Differences in velocity

[pharmseller]

If you plan on shooting far enough that BC becomes relevant, look at the 178 ELD-X. Very slippery bullet and I have data for that, too, also with Hunter.



P

 

[Grimm]

Do not use the Magnetospeed while shooting for groups. It will throw you off. Verify velocity then take it off when shooting for precision.



P

Have you found this to be the case? I just got it and have heard different results. Scott Satterlee claims that it changes POI but has no affect on group size which makes no sense to me. It has to open groups up.. It's a stick of plastic flapping back and forth which would cause wild inconsistencies in barrel harmonics.. At least I assume so. I'm obviously new and have already shot the thing at least once so what do I know?

 

[Grimm]

If you plan on shooting far enough that BC becomes relevant, look at the 178 ELD-X. Very slippery bullet and I have data for that, too, also with Hunter.



P

Do you have any results regarding how it performs on game? I'm really sensitive to meat loss where avoidable and if what I've read is true and they behave like sst's, I'm not interested. I shot a buck with an sst a couple years ago and had bloodshot from stem to stearn. I'm trying to stick with monolithic and bonded bullets for hunting especially with this new 300prc I just picked up.

 

[pharmseller]

I haven't kilt anything with the 178 but I've killed two elk with the 162 out of a 7mm Rem Mag, and helped gut two more with the same combo. Bloodshot was consistent with placement in all four cases. Bang a big bone and shrapnel causes problems. A poke in the ribs was inconsequential.

Still not the 178 but I've killed a few deer with the 150 out of a 7mm-08 and seen a few others, plus a 6x5 bull, all 7mm-08 150 eldx. My comments above apply equally. Ranges from 100-400 yards.



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[Whisky Tahoe]

Have you found this to be the case? I just got it and have heard different results. Scott Satterlee claims that it changes POI but has no affect on group size which makes no sense to me. It has to open groups up.. It's a stick of plastic flapping back and forth which would cause wild inconsistencies in barrel harmonics.. At least I assume so. I'm obviously new and have already shot the thing at least once so what do I know?

I use my magnetospeed in testing and about 50% of the time weekly matches.
I have not seen group size be affected out to 600 yards. No wild inconsistencies observed.
I'm able to compensate for any POI shift with my sighters.

Since every barrel is different, You can test a few groups with and without a magnetospeed attached and confirm this for your barrel.

 

[tac]

1. Shoot FIVE-shot groups, not four. Why? Watch Youtube's blokeontherange to find out why four shots is NOT representative figure.

2. IMO you are trying too hard - we ALL want the best out of our rifles, and owe it to the prey that we shoot that it is the best and most humane that we can make. But you ARE shooting a hunting rifle, not an F-Class long-range target rifle or benchrester. Moreover, your bullets may not all be the same weight, in spite of what it reads on the box. Unless you are prepared to spend serious money on bullets by Berger or JLK, every brand of bullet will vary somewhat around their declared weight, even the much-vaunted Lapua stuff that I shoot for fun, not game.

3. Remember that your target for deer or elk is inside a six-inch circle, not a infinitesimal and unattainable dot.

4. Get yourself a Labradar, and stop hanging stuff on the barrel.

 

[BigGame]

@Grimm
I agree that temperature differences could explain your velocities. Question: was there any differences in your cases between the first and second sessions; e.g., were you using new cases on the first outing?

FWIW, I do my seating depth testing first at a moderate charge, then work up the charge testing at my established seating depth. I might do some micro adjustments to seating depth after reaching the desired charge, but be cautious about increasing jump with a load that is near pressure, as increasing jump will increase pressure.

 

[Grimm]

1. Shoot FIVE-shot groups, not four. Why? Watch Youtube's blokeontherange to find out why four shots is NOT representative figure.

2. IMO you are trying too hard - we ALL want the best out of our rifles, and owe it to the prey that we shoot that it is the best and most humane that we can make. But you ARE shooting a hunting rifle, not an F-Class long-range target rifle or benchrester. Moreover, your bullets may not all be the same weight, in spite of what it reads on the box. Unless you are prepared to spend serious money on bullets by Berger or JLK, every brand of bullet will vary somewhat around their declared weight, even the much-vaunted Lapua stuff that I shoot for fun, not game.

3. Remember that your target for deer or elk is inside a six-inch circle, not a infinitesimal and unattainable dot.

Thanks, Tac. I certainly understand that it's unnecessary, it's just a hobby and why not play around with it? The post wasn't intended to try and get folks to help me shoot the smallest groups, I'm just asking about the velocity inconsistencies and what could cause a 50fps swing from one trip to the next. I'm fairly new to the game and wasn't sure if it was significant or not.

