Help Request with 1. OCW results .300 PRC - does not make sense to me

[tstanek]

Hi there guys,
I don't want to bother you with long texts (and hopefully question itself, in case my brain doesn't get it and it's something what's obvious in general...)...so I did it this way (hopefully it's not gonna be a bad idea) - the info I think is important is included on the pictures. I do know that my writing is kinda dysgraphic and horrible tho and I apologize for that. I'm a surgeon and it's common issue amongst us, .... anyways, if it isn't readable/understandable in general, I will be more than happy to write everything down here

It's basically the first proper OCW I did for my new Bergaga, I've never been shooting it with factory ammo as it hasn't been available in Czechia since .300 PRC was released to the public. I applied general rules of reloading, load devs. and Berger advices aboout loading VLD pills, and overall procedure/modification of the OCW test itself is as described in this thread (as I reload mainly 6,5 CM) https://www.65creedmoor.com/index.php?topic=6774.0 .

Thoughts, notes, changes - as I told before, I used the main idea and concept, not every single detail which I assumed it's not relevant (Gr increments, number of charge steps etc.), but I'm quite confident I did it right either when planning, reloading and shooting itself,.... Some differences and misc., so you musn't mess with metric vs imperial etc. - barrel cooling after each 7-string of shots (no one minute waiting between shots), shooting (and zeroing) distance 109.3 yards, CBTO 2.89 INCH (0,03' jump),.RS 76 - Reload Swiss 76 - swiss powder, common in europe, and most important - it's on stock all the time at almost every store in our lil country. Closest to H1000 from what I've learnt so far / some say it's just european version of RL25 named differently for US/EU markets, who knows...Last but not least, please be nice about the scope , but tbh it's not temporary or some real money issue thing, these optics just work for me on different rifles and cals.

BUT, to the point again (sorry)....I'd be very glad for any kind of objective and possible explanation for this from you guys, as here are many of pro's and supportive folks. I reload for one year, and neither don't shoot any competitions, or think I'm particularily good shooter, it's just my biggest hobby which I love. Question is - What could be the reason for consistent vertical drop, obvious on targets 2, 3, 4 and 5 of last, third, string (marked on targets). When 1. hit of that string doesn't seem weird and the last, 7. is totally of the chain - here I suppose it's just far from node. Sighter on the top left is due to fact I didn't make enough sighters/foulers I thought I'd have needed. Ofc there is considerable shooter's error, I do know that, but still, I'm not sure how (or if it's possible) to interpret the results. And if yes, how would you proceeed now?
Thanks a lot in advance and take care!
T.

 

[rustyinbend]

Do you track velocity? That would be helpful to know if bullets with the same charge weight are impacting all over the target. If velocity varies, look at your processes and tools. If velocity is constant ... well ... then look "within". Just a thought.

 

[tstanek]

I just "from curiosity" put my Magnetospeed on for those sighters - I know it's stupid and not logical when trying to zero the scope to put Magneto on It was just the urgency at that time that I wanted to know And the "results below are ofc irrelevant and crap...meaning stistically-wise, magneto was working as usual.

78 Gr - 1, 2791 fps 2, 2809
79,2 Gr - 1, 2830 fps
80 gr - 1, 2886

 

[Newbie2020]

I doubt a three round string tells you anything at all. Other than it gives you lots of wild geese to chase. @Ledzep

 

[tstanek]

I doubt a three round string tells you anything at all. Other than it gives you lots of wild geese to chase. @Ledzep

So you suggest to do the same test with 5 rounds each?

 

[Doom]

4,6 and 7 show similar POI. In an OCW that is what you look for. In this case I would load 79.6, 79.8 and 80 and reshoot this test. I would do this with 3 rounds each and if it repeats pick the load and test at distance and go with it or you can run a seating depth test to refine it if necessary.

 

[tstanek]

4,6 and 7 show similar POI. In an OCW that is what you look for. In this case I would load 79.6, 79.8 and 80 and reshoot this test. I would do this with 3 rounds each and if it repeats pick the load and test at distance and go with it or you can run a seating depth test to refine it if necessary.

