forward.

I will, as always, not get too technical and will try to explain the concepts and equipment in a way that is understandable for people that may not shoot guns, or reload ammunition. So, here goes, time to load and send it!

Overall length - and why it's important

Firstly, a rifle round needs to fit into the magazine, quite obviously. It also needs to be the right length in the chamber so that the bolt can close and it actually fires. It could be a little short, but too long and the projectile may press too hard on the lands of the rifling in the barrel and cause complications like excessive back pressure. Lands are the raised sections of the rifling in the barrel - The rifling provides spin to the projectile for stability in-flight.

Factory rounds are made to predetermined OAL's and always fit the intended rifle but when making my own ammunition I have the ability to adjust the length by seating the bullet further in, or out, of the case neck. This also allows room in the case for additional amounts of gun powder which may be required or desired. (A whole different post there.)

Seating the projectile in a more shallow position can also have the benefit of closing the gap between the projectile and the rifling of the barrel as the round sits inside the chamber. This gap is called the jump, essentially the gap the projectile has to travel once fired before it engages the lands and heads on down the barrel.

Some gun/projectile combinations like a different jump; Some are fussy and some are a little more easy-going. The rifle you see here isn't too fussy, but my .308 was very fussy and shot best with only a 20 thou jump, so 0.02 of an inch. A very small measurement.

So, how do I determine such a precise measurement to allow me to then manufacture those rounds to a set specification? With an OAL gauge of course.

You can see one below, the long red thing, along with the other bits and pieces required to do the job.

Above you are looking at (from the top):

  • 6.5mm creedmoor long range gun
  • Vernier caliper
  • Comparator gauge
  • Projectile
  • Modified case
  • OAL gauge

These are the bits required to gauge an OAL, along with a cleaning rod (too long to put in the photo), pen and paper.

The modified case - This is a case that get's screwed onto the end of the OAL gauge and inserted into the chamber. The picture below right shows the base of it. It is modified meaning it has a hole in it that fits the gauge. These are calibre-specific. This one is 6.5mm creedmoor and I have a .308, .243 and 7mm case also, all used in the respective rifles.

The process

The modified case is screwed securely to the threaded end of the OAL gauge and a projectile is inserted into the neck as per the image above left; The projectile is free to move in and out. You will note the grey rod that runs through the gauge...This allows the operator to gently push the projectile forward. Of course, this is only done when the OAL gauge is inside the chamber.

The gauge gets inserted into the chamber and the modified case sits there exactly where the actual rifle round would sit to be fired. Below you can see the gauge inserted into my long range gun on the left and the right shows the case on its way into the chamber...It's dark in there so I held it out a little for this image. Note the gap and flat section on the OAL gauge, below right...We will come back to that in a little bit ok?

So this is where it get's a little tricky.

I simply push the grey plastic inner shaft until the projectile stops; That's when it touches the lands of the rifling as mentioned above. At that point I tighten the locking nut, seen in the image below left, and that sets (locks) the gauge.

This has to be done with a deft hand and the same every time. Press even a little too hard and the measurement will be false. Remember, we're dealing with thousandths of an inch measurements here. I use my trigger finger for this part and apply the same amount of pressure I would for a trigger pull, about 2.0-2.2 lbs of finger pressure is where I set my triggers, so it's a fairly light press.

Once the lock nut is set the OAL gauge is taken out. Keep in mind here that the projectile is still stuck in the lands of the barrel; That's where the cleaning rod comes into play. I simply insert it from the muzzle-end of the barrel and tap the projectile out - It doesn't take any real effort.

Now I have the OAL gauge out of the gun, and set, it's time to measure.

The setting of the gauge simply locks the grey shaft into place so it won't move. It's important to make sure the flat section of the shaft is face up in the gap in the gauge as the image above right as that will permit access for the vernier caliper.

I simply drop the projectile back into the case neck and it will sit exactly where it did when in the chamber of the gun for measurement which you can see happening below.

The vernier caliper is zeroed and set to inches or millimetres (I use inches) and the measurement is taken.

I repeat this entire process ten times then remove the highest and lowest measurements from the list and average out the other eight to gain the overall length (OAL) measurement I will work from.

Below you can see the actual measurement taking place. Note on the right you can see I have seated the vernier caliper on that flat section of the inner shaft and snug up against the base of the modified case allowing for a very accurate reading.

As I said earlier, my .308 rifle was very picky about the jump in testing and was far more accurate with a minimal 20 thou jump so I had to set my OAL measurement with that in mind.

After the ten measurements and deleting off the top and bottom ones I ended up with an OAL of 2.3296 inches. Subtracting off the 20 thou as above, to keep the projectile off the lands, I was left with 2.3096 inches as my final OAL.

