Groups

[Norm]

Had an interesting fire forming shoot recently. Done 200 cases and another 100 to go. $$$$ worth of ammo just to fire form cases. This is not a poor mans sport!

These groups were with my .284win at 100 yards in a moderate wind about 6 to 8 mph.. The load is the same with these three groups but I adjusted the scope to get a different point of impact. Bullet is 168gn Sierra SMK.
Top left was a 40 shot group all shot with a Magnetospeed device on the barrel. Out rider was the first shot with a clean bore. 100fps slower than my average.
Top right was a 20 shot group with the Magnetospeed Bayo off the barrel. Outrider was first shot with clean bore.
Right was a 10 shot group with Magneto speed Bayo on the barrel. Outrider was first shot again with clean bore 60fps slower than my average.

Shot a number of other 20 to 40 shot groups with the Magnetospeed Bayo fitted but with different loads. First time I have done such a large number of shots with the magneto fitted and it seems to have little effect on accuracy compared to a bare barrel. The amount of neck turning into the shoulder did have a large effect on accuracy. The first few shots were also all over the place with regard to velocity but they still grouped ok at 100 yards.
Didn't think I would get much out of a fire forming session but I did discover some interesting things with regards to the effect on point of impact and velocity after cleaning. Also using Boretech Eliminator by itself is perhaps not a good idea.

[Brad Y]

Ive purchased a hydraulic form die for my 284 shehane. They are available from Whiddens for $150US and all they need to make your die is your reamer print. Saves burning valuable components. Not sure if a straight 284W would benefit from one though?

[saum2]

Hope your not burning out that barrel Norm.
Geoff

[williada]

Norm, you have appeared to have busted a couple of traditional myths. Firstly, that a shot from a clean or cold barrel will go low and secondly, that shots of greatly varying velocities will not group. I think there are few reasons why this occurred. Perhaps we need a little more information.
1. Was the slow, first outlier regularly high without the Magnetospeed device and was the outlier’s elevation reduced with the Magnetospeed attached?
2. How close was the charge to your normal tuned load? Was your tune based on a nodal tune?
David.

[williada]

Norm, got your email, see comments. David.

[AlanF]

Norm,

I wouldn't expect the Magnetospeed to affect group size at 100yd, but I would expect that adding (or removing) it would change the barrel harmonics in the same way as adjusting a tuner, so ladder testing for example would best be done without the Magnetospeed, and if MV info is desired, using a non-attached chrono.

Geoff,

Regarding using up new barrels on fire-forming, there is a common theory that barrels need at least 100 rounds through them before you do serious tuning, because amongst other things, velocity increases. Its also common to allocate at least 100 new cases to a new barrel, so to some extent, you can use the fire-forming to get the barrel up to speed. If I need more new brass for a very good barrel later in its life, then with the carefully matched chambers that Matt Paroz provides, I usually have the option of fire-forming in a "lesser credentialled" barrel.

Alan

[Brad Y]

Agree with the MS not changing group size, but yes can alter POI.

Alan- I see Norm is using the 168SMK and I have done this in the past. They arent very cheap at all! Just wondering if you have used those 168 Antipodeans yet on target and have any thoughts? Im also getting 2 barrels chambered for my new rifle and plan to use 168's as the first firing after hydro forming. Not only to look to develop a 168gr load but also to give the brass a lighter first actual firing before moving onto 180gr projectiles. I figure 2850-2900fps with a 168 and 2209 wont hurt the cases and still be competitive if I do my part.

[DaveMc]

Geez Norm - I hope you took the time with those 40 shot groups!!!???? < 40 sec between shots and you might have half a barrel gone already.

[AlanF]

Alan- I see Norm is using the 168SMK and I have done this in the past. They arent very cheap at all! Just wondering if you have used those 168 Antipodeans yet on target and have any thoughts? Im also getting 2 barrels chambered for my new rifle and plan to use 168's as the first firing after hydro forming. Not only to look to develop a 168gr load but also to give the brass a lighter first actual firing before moving onto 180gr projectiles. I figure 2850-2900fps with a 168 and 2209 wont hurt the cases and still be competitive if I do my part.

