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Old 04-06-2017, 07:51 PM
eod26
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52gr sierra HPBT OAL question



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Hey guys. new to the forum and seems to be a wealth of information here. I am loading for a CZ 527 varmint in .223 using benchmark powder, Winchester SR primers and Sierra 52gr HPBT projectiles. I determined my maximum OAL to be 1.886 (by putting marker on the projectile and chambering it) using a bullet comparator to measure. So I backed that off .020 which equals 1.866 to be safe from the lands. My OAL without the comparator is 2.213. This seems short to me especially because all of the load data/testing I have seen is done with 2.250 OAL. Am I missing something? I measured multiple times and results were repeatable. Thanks in advance.
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Old 04-06-2017, 08:06 PM
flangster

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You are talking about the length to your bullet's ogive, right? That's the part pf your bullet that will first contact the rifiling, and that's what the Hornady comparator measures. It is located where the bullet achieves its full diameter, not the tip. The manual's OAL (overall cartridge length) is bullet tip to case head, a little longer than the length to ogive. Folks worry about OAL because of the magazine dimensions. But there are variations in bullet length, and measuring to the ogive can be more useful for round-to-round consistency. Does this clear things up?
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  #3  
Old 04-06-2017, 08:06 PM
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dstoenner
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I shoot an AR15 in NRA High power and when I am doing a 100 yard reduced course match, I shot this bullet. My loaded OAL is 2.215. I use LC cases, 27.5 gn CFE-223 with BR-4 primers.

HTH

David
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Old 04-06-2017, 08:16 PM
eod26
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Yes flangster that makes sense. I guess my concern is because after doing all that to figure out exactly where the ogive comes in contact with the lands and backing it off it is only 1.866 (with comparator). When I measure the OAL (case head to bullet tip) it is 2.213 but most people load at 2.250/2.260. just seems like my OAL should be longer? I may just not be trusting my measurements and overthinking it.
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Old 04-06-2017, 08:20 PM
eod26
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Quote:
Originally Posted by dstoenner View Post
I shoot an AR15 in NRA High power and when I am doing a 100 yard reduced course match, I shot this bullet. My loaded OAL is 2.215. I use LC cases, 27.5 gn CFE-223 with BR-4 primers.

HTH

David
That makes me feel better about my measurement. I am new to reloading so have a lot to learn. Been reading forums and researching for a couple years but you cant learn everything without doing it yourself. thanks
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Old 04-06-2017, 08:25 PM
Squeezer
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COAL is for chumps

Quote:
Originally Posted by eod26 View Post
Yes flangster that makes sense. I guess my concern is because after doing all that to figure out exactly where the ogive comes in contact with the lands and backing it off it is only 1.866 (with comparator). When I measure the OAL (case head to bullet tip) it is 2.213 but most people load at 2.250/2.260. just seems like my OAL should be longer? I may just not be trusting my measurements and overthinking it.
My impression is that the COAL is an attorney-approved maximum dimension that SHOULD fit in any and all magazines.

I load based on the optimum leap I have determined experimentally for a particular weapon using the Hornady OAL Gauge and comparator, and don't worry about COAL.
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Old 04-06-2017, 08:38 PM
eod26
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That works for me. Need to but the hornady lock and load gauge to go along with the comparator. Didn't think I would need it but quickly seeing the advantage. Going to load some up tonight and see what they do tomorrow.
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Old 04-06-2017, 10:13 PM
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Originally Posted by eod26 View Post
That works for me. Need to but the hornady lock and load gauge to go along with the comparator. Didn't think I would need it but quickly seeing the advantage. Going to load some up tonight and see what they do tomorrow.
I measure several times using the Hornady OAL Gauge, but then I like measuring things

I have a straight one for my bolt rifles, and also recently got a curved one for semi-auto work (Ruger Ranch Rifle).

My bolt rifles seem to do best with 0.010~0.020" leap, but one likes the bullet to engage the lands.
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Old 04-06-2017, 10:56 PM
mikeinco2014

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MIGHT I SUGGEST YOU CHANGE YOUR APPROACH.
IF YOU START "at the lands" you will see max pressure for the load( not MAX,
just highest you will see with the length and powder load)
this allows you to find max powder fairly quick. bullet in the lands will give more pressure than off the lands...does any of this make sense ??
so look at all your load data pick a starting load and work up in .3 steps( aprox
1/100 of case volume). 3 shot strings. inspect case/primer/note easy of bolt lift in each string. if you find good accuracy with a load. then start backing off from the lands in .005 steps. looking for another sweet spot on the target. watch for pressure if you end up backing off a bunch from the lands.

if you start off the lands and then approach the lands you may be starting with a load that is too hot for close to the lands.

my opinion is that this is a safer approach..as long as you are not making large reductions in oal.
just my 2 cents worth
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Old 04-07-2017, 08:39 AM
Rimfire5
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eod26,

Have you ever tried factory ammo in your CZ 527?
Most factory ammo I've measured is seated for an OAL that is around 0.005 short of 2.250.
If your chamber is as short as you think it is, you won't be able to close the bolt.
If the chamber is really that short, I recommend that you send it back to CZ and I am sure that they will fix it.

