Reading pressure signs/other problems

[osprey]

A chrono is the best tool to evaluate press. Reading brass can be problematic. Consider a magneto speed chrono. It can be used at ranges without going downrange and is not effected by light conditions.

 

[awshoot]

A chrono is the best tool to evaluate press. Reading brass can be problematic. Consider a magneto speed chrono. It can be used at ranges without going downrange and is not effected by light conditions.

I have a magnetospeed and it works great for measuring velocity from rifles (or a pistol with a long exposed barrel, but not semi-autos or short revolvers). An even bigger positive is that you don't have to close down the range for the amount of time it takes to set up a shootable chronograph. It's a very convenient system.

The downside is that you're strapping something to your barrel which changes the point of impact and may (*) change the harmonics of the barrel too, meaning it may screw up any information you get from your target and the group size. With a shootable chrono or the labradar, there is no issue with collecting velocity data and group size information simultaneously because nothing touches the barrel.

The practical effect is that magnetospeed requires additional test shots (EDIT: if you believe it changes precision). The two ways to address this are to shoot without it, find the load, then make a set for velocity testing. Or to get data while going through the loads, make extra test shots, use some for the magnetospeed, take it off, then use the rest to print targets. Then put it back on to start the next series, take it off to finish that series, etc. etc.

(*) This is a topic with a dispute. Some feel it affects group size, others that it only affects point of impact. If it only affects POI, then what you print on your target is valid data. POI doesn't matter -- you can just adjust your scope later. does magnetospeed affect barrel harmonics at DuckDuckGo

 

[osprey]

I have a magnetospeed and it works great for measuring velocity from rifles. The downside is that you're strapping something to your barrel which changes the point of aim and may change the harmonics of the barrel too, meaning it may screw up any information you get from your target and the group size. With a shootable chrono or the labradar, you can collect velocity data and group size information simultaneously because nothing touches the barrel.

The practical effect is that the magnetospeed takes an extra trip to the range -- one (or more) to print your targets and select a load, and then another with the selected load to test velocity. If you want velocity data while testing, the magnetospeed is not ideal. I think the OP wants simultaneous data because he is just starting out and hasn't developed a feel for what is going to be OK yet. For that, it's labradar or a shootable one.

I have found it changes poi slightly but I have not found it to significantly effect group size. I just make sure final sight in is done without magneto speed after I am happy with all parameters of load. Here is an example of this poi shift from yesterday. Both groups are similar size but magneto speed group is slightly lower and to the left.

 

[awshoot]

@thermox9898 -- when you adjust your scope for testing loads, have it set to miss the bullseye. You want to have a clean bullseye to aim at and if you shoot it wholly or partially, you will get noise in the data from shifting point of aim.

 

[awshoot]

I have found it changes poi slightly but I have not found it to significantly effect group size. I just make sure final sight in is done without magneto speed after I am happy with all parameters of load. Here is an example of this poi shift from yesterday. Both groups are similar size but magneto speed group is slightly lower and to the left. View attachment 760677

Nice results. For me I have found that it actually tightens up my groups most of the time which is why I do separate velocity and precision tests. Using the magnetospeed has actually caused me to consider getting some of those weights you attach to the barrel for that purpose.

 

[thermox9898]

A chrono is the best tool to evaluate press. Reading brass can be problematic. Consider a magneto speed chrono. It can be used at ranges without going downrange and is not effected by light conditions.

I was thinking a labradar, actually. For the price of a magnetospeed might as well spend the extra couple hundred and get the labradar. I see a lot of reloaders on youtube using it with good results. Is the magnetospeed more accurate?

 

[thermox9898]

@thermox9898 -- when you adjust your scope for testing loads, have it set to miss the bullseye. You want to have a clean bullseye to aim at and if you shoot it wholly or partially, you will get noise in the data from shifting point of aim.

Solid advice, I will use that.

 

[awshoot]

I was thinking a labradar, actually. For the price of a magnetospeed might as well spend the extra couple hundred and get the labradar. I see a lot of reloaders on youtube using it with good results. Is the magnetospeed more accurate?

I think the magnetospeed predates the labradar and solved the "shooting the chrony" problem and the "close the range so I can take 5 minutes setting up" problem and continues to do so at a price point either 1/3 or 1/2 of a labradar.

I'm sure both are as good as reloaders need accuracy wise. Same is true with the shootable type.

 

[thermox9898]

I think the magnetospeed predates the labradar and solved the "shooting the chrony" problem and the "close the range so I can take 5 minutes setting up" problem and continues to do so at a price point either 1/3 or 1/2 of a labradar.

I'm sure both are as good as reloaders need accuracy wise. Same is true with the shootable type.

Lol you guys have me awful nervous about shooting my chrono now. I'm gonna draw a box on a paper target and put it 15ft away and make sure I know where this thing is shooting before I shoot through the chrono, haha

 

[awshoot]

Lol you guys have me awful nervous about shooting my chrono now. I'm gonna draw a box on a paper target and put it 15ft away and make sure I know where this thing is shooting before I shoot through the chrono, haha

It's surprisingly easy to do even if you can shoot 1" groups at a 100 yards.

