jwhittin

Glad it worked out. Thanks for asking the question. I learn a lot in these threads.

I'm going to take a swing at this as a relatively new CRO. The rules recommend collecting samples as randomly as possible. A true random sample of the 300 rounds, across two lots of reloads you intend to use, would result in 4 samples from each lot. That meets the wording in the rule book. I think using 8 rounds from the lot that has not passed a chrono test would be more appropriate to meet the intent of the rules (best way to ensure ammo meets declared PF). I look forward to hearing what the experienced folks say.

The ones I bought were advertised as frames from brand new unfired factory Sig P320s. I checked the serial number at the Sig Voluntary Upgrade Program webpage and they are recognized as being official Sig Sauer products. I guess the dealers realized they could make more money selling them as parts.

I bought two a month ago. Supply is gone. Saw one listed for $100. Found an M17 version for $50 at sigsauerparts (not affiliated with Sig). OP glad you figured out what the problem was. Have you talked to a Sig about the slide? Seems like it should last longer. I can see a barrel going bad at 78k rounds. Can’t hurt to call them. Sig might replace it.

Any update on your issue? Did you solve the mystery? I'm having accuracy issues with my P320 X-Series (GGP slide, Victory barrel, X-series grip) but I'm pretty sure its the barrel (poor fit). Will be troubleshooting more after Mile High Showdown this weekend. Didn't have much time to check it so I have to switch to Limited.

Reread Original post. what do you mean by this? What is the end result? Stove piped round? Is the round nose diving into the ramp? a picture would be helpful. Or a better description.

More likely to be OAL and/or bullet type (shapes). Is there anything you can surmise from what data you have now?

The problem with using only 3 samples is that the variation between measurement sets can make it very difficult to reach conclusions about your Avg Vel and STD with an acceptable level of confidence. If you take 3 or 4 or 6 data sets of 3 rounds each and calculate and compare the statistics (avg vel, STD, spread) for each set, you will see what I'm talking about. The results are all over the map. That is why I did the analysis and determined the Z parameter which relates 8 round measurement results to a confidence level of passing the PF check with the first 3 rounds.

You are correct about the overall process. I just wanted to improve the chance of passing using the first 3 rounds so not to stress out about it.

Per 37, one additional round is used. Could improve your chances or make things worse. It's a gamble. This is why I calculated the Z parameter using only 3 rounds. I didn't want to worry about what happens next.

Exactly!!! and that is the whole point of using the Z parameter and SD, not PF (as explained in my article). The Z parameter is based on the statistics of using 3 rounds for pass/fail (P/F). It takes into account your actual average velocity and SD ( measured using 8 rds) and provides a P/F confidence level as a guide). Once you go below 8 samples, you should use the T or Student distribution or your results will be skewed. Case in point, if you add 1SD to your avg velocity, as you stated the Normal dist tells you 68% will be within +/- 1SD (32% outside). But if the P/F criteria is determined using 3 rounds the Normal distribution doesn’t apply and your change of failing is actually about 44%. Not true. There are many different distributions who's statistics are well known (too many to list). The difficult part is determining which one applies to the case at hand. Final point - you will not see much variation in the measurements after you get 8 or so samples. The improvement is insignificant for our application. More than 8 to 10 samples is a waste of ammo. You can test this for yourself.

You only need 8 rounds to get a good statistical measurement (avg vel, SD). The question is what do you do with it? How does that relate to an official power factor check? You cant use your measured statistics directly to know if you will pass the official PF check. Here is why and how to use your measurements.

Nothing wrong with the Sig P320 X models.

Shoot what works best for you. Be cautious about trigger work - make sure you know how to do it and keep the trigger safe. Focus on training - recoil management and trigger control are HUGE! A light trigger can sure help but it can't replace this essential skill.

You should know or at least be aware. It does depend on what the gun is being used for but not the make or model. Look at the bullet trajectory which is determined by the bullet time-of-flight (how long gravity has to act on the bullet) and the mass. Take a look at a bullet trajectory calculator and you can get a better feel for the bullet path versus the POA at various distances. JBM is a good one as is shooterscalculator.

Nailed it! Made this mistake at our Local match. With no paint or way to identify shots, it just creates problems and potential for bad calls.

I have a bad case of leading. This post is really helpful! I'm also using the Dillon crimp die. I pulled some of my 0.356 dia reloads and they are 0.354. I will adjust my crimp and make sure the size is correct. Hopefully that will stop the leading. I adjusted and rechecked. Even without any crimping, the rounds come off the press at .380 mouth OD. I added a touch of crimp to keep it in spec and rechecked my bullets. They are still 0.356 dia now! Just need to load and shoot to see if the leading is gone.

I only briefly looked through the SRO. It did seem narrower (due to its round shape compared to the DPP). The SRO might be a tad bit taller. The DPP battery contact is held in place by tape (solder would just break) and has a tenancy to slide off the circuit board contact pads. I think the upgrade has a new board and has more adhesive area. I have the upgrade but I also added a thin plastic support between the battery contact and the rear of the housing to prevent the contact from sliding rearward off the circuit board pads over time. I'm at about 3K rnds and so far no problem.

There is an upgrade from leupold for the battery issue. I run the DPP On my Sig and I like the size of the glass. I run the 2.5 MOA and for the most part it’s bright enough. A little brighter would be nice. I don’t like the controls but the price was right.

For #1, see the notes on the right and left side of the diagram you reference.

Broadside - why do you say the RO interfered? Either its a penalty or not. No reshoot.

Sig X-Series weighted grip, Gray Gun competition trigger, and Gray Ghost Precision slide with a DeltaPoint Pro. Good setup. The GGP slide is light. That's something to consider if you are use to a heavier gun.

In general, everyone should show up at setup time and help setup at least one stage. After that you can do a early walk through.

These guys know what they are doing. Don’t know why they didn’t respond. Could try calling. If you have a chrono you could order some and check it.

I agree with echo, the locking lug edges look like they are rolled. This should not be happening if the barrel is fitted properly. Contract the maker and they should correct it.