Wow! thank you for a very detail advice.
That's what we do here.
Here is how I came up with that COL for my CZ TS2. I have a Redding T7 press so I loaded a dummy round with no powder and no primer and slowly seating the the bullet by .001" or .002" each time and dropped it in the gun chamber until it freely spun. And from there I seated it .010" deeper.
• You have captured the spirit of our method, and it will work. It's a LOT more labor, but it will do.
However, 1.040" sounds incredibly short !• I want you to back off by 0.015", which doesn't sound like that much more, but for competition (even if it's simply outshooting your buddy so that he has to buy the beer) this has important allowances.
I've tried the other method by finding a spent case and place a bullet on it, black marker the bullet and insert in into the chamber ...ect, but I have no success with this method.
• There is no black marker used.
• Use the instructions in this document:
https://czfirearms.us/index.php?topic=103620.0• 95% of the test is all about finding the proper case that fits the bullet.
• You simply find a case that allows the bullet to fit snugly inside it (not tight; not loose), set that at a OAL of 1.200" and slide it into the chamber of the barrel. The bullet will stop at the rifling, and the case will continue to slide over the bullet. Then carefully slide the test cartridge out and measure it. It should come out closer to 1.075".... which then gets 0.015" subtracted from it.
Do this 4 or 5 times until you keep getting the same reading.• The first time will take 20 min. The second time will take you 5 min. The third time will take you 1 min.
The only load on VihtaVuori website which I think similar to RMR 124gr JHP Nuke is the 125gr Sierra JHP. So do you think I should starting my load at COL 1.040" over 3.2gr N320 and walk up. Please correct me if I'm wrong.
• The Sierra 125gr JHP load data is the best in that book. With N320, the load is 3.2gr to 3.8gr at 1.035".
• However, the 2018 Vit data shows loads slightly higher. I show that because I believe you'll be at 4.0 or 4.1gr to reach a PF pf 130.
• Our OAL will be longer than 1.035/1.040" so we can use that data. (You can always go longer, but never shorter.)
• We
always begin at the
Starting Load, which is 3.7/3.8gr in my data. You can work up from 3.2gr if you like.
• Then load 8-10 at 3.7gr, 8-10 at 3.8gr, 8-10 at 3.9gr, all the way up to 8-10 at 4.1gr. All of my data shows me using loads in the 4.0/4.1gr range with 1.060" OAL. So your shorter OAL (if that's where you stay) makes it hard to figure.
• Note that the velocity at Max Load is 1069fps in my book and 1070fps on the web page. Basically the same number.
That's important to know. •
However the chrono will help you. You must
STOP when the
Avg Velocity comes close to 1050 fps. So the
velocity tells you when you reach
Max Load for an unlisted load like yours. That's why you need the chrono !! Loads come and go, but velocity tells the truth.
• Use 1 brand of brass only.
When I do this, I shoot from a sand bag or other stable rest for the bottom of the pistol grip. Then I
Reset the chrono and shoot another load group at a new target. The target should be at 30 to 40 feet. (Use the exact same distance for every test you ever do.) In the end you'll have 5 sets of velocity data and 5 targets, one for each load. It's long and tedious work. But if you do it correctly you won't ever need to repeat it. Write all the data on the target, like...
Make sure your target has a black "bullseye" about 2" in diameter. I use a NRA target number
TQ-2 from
National Target Co.
https://www.nationaltarget.com/ Very cheap (100/$3.60) and very small. Easy to store. I have targets from 20 years ago because they are easy to store. I can compare testing done in 2005 with next week's test because they were all shot at the same distance.
Hope this helps.
