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300 PRC update
- Thread starter DAVETOOLEY
- Start date
I think it was, but even their own stability calculator was showing 1/9 as sufficient. I'm sure this crowd is aware but Litz says faster twists aid stability and thus drag (especially entering transonic), which makes trajectories more predictable.
I am not sure if this is something for a new thread or just keep it here...
As a refresher, i am shooting a 300PRC, 30" barrel, 1:9twist, Berger 230gr HOTM and my average MV is 2972. I previously used a LabRadar to get my MV and have since moved over to the Garmin Xero. My scope is a Vortex Razor Gen III 6-36x56.
I setup my scope with a mount that allows me to set a 800yd zero with enough elevation to reach out to 2200yards.
I was at the one-mile on Sunday and the gun performed well. However, the predicted elevation was 46MOA but the actual elevation as dialed in on the scope was about 43.5 MOA. I received my calculation for windage using a Kestrel, Vortex Fury HD AB, and an app on my phone and all provided similar predictions of 46MOA. When i calculated what the correction would be to true the MV, the difference was appx 70fps (initial MV was 2972 and calculated correction was 3042MV). I previously noticed a similar correction needed back in March on the same Rifle/Scope during my first ELR experience.
My question is whether or not this is normal. I am guessing that the need for a correction could be caused by a number of different factors including differences in how the scope measures and other factors.
In the end, what I am trying to understand is what could be the cause of the difference and whether or not to manually update my MV in my calculation.
As a refresher, i am shooting a 300PRC, 30" barrel, 1:9twist, Berger 230gr HOTM and my average MV is 2972. I previously used a LabRadar to get my MV and have since moved over to the Garmin Xero. My scope is a Vortex Razor Gen III 6-36x56.
I setup my scope with a mount that allows me to set a 800yd zero with enough elevation to reach out to 2200yards.
I was at the one-mile on Sunday and the gun performed well. However, the predicted elevation was 46MOA but the actual elevation as dialed in on the scope was about 43.5 MOA. I received my calculation for windage using a Kestrel, Vortex Fury HD AB, and an app on my phone and all provided similar predictions of 46MOA. When i calculated what the correction would be to true the MV, the difference was appx 70fps (initial MV was 2972 and calculated correction was 3042MV). I previously noticed a similar correction needed back in March on the same Rifle/Scope during my first ELR experience.
My question is whether or not this is normal. I am guessing that the need for a correction could be caused by a number of different factors including differences in how the scope measures and other factors.
In the end, what I am trying to understand is what could be the cause of the difference and whether or not to manually update my MV in my calculation.
Have you tried truing the BC to match the actual MV and elevation you were using?
All I can say is those are incredible numbers. Berger's data shows they only got 2805fps with their max load of N565 (78.7, nearly a full grain more than your load). Yes, it was a 26" barrel vs yours at 30", but still that's a lot of difference. You're getting 167fps more than they did with 0.9gr less of the same powder, and truing a whopping 237fps higher at distance. Those numbers are higher than most 300 Normas are getting.
I’m getting 2960 out of a 28” barrel using 76.7 RL26 and 230 A-Tips. I’m using the AB mobile CDM and numbers are very close with observed dope. Switching between a G7 and CDM really only changes the data by about 1 MOA at that range.
Custom drag model is the way to go but truing the BC for the distance your shooting is actually what the bullet is doing during flight vs making up a velocity number to coincide with your elevation adjustment.
