HELP! Velocity Problems

[RAVEN]

Ok all you guru’s out there give me an answer to this problem pls
Ok Some background
7mm Rem Mag Tobler 28" HV Barrel
Load development concluded 63.5Gr ADI2217 lot# 4108 behind 175Gr SMK
VELOCITY 2780-2800fps under 500 rounds down tube
Purchased large tin of 2217 Lot # 3965
Same load over chrony 2530fps ok must be powder lot#
Go buy 500G of ADI 2217 Lot# 4108 to check if lot is faster
VELOCITY 2530- 2540 over 500 rounds down tube
YYYY do I have such a velocity drop any ideas?????
Any info would be appreciated
CHEERS
RB
Did load test over chrony on weekend up to 4Gr over max (ADI Data) for 2740fps no pressure signs yet!

[Guest]

Can you double check with another chrony ??
Do you now need more come ups at the longer ranges than before ??
Do your come ups coincide with the projected computer come ups ??

Matt P

[Tony Q]

I think i just had this also. Mels rifle shoots 70 - 80 fps faster than mine as such her drops are about 1 MOA less than mine.

I just loaded rounds, for my rifle only, from a new can of 2208 (i use 4kg lots) and my velocitys were up by around 70 fps. (estimated)

Ewery one else yesterday were shooting their same drop settings, including Mells rifles ... but mine, with the new powder .. quite different.

Looking for some time this week to chrony it.

No signs of exess pressure.

[RAVEN]

Hi Matt
Yes my come up chart is out by at less a minute or more
I am using a CED millennium Chrony which is very good
Ben Davies put 7 or 8 round over it with his 6.5X284 and the velocity was a bit more than what he had clocked over his Shooting Chrony 1ft screen
I am using 8ft screen CED have check it against 2ft CED screen which is what I did my original testing with and the velocities are the same I will check it against an Oehler P35 Chronograph but I would say it would be similar.
I will report back on that 1
I did load 4 Grains over ADI max and there is no sigh of primer cratering I will go high until I see signs but I find this unusual to be so may grain over the published data so we will see
Thanx
RB

[AlanF]

RB,

That is a very big difference . It has to be either a crook chrono, or some major component that is different. Are you sure everything else is the same - e.g. definitely the same barrel (I've seen people forget they changed!). Could it be your powder scale? You haven't got your 168 gr projectiles mixed up with the 175s? You haven't molyed the projectiles? Its probably too much for things like different primers or seating depth.

Let us know what you find .

Alan

[RAVEN]

Hi Alan
Yep its the same barrel
I haven’t compared it with another chrony yet but I will on the weekend coming
Ben Davies put a dozen or so shot over out of his 6.5X284 and the velocity was up compared to his Shooting Chrony Beta results
The digital scale check out as I weigh bullets (which read right) and have check against my Redding balance beam scale this also checks out.
The only component I have change is primer FED 215 GM to CCI 250M
Only using 175Gr SMK
Never have used moly

When I have compared chronys and get the result if it is the same I will contact ADI and see if they can give me an explanation.

CHEERS
Richard

[a.JR]

ED

[RAVEN]

Thanx JR
I will take that onboard and check it out when I can.
I am sure I put the 2 primers over chrony searching for better SD thats Y I am using the CCI250 over the FED215M as the SD was less with the same load must check my note but cant remember any significant velocity changes at the time
Cheers
RB

[Guest]

Raven
Are you only out by 1 MOA on your elevation ??If so I would say your chrony is out or was out when U first checked your MV.270 FPS slower would drop your POI lower than 1 MOA.

Matt P

[Shane]

Your primer change will be the most likley problem, but maybe not!
How much wear is in your throat after those 500+ rounds, not likley the problem but check your throat erosion.
regards,
Shane

[Ken M]

Richard,

I will check results of the the two Lots of AR2217 that you have used and see what the acceptance proof results were, but I am sure they won't be that far apart. I agree with Matt chronographs can be like scopes and sometimes giving you the incorrect results. We use Oehler chrono's set at 5' and 20' to give a 15' mid point velocity this is to SAAMI requirements, but we also have muzzle blast panel before the start screen, which can cause problems.

Will let you know the results.

Regards and good shooting
Ken

[RAVEN]

Hi SHANE

Your primer change will be the most likley problem, but maybe not!
How much wear is in your throat after those 500+ rounds, not likley the problem but check your throat erosion.
regards,
Shane

I don’t think it is the primers I actually did a test with CCI 250 av Vel 15 rounds 2806fps Fed215 av Vel 30 rounds 2734fps and Fed 210 av for 20 rounds 2776fps the FED 210 gave me more velocity go figure
but the throat erosion is interesting
Well I know I do have some as I seat my bullets with 10T jump and I am continually chasing it this barrel as had 1100 round down the tube
Is it the increased friction at the throat that’s the problem??? because I have never heard this before and would be interested to hear more
Cheers
RICHARD

[RAVEN]

Richard,

I will check results of the the two Lots of AR2217 that you have used and see what the acceptance proof results were, but I am sure they won't be that far apart. I agree with Matt chronographs can be like scopes and sometimes giving you the incorrect results. We use Oehler chrono's set at 5' and 20' to give a 15' mid point velocity this is to SAAMI requirements, but we also have muzzle blast panel before the start screen, which can cause problems.

Will let you know the results.

Regards and good shooting
Ken

Hello Mr Melgard
I do Agree with the proof results that I am sure between lot# you would expect some difference but 200+fps is excessive I was disappointed when I purchased the same lot # that I use for testing (I know this because I keep all my containers) that the velocity was virtually identical to the powder I am currently using.
Hopefully the chrony comparison will reaveal some results

P.S. ken I started working up powder charges for this ADI2217 lot #3965
The load I was using is 63.5Gr I have gone as far as 68.5 with out any pressure signs velocity is 2748fps
When the barrel was new the velocity gain per inch averaged at 40fps the ADI Load Manual give a MAX 64.5Gr 2692fps out of 24" barrel which coincides with the chrony readings I previously recorded
CHEERS
Richard

[Ken M]

Richard,

I check on the proof results this morning and for the two Lots of AR2217 are as follows, Lot MEM 4108 was -20 ft/s & +300 Psi from our Reference propellant, Lot MEM 3965 was 0 ft/s & +600 Psi from the Reference lot.

Note, that the 7mm Remington Magnum data was obtained using a 175 grain Nosler Partition projectile, so this may differe from the Sierra 175 grain HPBT match projectiles as used. The manual is only a guide and differences in bore & goove dimensions can very, as will cases, primers and projectiles.

I hope this helps, if I can help with any further questions please advise.

Regards

Ken

[RAVEN]

Thanx Ken I will post my result when I test on saturday
Cheers
RB