That measurement ended up becoming the length at which I make the rounds and some precise work is required to set my press to that measurement. This is done manually, there is no gauge for that. It is a long process and one I have to repeat each time I reload for that calibre. I always check and re-check as precision rounds are what I am after.

So that's about it although...

I haven't yet mentioned the comparator gauge so here's a little word on that.

Because the tip of a projectile can vary its an inaccurate way of gauging measurements from. So, we use the ogive of the projectile instead. The comparator gauge allows this to happen. They are simply a gauge that screws onto the vernier caliper and allows the projectile to seat inside it at the ogive of the projectile which is constant and precise. Consistent measurements are now possible. Of course each calibre will have its own comparator gauge and again, I have many different ones.

Below you can see a couple of close ups of the 6.5mm creedmoor comparator gauge used for this post. The hole in the gauge and the right shows the projectile inserted; Where the projectile meets the gauge is the ogive.

I threw this image below into this post because I like it...There's really no relevance to the post other than the fact it is a 6.5mm creedmoor projectile, the Sierra 142gr. HPBT (Hollow point boat tail) and in the background is the comparator gauge.

So to wrap it all up...This is not the only way to determine overall length although it's my preferred way. My friends do it differently on occasions and sometimes I wear a bit of flak for using this gauge but it's all good because the guy that sends the flak is a shit shooter! Lol. For me it's simple and effective method and that sort of sums me up as an individual too, so it works.

Again, I have tried to keep this post a little basic but get the message across and I'm sure if some gun-dude, or dudette, reads it there may be differing opinions and that's ok...I've never professed to be a know-it-all gun guy, just a dude who knows some stuff about some stuff and that's good enough I guess.

Thanks for reading.


Design and create your ideal life, don't live it by default - Tomorrow isn't promised.

Be well
Discord: galenkp#9209

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Fascinating. I wasn't even aware there was a jump. Seems counter-intuitive. Why not just have the projectile nested into the rifling?

Most don't realise, even shooters. The jump is minimal, I mean, it's not like an inch or something.

Some rifles like it nestled right up there, some don't. My 6.5mm creedmoor doesn't mind a bigger jump. Besides, with the projectiles I use I can't minimise the jump much as they don't fit in the magazine. My .308 on the other hand...Smaller the better. I only have 20 thou in there for safety purposes, a buffer. I'd run it right up to the lands but again, the magazine dictates maximum length.

Sometimes running it right up at the lands can cause more back pressure and with larger calibres that can be dangerous. Most guns it doesn't matter if there's some jump though but for long range shooting it is often best to plat around and see what works best. I tried different seating depths and determined 20 thou jump to be the best.

Running it jammed up also causes issues if a round has to be removed prior to firing but after the bolt closes. It will often pull the projectile out of the case and pour gun powder all over the place. Most long range shooters run very loose neck-tension to impede the bullet less when fired.

It's interesting though huh?

Oh, right. Of course. You don't want it to hang onto the tip. Fascinating.

Shooting is fun, but I get as much enjoyment out of this aspect, the technical stuff and fiddling around, than I do with the actual shooting. It can all be frustrating though, when things are not going to plan. 😊

That's all very interesting stuff thanks mate.

You're welcome. Hopefully it read quite easily and all made sense.

It's real rocket science, did not understand 80% of it lol

It can be a lot like that, and this is the easy stuff to be honest. It's very much like a science...Ballistics, chemistry, meteorology, mathematics etc. It all comes into play. I've done many posts and the hardest thing is putting it in a way people will understand. Thanks for trying though, and commenting. I really appreciate that more than anything else.

It does a little bit intimidating. But i am sure it'll get better with time. So keep posting.
I felt something like that the first time I've opened photoshop now i'm more or less comfortable with it.

Thank you for taking your time to put it down. I'll keep trying :)But my credit goes for your deep knowledge on the topic for sure.

I've been shooting for almost 30 years, I'll never be in a position to know everything, firearms are that sort of thing. I know a lot, quite clearly and am content to learn more as I go. I'm not really a novice though.

Perfect timing, I just got 2 of the ".223 WYLDE" Ar15 uppers, going to finish out some builds that were sitting around collecting dust. (on the boxes at least LOL) The .223 Wylde has a shorter leade (or jump, for the peanut gallery) which leads to higher accuracy down range. But it is also deemed SAFE for shooting 5.56 NATO in the .223 based chamber. This is the major difference between 5.56 nd .223 as you well know, @galenKP

I have an old USMC friend (not implying I am a vet, but he is, and he's an old Marine) who bought a .223 Wylde upper, says it is the most accurate AR he's ever shot. Pretty much dead-on out to 5 or 6 hundred yards. But then again Marines train at 600...