What I do is set up my bag with some sort of stick on it as a substitute for the rifle set at about the height a rifle will be, drop the chrono on my way out to the target stand, and when I get to the target stand turn around and line up with my bag before tacking the target. Then I walk back and get behind the table, aim the stick at the target and note where the chrono is in relation. Then walk out and move it around a bit. Then go back behind the bag and sight down the stick through the chrono, then go around and move the chrono a bit. rinse and repeat till good. A broom handle makes a great stick for this purpose.

EDIT: then use a real rifle after the range is made hot. Then annoy everyone telling them I need to make another adjustment. You'll want to sight down the barrel like a shotgun -- looking through the scope you probably won't see the chrono.

 

[TTSX]

To keep with the theme of the thread, I blew a primer today. Bolt was very stiff and there was an unmistakably unique smell. I think the bulk bullets I bought are much heavier than what I ordered. This happened on a mid level charge, several grains below max listed. Surprised the heck out of me. Get to pull down the remaining 3 rounds and see WTF.

 

[edzz]

It's surprisingly easy to do even if you can shoot 1" groups at a 100 yards.

What I do is set up my bag with some sort of stick on it as a substitute for the rifle set at about the height a rifle will be, drop the chrono on my way out to the target stand, and when I get to the target stand turn around and line up with my bag before tacking the target. Then I walk back and get behind the table, aim the stick at the target and note where the chrono is in relation. Then walk out and move it around a bit. Then go back behind the bag and sight down the stick through the chrono, then go around and move the chrono a bit. rinse and repeat till good. A broom handle makes a great stick for this purpose.

EDIT: then use a real rifle after the range is made hot. Then annoy everyone telling them I need to make another adjustment. You'll want to sight down the barrel like a shotgun -- looking through the scope you probably won't see the chrono.

And all that rigmarole would have helped me in my ill fated attempt to chrono a round from my .32 acp Seecamp how?
Ya it was one of those brain fart days.
Took the parts home, fixed it and tested it with an air rifle, all good. Set it on the back bumper of my SUV went inside asked my wife what she wanted from the store. Came out side and headed for the store, as I backed out of the garage the chrono fell off the bumper and I'll let you guess what happened next.

 

[awshoot]

... Took the parts home, fixed it and tested it with an air rifle, all good. Set it on the back bumper of my SUV ... I backed out of the garage the chrono fell off the bumper and I'll let you guess what happened next.

You did your best to cheat fate, but fate always wins.

EDIT to add -- at least you shot yours with a pistol that's likely hard to shoot giving you an excuse. I shot mine with a pretty accurate rifle so it was 100% on me.

 

[thermox9898]

So I managed to succesfully chrono my 308 rounds today. I suspect this Tavor is pretty severely overgassed, because it launches cases about 10 feet and is absolutely vicious on the brass. I fired about 30 rounds of two different brands of ammo through it and had pretty severe ejector and extractor imprints on the caseheads. Primers looked fine to my eye, definitely flatter but I'm pretty sure to a normal degree. I got about 2600FPS out of the 16" barrel. The factory ammo had about 2800FPS on the box, so checks out since I'm sure they tested out of a much longer barrel.
I'm SO glad I brought factory ammo because if I hadn't seen all the damage to the cases on the factory stuff before I shot my handloads I would have been pretty freaked out.
My handloads were 40 rounds total, groups of 5 rounds in .5 grain increments. First group was a little over starting charge and last group was a little under max. I stopped at my second to last group because I was getting primer cratering and the brass was just getting beat to crap. Even my lightest load cycled the gun no problem. I tried running it on "suppressed" mode but it wouldn't cycle the gun even with the hotter rounds.
I'm exhausted and haven't entered my numbers into excel yet, I will post my data tomorrow along with some pictures of some caseheads.
I suspect this gun could use some sort of adjustable gas block. Not sure if they even make one for the Tavor 7 yet. I will have to do some research. IDK how damaged a casehead can be from extraction/ejection but I doubt some of these would be good for very many cycles even if they already aren't ruined.

 

[Certaindeaf]

Didn't really read the whole thread but signs of reading pressure are headaches and chewed pencils.

 

[osprey]

Didn't really read the whole thread but signs of reading pressure are headaches and chewed pencils.

Pressure signs can be caused by many things, obviously including overpressure. Many times it is other factors related to the reloading process and the individual platform. Gas guns are the worst of the bunch to discern. Always good to be vigilant and watch for signs but velocity is the true sign. If you are getting over book velocity accounting for barrel length you are overpressure no matter what the brass says! With todays tools for landing a bullet on target max velocity is rarely needed and by happy coincidence accuracy nodes seldom reside at max loadings. To the OP, many auto battle rifles are overgassed to provide consistent function with all ammo and all field conditions. For this reason I have gravitated to the FAL as it's adjustable gas system is a reloader's dream in regards to maximizing brass life. Good luck and stay safe!

 

[awshoot]

.... IDK how damaged a casehead can be from extraction/ejection but I doubt some of these would be good for very many cycles even if they already aren't ruined.

