Glock chrony confusion

[HookedOnTheOutdoors]

I am currently working on SIG reloads again. I'm loading 7.5 gr of Unique with a 124 gr XTP and a CCI small pistol primer. The load seems fine but I noticed in my loading manual that the max velocity that I should get with that bullet / powder / primer combo is 1300 fps when using 7.9 grs of Unique.

I am using 7.5 grains of Unique with the same bullet and primer and average 1352 fps.

How is that possible?

should I reduce my load until I reach less than 1300?

I find it particularly disturbing because its the same powder / bullet / primer style. My thinking is that exceeding the max velocity when using the same components equates to excessive pressure.

The differences are that I am using a G32 Gen 4 which is something like .18 inches longer than the one used to develop the data... and of course the rifling in my Glock is different.

I did notice that if I go to 7.6 gr the velocity doesn't really change. I guess some of the powder isn't being burned?

Not sure what to do. I'm tempted to pull the bullets and load 7.2 instead.

I can say that I have shot 100s of these without issue. I'm just concerned that one day the barrel will decide to give up the ghost.

 

[mavracer]

All guns are they're own entity that's why you work up the load, are you getting any pressure signs? if not don't sweat it.

 

[Wreck-n-Crew]

All guns are they're own entity

That and it's not unusual for differences of +/- 60fps and more even in the same gun. Some of it may be chrony...some the round itself.

 

[HookedOnTheOutdoors]

No, no pressure signs that I have noticed. Primers look O.K., cases aren't cracked. There are some extractor marks and an occasional ejector dent. Another strange thing is the same load came in around 1300fps during the winter.

I can say that out of the 1000s of rounds of sig that I have fired, these seem a bit snappy. that is what is making me nervous.

My practice ammo used to be Rainier 124 gr CPHP with 7.5 gr of Unique. I now use the Berry's 124 gr HBTP (Hollow Base Thick Plate) and like them much better. The Rainier 124 gr HPs varied quite a bit in length and really didn't have the amount of bearing surface that I wanted for bullet retention.

I guess my real question is that I have read posts that said pistol reloads don't always show signs of overpressure before the barrel ruptures. Is this true? Or can I count on some warning before things go south?

 

[HookedOnTheOutdoors]

Something else I just realized.... All of the chrony work I did last winter was done with a different batch of Unique. Maybe that is why the results are varying? Maybe I should go back down to 7.0 and work my way up again?

 

[mavracer]

I would say that you're in the safe zone. Why drop it to 7 if there's no pressure signs with 7.5?
Unique is a pretty forgiving powder, it doesn't spike pressure like some others will. IIRC proof loads for 357 sig are 60,000 you're not getting anywhere near that without signs.

 

[jmr40]

It is not unusual for a Glock to shoot 50-100 fps faster than most other guns with the same loads and comparable barrel lengths. I think you are fine.

 

[Brian Pfleuger]

A few points:

1)Powder lots are not perfectly uniform. Their burn rates can vary at least as much as 5%. It is standard practice to back off max loads at least 5% when switching lots.

2)You have (apparently) only a single data source. You might as well make a velocity chart and roll dice and use it to guess velocity versus charge in your gun as to get it from that one source.

3)Technically, you do have a pressure sign.... excess velocity, or so you think.

Alliant's online data shows a max charge of 8.0gr Unique under a 124gr Speer GD set at 1.135", with a speed of 1,344fps for a 4.0 inch barrel. You'd have to compare the length of the XTP and your OAL to know how that compares to what you're doing. Multitude of sources gives more confidence.

You have to realize, you say you're using the "same bullet and primer" but you're not. You're not even using the same powder. There are slight variations between primer and bullet lots too. You're using a bunch of components WITH THE SAME NAME as what they used in their data.

You have a different chamber, different brass, different powder, different primer, different bullets, different barrel length, different shooter and different environmental conditions. It would be rather unreasonable to expect the same results.

 

[HookedOnTheOutdoors]

O.K... sounds like the general consensus is if it ain't broke don't fix it.

Thank you for all of the replies.

What does IIRC proof loads for 357 sig are 60,000 mean?