I have a CZ 527 Varmint 1.9 twist and it liked the 52 SMKs seated at 2.260 OAL when it was new. Even new, the chamber was so deep that 40 grain bullets would fall out of the cartridge when I measured them to the lands.
With the 52 SMKs # 1410 and the jump was 0.050 at that OAL.

My rifle now has over 6000 rounds through it and it still shoots very accurately. I seat out at 2.270 to 2.280 and the jump is much greater than 0.050 because the throat has eroded over time. I don't seat them out much further because I am concerned that the bullet bearing surface in the neck will get too short to maintain consistent neck tension. With the 52 SMK the bullet base to ogive measures 0.360, so the boat tail reduces the bearing surface by 0.060 to 0.240. Seating out 0.020 drops the bearing surface in the neck below the .224 bullet diameter. I figure that I could stretch it out to an OAL of 2.290 but it still shoots accurately at 2.270 so there is no need to do that yet. Maybe with a bit more wear in the throat, I'll try seating them out further.

The flat base bullets have more bearing surface since there is no boat tail so you probably seat them out further, but I seat all my 52s and 53s at the same OAL and get good results with all of them.

I suggest you also try the 53 grain flat base SMKs # 1400 and the 52 grain Berger # 22408 flat base bullets in your CZ. The 53 grain FB SMK and 52 grain FB Berger bullets hold 20 of the top 25 loads with my CZ. The 52 SMKs hold only 4. The last position is held by a 40 grain Nosler BT load. Overall, I think the Berger bullets are a bit more accurate than the Sierras in my .223. It is just the opposite in my .22-250s.

In my CZ .223, N133 and CFE 223 powders hold all but one of the top 25 loads with H335 managing to grab one. I've tried 7 different powders and 22 different bullets from 35 grains up to 75 grains but the 52 and 53 grain bullets work the best.
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Old 04-07-2017, 09:37 AM
danoh
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Quote:
Originally Posted by Rimfire5 View Post
eod26,

Have you ever tried factory ammo in your CZ 527?
Most factory ammo I've measured is seated for an OAL that is around 0.005 short of 2.250.
If your chamber is as short as you think it is, you won't be able to close the bolt.
If the chamber is really that short, I recommend that you send it back to CZ and I am sure that they will fix it.

I have a CZ 527 Varmint 1.9 twist and it liked the 52 SMKs seated at 2.260 OAL when it was new. Even new, the chamber was so deep that 40 grain bullets would fall out of the cartridge when I measured them to the lands.
With the 52 SMKs # 1410 and the jump was 0.050 at that OAL.

My rifle now has over 6000 rounds through it and it still shoots very accurately. I seat out at 2.270 to 2.280 and the jump is much greater than 0.050 because the throat has eroded over time. I don't seat them out much further because I am concerned that the bullet bearing surface in the neck will get too short to maintain consistent neck tension. With the 52 SMK the bullet base to ogive measures 0.360, so the boat tail reduces the bearing surface by 0.060 to 0.240. Seating out 0.020 drops the bearing surface in the neck below the .224 bullet diameter. I figure that I could stretch it out to an OAL of 2.290 but it still shoots accurately at 2.270 so there is no need to do that yet. Maybe with a bit more wear in the throat, I'll try seating them out further.

The flat base bullets have more bearing surface since there is no boat tail so you probably seat them out further, but I seat all my 52s and 53s at the same OAL and get good results with all of them.

I suggest you also try the 53 grain flat base SMKs # 1400 and the 52 grain Berger # 22408 flat base bullets in your CZ. The 53 grain FB SMK and 52 grain FB Berger bullets hold 20 of the top 25 loads with my CZ. The 52 SMKs hold only 4. The last position is held by a 40 grain Nosler BT load. Overall, I think the Berger bullets are a bit more accurate than the Sierras in my .223. It is just the opposite in my .22-250s.

In my CZ .223, N133 and CFE 223 powders hold all but one of the top 25 loads with H335 managing to grab one. I've tried 7 different powders and 22 different bullets from 35 grains up to 75 grains but the 52 and 53 grain bullets work the best.
Great reply! Here's a fellow who's done his homewok!
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Old 04-07-2017, 11:59 AM
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I just loaded 50 rounds of .223 Remington with Hornady 50 grain A-Max bullets and IMR 4198 powder. Each round has a length-to-ogive of 1.859 inches for some load development I am doing with a Savage Target action. I have one barrel that is chambered in .223 and another in .222. I don't measure the COAL, unless the l-t-o seems odd for a particular chamber/rifle.

I got the chamber measurement by using Hornady's lock-n-load guage, taking 12 measurements, throwing out the high and low and averaging the rest. I then fitted a dummy round (no primer or powder) and tested by closing the bolt with the test bullet blackened to see whether I was jamming the lands at the indicated seating depth.