Thanks a lot Sir! that was kind of answer I've been hoping to get

 

[Darkside-Six]

I doubt a three round string tells you anything at all. Other than it gives you lots of wild geese to chase. @Ledzep

Then you do t understand the purpose of an OCW test.

 

[Darkside-Six]

6, and 7 have the same POI and 7 (80 grains) is also a nice group. If it were me, I’d start on that area. My next step would be to load 5 round groups every .1 grain from 78-82 and shoot each group at its own target. Chronograph your groups with your magneedospeed.

 

[tstanek]

6, and 7 have the same POI and 7 (80 grains) is also a nice group. If it were me, I’d start on that area. My next step would be to load 5 round groups every .1 grain from 78-82 and shoot each group at its own target. Chronograph your groups with your magneedospeed.

Cheeers! And seating depth testing after that or..?
EDIT. just the bullets availability is pretty bad, especially in Europe with Berger's....seems like getting there would lead to empty stash
And is it "necessary" to go 0.1 gr steps in the case of this cartridge? Just thinking...

 

[Darkside-Six]

Cheeers! And seating depth testing after that or..?
EDIT. just the bullets availability is pretty bad, especially in Europe with Berger's....seems like getting there would lead to empty stash
And is it "necessary" to go 0.1 gr steps in the case of this cartridge? Just thinking...

If you’re running scarce on components then start right at that 80 grains. But yes, after charge weight is seating depth…of needed. Maybe load up 5 and 80 and run it over your chrono. See what the numbers are and how it groups. May just be able to call it good there.

 

[Rockdoc173]

I'd load up 10 of the #6 (79.6gr) and go shoot them over a chronograph. If the velocity is where you want it and groups are satisfactory then you're off to the races. If groups need tweaking, play with seating depth. I usually start 0.010" off the lands and go from there. When you get chronograph data, keep in mind that OCW doesn't place a huge emphasis on SD. If you can't fiddle with it and get that particular data point where you want it, then you may have to adjust fire and reengage.

 

[tstanek]

All of the suggestions totally make sense to me and thanks for that, now I guess I just need to decide which way to go. Or whether to do more than one approaches "simultaneously". Just the last point which came to my mind, the purpose of the load, use of this rifle and 300 PRC respectively, is long range target/steel shooting max up to 1200 metres (+ - 1310 yards), at some point in the future. I (and the rifle itself let's be honest) don't have some ELR ambitions, which are not even possible in my home country. I think (believe) this load (esp. bullet weight) is capable of that effectively. Correct me if I'm wrong

 

[Baron23]

I too would go w 80 gr. Nice group and dispersion is horizontal and not vertical so wind, you, or bit of both

 

[Darkside-Six]

All of the suggestions totally make sense to me and thanks for that, now I guess I just need to decide which way to go. Or whether to do more than one approaches "simultaneously". Just the last point which came to my mind, the purpose of the load, use of this rifle and 300 PRC respectively, is long range target/steel shooting max up to 1200 metres (+ - 1310 yards), at some point in the future. I (and the rifle itself let's be honest) don't have some ELR ambitions, which are not even possible in my home country. I think (believe) this load (esp. bullet weight) is capable of that effectively. Correct me if I'm wrong

More than capable. Find a consistent speed with good grouping and low SD (preferably single digit SD)

 

[Precision Underground]

Did you shoot these round robin? This is a detail that the majority of people skip but it's incredibly important IMO. Shooting RR all but eliminates the question of "was that me or the charge weight". That aside, if we assume you did shoot it RR and/or there is no shooter influence on the target, I'd be looking at 79.2 and doing seating depth. The small group charge weight on your target is very close to the scatter immediately after it.

 

[mtang45]

4,6 and 7 show similar POI. In an OCW that is what you look for. In this case I would load 79.6, 79.8 and 80 and reshoot this test. I would do this with 3 rounds each and if it repeats pick the load and test at distance and go with it or you can run a seating depth test to refine it if necessary.