Great Article, but THANKS, now I have another expensive tool to buy LMAO
Sonny Boy and I are prolly going to be loading this year, I got him a new rockchucker for Christmas or B-day, I forget because the 2 are close together. Oh, it was B-day cuz he got more support items on Christmas.

There's always another tool or item to buy when guns are concerned right? Lol.

I'm really looking forward to your posts in The Pew. We all have something unique to bring to the table and it's great to read stuff that others are doing. It's a great resource.

Nice setup!

My dad loads all his own rounds for his Ruger 6.5 Creedmoor and has been getting them dialed in at 500 yds. His spreadsheet and data are pretty extensive for all the varying loads and projectiles. It is a serious endeavor to get the rounds matched to the rifle but once it is dialed in they can be nice and consistent.

He also has a Thompson Contender with a crazy barrel on it. 30-06 necked down to 7mm and he had to make his own brass for it. He has about 200 that are all indexed for the barrel and have a very precise load. One hell of a hand gun to fire and insanely accurate to well past 500yds, even for a 30+ year old gun.

Hey mate, sounds like your dad is right into it. The hobby does have a habit of taking over I guess. Lol. It's rewarding to go through the process, make the rounds and then fire them accurately. The process all comes together at the end and it's such a good feeling. I'm sure your dad would agree.

Do you shoot yourself and if so do you hand load. If you don't shoot why didn't you follow in your dad's footsteps?

I have my various arms but I have not gotten down to reloading. I have the setup but it is more to have in case ammo is not available. I do save all my brass though to make sure I have a good stock. My father is a super meticulous person and thrives on these sorts of things. My mentality is not the same. I enjoy shooting but have so many other interests it just hasn't taken precedence.

Now typing this though it reminds me I am going to take a few with me this weekend when I go climbing and run a few clips through each. Haven't had em out in a while so need to get them cycled a few times.

Get shooting mate! Life's too short not to. Lol.

Reloading is a good skill to have so knowing how to do it, before you need to, is a good plan. I keep loads of ammo on hand, but am always able to knock out a few more when needed. I also largely stay with popular calibres so I can easily get the bits I need.

Don't forget to post anything firearms-related into The Pew community. I curate in there every day, as do others.

I wonder if re-loaders are the only ones that buy calipers anymore. We I was a beginning re-loader I did not have one, after about 3 months I needed to buy one. I used to spend hours finding the right combo of powder, and case, and bullet to try and get that perfect consistent round. Hand Loading was a fun hobby for several years before life got to complicated. (one of the locations I lived you had to have the powder shipped via barge, they would not fly gun powder in).

I couldn't do with my my vernier caliper. I use it multiple elements of the reloading process. Case length and OAL. My set is pretty good quality. I had a cheaper set but they weren't accurate enough.

Hand loading can be a fun thing, serious of course, but I find it relaxing. It gives me time to just focus and exclude everything else.

The process of load development is quite pleasing too..chasing that perfect load, the barrel node, recording the information, retesting...I find it fun. There's nothing quite like finding the right load, making it and sending it out to great distance and putting it on target. Very rewarding.

I didn't know you were a hand loader.

A long time ago, a friend got me into it, about 30 years ago. I started with the hand held dies and then graduated to the pull the lever and everything was done. I used to love shooting even won a hat at a bowling pin shoot once for the fastest table. I think everyone should experience a bowling pin shoot at least once in their lives.

Have you ever done a log chop?

The best I went to was a team one where each team of three shooters had a post between them to chop. There were 12 poles so 36 guns...It was hectic. What's a bowling pin shoot?

On standard size sheet of plywood 4X8 Feet, on two saw horses, and four bowling pins set about one foot from the back edge of the plywood, object is to shoot all four off the table as fast as possible. Not as easy as it sounds, if you don't get very close to center of gravity on the pin, then it will drop on the table spin and be hard to shoot off the table. It was quite a challenge.

Ah that's cool. I think we would be able to adapt something like that to suit or rimfire .22LR challenge competition that I run. Not bowling pins though, something else.

Have You ever had a round malfunction or Mis-Fire?

Not really no, not rifle rounds. I've had a few light primer strikes but that was rifle related and the manufacturer sent out a new bolt shroud and it cleared up. It was a design thing.

I've had misfires with handgun rounds though. I just rack the gun again, eject it and keep rolling. It could happen for a number of reasons, mainly a dud primer though. It's rare.

My Old Bersa Thunder does not like the square nose .380 rounds. jams at about 10-20% rate. Round nose are pretty much flawless. I do not recall any mis-light fire primers. But then again, I have only shot hundreds of rounds thru it. Not THOUSANDS like You. Haahahahah. Not a bad thing, I am Jealous!

