Velocities all over the place

I

ivo

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First of all I'm shooting a PGW Coyote in 7WSM, 24" barrel with Winchester brass, Reloader 25 and Berger 180s. The groups are pretty good averaging in the .4s and .5s(MOA).

I am using between 66 and 67 grains of RL 25 and am getting huge velocity fluctuations and wierd patterns that don't make any sense. Here are my loads and corresponding velocities:

66.3 gr RL 25

2945
3220
3112
3196
3167
avg 3128
ES 275

66.6 gr RL 25

3142
3082
3057
3102
3039
avg 3084
ES 103

66.9 gr RL 25

3030
2988
2993
3056
3037
avg 3020
ES 68

The extreme spreads are really bad and the average velocity makes no sense because as I go up in powder the velocity gets slower!

To answer some questions in advance:
1.)These results have been repeated and are not just from one outing.
2.)I have used both CCI BR2 and FED 215M primers with the same general results.
3.)The chronograph seemed to be working fine before but I haven't tested it with another rifle since these results.
4.) I tried fully preped brass and basic prep brass with the same results.
5.) My other groups saw velocities up to 3394 FPS with the last load:eek:.

I don't know what to do at this point. I will check the chronograph with another rifle maybe on monday, other than that where should I start?

Ivo
 
I've had what I thought were weird results before and they were just about always right. I would say you are having pressure issues of the wrong kind, maybe too low.


I think reloder 25 is way too slow for a 7mm WSM. I used to H4350 with a 300 WSM with excellent results, re25 is too slow.
 
x2 Ganderite. Chronies can be a pain in the butt. If you're getting groups like that, your velocities must be very close and consistent.
Varying degrees of light will also effect the readings.

Back in the day, I used to mount a couple of 12 Volt bulbs over the screen, under a cover. Tests were done at least 20 feet or more from the muzzle. I finally quit using them. If the groups are where I want them and consistent, that's where I want to be. Velocity is nice but not nearly as important as accuracy.
 
Poor choice of powder would be my first guess.

If your chronograph is correct you are running pressure that could qualify you for a Darwin award....

Look up a reloading manual you will see your loads are just about right for a 7MM RUM and 150 grain bullets?!!?? :eek:
Just because you don't feel anything in the bolt drag or see it on the case doesn't mean it extreme pressure isn't there.
I would think you should be looking for around 2800 fps?

You would be better off with RL-22, H-1000, or IMR-7828.
 
Look up a reloading manual you will see your loads are just about right for a 7MM RUM and 150 grain bullets?!!??
Click to expand...

It is you that needs to look in a loading manual,150gr loads for the 7mmRUM max out at 88gr of R-25 in my new Nosler manual.175gr loads max out at 86gr.The 7mmRUM will safely drive a 175gr bullet to 3300fps,and a 150gr bullet to 3500fps.

However your comment on the velocity expected for the 7mmWSM is quite realistic.2800fps would be a more reasonable velocity for a 180gr bullet.
 
Check your chrony.

If you must use RE25, also try a hotter primer. Sometimes this helps with velocitiy fluctuations. Maybe some WLR.

But check your chrony.
 
try cci 250 primer.

put powder in a drawer with a 60 watt bulb for a few days which should dry it out. if you suspect bad powder. never had damp powder but have shot some older loads which weer stored damp and they were 3 inches low at 100
 
my guess is that you are running pressures too high and the powder is peaking.

I used Re25 in my 7RM and it was awesome but my loads in a larger case and lighter bullet were LESS then what you are using with the 180gr.

Consider a velocity around 2900fps and I bet all this issues will fade. But that will be a case that is very low in charge density.

I am presently using Retumbo in my 7RM behind 180's and it is working very nicely. I would suggest you change to a slower powder and try for around 2900 to 3000fps MAX.

hope this helps.

Jerry
 
MP, I'm a bit surprised by your answer. Retumbo and Re25 are almost identical in quickness. The difference between the two should be minimal.

The key to this is the mention of consistent sub MOA groups. That just won't and can't happen with pressure spikes or inconsistency. Re25 and Retumbo are both stellar performers in cases of larger capacity. I think to many people put far to much faith in problems such as this being solved at the reloading bench. There is no mention of vertical stringing that would indicate pressure problems or inconsistent ignition. I do agree that he should be using Magnum primers though.

If there are no obvious pressure signs and the rifle is as accurate as described, a half grain of powder one way or the other at the volumes described will make little if any difference. Accuracy at safe pressures is the aim of reloading. Velocity is nice as well but it is the least of his worries. I would suspect any decent manual will give him a ball park figure as to what his velocities are. A few sessions at ranges from 100 to 300 meters will tell the rest. The trajectory tables don't lie.

As we all know, different barrels, even from the same maker and with identical chamgers, will give different velocities from one another, even when all else is equal. That's one reason why I am tongue in cheek, when someone posts a killer load that will turn every rifle chambered in that particular configuration into a laser.
 
Thanks Jerry,

I don't shoot the cartridge in question so my recommendations may be out to lunch. I do shoot the 7mag in a hunting rifle and know the powders I suggested are accurate and safe at the velocity suggested.

Bearhunter,
Retumbo is a fair bit slower than RL-25....At least it has been in my rifles.
Accuracy can be very good with fairly wild velocity fluctuations. If it shoots extremely well at 1000 yards I would suggest the Chrony is Kaput. Vertical stringing might not show up inside 200 yards.

IVO,
My concern is the PGW action is built so well it is hiding the pressure you would normally see...Be careful bubba!
Nice rifle BTW!
 
