SmallCaliberCentral

Keith in Ga wrote:I talked with Rob Behr (before he left Cooper) and he gave me an oal of 2.235

This sort of bothered me to read. It reminds me that I started out loading at 2.251 COAL for my AR-15, only because it looked like that was about the max that looked like would fit, with a little to spare, in all the different AR-15 magazines I have. (My .204 is an AR-15.) The reason it bothered me, is I have the Hornady OAL gauge, and the .204 dummy round to check the chamber, yet never even checked the chamber on mine, because I ASSUMED that I could only load to the length that would fit in the AR-15 magazine, and feed correctly. Now you're saying an OAL as short as 2.235 is recommended for a bolt action the likes of Cooper. That makes me wonder if maybe mine should be shorter. They should feed even easier through the AR-15 action when shorter, and there's a possibility that every one of my cartridges, when being fed (semi-auto) is hammering the nose of the bullet out of shape, or putting a flat spot on it.

Now Keith, you may be be using a gauge that measures off the ogive of the bullet. If that is the case, you need to be clear when you tell people what that "OAL" really means. Maybe I'm uninformed in thinking that means the same as "COAL", and if it does, may push a max charge of any given powder charge, past the safety zone if loaded too short. I hope I'm clear enough here. I'm saying your comment makes me want to check the chamber on my AR-15 upper in .204 Ruger to see if I can load these cartridges shorter. Maybe I'm actually jamming each round into the lands? ? Maybe loaded at 2.251", each bullet is hitting the top of the chamber as it feeds out of the magazine? My main concern is that if someone takes "2.235" as "COAL" (Cartridge Overall Length), then there is risk of loading charges that exceed safe pressures. If someone could look up the SAAMI "COAL" on .204 Ruger, I'd appreciate it. ammoguide.com lists "Max Overall Length" at 2.260, wherever that comes from.

I'm probably the least knowledgable of anyone on here when it comes to reloading, so please feel free to verify or dispell my concerns here. I'm off to measure the chamber on my rifle! Thanks!

This is not the first time we have had this conversation on this board. COAL could mean cartridge overall length, comparator overall length or case overall length. You really need to specify when using the term or others reading your post are in the dark.

I read the post by birddog and I'm a little confused myself. I'm trying to understand why someone would load 25 cases with the same minimum charge weight but different OALs. At that rate he will shoot out his barrel before finding the right combination. It would be better to load 5 at the minimum charge and then increase the charge weight by .2 grains for the next five and so forth until you reach maximum charge. All those bullets would be the same Overall Length. Then when you found a charge weight that produced the best group, start varying the Overall Length to see if you can tighten the groups up even further.

When you get a new rifle you really should measure the distance to the lands and write that down somewhere. Without this measurement you are guessing how far off the lands you really are. This could be dangerous. If you are shooting a factory stock rifle like the majority of members, you will probably find that your chamber is so long that you will never reach the lands with any bullet left in the case.

I tried an experiment with my XR-100 that was an eye opener. I loaded five each of my favorite charge weight at the recommended OAL of 2.250 and then increased the OAL by .005 for the next five and so forth until I reached the lands. I found that a length of 2.255 produced the best groups. My 204 liked a little jump to the lands.

Your AR, and any other magazine fed rifle is limited by the magazine length. That doesn't mean that the magazine length is the best length for your rifle. You really are doing the right thing by measuring your chamber to see how far it is to your lands. That takes all the guess work out of it, besides insuring that you aren't jamming your rounds into the lands without even knowing it. So my advice is to experiment and find yoiur rifle's own sweet spot. Every rifle likes what it likes regardless of recommendations from others with the same rifle. Recommendations can be good starting points for experimentation, but that's all.

I will make a disclaimer: Do not try to take a load from one rifle, or measurements from one rifle and expect it to work across the board. I would NOT expect measurements from a bolt gun to work exactly the same in a semi gun of the same cal. However, I would expect measurements from the same mfg of a gun MIGHT apply to the same mfg rifles of the same cal. My two Cooper rifles in .204 don't like the same powder charge, but the oal measurements work the same for both.
Bottom line: you have to rely on a good reloading manual, start low, and experiment with various powder, bullets, primers, and oal to find what works for you. I also agree with Skipper, no reason to load so many rounds to test, I usually load six each and shoot two three shot groups.
I was trying to help Birddog with some shortcuts, but maybe in the future, I should keep comments and suggestions off the board.

Keith in Ga wrote:I was trying to help Birddog with some shortcuts, but maybe in the future, I should keep comments and suggestions off the board.

Keith,
I wasn't getting on your case for posting a cartridge length recommendation. I just asked what you meant by "OAL", because depending on where you measure from (the tip of the bullet or the ogive), pressures would be much different. And 2.235 seems so extremely short, it made me figure you must be measuring from the ogive, but I don't know. Like I said, I'd actually be pretty excited if I could load mine a bit shorter, because they'd feed better.

