7mm rem mag velocity conundrum!?!!

[johnmventers398]

he folks!,

just been out the range and shot my self a ladder test over the chrono using the 6.5 guys recommended Scot something-or-others 10 shot method. it has worked for me in the past with this rifle.

however i shot my string and the velocities are nothing like what i would expect.

shot one through ten are in order
1004
2699
2594
2695
2547
2634
2687
2661
2798
2811

these are all up .5 grain increments seems really sporadic to me.

is it likely that my chronograph is shot? the book says my starting vel should have been about 2900 and end should be 3 something?

i mean these velocities simply will not work for me.

ideas?

 

[CTK]

New chronograph or new powder scale. Bad powder?

 

[johnmventers398]

New chronograph or new powder scale. Bad powder?

hopefully its not the powder. its a new tub of h4831sc and no in fact i've had really good and predictable results with 139 GMX, with it. likewise with the scale its a balance beam type so not really a whole lot to go wrong there..

i think i need to try a new approach to the load work up and get my velocity by using... MATH!!!

 

[AckleymanII]

Try 65-66g of IMR 4350, Rem case, Rem 9 1/2 primer, 140g Nosler accubond, you will be very, very happy 3200-3300 fps depending on the rifle and tweeked 700's, A bolts, and two Savage factory shoot bug holes with this load. 2.5- 3.5" groups at 600 is normal..tweeked 700's and Brownings A Bolts.

Also, 140g Nosler, 65-67g of R#19, Win brass, fed 215 can shoot very tiny groups, 3300 fps.

Key: touch the lands with the bullet, accuracy opens up with the smallest amount of jump.

Keep the copper out of your barrel, clean often.

I shot H4831 with 160g and heavier, only...that is just me.

Good luck!

 

[johnmventers398]

Try 65-66g of IMR 4350, Rem case, Rem 9 1/2 primer, 140g Nosler accubond, you will be very, very happy 3200-3300 fps depending on the rifle and tweeked 700's, A bolts, and two Savage factory shoot bug holes with this load. 2.5- 3.5" groups at 600 is normal..tweeked 700's and Brownings A Bolts.

Also, 140g Nosler, 65-67g of R#19, Win brass, fed 215 can shoot very tiny groups, 3300 fps.

Key: touch the lands with the bullet, accuracy opens up with the smallest amount of jump.

Keep the copper out of your barrel, clean often.

I shot H4831 with 160g and heavier, only...that is just me.

Good luck!

thanks powder is rather hard to come by around here so i tend to buy it in large quantities well reasonably so i have a few pounds of h4831 that i have to get used. i also have 290 150 grainers that i want to use and a about 900 primers or what ever brand they are i canna mind of the top of my head. so i am reluctant to change too many variables in order not to waste resources. just the results today rang big old alarm bells. mind you ive got no pressure signs so im just gonna keep working up until i get something i like.

i shal forgo the chrono and do it the hard way and then calculate the velocity from the drop at range. uuugh never mind...

 

[AckleymanII]

H4831 will work in spades and I would use 150g. Your powder charges for the loads above are light to say the least. 150g Nosler BT and Sierra BTSP will be accurate in the area at a minimum of 3050 fps and perhaps as high as 3150...hard to say...you have not told us what kind of gun, barrel length, and especially how much freebore is in the particular barrel you are using.

However, as a general rule of thumb, the 150g Nosler long range accubond has liked a LOT of jump in my rifle.

H4831 likes a HOT primer in the 7 mag, cci 250, Fed 215, and win mag. Primers make a whale of a difference with this very slow burning powder, and you may have to adjust your load for primers with less flame, incandescent particles, etc

I Kiss the lands, find pressure, back off 2.0g, work up in .3- .5g increments usually equals a home run.

A long time ago, I worked up a load with H4831 and a 139g Hornady, the case was darn full of powder North of 68g with a fed 215, accurate and fast. Lot# of powder change, and I will not say the exact load because it was so long ago.

 

[seymour fish]

thanks powder is rather hard to come by around here so i tend to buy it in large quantities well reasonably so i have a few pounds of h4831 that i have to get used. i also have 290 150 grainers that i want to use and a about 900 primers or what ever brand they are i canna mind of the top of my head. so i am reluctant to change too many variables in order not to waste resources. just the results today rang big old alarm bells. mind you ive got no pressure signs so im just gonna keep working up until i get something i like.

i shal forgo the chrono and do it the hard way and then calculate the velocity from the drop at range. uuugh never mind...

So, what did the Target reveal ?

 

[johnmventers398]

H4831 will work in spades and I would use 150g. Your powder charges for the loads above are light to say the least. 150g Nosler BT and Sierra BTSP will be accurate in the area at a minimum of 3050 fps and perhaps as high as 3150...hard to say...you have not told us what kind of gun, barrel length, and especially how much freebore is in the particular barrel you are using.

However, as a general rule of thumb, the 150g Nosler long range accubond has liked a LOT of jump in my rifle.

H4831 likes a HOT primer in the 7 mag, cci 250, Fed 215, and win mag. Primers make a whale of a difference with this very slow burning powder, and you may have to adjust your load for primers with less flame, incandescent particles, etc

I Kiss the lands, find pressure, back off 2.0g, work up in .3- .5g increments usually equals a home run.