The following was using 230gr Berger HOTM, 77.8gr N565, CCI #250 Magnum Large Rifle Primers
| 300PRC one-mile at Clinton House SC | |||
| # | Speed (FPS) | Δ AVG (FPS) | Time |
| 1 | 2996.8 | 23.9 | 11:06:16 AM |
| 2 | 2963.7 | -9.2 | 11:08:12 AM |
| 3 | 2961.6 | -11.4 | 11:10:46 AM |
| 4 | 2978.6 | 5.7 | 11:12:22 AM |
| 5 | 2974.2 | 1.3 | 11:13:57 AM |
| 6 | 2954.0 | -19.0 | 11:15:49 AM |
| 7 | 2961.6 | -11.4 | 11:24:44 AM |
| 8 | 2972.9 | 0.0 | 11:27:12 AM |
| 9 | 2979.9 | 7.0 | 11:28:59 AM |
| 10 | 2961.2 | -11.8 | 11:30:59 AM |
| 11 | 2991.5 | 18.6 | 11:33:08 AM |
| 12 | 2967.6 | -5.4 | 11:36:53 AM |
| 13 | 2984.6 | 11.7 | 11:40:33 AM |
| AVERAGE SPEED | 2972.9 | ||
| STD DEV | 12.4 | ||
| SPREAD | 42.8 | ||
| SESSION NOTE | 0.0 | ||
| DATE | June 23, 2024 at 11:02 AM |
My preferred method is to put a cheap chrono behind the steel plate your shooting and at the distance you are shooting. I did this for my 6.5 CM and trued the BC to actual speeds. Now that I have the 300PRC new loads tested I might try the same thing at 1000yds next time I'm shooting.
Got a decent group at 1250 with 32.5 MOA on the Ivey base. I made new dopecards, working on my dial base. I'm looking for a place to stretch it to a mile now - somewhere in TN/AL/GA. I think all the events/days in Blakely are filled. I found some 230 Bergers and may load them up.
What bullet what would be best trans-sonic? 198 PV solids, 220ELDX, 230Bergers
What bullet what would be best trans-sonic? 198 PV solids, 220ELDX, 230Bergers
Looks like they are jamming the lands. Lucky to get it out without powder spill into trigger area. What round and barrel/rifle?
I think he was looking for .....
bullet grain, bullet type, COAL
Sorry for the bad pics. I took a pic of another phones screen, so it’s not nearly as clear and detailed as it actually was. Chambering doesn’t look too bad. But the rifling…..
The chatter runs the entire length of the barrel in all 6 rifle grooves.
The chatter runs the entire length of the barrel in all 6 rifle grooves.
Attachments
What makes it worse (and scary) is that the minor measurement that should be .300 dead nuts, we couldn’t fit a .295 in the barrel. It was too big!
I shot 5 rounds down this brand new barrel, and the fire cracking in the throat looks like 1000 rounds
I shot 5 rounds down this brand new barrel, and the fire cracking in the throat looks like 1000 rounds
2,761 fps average.
I'm not really aiming for a high velocity, as long as it's not too slow and as long as I can hit the target at a mile.
this group POI is a bit lower than the one to its left and its right. wouldn't that be a problem?
I didn't hit any pressure signs for any of those loads. the "max load" refers to what the manufacture websites recommend.
I was so excited when I saw that group. up until that point, I had shot about 100 rounds and the best groups were 0.7MOA. I began to think there might be something wrong with the barrel.
Yeah, but my point is that I don’t think that’s right. I have data sent straight from Berger for 230gr LRHT. With Retumbo their STARTING load isn’t much less than what you’re showing as “max”. For the 230, they start at 75.9 and go to a Max of 83.4. Obviously, your lighter 220gr bullet should allow the charges to be even higher. I started to bump into pressure at 80.0 with the 230, but you shouldn’t even be really in the ballpark at 76.4, especially with a 220.
I used the data from Hodgon. Yes I have seen that table from Berger. Not sure who is correct so I used the lower ones.
I think I will pick that for my seating depth test. One question, is it necessary a bad thing to see the vertical strings in this group and the two next to it?
For me, and I’m only slightly better than a novice, unless I have the rifle strapped to a sled, vertical stringing could be heartbeat, but that’s just my personal feeling on that. How much is the bullet and how much is my heartbeat?
If you can put it in a sled where you don’t factor into movement guaranteed, that’s when you’ll know for sure.
Just my 2c which is usually worth less than a dime
If you can put it in a sled where you don’t factor into movement guaranteed, that’s when you’ll know for sure.
Just my 2c which is usually worth less than a dime
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