Home Forums Hunting & Shooting Custom Rifles & Wildcats More 7mm Mashburn Velocity Test

Hi, this is an update on my 7mm Mashburn Mag load testing. Around May
last year, I had my custom 700 re barreled. I went with a Douglas 25"
in the mag contour to fit my stock. And using my PTG reamer my gunsmith
re did the rifle for me. It was throated to 175 Nosler at 3.600 and 0.020
jump to lands. So up till Oct. last year I finally found several good
loads and near max or max in the loads. On 1/21/15 I finally went out
to the range to test my loads.

Bullets used in the test:

150 Nosler Solid Base (old, not made any more)
160 gr Nosler AB
160 Nosler Part.
160 Rem Bonded CL
175 Sierra BT
175 Nosler Part
175 Nosler Part Semi Pointed

25 inch Douglas barrel long throat
All brass neck reamed WW 300 Win mag once fired
All primers Fed 215

Total of 32 rounds fired, 4 round strings

175 Nosler 74 H1000 3.575 OAL 3043+, 3008-,3029 m

160 AB 75 H1000 3.580 OAL 3153+, 3116-, 3139 m

160 AB 77 H1000 3.580 OAL 3217+, 3192-, 3198 m

160 Part 78 H1000 3.550 OAL 3237+, 3230-, 3253 m

160 Rem BCL 75 RL-25 3.525 OAL 3148+, 3124-, 3132 m

175 Sierra 71 RL-25 3.565 OAL 2946+, 2929-, 2938 m

150 Nosler SB 72 IMR7828SSC 3.558 OAL 3177+, 3155-, 3167 m

175 Nosler Semi Pt. 72 Retumbo 3.510 OAL 2920+, 2904-, 2910 m


Notes: When I went to load these rounds last Nov. I had to use a
new lot of H1000 powder. The new lot is a little hotter and the
77 and 78 gr loads were a little hotter than what I got in my
load work up last year. So I will work again with the 160 Part
from 75 gr of H1000 up.

The most accurate loads fired last year were:

162 Hornady SPBT 75 H1000 3.510 OAL # 215 3/8" 3 shot pulled #4

175 Sierra BT 71 RL-25 3.525 OAL # 215 5/16" 3 shot pulled #4

160 Part 78 H1000 3.565 OAL # 215 2 shots landed in 3/8" pulled 2
it may work. In velocity test it has 3 fps spread

The 175 Sierra load had a 8 fps spread

I am leaning to the 175 Nosler as a favorite.
I really like my Mashburn rifles and the 700 is a great rifle.

Have you done any work or testing with lighter bullets? 120's-140's?

Hi, I have only loaded 139 to 140 gr for fire forming use and 150 to 175 for hunting loads. I have used some 145 Speer and 150 Hornady and Nosler for fire form use when I did not have lighter bullets. Thanks Randy

Thanks anyway. My 7Mashy is a deer only rifle, even though it certainly can do more than that. Don't need the heavies for Mule Deer.

Thanks for the updates and load data, anyway. I can perhaps use your 150 data as a starting point with 140's.

I have used 70 gr of IMR 7828 with a 150 to 154 gr for fire forming. Randy

I fireform mine using the COW method and don't waste bullets or much powder.

Not to hijack, but what are you using for your COW? Mine formed alright, but I still had a bulge in the base of the neck compared to Dobers fire forming load of IMR4350 and Hornady 140s.

Great info. Should have mine in a few weeks. Nearly 3200 with the 160 PT's looks pretty deadly. As does the 175 PT just over 3000.. Great intel. Thank you.

My COW technique is pistol/shotgun powder; I have used Unique, Blue Dot,and others. A bit of toilet paper as wadding and then Cream of Wheat because it fills better than corn meal followed by a plug of canning wax. I have formed several hundred rounds with no losses or failures. YMMV

Interesting, I just stacked cornmeal on top of 14 grains of Titewad, but never used a "wad" to layer between the powder and cornmeal. I'll have to give that a try.

I scored and 8lb jug O H1000 so I'm going to experiment with 150 E-tips and get a little less compression compared to the very long 168 LRXs

I'm using 13 gr Alliant Bullseye,large PISTOL primer,RCBS corn husk tumbing medium(no polishing compound in it),and a wad of tissue paper.

The cases come out fine and I then run full house Mashburn loads from there. Works the berries.

Of course i also run the Dober FF load of IMR4350,139 Hornady. Can hunt with that load easily.

The Chanlynn barrel is 26 inches and has a 1-10 twist.

The load is a 168g Berger classic hunting bullet with a Norma case and a Tula mag primer.Powder is H1000.

Measured 10 feel from the end of the barrel with my old Oehler model 33 with a 10 foot spacing.4 shot groups except where noted..No errors on the chrono at all this session..

72g 3 shot
L.. 2970
H.. 3051
ES.. 81
A.. 3013
SD.. 40

73.5g
L.. 3035
H.. 3041
ES.. 16
A.. 3032
SD.. 6

74.5g
L.. 3083
H.. 3125
ES.. 42
A.. 3099
SD.. 18

75.5g
L.. 3118
H.. 3137
ES.. 19
A.. 3126
SD.. 8

76.5g
L.. 3162
H.. 3186
ES.. 24
A.. 3171
SD.. 11

77.5g 3 shots
L.. 3215
H.. 3231
ES.. 16
A.. 3221
SD.. 8

Im thinking a person could actually run the 77.5g load but just looking....im afraid they would open the primer pockets over time. Ashame as the 77.5g load shot the second best accuracy at 400 yards.

I ended up running the 75.5g load of H1000 with a seating depth adjustment.Say about .03 off that lands.
The load I hunted with gave a 2.5 inch and a solid 1 inch group at 400 yards before the season.
Might be just a touch slow.But when it shoots like that.
Ill take it everyday and on sunday..

Thanks for the info guys and the comments. Beretzs I am looking forward to hearing about your rifle when it is done. Randy

One of my Mashburn guns likes 76 gr RL-25, 162 gr Hornady interlock, Federal 300 Win case. Avg is 3275. I have reloaded the cases until I have needed to anneal and then keep reloading the cases. I have had no primer pockets open up. This is going on 10 yrs. now for this rifle.

Docbill, I will give that load a try. Randy

DB

I found Rel 25 pretty dirty compared to H1000.

dave

H1000 seems to make many of the various 7mags sing. However I prefer H4831 with 150's and below.

OP, try out some 180 scenars as an accuracy bullet, they are pretty impressive. Like dave, the 168 berger classic also shot superb for me (7 weatherby). Wonder if D7's 10 twist would shoot the 180's?

Rosco I may give them a try, 7mm bullets sometimes here in the Dallas area are not a big selection of types. For some reason in this rifle H1000 out runs RL-25 and Retumbo. Randy

I found a few lb's of H1000 and an 8 lb jug of RL33. I am thinking RL33 might be good in the Mashburn?

Anybody have any experience with it?

Hi, I like H1000 in my 700, it acts as a slower powder than RL-25 and Retumbo taking a few more grains. RL-33 looks like something new to try, do they have 7mm Wby data out for it? Randy