6, and 7 have the same POI and 7 (80 grains) is also a nice group. If it were me, I’d start on that area. My next step would be to load 5 round groups every .1 grain from 78-82 and shoot each group at its own target. Chronograph your groups with your magneedospeed.

@Doom and @Darkside-Six both have read the OCW the same as I would. Look for a string of groups with nearly the same POI on the target. I might even add 3 as part of the string of groups with similar POI. 2 and 8 are definitely a shift in POI from 3 through 7. Don't worry about group size. If you have the components, run again with .2 gr increments from 78.8 through 80.0. Or, just pick a load in the middle of that 3 to 7 range and run a seating depth test to fine tune.

 

[2aBaC̶a̶]

Go with number 5, definately number 5.

 

[tstanek]

Go with number 5, definately number 5.

I'm thinking kind of same...to go with this charge, verify 5 shots group if its repeatable and do some velocity measurements with seating depth tweaking afterwards

 

[Rockdoc173]

All of the suggestions totally make sense to me and thanks for that, now I guess I just need to decide which way to go. Or whether to do more than one approaches "simultaneously". Just the last point which came to my mind, the purpose of the load, use of this rifle and 300 PRC respectively, is long range target/steel shooting max up to 1200 metres (+ - 1310 yards), at some point in the future. I (and the rifle itself let's be honest) don't have some ELR ambitions, which are not even possible in my home country. I think (believe) this load (esp. bullet weight) is capable of that effectively. Correct me if I'm wrong

if you have the components, time, and inclination to spare, you might start at 78.8 and go up in 0.3gr increments to further refine your results, then play with seating depth as needed. Honestly though, that's why I like OCW so much, resiliency is built in so, in my experience, it's not really necessary to get down into the weeds. I used to have a three to four step process for all this but now I've KISSed it down to two, the initial test and seating depth, and 9/10 times seating depth isn't necessary. My experience, YMMV

 

[tstanek]

if you have the components, time, and inclination to spare, you might start at 78.8 and go up in 0.3gr increments to further refine your results, then play with seating depth as needed. Honestly though, that's why I like OCW so much, resiliency is built in so, in my experience, it's not really necessary to get down into the weeds. I used to have a three to four step process for all this but now I've KISSed it down to two, the initial test and seating depth, and 9/10 times seating depth isn't necessary. My experience, YMMV

That's the complexity and different opinions that make it a bit complicated for beginner tbh For example Berger's - either manual, when you call them, or web + Brian Litz consider these deep OCW as pointles with Hybrid bullets and advice to concentrate mainly on seating depth...then there's "Scott satterlee likes", Eric Cortina...whos running just basic velocity ladder and then seating depth...and don't care about grouping/POI at first place. For me reloading for like not even a year, and shooting for few months longer starting with velocities is obviously easier, but in the sense OCW somehow feels like the most logical way to go (but itself could be or is biased by shooter's skill)
second EDIT sorry.. doing OCW with magneto attached is nonsense, right? i guess one could not assume it would be changing POI constantly

 

[ShtrRdy]

The 80 grain group is tempting but I like to go after where the point of impact was similar with different powder charges. Between 79.2 and 79.6

 

[nn8734]

Did you shoot these round robin? This is a detail that the majority of people skip but it's incredibly important IMO. Shooting RR all but eliminates the question of "was that me or the charge weight". That aside, if we assume you did shoot it RR and/or there is no shooter influence on the target, I'd be looking at 79.2 and doing seating depth. The small group charge weight on your target is very close to the scatter immediately after it.

Yep, agree at 79.2 and seating depth (maybe 79.4 as a close alternative). And shooting RR is vital IMO as well.

Do you track velocity? That would be helpful to know if bullets with the same charge weight are impacting all over the target. If velocity varies, look at your processes and tools. If velocity is constant ... well ... then look "within". Just a thought.

MV is largely irrelevant at the time of initial OCW. I dont bother tracking it until i have 30-40 rounds made up and shooting drops on the KD range.