As far as the 4 shots vs 5 shots goes, my initial trip was 5 shots and the second one I just did 4. I'll look into the problems with that sample size.

 

[Grimm]

@Grimm
I agree that temperature differences could explain your velocities. Question: was there any differences in your cases between the first and second sessions; e.g., were you using new cases on the first outing?

FWIW, I do my seating depth testing first at a moderate charge, then work up the charge testing at my established seating depth. I might do some micro adjustments to seating depth after reaching the desired charge, but be cautious about increasing jump with a load that is near pressure, as increasing jump will increase pressure.

THANK YOU! That's what I was worried about was a jump in velocity once I start pushing the bullets back into the case further.

With regard to the brass, I do think that my first trip out it was brand new and this was the second time being fired. I hadn't even considered that being a factor. Makes sense I guess. To tell you the truth, I'm really bad about paying attention to how many times the brass has been fired and need to come up with a better system for recording it than what I've got.

 

[BigGame]

With regard to the brass, I do think that my first trip out it was brand new and this was the second time being fired.

You're always going to get dampened results when shooting new cases. By that I mean the velocity you see at 56 gr with a new case will be achievable with only 55 gr in a fire-formed case.

I don't put much stock into results with new cases. Usually when I'm fire-forming new cases I simply use that time to run seating depth tests and scope adjustment tests (if a new scope). Any velocities you see with new cases will increase using the same charge in a fire-formed case, so back off at least a grain (maybe more) with formed cases and work back up.

 

[Spitpatch]

Do not use the Magnetospeed while shooting for groups. It will throw you off. Verify velocity then take it off when shooting for precision.



P

Huh?

Perhaps in an abstract psychological sense (the chrono being a present distraction when concentration is required).

Otherwise I'm having a hard time understanding how the speed measurement process affects group size.

I DO understand and have repeatedly experienced that the lowest SD load is quite often not the most accurate one.

 

[Spitpatch]

You're always going to get dampened results when shooting new cases. By that I mean the velocity you see at 56 gr with a new case will be achievable with only 55 gr in a fire-formed case.

I don't put much stock into results with new cases. Usually when I'm fire-forming new cases I simply use that time to run seating depth tests and scope adjustment tests (if a new scope). Any velocities you see with new cases will increase using the same charge in a fire-formed case, so back off at least a grain (maybe more) with formed cases and work back up.

Huh?

A fire-formed case is of LARGER volume than a factory new case. Greater case capacity with the same powder charge usually results in LOWER velocities. Just as seating a bullet shallower increases utilized volume in the case, lowering pressure (unless bullet is touching rifling), lowering velocity.

 

[BigGame]

Huh?

A fire-formed case is of LARGER volume than a factory new case. Greater case capacity with the same powder charge usually results in LOWER velocities. Just as seating a bullet shallower increases utilized volume in the case, lowering pressure (unless bullet is touching rifling), lowering velocity.

I certainly agree that a larger volume with the same charge, all things being equal, would result in lower velocity. But things aren't equal. There is much more work done on a new case as the pressure expands it to the chamber size. This work on the case saps energy for downrange velocity. Once fire-formed, firing the load does not expend as much energy blowing out the case and that power goes down the barrel.

But you need not accept this as an abstract idea. It's easy to test yourself, and every handloader should witness it with their own loads/cases. This is another reason why keeping good records of your velocities and observed pressure is important every time you shoot during load development.

 

[Spitpatch]

My challenge regarding velocity measurement on a Magnetospeed affecting group size was (admittedly) without experience toward that instrument.

If that instrument encounters the bullet in any physical fashion, then:

1) Certainly it could affect group size
2) And so (if true) for that reason I would not own one.

My Oehler chrono does not and cannot affect group size.

As to "Three Shot" vs. "Four Shot", vs "Five Shot" groups (one prominent current writer wrote a lengthy diatribe forwarding the absolute value of a "Seven Shot" group):

The size of the group should coincide with the potential usage of the gun: A fat-barreled varminter that may see 2-300 rounds in the course of one day with little stop for cooling should be tested with probably a 10-shot group (uncooled).

A big-game rifle (that may only on rare occasions be fired more than once in the field at one animal) can be tested with three-shot groups. (Uncooled).

A Blackpowder Cartridge gun may need a significant string of shots (with cooling, swabbing, blow tube technique applied) to measure not only the gun and load but those techniques and their effect on accuracy.

A Savage Model 24 (Over-Under, centerfire rifle on top) Should be tested only by firing one shot, allowing entire cooling before firing the second or third (these guns are very accurate but walk when warmed). Also, field use of this gun almost dictates only one shot will be fired, and that on a cold barrel.