Xfan, just going by the powder quickness charts.
I'm hesitant to agree that vertical stringing won't show up much closer than 1000yds as well. It certainly shows up quickly on any other cartridge combos I've put together. Trajectory is one of the surest signs of advancing pressures and therefore vertical stringing. I would need your theory proven to me. You seem to know your stuff, so I will be the first to admit, I may be wrong.
I've had "varying pressure" problems with deteriorated lots of primers and with poor powder/bullet/primer combinations and the first panel in the thread indicated none of this. In all cases,in my findings, the groups were inconsistent.
High pressures will not, usually, relate to inconsistency in groupings or accuracy. Trajectory measurements at known ranges will tell the story immediatly. Higher velocity/ will give flatter trajectories at any range and higher pressure will increase velocity. If you have varying velocities like the ones first stated, vertical stringing will, IMHO, be a natural result at any given distance. Gravity will see to that.
You could very well get tight groups at any range with high pressures but only if the pressures are consistent from shot to shot.
 
bearhunter said:
High pressures will not, usually, relate to inconsistency in groupings or accuracy. Trajectory measurements at known ranges will tell the story immediatly. Higher velocity/ will give flatter trajectories at any range and higher pressure will increase velocity. If you have varying velocities like the ones first stated, vertical stringing will, IMHO, be a natural result at any given distance. Gravity will see to that.
You could very well get tight groups at any range with high pressures but only if the pressures are consistent from shot to shot.
Click to expand...

As was said, Retumbo is much slower then Re25. In my rifles, approx 10% slower (not be used as load data) with a much slower peak curve.

Elevated pressures WILL greatly affect accuracy, consistency AND group orientation. Test at 200yds and beyond and this becomes very very obvious.

All of these cartridges, 7WSM and RM are very well tested cartridges with magnum pressure limits. Of course, we all know a combo of rifle and ammo can change safe velocites but not by several hundred FPS - given similar parameters.

The WSM is smaller then the RM so with equal effective barrel lengths, velocities for the RM will be faster then a WSM.

I am running a 7RM in a 26" Shilen at 3050fps and it is definitely a warm load. Reported velocities peaking well above that is a sure indication that something is up.

Powders do not behave in a linear fashion once they go past magnum pressures so 1/2gr change in a magnum case at pressures in the 70,000psi range can lead to extremely dramatic results.

Try it... but be very careful.

Pressure curves can go ballistic above 70,000psi. I have found the Hodgdon Extreme lineup to be the most linear powder at elevated pressures but they will definitely pop if you go too far.

My experience with Re25 has been excellent but it will definitely pop with less powder change at max loads.

A true custom action can easily mask pressure signs well into proof pressures loads (80,000psi) so using bolt lift as an indicator is not a safe measure. And yes, there are quite a number of 'proven' competition loads that if ever put on a pressure guage would likely cause their owners to soil their pants.

One well documented wildcat was the commercializing of the 7STW.

Velocity, although still limited, is a much better indicator and if a well tested commerical cartridge magically performs at levels a couple of case sizes larger, you should know that you are not anywhere near SAAMI specs.

If you look at my website, I have a series of article on load tuning for LR accuracy. In a few dozen rifles and all manner of cartridges, the process has proven reliable and repeatable. Process has also worked for a number of other shooters who have read and tried it.

There is no free lunch and a 7WSM with 180's will simply not shoot over 3100fps without elevated pressures unless you are talking 30+" barrel. Remember the pressure limit is 65,000psi so there is no upside to this cartridge without running elevated pressures.

So who cares about shooting at elevated pressures if the rifle shows no obvious pressure signs and the brass lasts for many reloads?

Simple, all actions are made from similar steels. No matter the tolerance or quality of manf, this steel rapidly degrades when subjected to the force of firing cartridges over 80,000psi - or PROOF pressure loads.

An action that might last 250,000rds of fire at 65,000psi, may only survive 1/4 the number at 80,000psi. A few hundred or thousand above that.

So the issue is your personal safety.

Google proof pressure testing of firearms, White laboratory, etc. Some very interesting info out there on testing to structural failure of firearms.

Jerry
 
Thanks so much for all the replies guys,
I am using a Lyman DPS 1200 but it has been very accurate in the past.(I'll check it anyways)
Other than CCI BR2s I have used Fed 215M with similar results.

At 200m there was some vertical stringing, in fact this seems to be how my groups are "stretching".

I may load down from here or completely drop the RL 25 and go with RL 17. I've tried RL 22 with 162 AMAXs getting less than impressive results.

I can't believe that the pressures are getting this high without showing signs like flattened or blown primers hard bolt lift...

I may get out tomorrow, if so I'll report back with the results.

BTW I'm not a velocity freak, as most people who know me can attest, I go for accuracy first and even prefer if my best accuracy is below max velocity/pressure if at all possible. I'm not into pushing safety limits to get a few FPS more, these loads are going off of other shooters loads including Vince Bs world record load of 66.7 gr RL 25, and with no pressure signs I didn't feel I was pushing the limits. Deep down I'm still thinking its a chrony problem but now I know some more signs to look for.

Jerry, shouldn't I be looking at a faster burning powder instead of a slower one to get complete burn and avoid pressure spikes?

Ivo
 
ivo, if you go to the powders mentioned, you will be in decent territory. Another old standby, that is very well behaved is H4831. I am actually a bit surprised that you actually had pressure problems, with the slower RL25.
Stay away from maximum loads, they really do nothing for you in the end, other than cause extreme wear and tear on your firearms. Jerry is giving you some good advice in his last post. Especially in the metalurgical department.
Velocity may be ###y but so are some of the hookers on the street, they are both extremely dangerous to your health and well being. It just isn't worth it.
 
Just an off-thought. You said you are using Winchester brass. If all else failed, I might try weighing them. If the cases weighed significantly different, then I might try checking out case volumes using either water and a graduated cylinder or else something consistent like fine lead shot and then weighing it.
 
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