A long time ago, I worked up a load with H4831 and a 139g Hornady, the case was darn full of powder North of 68g with a fed 215, accurate and fast. Lot# of powder change, and I will not say the exact load because it was so long ago.

my 139 load is 68.7gr with a vel of 3107 ES acording to the chrono was 3 FPS.

i am using a factory tikka t3 super varmint with a 22" tube. i have had 1.5 " groups with it with norma 150 gr FMJ and hoped to replicate that with the 150 ablr's

i have no idea what the free bore is. i planned to load to mag lenth find a load it likes and tweek caseward from there to tune it up.

the target was inconclusave because i was ruching an never set my camera up properly and i was aiming for chrono readings like i used before to get my 139gr load.

my starting load was 61 gr and last round was 65.5 with no pressure at all.

i was using nosler data for starting and max charge. but hodgdon have two difrant max charges on there site for 150's one at 62 gr and one at 68gr

it will be the weekend before i get to re-do the test a real life gets in the way.. i will hopefully be back with some answers.

anyway its not all wasted, time behind the gun is always worthwhile.

 

[Zero333]

I've run into this type of conundrum with one of my 243win rifles with H-4831 shooting 105 grainers.

Hodgdon's data showed 41 gr MAX making 2,846 fps (24" bbl)
My rifle at 41gr (same bullet, same brass, same primer but longer COAL and 22" bbl) chrono'd 2,640 fps. Needed 44 gr to make 2,800 fps and went up to 45.8 gr (4.8 gr above Hodgdon's MAX) with out any pressure signs and made 2,945 fps. Took me 3 range trips to try and find the max in my rifle. But never found it.

Tell us about your load... You said 61 to 65.5 gr H-4831.
What bullet ?
What COAL ?

Maybe someone ran a similar load in the 7mm RemMag and will chime in with what velocity they got.
I can also run the load data in Quickload and post the predicted velocity.

 

[johnmventers398]

I've run into this type of conundrum with one of my 243win rifles with H-4831 shooting 105 grainers.

Hodgdon's data showed 41 gr MAX making 2,846 fps (24" bbl)
My rifle at 41gr (same bullet, same brass, same primer but longer COAL and 22" bbl) chrono'd 2,640 fps. Needed 44 gr to make 2,800 fps and went up to 45.8 gr (4.8 gr above Hodgdon's MAX) with out any pressure signs and made 2,945 fps. Took me 3 range trips to try and find the max in my rifle. But never found it.

Tell us about your load... You said 61 to 65.5 gr H-4831.
What bullet ?
What COAL ?

Maybe someone ran a similar load in the 7mm RemMag and will chime in with what velocity they got.
I can also run the load data in Quickload and post the predicted velocity.

so i am using norma once fired brass from there 150gr jagdmatch line, 150 gr accubond lr's
i've now worked 65.5 thru 69 gr H4831sc with no pressure signs and in the vel region i am more happy with. over all length is 3.331 base to point.

diagnosed the chrono issue as light conditions. as clouds rolled in and it darkened the readings wobbled.

 

[Zero333]

so i am using norma once fired brass from there 150gr jagdmatch line, 150 gr accubond lr's
i've now worked 65.5 thru 69 gr H4831sc with no pressure signs and in the vel region i am more happy with. over all length is 3.331 base to point.

diagnosed the chrono issue as light conditions. as clouds rolled in and it darkened the readings wobbled.

According to Quickload...

7mm RemMag
150 gr Nosler Accubond LR
3.331" coal
22" bbl
H-4831

65.5 gr = 2,898 fps @ 55,224 psi

69 gr = 3,061 fps @ 65,506 psi

---------------------------------------------------

I suspect Norma brass has a slightly more internal capacity in the 7mm RemMag bringing down the velocity and pressure a little compared to the Quickload estimate.
I say this because for the 300winmag, Norma brass has more capacity than other brass.
It's always better to know the exact internal capacity of the brass when running the #'s in QL.
The QL default H20 capacity for the 7mmRemMag is 82 gr.

 

[johnmventers398]

According to Quickload...

7mm RemMag
150 gr Nosler Accubond LR
3.331" coal
22" bbl
H-4831

65.5 gr = 2,898 fps @ 55,224 psi

69 gr = 3,061 fps @ 65,506 psi

---------------------------------------------------

I suspect Norma brass has a slightly more internal capacity in the 7mm RemMag bringing down the velocity and pressure a little compared to the Quickload estimate.
I say this because for the 300winmag, Norma brass has more capacity than other brass.
It's always better to know the exact internal capacity of the brass when running the #'s in QL.
The QL default H20 capacity for the 7mmRemMag is 82 gr.

quick load seems pretty close! 69 gave 3027.

what did it say about barre time?

i wonder if i will manage to get to 3107 safley.

 

[johnmventers398]

According to Quickload...

7mm RemMag
150 gr Nosler Accubond LR
3.331" coal
22" bbl
H-4831

65.5 gr = 2,898 fps @ 55,224 psi

69 gr = 3,061 fps @ 65,506 psi

---------------------------------------------------

I suspect Norma brass has a slightly more internal capacity in the 7mm RemMag bringing down the velocity and pressure a little compared to the Quickload estimate.
I say this because for the 300winmag, Norma brass has more capacity than other brass.
It's always better to know the exact internal capacity of the brass when running the #'s in QL.
The QL default H20 capacity for the 7mmRemMag is 82 gr.

and thanks for doing that

 

[Zero333]

You're welcome. You can PM me anytime you want me to run some #'s in Quickload.

 

[johnmventers398]

You're welcome. You can PM me anytime you want me to run some #'s in Quickload.

You're welcome. You can PM me anytime you want me to run some #'s in Quickload.

final load is 70.2gr still no pressure but 5fps ES so happy with that.
now to sight it in and test at 300-1000m if the weather improves.
velocity is 3044