Brad,

I have had 200 168gn Copperheads which went extremely well once I found the right barrel for them. I agree 168s with moderate loads are a good option for fire-forming. I've found twice or thrice-fired cases to be the best compromise in terms of consistent headspace and straight necks, with the necks still working well and not too much carbon build-up inside (I don't anneal or clean inside).

Alan

[Brad Y]

Apologies, I was thinking Anti's when they were copperheads.

[plumbs7]

Hi , my experience with the mag speed is if the spacers aren't flush with the muzzle, and the instruction say to be back 40 mm from the muzzle . Is that the groups are a little wild! Something I was caught out just recently! But will group just fine if the magspeed is as far forward and like I said before , flush with the muzzle .

Only have noticed that the POI changes to going about a minute high in most cases.

Like I said , that has been my experience with magspeed !
Regards Graham.

Ps Nice groups Norm!

[Norm]

Hi Lads,

Geoff, Dave, The barrel is an old one with a chamber cut to match the new barrel. So the new barrel is not being worn out fire forming. Not real worried about wearing it out as its doing a job. Still I kept an eye on the barrel temperature and gave it a rest to cool a bit every 10 shots or so to simulate a typical match.
I used the 168gn Sierra's as I had some spare and did not see them being so good at long range with a low BC. They do shoot ok at short range though so might have to get some more for the shorts? They are more expensive than Bergers!

The Magneto did not seem to effect point of impact much as can be seen from the groups. I did dial across between groups and the groups ended up where expected. The Bayo is fairly light and the barrel fairly heavy. Also the loads were only light. Heavy loads on the edge may have resulted in a different result.
With lighter barrels I have seen point of impact changes of about 1 moa but the change is usually half this.

I have another 100 cases to form so will doing some experiments with cleaning methods and their effects on velocity for the first few shots after the clean. Got to get some benefit from blasting off all this ammo.

Dave, I will drop you are email and pick your brains.

[KHGS]

Hi , my experience with the mag speed is if the spacers aren't flush with the muzzle, and the instruction say to be back 40 mm from the muzzle . Is that the groups are a little wild! Something I was caught out just recently! But will group just fine if the magspeed is as far forward and like I said before , flush with the muzzle .

Only have noticed that the POI changes to going about a minute high in most cases.

Like I said , that has been my experience with magspeed !
Regards Graham.

Ps Nice groups Norm!

My experience with my Magnetospeed as well, except that I have noticed very little poi change.
Velocity spreads will usually be higher with fireforming, particularly when fireforming out to an Ackley improved chamber. Short range accuracy does not seem to be greatly affected by this velocity variation. I have shot possibles out to 600yds when fireforming my 280 H.I. brass. I make the cases out of 30/06 brass, so some of the unformed ammunition is ugly in regard to being straight & the amount of blowing out that is required. I do not hesitate to fireform during club shoots & am surprised at how tight the groups are most of the time & when I do my bit, possibles are not uncommon, weather permitting.
Short range benchresters often win matches with loads that have by our standard, huge velocity shot to shot variations.
Low velocity spreads doesn't always indicate the most accurate load, but low spreads are a requirement at longer ranges to reduce vertical groups. A bit of juggling required! Tuner perhaps????
Keith H.

[DaveMc]

My experience with a magnetospeed on heavy barrels is almost no change to group size and tune. I have seen it change POI though. If not tight enough and starts to slip off - twice I have been shooting groups in a known good area and all of a sudden a significant POI change to a new goup - sure enough the magnetospeed had come loose.

I believe it is light enough and with the rubber coupling does very little to the heavy barrels I play with - I am happy enough to tune with one and take it to a queens. The change in POI I put down to running a bullet past a surface does create a little extra drag on one side ((or reduces? something written about it somewhere??) - and perhaps this varies greatly with distance from surface such that some don't see this.

I do take the time to make sure the height is spot on and keep a consistent distance from muzzle as well.

A very handy tool.....

[AlanF]

Dave,

If you are not seeing a change in tune by adding or removing the Magnetospeed, it would imply that making minor adjustments to a conventional rotating tuner wouldn't affect that barrel either? Because in affect a tuner adjustment is adding weight to one position on the barrel and removing same from another.

Alan