So, numbers of shots in the group are more critical (in hunting guns) toward the gun and usage intended, than any statistical advantage from shots in the group.

Certainly, if one is focused on "testing the load itself", then statistical examination of numbers of shots in the sample might be beneficial. Such is a waste of time if one is testing the gun, scope, ammunition and shooting technique for practical application of a hunting rifle in the field.

 

[Spitpatch]

I certainly agree that a larger volume with the same charge, all things being equal, would result in lower velocity. But things aren't equal. There is much more work done on a new case as the pressure expands it to the chamber size. This work on the case saps energy for downrange velocity. Once fire-formed, firing the load does not expend as much energy blowing out the case and that power goes down the barrel.

But you need not accept this as an abstract idea. It's easy to test yourself, and every handloader should witness it with their own loads/cases. This is another reason why keeping good records of your velocities and observed pressure is important every time you shoot during load development.

Has not been my experience.

 

[BigGame]

Has not been my experience.

I agree that we should test what we read against our own experience. I once had a situation very much like the OP's where I was getting significantly higher velocities on my FF1 rounds compared to firing with new cases. I wasted a lot of time and components before finally backing the charge down enough to reach stable, accurate loads without pressure signs. I then did what the OP did and looked around online for help explaining the situation. Luckily, I had kept good range records, including charge, velocity, and atmospheric info. I read advice suggesting this difference between new cases and fire-formed cases that I have repeated above. I then experimented further with my own loads and confirmed the effect. I found it to be more pronounced in some cartridges/case brands than others, but it was consistently observable. This led me to my own protocol for what information I could get from firing new cases verses information I needed to wait on until using fire-formed cases.

I think reaching out for thoughts like the OP did is the right thing to do when we run into handloading questions. I'm also a big proponent of testing anything you read yourself with your own loads to confirm the effect. In the end, it's working through these challenges with both advice and testing that helps us to become more experienced handloaders.

 

[tac]

pd

 

[Spitpatch]

"but be cautious about increasing jump with a load that is near pressure, as increasing jump will increase pressure."

Perhaps this should be rephrased. Increasing seating depth will increase pressure. Roy Weatherby made his fortune on the premise that increasing jump reduces pressure (and/or mitigates it over the curve).

 

[DizzyJ]

Seating the bullets deeper MAY increase pressure or it MAY decrease it. Depends on how close to, or possibly "jammed" the bullet was to begin with. If the bullet was touching, close to touching or jammed, then setting the bullets deeper will probably lessen the pressure. And of course vice versa.

The Magnetospeed may or may not change the group size when strapped to the barrel. I've seen very experienced shooters and loaders claim both. My suspicion is that IF you are square in the middle of an accuracy node that is wide, then you may not see any difference in group size as the load and components are not hyper sensitive at that particular combination. If you have a very narrow node then it seems quite plausible the Magnetospeed could change the harmonics enough to throw the rifle off of its accuracy node.
By the way, there ARE platforms that allow you to use the Magnetospeed without attaching it directly to the barrel. Also, the Labradar CAN have its own possible issues. Add to this the expense, and many choose to go the route of the Magnetospeed. Neither is 100% wthout issues or limitations.

As far as changing the charge by a full grain from virgin to once fired brass, I've not personally seen that, and it seems like a pretty big jump. Not saying it's not true in some instances. It is something I'll want to check out though now that I've seen it mentioned here. I have a very close friend who has a lot of gold medals from F-class 1,000 matches and I don't recall him mentioning anything about this when I've picked his brain about precision reloading, and load work ups. Doesn't mean he didn't mention it, just means I don't recall that in any of our conversations.

As always I'm constantly learning, and definitely don't have a stranglehold on all of the answers. One's perception of the "truth" is usually gained from personal experience. I've more than once had to re-learn what I "knew" to be fact. I sincerely doubt I'm at a place where that will never happen again. I certainly strive to always be learning and many here have helped me in that regard.

 

[Grimm]

Maybe I'm blaming the Magnetospeed for something that doesn't exist then. The groups I was laying down while testing were way larger than I typically see, even during load development. The chrono is new so I've just started playing with it. Just makes sense in my head that it would cause additional whip from a lightweight hunting barrel profile.. Further testing will decide that. I'm going to take the load that gave me the best es and SD and test it w/o the chrono to see if they're any different.

Also, when playing with oacl, how big or small of changes should I be making? .005, 010? Not really sure what incriments to make my adjustments in.

I did make a device for my ar10 that attaches it to the mlok rail to get it off the barrel although that's because it shifted once and I shot the tip of it. Oops.