I feel like I haven't shot for a long time to be honest, although the range will be open soon I think. I was there building walls today, working on some new ranges...It's coming together really nicely and I'm looking to get back there to shoot. You need to get out and shoot a bit mate.

I have a bunch of need to's!

We are going in to our credit union, (bank), this Friday,(tomorrow)... or is it Friday there already? You are 14 hr ahead?

Submitting an application for a 1% Gov covid loan. I could never get credit interest rate that cheap, so we are gonna grab what we can, and they forgive the first 10k. Why would anyone pass that up?

2 year payback, so probably gonna grab 25k. Also anything We can prove we used for Mortgage interest, office expense, business costs due to covid, etc. May also be forgiven. So We are going to try it. Just always makes me wary when the word FEDERAL GOV is in the mix. They are such LIARS and CROOKS...!!!

You guys have run your business for a long time and I'm sure will make intelligent and relavent decisions around this potential loan. Yes, it seems too good to pass up and why not take advantage of what's on offer to get a little ahead? I think it's smart. We have credit unions here, they always seem a little better than the banks for some reason so maybe it's the way to go and you can make it all work well in your favour?

Not Friday yet, it's 9:30pm Thursday night. We are 13.5 hours ahead of Miami time. So it's 8am there now.

I have no idea about firearms. But good to get some knowledge here.
I didn't know about #whereonwednesday. I guess any post is welcomed here!

Basically #whereonwednesday is all about writing about where you would rather be, or what you would rather be doing on a Wednesday, the middle of the typical working week. It's pretty open to anything really. You could write about where you have been, where you want to be, go or do, or pretty much anything you like, as long as it's Wednesday.

Sounds great. I will use the tag soon!

Aaaand... It gets more complicated. I never knew firearms can be this intricate, and equally exciting! It's like going back to Chemistry class in school. I'm going to have to go over this one again. Mad respects to you, mate.

I much be a fucking genius! Lol.

It's cool though huh? People think it's all pulling triggers and popping cans in the back yard after drinking 15 beers...What i do is a science and is part of the attraction to the whole thing you know?

My only regret is that I don't have a son or daughter to impart my knowledge to.

Thanks for your comment.

It's cool though huh? People think it's all pulling triggers and popping cans in the back yard after drinking 15 beers...

Substitute beer with Scotch, and I think this would be a ironical description of my entire life XD. I do have to admire all the science that goes into something that for most of my life, looks pretty simple. Bullet in chamber, pull trigger, and boom.

Yet, it's amazing to explore more about how they all work! On the subject of passing over the knowledge, there's always us. We can be your children, just not as Mocha in some cases, nor as obedient 😅. There's also Grouchy, who could be a good disciple of firearms, if you have the patience for it!

😁 Grouchy and firearms...Not a good mix I think. He's probably hold up a bank and buy a Harley to replace his scooter from the other day. Speaking of which, he'll be having some adventures soon.

Haha, you're probably right. And the bad thing is, given Grouchy's diminutive size, he'll just scurry his way around. It's quite a hard target for the cops to shoot at, you know? I'll be awaiting the adventures of Grouchy and the Scooter :-)

I absolutely love the intimacy that you get with your rifle when reloading. Literally knowing the twenty thousandths preference on a rifle is something few people will ever experience. Your fine tuning is inspiring. Excellent post, and I have something else to add to my shopping list.

It's a good way of putting it actually; It is a really is a close relationship and to get the best out of it a shooter/reloader must know the rifle intimately. I like the load development process although it can be frustrating too. But when it comes together, when you're out sending projectiles down range, a long way down range and they ping that target...That's rewarding.

Did you end up seeing that response I left you about your question about how far I'd ranged m 6.5mmCM out to? A few days ago.

You must have a long shopping list. Lol.

I did see! Sorry, I have a tendency to drop online conversations kinda short lol

How far is your load supersonic? I understand that's an awesome aspect of the 6.5 CM round.

1200m give or take. Here's a part of a FFS table from StrelokPro...metres, elevation, windage.

Screenshot_20200516-111437_Strelok Pro.jpg

Yeah, I thought it was something like that. Like you said, laser beam. Easy to see why people love it. I might have to add a 6.5 bolt gun to the list too.

This is getting expensive. Perhaps I should make more blog posts lol (blogging provides a lot of my play money)

More blogs = more guns then! Yeah, it's a good thing...Keep your quality high and you'll get more and more as you go. Engage with people too, relationships is how you build you rewards.

65CM has to be in your arsenal mate...Seriously it's a great round. I get an average MV of 2841fps with a 142gr pill...Good numbers. Goes a long way, accurately and will impart a goodly amount of energy when it hits. 660ft-lbf at 1000m! Enough to not want to get one in the chest.