The 100 yard ladder test looked like this:



The target seemed to indicate good/close vertical groupings at 21.2 to 21.5 grains of powder, so I neck sized the same cases and made a batch of 50 rounds between 21.2 to 21.5 grains in 0.1 grain intervals and the same seating depth of 1.859. When I zero in on a promising node, I will play with seating depth as a variable. But you see why the OP's length to ogive of 1.866 inches doesn't seem outrageous to me?
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Old 04-07-2017, 02:05 PM
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( that is not a ladder test, that is just a load development group powder step test.
a ladder test is aprox 10 or so rounds fired at a single point of aim in small powder steps. a ladder is designed to find nodes without firing groups.)
the idea of the ladder is to shoot less powder/bullets to find the nodes.

Quote:
Originally Posted by flangster View Post
I just loaded 50 rounds of .223 Remington with Hornady 50 grain A-Max bullets and IMR 4198 powder. Each round has a length-to-ogive of 1.859 inches for some load development I am doing with a Savage Target action. I have one barrel that is chambered in .223 and another in .222. I don't measure the COAL, unless the l-t-o seems odd for a particular chamber/rifle.

I got the chamber measurement by using Hornady's lock-n-load guage, taking 12 measurements, throwing out the high and low and averaging the rest. I then fitted a dummy round (no primer or powder) and tested by closing the bolt with the test bullet blackened to see whether I was jamming the lands at the indicated seating depth.

The 100 yard ladder test looked like this:



The target seemed to indicate good/close vertical groupings at 21.2 to 21.5 grains of powder, so I neck sized the same cases and made a batch of 50 rounds between 21.2 to 21.5 grains in 0.1 grain intervals and the same seating depth of 1.859. When I zero in on a promising node, I will play with seating depth as a variable. But you see why the OP's length to ogive of 1.866 inches doesn't seem outrageous to me?
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Old 04-07-2017, 02:28 PM
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Yup. I understand. This is an experiment of mine designed to do the same thing, but give me a way to tell whether shooter or reloading error has influenced the results. It is more wasteful, as you correctly point out, and it is not what folks mean by the term "ladder test." But I'm hoping it will lead me to some useful data in load development.

[Edit: Let me re-phrase the above as a problem-statement. I tried a traditional ladder test with an earlier load for a different rifle, at the time I wasn't sure from the impact data on the target (e.g. height from point of aim) or chronograph data (which sometimes had larger speed variation within a load than I would have thought likely) what the results were telling me. Problem? Well it could have been rifle cant, different placement of the forearm on the bags, variation in trigger pull, bullet runout, neck tension . . . or even confusing bullet hole #1 with bullet hole #5. Basically, this is the universe of factors other than purely the charge weight or the length-to-ogive, which seemed pretty well controlled in my test. Well, what to do?

First, I figured that I could change the "ladder" from vertical to horizontal. I could still measure the group mean distance from the x-axis and see how that tracked changes in velocity, but it would allow me to segregate differences in charge more easily than trying to shoot and then identify which hole was the "new" hole in my ladder. So now I am looking for adjacent good groups with the least vertical dispersion where the change in charge weight occurs. That is what I think the groups marked 21.2 and 21.5 are telling me. They are sub-MOA groups with about the same mean vertical off the x-axis (the point of aim) but at adjacent charge weights. I should probably call this something other than a ladder test. "A Fallen Ladder Test" ? "A Sleeping Ladder Test"? "A Waste of Powder Test?" Somthin' Anyway, that's why the target looks the way it does] My next test with this powder will be 10 shots at each 1/10 grain charge weight from 21.2 grains to 21.5 grains, inclusive. The charge weight for best performing group will be where I start testing variations in seating depth. Make sense?]

[Edit #2: Look at this target for a CZ 527 .222 Remington American:

EDIT - IMPORTANT: I deleted the picture in this thread because the target had a dangerous error on it [Explained in next post]


The amazing thing about this is how little vertical change there is between charge groups. POA in each case was the X where the hatch mark crosses the x-axis. What I think this 100 yard target is telling me is to check out charges between 21.8 and 22 grains of H355. Looks promising. To complicate matters, I have just had my 1010 scale recalibrated, but it now agrees 100% with my RCBS chargemaster in this weight range, so I have hopes that the data is still good.]
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Old 04-08-2017, 10:00 PM
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Folks: for any following this thread, my post above this had a dangerous error in it. The picture of the target indicated that the loads were for H322. In fact, the rounds contained H355.

Many of the charge weights listed on the target would likely produce dangerously high pressures if loaded with H322. I have removed the image of the target with the erroneous information.

I discovered this when double checking my manual for the loads that I wanted to focus on and saw that H322 is not listed in the Sierra manual for bullets of this weight to be chambered in a .222. The load data online at Hogdon's website does list it, but lists the max load at below where my target indicates I was shooting.

Please remember: check all loads against your own manuals and data. The consequences of a mistake could be serious, even in a .222 cartridge.
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