That's the complexity and different opinions that make it a bit complicated for beginner tbh For example Berger's - either manual, when you call them, or web + Brian Litz consider these deep OCW as pointles with Hybrid bullets and advice to concentrate mainly on seating depth...then there's "Scott satterlee likes", Eric Cortina...whos running just basic velocity ladder and then seating depth...and don't care about grouping/POI at first place. For me reloading for like not even a year, and shooting for few months longer starting with velocities is obviously easier, but in the sense OCW somehow feels like the most logical way to go (but itself could be or is biased by shooter's skill)

Welcome to reloading.

I like OCWs because i like confirming stability in POI relative to POA across adjacent charge weights but other folks like ladder / saterlee tests and some will just pick a charge weight, load up three -to-five groups of different seating depths and run with the tightest group.

 

[tstanek]

Thank you very much for all of the input and overall willingness to help. I will proceed the way you suggested in the last reply, I might do seating depth testing loads for both 79.2 and 79.4 charges. The current jump from the lands is 0,03 thou , I’m thinking doing 0,03 0,05 0,07 and 0,09 steps since hybrids seem to like longer jumps and 0,02 jump on previous testing wasn’t ideal. Does it seem reasonable ? Just one more thing, should I concert about velocities at all regarding all the factors I mentioned? I mean even if it was just one measurement for 79,2 charge which is 2830 fps, it appeals to me kinda slow considering relatively light bullet etc. And the manuals values are faster like +120-150 fps, with shorter barrel etc.

 

[Rockdoc173]

That's the complexity and different opinions that make it a bit complicated for beginner tbh For example Berger's - either manual, when you call them, or web + Brian Litz consider these deep OCW as pointles with Hybrid bullets and advice to concentrate mainly on seating depth...then there's "Scott satterlee likes", Eric Cortina...whos running just basic velocity ladder and then seating depth...and don't care about grouping/POI at first place. For me reloading for like not even a year, and shooting for few months longer starting with velocities is obviously easier, but in the sense OCW somehow feels like the most logical way to go (but itself could be or is biased by shooter's skill)
second EDIT sorry.. doing OCW with magneto attached is nonsense, right? i guess one could not assume it would be changing POI constantly

I hear ya, handloading is a cesspool of opinions, witchcraft, and voodoo, with a little science and math mixed in somewhere. Don't fret though. The best way to overcome the head spinning is to read and then to shoot, rinse and repeat. Eventually, you'll look up and realize you have opinions as strong as anybody else lol.

Oh, and as far as a chronograph attached when doing the test, try this. It gets it off the barrel allowing you to shoot for accuracy and velocity. Mine works great.

 

[nn8734]

Thank you very much for all of the input and overall willingness to help. I will proceed the way you suggested in the last reply, I might do seating depth testing loads for both 79.2 and 79.4 charges. The current jump from the lands is 0,03 thou , I’m thinking doing 0,03 0,05 0,07 and 0,09 steps since hybrids seem to like longer jumps and 0,02 jump on previous testing wasn’t ideal. Does it seem reasonable ? Just one more thing, should I concert about velocities at all regarding all the factors I mentioned? I mean even if it was just one measurement for 79,2 charge which is 2830 fps, it appeals to me kinda slow considering relatively light bullet etc. And the manuals values are faster like +120-150 fps, with shorter barrel etc.

Id jump .050, .070, 090. If you cant get it to group at one of those I would look to rule you out as the source of the problem first. If its not you I’d consider swapping to a different bullet and/or powder (you should be able to get the 200g Berger should group .75 or better).

Re: slow velocity- Any over pressure signs at 80.4? If not see if you can push on it a little (80.6, 80.8, 81) but if you hit pressure you’ve reached the limits of your barrel with that mix of components. Your barrel may just be slow (it may also speed up a bit after a hundred rounds or so)

Again, wouldn’t worry too much about muzzle velocity as the target won’t care either. Id rather have a consistent, safe, reliable tight-shooting load with the stuff that’s available to me, all things equal.