I understand what is being said about not really the same powder, primer, etc. I'm just trying to avoid blowing my gun, or my hand.

What made me recheck the data in the first place is how the recoil felt. It didn't seem "right" to me. Maybe I'm shooting too much 9... I don't know.

I ran into a problem with my sig reloads not wanting to chamber correctly right after I got my Hornady Lock N Load press. I spent a lot time trying to figure out what was going wrong and finally gave up. I took the .40 barrel out of my G23 Gen 3 and dropped in my G32. I carried it like that for a month an half or so.

I started missing my sig last weekend and pulled the dies back out. What I discovered was no matter how I adjusted the RCBS die in the Hornady press it would not resize the brass near the web of the case. I pulled out my Rockchucker and resized them in it, then ran them through the Hornady press to finish loading them. Worked like a charm.

Anyways, that may be the issue. I hadn't shot any sig in six weeks or so. I had been shooting some .40 and a lot of 9mm out of a LWD barrel.

I think I will just relax and enjoy having my favorite back.

 

[Brian Pfleuger]

What does IIRC proof loads for 357 sig are 60,000 mean?

IIRC means If I Remember Correctly.

Proof Loads are the loads that a firearm is required to handle in order to be in compliance with the organization that issues the "Proof".

SAAMI proof loads for .357sig are 57,500psi, I think, and normal max is 37,500. Proof loads are 50% over normal max, give or take slightly.

 

[HookedOnTheOutdoors]

So, I am not even close to blowing / or abusing my gun then. That's nice to know.

Why do they quote the max pressure in load data and not the proof pressure?

This really makes me wonder how people are blowing guns in their hands... not from reasonable reloads I bet. More like failing to check a barrel after a squib round or poor reloading practices.

I was being asked about my sources for reloading data. I have the current Hornady manual, Lyman manual and the little paper back books that condense them all into one. The problem is that the Hornady manual does not list a Unique load for the 124 gr XTP. Neither does the Lyman. The paperback does and that's the source that I was using. Aliant's website doesn't even have a Sig load for a 124 gr XTP. All they have is 125 gr Speer Gold Dot loads.

I wasn't really sure if I could use that data or not. It wasn't the same bullet name or weight.

Anyways... better safe then sorry. Thank you for the great replies.

 

[mavracer]

Why do they quote the max pressure in load data and not the proof pressure?

Max pressure is the safe working load and takes into account a buffer for vairiables like temprature case wall thickness and many other things.

This really makes me wonder how people are blowing guns in their hands... not from reasonable reloads I bet. More like failing to check a barrel after a squib round or poor reloading practices.

Yep most of the time it's cause the operator did something stupid.
There's a lot of practices you can get into that help prevent issues and it sounds as though you are using some.
Watching things like neck tension and the fact that you're using a rather bulky powder for you're application, you are getting a good case fill making it easy to see powder before seating the bullet and making a double charge impossible.

 

[Sevens]

This really makes me wonder how people are blowing guns in their hands... not from reasonable reloads I bet. More like failing to check a barrel after a squib round or poor reloading practices.

There are a few answers to this but the biggest problem when investigating these incidents is that most of all the key evidence is burned up, blown up and destroyed, or nearly so.

I would suggest that most people believe it happens because a handloader throws a double charge in to a case and doesn't realize that he's done so. It could be argued that this is more likely to happen when ammo is constructed with a progressive press, but the folks who load on progressive presses tend to not like that argument. The point is that when you hold a tray of 50 charged pieces of brass over a light source, you can visually check to see a very similar powder level. You'd NEVER see one extra full grain of powder, but you would see an empty and/or a double charge. With a progressive setup, it's a much bigger roadblock to getting a visual on the charged case. I have seen a proper powder cop die in action and it's a fine tool.

I would say that your own suggestion of a squib load followed by a fully loaded round is possible as well.

But I have long held a theory that I simply have no evidence to back, but only have seen literally hundreds of thousands of loaded rounds at my own bench and there is something I am extra vigilant about that doesn't seem to garner as much attention as I believe it should: case mouth tension/bullet pull

It's been my theory that many kabooms are the direct result of bullets not having solid bullet pull and being forcibly shoved deeper in to the cartridge case, ultimately raising the pressure in the extreme. And when coupled with certain particular conditions, the problem is exacerbated such that catastrophe is the result.

