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7mm 08 enquirie

16 Oct 2021
@ 11:41 am (GMT)

GRH

I have a Marlin Xs7 in 7 mm 08 caliber with a 2 - 8 x 32 Vixen scope which I have owned for 8 or so years for hunting fallow deer.

I have floated the barrel, epoxy bedded the action, and stiffened the fore-end of the factory injected molded plastic stock. I have also replaced the plastic trigger guard with an alloy facsimile.

I developed a load using 145 gn Speer Hot Cor projectiles and 40 grns of AR 2208 with a COAL of 2.83" which provided the best accuracy I could achieve from the rifle using this bullet/powder combination. Results were underwhelming with three-shot groups averaging 1.54" at 100 metres (with major inconsistency over time between the smallest at 0.63" and largest of 3.19").

I then moved on to try Sierra 120 gr Prohunter projectiles with AR 2208. The rifle clearly liked this bullet/powder combination quite a bit and loads tested between 42.9 gr - 44.1 gr in 3gr increments delivering four-shot groups at 100 meters averaging 0.97" (the best load shooting a group 0.75" and the worst 1.22"). Further refinement of the best powder weight/COAL has delivered very consistent accuracy (best three-shot group of 0.45", five-shot group of 0.75" and a test 9 shot group of 1.14") and the load shoots close to zero from a cold, clean barrel.

This was satisfying other than the fact that I have harboured nagging doubts in the bullet's capacity to cleanly kill the intended quarry (with body weights around 40kg and perhaps maxing out at 75 kgs) out to a self-imposed maximum range of 300 meters (with the majority shots inside 200m). Thus far it has done the job on the animals shot but they have all been at ranges no greater than 100 or so meters and no animal weighing greater than 45 kg.

Seeing the rifle liked the lighter projectiles, I thought I might try 130 gr Speer Hotcors hoping to find accuracy and reliable terminal performance. It proved to be an unmitigated disaster with the rifle completely rejecting this powder/bullet combination with some extraordinarily large (5" plus three-shot groups) and an average over 2.5" at 100metres.

The rifle seems to be pedantic with respect to the bullets it will shoot accurately. I have also run (very small numbers) of Hornady 139 gr SST and Nosler 120gr BT. Both showed promise and were more accurate than the 145gr Speers (~ 1.2" at 100metres for both). I am a bit reluctant to use the SST's as others who have used them out of the 7mm 08 on fallow report that they can be quite explosive and result in excessive meat damage in shots under 100 meters.
I am tossing up whether I might try the 139 gr Hornady Interlock (hoping that it may deliver similar accuracy potential in my rifle to the 139 gr SST's) or the 140gr Sierra Prohunters as cost-effective options for my purposes. I am not overly keen from a perspective of budget and component availability to chase the rabbit down the burrow that is testing alternative powders.

To my question - does anyone have experience of the terminal performance of the Sierra 120gr Prohunters in 7mm08 or 7x57 cal on deer of the size described above that confirms that these bullets will consistently deliver clean, timely kills out to around 300 meters or to the contrary.

Many thanks for your input.

Rob

Replies

17 Oct 2021
@ 06:59 am (GMT)

Quote this

Nathan Foster

Re: 7mm 08 enquirie

Hi Rob, there is a lot to think about here.

I have to do a bit of guess work here but I will take a punt that the muzzle velocity of your 120gr load is about 2850fps. The short answer is yes it will produce expansion at 300 yards as the bullet is still travelling at 2060fps. The bullet energy is however only around 1100 ft-lb. Wounding is fairly mild but sufficient at this impact velocity. Shots that strike behind the shoulder will result in dead runs so you may have to track your deer for a little bit. Anyone who has used the .257 Roberts / 6.5x55 / 120gr Sierra will be familiar with this. There is no great wow factor, but it gets the job done. If you are trying to maximise meat preservation, you will not be taking any raking shots so there is no need to worry about obtaining extra penetration.

When hunters (or copper bullet makers) talk about a bullet being good because it produces 'less meat damage', they neglect to understand that a bullet kills via tissue (meat) destruction. If a bullet maker claims that their bullet causes less meat damage than another, they are saying that their bullets produce reduced performance. This seems to be the age we are living in where a business may market the poor performance of a product, as being precisely the reason you need to buy it. It is therefore of the utmost importance that we investigate matters for ourselves and maintain some personal dignity / pride etc in our own intellect.

Most 140gr 7mm08 soft points behave much the same. So much so that it is near impossible to tell wounding / penetration apart. The mild MVs and impact velocities, the basic cup and core bullets, all amount to about the same. A 140gr generic soft point may produce a somewhat deeper penetration than your 120gr, less wind drift and may retain more energy (eg using a BTSP), but out to 300 yards, there is no great increase in performance. Having said this, there is some difference between the likes of the soft 145gr Speer BTSP versus the slightly tougher 145gr Hotcor projectile. The former is better suited to lighter game / mild muzzle velocities. It is also easier to seat with regards to obtaining concentric loads. These smaller matters aside If you want to enhance performance then yes, you will need to try the wide wounding 139gr SST which is essentially a hollow pointed bullet.

Regarding the XL7, keep in mind that any flexing of the stock or action during the bedding process may have a profoundly negative effect on results. Make sure the rifle passes the 1 oclock test (book 1 - inspecting bedding) after bedding. If the rifle needs rebedding, take the time to do it as it will save money in the long run.

It is good to hear that you are utilizing an ali guard. The plastic guard is a major weak point of this rifle design (as well as the Remington branded / version of this rifle M783).

As always, make sure shooting technique is sound. Lay off using a bipod or a suppressor until you have worked through this phase (consider each as variables, not aids). See the Shooting book for more info on methods, aids etc.