jlow

What I meant by 3.2 grains of TG is not a light load is the load is not light enough to cause a pressure spike (i.e. Drewbeck's comments on page 1). It is clearly not a heavy load but it is also clearly a SAFE load that many people use, and which CANNOT cause the problem he saw. let's not argue over semantics but looking for the reason for the OP's problem.

The 3.2 grain of TG under a 147 grain bullet is not a light load. Most likely you have a step case with fatigue and resulted in case head separation which is not a dangerous situation. You get a little leakage but the real problem with this is normally the bottom of the case will eject but the neck stays in the barrel which makes loading another round impossible so a show stopper for your stage. Easy to remove – just run a brass bore cleaner into the barrel and pull it out.

Apart from an OAL that affects feeds with your mag and barrel, OAL is all about "barrel time". Barrel time is the time that it takes a bullet to exit the crown of the barrel once the round is fired. The reason this is important is because when a round is fired, the barrel rings like a bell due to the concussion. The concussion travels like a wave from the chamber to the crown where it is reflected back and this repeats. When the concussion is at the crown, it is the worst time for the bullet to leave the barrel because as one can imagine, the concussion can distort the crown and cause uneven gas leaks and the concussion can impart a slight uneven lateral force on the bullet in an unexpected direction. What is ideal is to have the concussion as far away from the crown when the bullet leaves the barrel i.e. during the quiet time. One can do this a number of ways. A crude way is to adjust powder weight which of course change the speed of the bullet, making it arrive at the crown at a different time. A finer way to do this is to change OAL. The reason is changing OAL changes the volume of the case which in turn affect pressure. Pressure of course affect again the speed of the bullet which of course allows you to time when the bullet arrives at the crown. This is well known for centerfire rifle reloading and a handgun is no different.

This topic is interesting because I have been sorting brass for precision handgun reloading. Just sorting a whole bunch of brass by neck thickness (Mitutoyo digital ball micrometer) I found relatively good consistency within each headstamp but between the different brands, of the 9 brands that I measured, neck thickness ranged between 10.25 to 15.48 thousands - that is a 50% difference which is huge and could be at least partially responsible for what the OP is seeing. One other interesting difference is consistent difference in case weight AND volume within a headstamp - Federal. It appears that most are around 60 grains but about 1/3 are around 55 grain which again is a huge difference (~~10%). No step in FC of course and that clearly will also affect volume. Coming from Precision rifle, I can tell you that case volume affect pressure. The less the volume, the more pressure. More pressure apart for safety affects MV.

Well I went out today in the cold and did a powder weight charge study with the Zero 115 gr JHP using Titegroup - pretty happy! Got two charge that gave me sub 2" 5 round groups at 50 yards. Best group was 1.8"!

Yes crimped primer. Of course, a lot of range pickup are reloads and so the crimp may be gone....

It affects accuracy by affecting neck tension, that in turn affects when bullet is released which affects when the bullet leaves the crown of the barrel. Look up OBT (optimal barrel time) on the web to understand why that is important. We are talking about very slight differences in when the round is released by the case, milliseconds.

Taper crimp also contributes to neck tension. ANYTHING that reduce the diameter of the neck and crimps down on the bullet contributes to neck tension. If you taper crimp ONLY to reduce the bell then yes, but if you crimp further then NO. Please read this article first: http://bulletin.accurateshooter.com/2015/06/precision-handloading-for-pistols-tips-from-the-usamu/ Note where it says: "Optimize the Taper CrimpOne often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of crimp and its effect on accuracy. Different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors. It is not unusual for our Shop to vary a load’s crimp in degrees of 0.001″ and re-test for finest accuracy."

First of all it depends on the bullet. If you are using a plated bullet, they you really only have a soft lead bullet with a thin film around it and too much crimp (which could be normal crimp for an FMJ) can squeeze the bullet so much that you get a bullet that is too small and don't get enough spin by the rifling and this is one good reason to get bullet tumble - I've seen it many time guys who goes from FMJ to plated and do not change their crimp. For a jacket bullet, crimp controls two things (apart from taking off the bell). One is it can prevent bullet setback in a mag fed gun especially if you use a taper crimp. Another effect is it affects how much pressure builds up before the bullet is released. Done in moderation, it allows you to adjust precision. However, done too much and wrong, you can get into a scatter node. Also keep in mind that with any crimp, the amount of crimp you get depends not only one what you dial in but the thickness of the brass case. Case wall thickness can vary by as much as 5 thousands and so using range pickup mix headstamp can get you a big variation in the degree of crimp with the same crimp setting.