 

[tstanek]

Id jump .050, .070, 090. If you cant get it to group at one of those I would look to rule you out as the source of the problem first. If its not you I’d consider swapping to a different bullet and/or powder (you should be able to get the 200g Berger should group .75 or better).

Re: slow velocity- Any over pressure signs at 80.4? If not see if you can push on it a little (80.6, 80.8, 81) but if you hit pressure you’ve reached the limits of your barrel with that mix of components. Your barrel may just be slow (it may also speed up a bit after a hundred rounds or so)

Again, wouldn’t worry too much about muzzle velocity as the target won’t care either. Id rather have a consistent, safe, reliable tight-shooting load with the stuff that’s available to me, all things equal.

The load we're discussing is actually the second one, first went up to 80,5 Gr with no pressure signs except of slight ejector marks at 80 and 80,5 gr, which are not present at this one at all. No bolt difficulties, or other important stuff. And yes, the recoil was heavier, but nothing serious, more like on the edge of being able to feel some difference there. I'm quite confident that even that .010 longer jump suits it better. I guess for my intended purpose of this load + rifle and mby considering a lil bit of more barrel life, it is not necessary to chase some higher velocies in general.

 

[nn8734]

I'm quite confident that even that .010 longer jump suits it better.

Where is this confidence coming from? What are you basing that statement on? You already shot the above OCW at .030, correct? That’s what’s written at the top of the target.

.010 won’t make a damn bit of difference. Start at .050 or .060 off and shoot another at .080 or .090. Then refine from there…If the groups don’t tighten, it’s either you or the bullet and barrel don’t get along with that powder, primer, brass combo at those charge weights.

 

[Evintos]

Thank you very much for all of the input and overall willingness to help. I will proceed the way you suggested in the last reply, I might do seating depth testing loads for both 79.2 and 79.4 charges. The current jump from the lands is 0,03 thou , I’m thinking doing 0,03 0,05 0,07 and 0,09 steps since hybrids seem to like longer jumps and 0,02 jump on previous testing wasn’t ideal. Does it seem reasonable ? Just one more thing, should I concert about velocities at all regarding all the factors I mentioned? I mean even if it was just one measurement for 79,2 charge which is 2830 fps, it appeals to me kinda slow considering relatively light bullet etc. And the manuals values are faster like +120-150 fps, with shorter barrel etc.

No, for velocity concern. Barrel length, lot numbers of powder, primer combinations, etc. can affect your real world velocity versus the manual.

I'm going to mention "positive compensation theory." Brief overview of it is -
1. More powder = more velocity, less powder = less velocity.

2. Slower velocity bullet impacts lower than higher velocity bullet, given the same barrel position as the bullet exits the muzzle.

3. The barrel oscillates when the round is fired; this we can see and basically prove with high quality slow motion footage. Different loads oscillate the same barrel differently.

4. The theory - it is possible to time the bullet exit with the oscillation so that the bullet impact at distance for a slower velocity bullet is the same as a higher velocity bullet.

Your groups #4, 6, and 7 (less so 7 since it starts to shift impact closer towards the center again) as @Doom has mentioned shows similar point of impact for a load that spans a whopping 0.8 grains; basically at the 5-6 o'clock position. You can refine this by doing load development in 0.2 grain increments from 79.2 to 80gr to narrow down the range. Hypothetically, if your results hold true for 79.2 to 80gr, your powder choice would then be 79.6gr and you can have a +/- 0.4 gr powder charge difference or whatever 0.4gr would be equivalent to in velocity. The result is your velocity SD/ES can be double digits and still have the same POI. Record average velocity to use for your ballistics calculations.

Do a gross seating depth in 0.005" increments after establishing the middle range of the powder load.

So starting from your jam minus 0.030" to get your CBTO of 2.890", the remainder will be in 0.005" increments for 2.885", 2.880", 2.875", 2.870", 2.865" so on and so forth.
You can fine tune the seating depth even further by doing 0.003" increments. CBTO 2.890", 2.887", 2.884", 2.881", 2.878" so on and so forth.