Don't take my need for clarification like your information is unwanted. I know it may sound like I'm arguing sometimes, especially to those who know much more than I do, but sometimes I'm just double checking.

Skipper,
I plan on measuring to the lands today. One question though:
I understand that the bullet tip is a very innacurate measurement because of the wide tolerances found in something that bounces around in a bag or box until it gets loaded, and ogives vary with different bullet manufacturers/models, BUT... I have to bet that my measuring device that measures from the ogive may be just a hair different than your device that measures from the ogive, and someone else has one that has an even different device. How do we, on a message board like this, really trade that length info reliably? I don't know if we can, unless the difference in measuring devices is very small.

Keith,
I just read your comment in birddog's Cooper thread. Thanks for clarifying. That length (2.235) is the actual length to the tip of the bullet. What bullet do you use that length for? I ask because I think some bullets have a different ogive shape (curve) and the bullet is actually shorter/longer depending on weight/design. If one were to seat 5 different bullets, measuring from the tip, the distance from the ogive to the lands may be different in all 5 loaded rounds. Food for thought. Someone please correct me if that's wrong.

This is a great thread. Let me give some clarification to my original post and why I'm doing what I'm doing.

There are many variables that impact accuracy. Usually, when I work up a load, I start by varying the powder weights. However, for the next few months, I won't have much time to go out to the range, so I needed to do something that would allow me to run enough bullets through the new barrel to break it in on my first time out. I didn't want to load up a bunch of different powder charges, only to run into pressure problems and risk having to stop my day at the range. I plan to spend a lot of time with the barrel break in procedure, which means I'll be cleaning alot betwee rounds. If I had to stop due to pressure problems, my day would be lost and it may be a while before I could get back.

So, instead, I decided to work up some rounds where I kept the powder fixed (at a low charge) and varied the Overall Length of each cartridge. That way, I wouldn't have pressure problems and would be able to run 50 bullets down the barrel and get it broke in on my first trip out to the range. Once I find an OAL that works well, I was going to start varying powder charges to find what works well there (holding OAL fixed and loading up 3 rounds each with varying powder charges). But, I can't do that in "one trip", so I decided to try this approach.

I had no idea that such a short overall length might be good for accuracy. Based on what I'm reading here, instead of varying the lengths to the lands in increments of .010, I may instead spread it out more. Maybe I should start at .010 and then do: .030, .050, .070 and .090? That last one would get me to the suggested OAL of 2.235 (although I wonder how much of my bullet will be left sticking out of the brass with that one).

I measured my distance to the lands in my rilfe using the "test bullet thingy" that came with my RCBS precision micrometer. It showed that 2.325 is the overall length (measured using a caliper from the tip of the bullet to the base of the cartridge) for this rifle. The RCBS precision mic also measures the length to the ogive, but I've recorded those measurements, but haven't posted them here as I'm not sure exactly what they mean. I just validated them for consistency.

I realize this is probably backwards from how most folks do it, but as I said, I really wanted to get 50 bullets down the barrel at this range session as it may be a while before I can go again.

birddog wrote:That last one would get me to the suggested OAL of 2.235 (although I wonder how much of my bullet will be left sticking out of the brass with that one).

I think most seem to be trimming their 204 Ruger cases to somewhere close to 1.84". If that's the case, you'd have .395" of the bullet showing.

Here's the measurements I just took using my chamber (1.843 dummy case length)

40gr Nosler BT = Cartridge OAL is 2.072" to the ogive (comparator) and 2.432" to the bullet tip
Bullet length is .746" or .387" to ogive (comparator)

39gr Sierra BK = Cartridge OAL is 2.090" to the ogive (comparator) and 2.438" to the bullet tip
Bullet length is .726" or .371" measuring to ogive (comparator)

40gr Hornady V-Max = Cartridge OAL is 1.955" to the ogive (comparator) and 2.324" to the bullet tip
Bullet length is .751" or .385" measuring to ogive (comparator)

Keep in mind these numbers come from 1 single bullet out of the box. Each box will have a range of bullet lengths, even when measured to the ogive.

I'm too hungry right now to do any more computations with these numbers, but if anyone wants to play with them and tell me something enlightening, be my guest. One thing I noticed, is my comparator that attaches to my digital caliper is exactly 1.001" thick when assembled and attached. The surface (edge) that hits the ogive is an insert, and is changeable. This one is made for .204, but it's a beveled edge that contacts the ogive, so I don't know if the 1.001" could be used for anything.

I would appreciate it if some of you do have your chamber measurements handy, to post them so I might see if my chamber throat is any longer or shorter than average. Again though, don't these numbers require use of the same gauge with both chambers if any comparison is to be done? I know we can get close using our own gauges, but how close?

This all seems so picky, but hey... ?

I was sitting here looking at these numbers and had to do some calculations... Something seemed odd so I measured again, and sure enough, the numbers are just that weird. This is why I asked about the difference in measurements in the first place. They depend greatly on bullet design, and dimensions of the ogive.