Thank you!

This is a reloading question but it is specific for PCC and it was suggested by the guys in the reloading section that I aske it here. This bullet was recommended to me. I have done some research on the Hodgdon website and found a load for 115gr Speer Red dot JHP which I presume is close to the Zero's 115gr JHP. Looks like they recommend a COAL of 1.125" and titegroup range between 4.5gr (low) to 4.8gr (max) for an MV between 1,135 and 1,258fps. FWIW, I cannot do a plunk/twist test for this gun because of the generous chamber because the barrel is meant for a sub gun. Anyone use something like this and I wonder how well that works?

Hi-Power Jack you are correct. One cannot do a plunk and twist test on this gun as there is a ramp on the start of the rifling and even a very long OAL round does not touch the rifling. The reason is this is meant to be a sub gun and there is more room for gas to escape. Thanks for your suggestion, I will ask this question in the PCC section.

Thank a bunch for your input Aircooled6racer! Can you tell me what grouping size can you get at 50 yards?

This bullet was recommended to me. I have done some research on the Hodgdon website and found a load for 115gr Speer Red dot JHP which I presume is close to the Zero's 115gr JHP. Looks like they recommend a COAL of 1.125" and titegroup range between 4.5gr (low) to 4.8gr (max) for an MV between 1,135 and 1,258fps. Anyone use something like this and I wonder how well that works?

Thanks a bunch! Will do.

Trimming based on advice from here under "Importance of uniform COAL" which makes good sense to me. http://bulletin.accurateshooter.com/2015/06/precision-handloading-for-pistols-tips-from-the-usamu/

Well that is of course the NORMAL reason to do chamfer and deburr, but in this specific case since I am doing a taper crimp, those operations will thin the lip of the case affecting the degree of crimp.

For those reloading for bulleye shooting, I understand the need for trimming to obtain a consistent crimp. My question is should the case be chamfered and deburred after trimming? In rifle, this is a must, but at least considering that with a 9mm, the bullet will be held by a taper crimp, chamfering could affect the crimp in a inconsistent manner?

Looks guys, I appreciate the input, but I am not here looking for advice on shooting, a new load, new bullet, new powder. I am just looking for feedback from people who have used this taper crimp die - how you optimize it and how well it works.

It's a SIG MPX and I have both a 4.5" and an 8" barrel, so it is actually a sub gun, just semi-auto. The advantage of the 147 is of course no sonic crack as I also intent to also use a can. FWIW, the Precision Delta 147 reloads I currently shoot (and I am trying to optimize here) I can hit a reduced size USPSA target 75 yards away shooting off hand with an off the shelf factory tactical handgun with a 5.25" barrel no problem. I am of course not shooting bulleye with this gun but I would like to shoot this gun in a 2-gun match (for practice) where there are frequently targets out to 100 yards. Now I can hit those easily with an AR shooting cheap Russian ammo, but I would just like to reduce the MPX 4" groups to 2" groups. FWIW, I have shot this gun in those 2-gun matches before and come in the middle of the pack against ARs, but it would be nice to do better (like when I shoot an AR) and be a bit more accurate. Not trying to shoot 1/2 MOA groups as I have plenty of centerfire rifles that can do that.

For good precision, it is always a combination of a number of things and not one thing. Obviously the shooters skills, quality of the barrel/rifle and components, and of course the load. Being a precision rifle shooter, I am completely aware of these and so although I appreciate the reminder, I am here to look for information on the reloading process not the rest.

Yes, IDescribe is correct, we are talking about a taper crimp die not a seater. Yes, one reason for the micro-adjust is to be able to make changes easily, but ease of adjustment is not the point here. The question is improvement in precision of the rounds at target and at 50 yards. I am using Delta Precision 147 gr FMJ and so they are sub sonic so no problem dealing with transition to sub-sonic. My understanding is adjusting crimp allows you to adjust the timing of the release of the bullet from the case, this I presume adjust “barrel time” i.e. the time the bullet exits the crown of the barrel which allows you to exit at the time when barrel harmonics are ideal. These last bit is from precision rifle reloading so I apologize if I am getting into technical outside of what most pistol shooters deal with. Mostly I think only bulleye shooters deal with the precision that I am looking for.

Anybody use this to significantly improve 9mm group size at 50 yards? Looking to improve precision for PCC. I have quite a bit of experience in precision rifle reloading, similar for regular 9mm pistol reloading, but no experience with precision pistol reloading. Would appreciate hearing from someone who as done this.

Thanks! That makes sense. Much appreciated!

Thanks! This is what I had to do!