Next time you're at the range on a busy day, watch the people with bolt actions. The one's who yank the bolt and send the case flying off to hit the pavement -- 95% chance they don't reload. The ones who are reaching over their scope to block the ejection port with their week hand while extracting? 95% chance they do reload. The ones with custom actions that eject to the opposite side of the bolt handle? 100% chance they reload.

As a reloader, you're going to care about your brass a lot more than people who don't. The issue with semi-autos though, is that they are machines designed to behave like people who don't reload and chuck brass everywhere. Nothing you can do about it. It probably will hurt the brass to some degree. The plus side, at least in normal times, you can usually find all the .223, .308, and 9mm brass you need for free at any range on any day.

 

[CLT65]

Way back when I was a new reloader, I was led to believe that flat primers were the be-all and end-all of pressure signs. Over the decades I came to realize that they are a very unreliable sign.

Here's one for example. Scary high pressure, right?



Well, actually not. I found this one on the ground at the range. The brass was bulged such that it was clearly fired in a 9mm. I believe that due to the poor headspace, the brass moved forward in the chamber when hit by the firing pin, the primer backed out upon detonation, and then once the bullet hit the rifling the chamber pressure pushed the case fully back, flattening the hell out of the primer. The actual chamber pressure would have been less than a normal 9mm round.

I've seen this with revolvers too. I once had a S&W 686 that would flatten primers on everything because of this.

 

[thermox9898]

So I managed to enter my chrono data into excel today. Was super busy and didnt have time to take pics of cases but I will do that this week.

Factory Hornady Superformance
Hornady 165Gr SST
Shot #	Velocity
1​	2673​
2​	2696​
3​	2678​
4​	2675​
5​	2658​
6​	2680​
7​	2677​
8​	2672​
9​	2677​
10​	2675​
Avg	2676.1​
Std Dev	9.267026​
ES	38​

Factory Hornady Whitetail
Hornady 150Gr Interlock
Shot #	Velocity
1​	2665​
2​	2631​
3​	2601​
4​	2641​
5​	2611​
6​	2624​
7​	2656​
8​	2646​
9​	2615​
10​	2623​
Avg	2631.3​
Std Dev	20.4779​
ES	64​

With both types of factory ammo I got pretty bad extractor and ejector marks on the brass. Deep marks, large burrs. Pretty unacceptable in my opinion.
And here's my handloads:

Handload
Hornady 150Gr FMJBT
43.0Gr W748
Shot #	Velocity
1​	2615​
2​	2657​
3​	2593​
4​	2544​
5​	2585​
Avg	2598.8​
Std Dev	41.46324​
ES	113​
notes: cases look good much better

Handload
Hornady 150Gr FMJBT
43.5Gr W748
Shot #	Velocity
1​	2631​
2​	2669​
3​	2590​
4​	2630​
5​	2667​
Avg	2637.4​
Std Dev	32.46999​
ES	79​
notes: cases still look good

Handload
Hornady 150Gr FMJBT
44.0Gr W748
Shot #	Velocity
1​	2692​
2​	2642​
3​	2669​
4​	2665​
5​	2672​
Avg	2668​
Std Dev	17.87456​
ES	50​
notes: cases a little worse

Handload
Hornady 150Gr FMJBT
44.5Gr W748
Shot #	Velocity
1​	2725​
2​	2742​
3​	2718​
4​	2698​
5​	2715​
Avg	2719.6​
Std Dev	15.97811​
ES	44​
notes: cases even worse

Handload
Hornady 150Gr FMJBT
45.0Gr W748
Shot #	Velocity
1​	2737​
2​	2777​
3​	2755​
4​	2722​
5​	2711​
Avg	2740.4​
Std Dev	26.30209​
ES	66​
notes: cases about as bad as factory ammo

Handload
Hornady 150Gr FMJBT
45.5Gr W748
Shot #	Velocity
1​	2814​
2​	2776​
3​	2779​
4​	2801​
5​	2786​
Avg	2791.2​
Std Dev	15.99062​
ES	38​

Handload
Hornady 150Gr FMJBT
46.0Gr W748
Shot #	Velocity
1​	2826​
2​	2799​
3​	2787​
4​	2778​
5​	2816​
Avg	2801.2​
Std Dev	19.86706​
ES	48​

Handload
Hornady 150Gr FMJBT
46.5Gr W748
Shot #	Velocity
1​	2883​
2​	2856​
3​	2850​
4​	2885​
5​	2841​
Avg	2863​
Std Dev	19.91231​
ES	44​

At no point did I see anything super alarming but towards the end of the ladder the brass started to get a little more beat up than the factory ammo
Like I said I'll post up some pics tomorrow, I'm sure you guys will have some thoughts on it.

 

[thermox9898]

Someone mentioned either here or somewhere else, that my ejector/extractor marks may be from excessive headspace. Because I didn't have any fireformed brass out of this gun yet, I modeled shoulder bump off of the factory rounds I had with a headspace comparator. I knew this was going to be more headspace than I eventually want to have, but I wasn't sure where to start and I figured going off a factory round would be a sane place to start. Does it take more than 1 firing to fireform brass or should the fired brass from this last outing represent my chamber pretty well? I think it's important to note that my lowest charges had very little marks on the caseheads.