The lack of bullet pull in a semi-auto pistol round is not something that can (or should?) be rectified with a "crimp." It's a problem that should be addressed before it happens, not attempted to be corrected after the fact.

 

[HookedOnTheOutdoors]

I just came in from shooting some of the Sigs. Felt good. No issues. Go figure.

Plus 1 on the powder cop die. It doesn't really help much with my sig Unique loads because the powder is very close to the neck of the case. Its pretty easy to see. I load 40s with CFE Pistol and 9s with TiteGroup and the powder cop die is handy with them.

I tend to check each round with a beam scale when I am loading the self defense rounds. They are closer to max than my range ammo and I want to make sure I make them each as close to the same as I can. All I do is set the powder measure so that it throws slightly less than what I need then trickle the rest. Its a slow process but still much faster than using the Rock Chucker without a powder measure. For my range ammo I tend to chose a load that will be fine even if it is + or - a few tenths of a grain. I found that the powder measure that comes with the lock n load meters quite well and with the added benefit of the powder cop die I'm pretty comfortable with the loads that a produce.

I picked up some LongShot and some 200 grain XTPs for my Glock 20. Cant wait to try them..

 

[Nick_C_S]

Others pretty much covered the nuts n bolts of this.

My only addition is just my approach: I look up load data - usually in manuals. I load my test ammo by scaling each powder load, one at a time - so my data is consistent and accurate. I chronograph. I check for signs of pressure. I continue to the next step up (if safe and applicable). Repeat as needed.

Nowhere in this process do I compare my velocity with the manual's result. It's apples n oranges.

 

[HookedOnTheOutdoors]

Thanks again for all of the replies.

I'm not sure if anyone has followed the logic in my thought process but it appears to be flawed with variables any way.

Can we all safely say, without a doubt, that there will be warning signs on the brass before things go south? If so then I'm fine. I've only every seen 3 or 4 cracked brass that I can recall since I started reloading many years ago. Ditto on flattened primers. As with most of you I'm sure, I tend to error on the side of caution. That extra little velocity isn't worth the risk in my world.

 

[Brian Pfleuger]

Can we all safely say, without a doubt, that there will be warning signs on the brass before things go south?

Sorry but.... nope.

The weak link is sometimes chamber support, which will cause the infamous "Glock Smilie" but most guns (including newer Glocks) don't "smilie" brass.

The good news is that most guns are ridiculously strong. Forum member Clark has loaded many handgun cartridges to the point that the necessary recoil spring makes it so the slide can barely be actuated by a very strong man and the recoil is so painful that the gun is practically unshootable.

This is not to give you the idea that it's wise to exceed factory data because it's not. Unless you have the necessary knowledge and experience your only indicator may be the catastrophic disassembly of your firearm (and hand).

If you're concerned that you're over-pressure, just back off the load. What's the down-side? Less wear and tear on the gun, less recoil and more loads per pound of powder.

 

[HookedOnTheOutdoors]

You guys are awesome. Thank you for sharing.

I'm not going to pull these bullets but I do plan to back down some and do some chrony work before I load the next batch. I only have about a box and half left and it will give me an excuse to shoot more...

 

[WESHOOT2]

when I say "many", I mean "way too many"

many kabooms are the direct result of bullets not having solid bullet pull and being forcibly shoved deeper in to the cartridge case, ultimately raising the pressure in the extreme. And when coupled with certain particular conditions, the problem is exacerbated such that catastrophe is the result

This is the theory I adhere to, as I have investigated many.

Doubling a charge is always a possibility, too. Seen that, too.
But then again, I've seen issue ammo in duty guns (all highest quality), tailored handloads in expensive custom competition guns, and novice loads in every brand.

1 = case neck tension / set-back
2 = bad case / set-back or rupture
3 = charge weight or powder
4 = bore obstruction (I believe-but-cannot-prove THIS was the "2.7g Bullseye / 148g WC 38 Special" issue)
5 = 'other'
6 = I been wrong before