pointing gun down before chrono leads to low velocity

[motosapiens]

This is shooting 4 grains of clays with a 230 grain bullet in .45.

Well, I learned something. I was trying to kill multiple birds with one stone, and using my chrono tests to also draw and shoot 5-6 shots into a 2" circle at 7 yards, for practice on accuracy. I kept getting big SD's, and eventually noticed that the first shot was typically 5-10% lower velocity. In my diagnosis, I also found that lack of crimp was causing some variance as well. Anyway, today I confirmed experimentally that if i point the gun down, so that the powder all collects away from the primer, I get lower velocity for the first shot. For following shots, it appears that recoil spreads the powder back out so velocity goes back to normal. I've never noticed this issue with .40 (shooting 3.1 gr of clays), so maybe it's just due to the large case volume of .45 and the small amount of powder.

It didn't appear to make a significant difference if i tipped the gun back before each shot, compared to just holding it flat. The only thing that appeared to matter is to not hold it down before the first shot. Hopefully this info will save someone else some worry.

[Guy Neill]

Standard ammunition testing by SAAMI specifies the powder be next to the primer. Rounds are actually rotated to end up bullet up, and then kept as vertical as possible while loading into the pressure gun.

Power forwarrd, against the bullet will normally give lower velocities.

Guy

[motosapiens]

Standard ammunition testing by SAAMI specifies the powder be next to the primer. Rounds are actually rotated to end up bullet up, and then kept as vertical as possible while loading into the pressure gun.

that makes sense from a standardization perspective. But what I'm really interested in is the policy of the chrono stage at a major match. USPSA doesn't really address that, so there's nothing to stop someone from tilting the barrel down (intentionally or inadvertently) before each shot. I think the IDPA chrono procedure specifically addresses that issue.

[kevin c]

Standard ammunition testing by SAAMI specifies the powder be next to the primer. Rounds are actually rotated to end up bullet up, and then kept as vertical as possible while loading into the pressure gun.

that makes sense from a standardization perspective. But what I'm really interested in is the policy of the chrono stage at a major match. USPSA doesn't really address that, so there's nothing to stop someone from tilting the barrel down (intentionally or inadvertently) before each shot. I think the IDPA chrono procedure specifically addresses that issue.

I've never seen any chrono officer point the gun down prior to shooting. AAMOF, since most of them are seated, shooting over a rest sitting on top of a table, it'd be pretty awkward to do safely without taking a lot of extra time that may not be available (several matches I've gone to even have the chrono check share a time slot with a speed shoot stage on the same bay, so time is short).

I think that IDPA tilts the gun up as part of their "benefit of the doubt goes to the shooter" philosophy, but, personally, I don't see why any match should go out of their way to accommodate marginal ammo.

[motosapiens]

I think that IDPA tilts the gun up as part of their "benefit of the doubt goes to the shooter" philosophy, but, personally, I don't see why any match should go out of their way to accommodate marginal ammo.

I would see it more as standardization and repeatability rather than 'accomodating marginal ammo'. Why not use similar procedures as the SAAMI specs require?

[kevin c]

I think that IDPA tilts the gun up as part of their "benefit of the doubt goes to the shooter" philosophy, but, personally, I don't see why any match should go out of their way to accommodate marginal ammo.

I would see it more as standardization and repeatability rather than 'accomodating marginal ammo'. Why not use similar procedures as the SAAMI specs require?

Pointing the gun up or down is not SOP in a scenario/COF in either IDPA or USPSA (it might even end your day if the muzzle ends up in an unsafe direction). If one makes the assumption that you're trying to duplicate field conditions, then tilting up or down would actually be counter to that particular intent.

But I don't make the rules. I'll do what the rules say, and expect the same of the Chrono RO, and that he be consistent in his application of whatever method he uses, authorized or not. I will say, though, that I'd rather load to 135 PF (as I do for SSP/Production) than load to pipsqueak levels and then pause between each shot on an array of steel to tilt my gun up and get those extra couple FPS.

Edited August 16, 2013 by kevin c

[cautery]

I think that IDPA tilts the gun up as part of their "benefit of the doubt goes to the shooter" philosophy, but, personally, I don't see why any match should go out of their way to accommodate marginal ammo.

I would see it more as standardization and repeatability rather than 'accomodating marginal ammo'. Why not use similar procedures as the SAAMI specs require?

As a USPSA RO the whole "Benefit of the doubt" deal gives me the "willies".

Here's my question... Why on earth would you work up a load using a powder that fills so little of the case volume? Especially, if you want conisitent SD/ES or are hangin' onto Major (or worse the power floor) by the skin of your teeth.

I use Titegroup in my 40S&W ammo and it doesn't fill the cases as much as I'd like, but I make allowances for the chronoman... I don't try to run 165 on the dot...

Choose a different powder... I would make a HUGE stink at any match I was at (as a shooter OR RO) if they started dicking with the chronoman trying to institute some BS gun manipulation procedure...

[kevin c]

...As a USPSA RO the whole "benefit of the doubt" deal gives me the "willies"...

...I would make a HUGE stink at any match I was at (as a shooter OR RO) if they started dicking with the chronoman trying to institute some BS gun manipulation procedure...

I'm guessing you don't shoot much IDPA? Chrono at an IDPA sanctioned match is bound to follow the rules, which actually specify tilting the muzzle up prior to each shot over the sensors. It might be BS in your book, but not in IDPA's. Same for the "benefit of the doubt goes to the shooter" in IDPA scoring. It's right there in black and white from HQ.

[cautery]

...As a USPSA RO the whole "benefit of the doubt" deal gives me the "willies"...

...I would make a HUGE stink at any match I was at (as a shooter OR RO) if they started dicking with the chronoman trying to institute some BS gun manipulation procedure...

I'm guessing you don't shoot much IDPA? Chrono at an IDPA sanctioned match is bound to follow the rules, which actually specify tilting the muzzle up prior to each shot over the sensors. It might be BS in your book, but not in IDPA's. Same for the "benefit of the doubt goes to the shooter" in IDPA scoring. It's right there in black and white from HQ.

Mmmm.... nope.

I don't doubt you at all that those things are in the IDPA rule book. It was not my intention to cast dispersions on any gun sport. Whatever gets folks to shoot is great.

My reference to "BS" was my opinion as it relates to the thankless and exacting job of being the chrono guy/gal. They have enough to do without injecting additional (and IMHO, needless) procedural requirements into the mix.

I'm not well-versed in the rules for IDPA, in fact, I don't think I have ever read the entire rulebook thru word for word. My opinion is based on my experiences and training. And my opinion is based on a simple philosophy in this regard. The shooter is responsible for his conduct on the range and making sure that his equipment is safe, functional, and meets the minimum standard set forward in the rules for the "game".

In IPSC, there is a power floor and a power threshold separating minor and major. It is a critical factor in scoring. In our book, there is no provision for "only requiring power factor/floor to be met under a single/special set of circumstances.... The weapon is used in multiple attitudes, angles, etc... and the ammo should function and meet standards under all required circumstances.

BTW, Hodgdon advertises Titegroup specifically to be consistent no matter how the powder is oriented in the case upon ignition. I love it. YMMV.

So, far from "picking" on any game, my point is that perhaps one shouldn't ride so close to the edge unless you are willing to risk falling off.