40gr Nosler BT = Cartridge OAL is 2.072" to the ogive (comparator) and 2.432" to the bullet tip (A difference of .360")
Bullet length is .746" or .387" measuring to ogive (comparator) (A difference of .359")
The differences here look close enough to account for measuring mistakes.

39gr Sierra BK = Cartridge OAL is 2.090" to the ogive (comparator) and 2.438" to the bullet tip (A difference of .348")
Bullet length is .726" or .371" measuring to ogive (comparator) (A difference of .355")
The differences here look like I should measure again.

40gr Hornady V-Max = Cartridge OAL is 1.955" to the ogive (comparator) and 2.324" to the bullet tip (A difference of .369")
Bullet length is .751" or .385" measuring to ogive (comparator) (A difference of .366")
.003 difference when measuring just the bullet? Do I need a new caliper?

Does this test and measurements above at least show us that we need to use the bullet we plan on loading when measuring to the lands, because of differences in bullet design?

BabaOriley

You are correct that you will need to re-measure the distance to the lands with each bullet you intend to load for. Here is a picture of some of the various bullets I have showing the differences in base to ogive length and differences in bullet profile.



Pick a bullet and measure that with your OAL gauge. Take two or three measurements to be sure and average them. Use that to determine length to the lands, for that bullet.

To measure your chamber length you can use one of these devices.



Both of these measurements will probably tell you what you don't want to know. That you can't load your bullets to .010 off the lands because there won't be any bullet left in the case. Manufacturers cut these chambers to lengths that defy loading to the lands nowdays. I guess it's a liability thing.

If you are fortunate enough to have a chamber cut so that you can reach the lands, you're lucky. I would take advantage of that situation and try loading from short of the lands to jammed into the lands. Let your rifle tell you what it likes. When you feed it the right bullet, powder, primer combination at the right OAL it will reward you with those one hole groups. The .204 Ruger is capable of amazing accuracy.

If I came off like I was jumping on someone, I apologize. I wasn't trying to. I just was wondering why someone would take such a round about approach to load development. It's really easy. Start near the minimum charge weight and load about 5 rounds. Then increase the charge weight about .2 gr. (the 204 builds pressure rapidly in such a small case) and load 5 more. keep going every .2 gr until you reach max. Now take them out and shoot. Watch for signs of pressure like pierced or flattened primers, a hard to lift bolt or signs of case head separation. A chronograph will help immensely. See which charge weight makes the smallest group and then use that charge weight to load more while varying the OAL to see if you can tighten the group up farther. Finding a charge weight that will put the bullets the same impact point as the charge weight .2 gr. higher and lower will result in a combination that is very forgiving of variations in charge. Keep everything consistent from case to case and you will be on the road to some great accuracy.

Of note, a great place to start with 204 rounds...is 0.050" off the lands.

Some barrels like a little less, some like a little more.

One item that I include in my reloading notes.....regarding OAL/COAL.... I tack on an "SP" at the end - stands for Stoney Point - the originator of the OAL/COAL measurement gauge using a special made brass.

This note alerts me instantly that I worked this load up using the SP cartridge and gauge. I also note the actual COAL and OALSP in my reloading book.

I am lazy at my load book...and suffer when I work up a great load (you know..you are in the groove)...and FORGET to write the notes down.

One excellent tool to help you....ESPECIALLY when working up loads...a SHARPIE. Write the load, COAL/OAL/OAL SP (pick one and stick with it), on the side of your brass.

I mark the powder, charge weight, primer, etc, etc on the cartridge...and keep track of the load workup by numbering the targets as well. You don't have to walk 98 times to the targets...just a notepad/load book and your scope.

I agree, different bullet types will have different overall lengths as measured to the tip of each bullet.

However, I use the freebore tool included with my RCBS precision mic to determine where the curve of almost any bullet design will touch the lands of my rifle. I then use the mic provided in this kit to get a measurement of that location and use it as a reference when loading any bullet type.

Here's the tool I use:



It turns out that the chamber for my new rifle is such that I can easily load right to the lands. I get a measurement using this RCBS precision mic of ".164". I then load any bullet design and seat it such that it reads at ".164" in this tool if I want it to touch the lands. I load any bullet design and seat it such that it reads ".154" if I want it .010 off the lands (and so on). The overall length (measured to the tip of the bullet) of different bullet designs will vary, while the reading from this tool will not.

Like I said, I normally work up loads as suggested, by varying powder weights first, then messing with the seat depth. However, I didn't want to risk running into pressure problems on my first time out and wanted to use the entire time to break in my barrel and be sure I could run 50 bullets down the barrel. I rarely get a chance to spend an entire day at the range and I've got that opportunity on Saturday. If for some strange reason I started to see pressure problems after shooting 60% of my loads, I'd have to head home and lose the rest of the day. I don't want to risk that, which is why I'm doing this butt backwards.

I can still easily re-seat some of my loads so that they are further from the lands and I'm wondering if I should do that. My current loads are 0, .010, .020, .030 and .040 off the lands. Should I spread them out further?

thanks,

Birddog