17HMR Ammo Test & Ejection Failure Explanation

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  • 17HMR Ammo Test & Ejection Failure Explanation

    I added the below to the Marlin 917 thread but thought I'd add a separate thread just for this, for possible other avenues of discussion.

    17HMR Ammo Test & Ejection Failure Explanation

    As we all know, or at least Should know, running different ammo through your firearm is a wise thing to do. By doing this you will discover which ammo configuration - brand, projectile size, etc., - is preferred by your gun.

    In a previous test I compared the Hornady VMax against the CCI equivalent and the Hornady won. Now it was time for another test. The candidates were (in the order shot)...

    Hornady Vmax 17gr
    Federal 17gr
    Hornady 20gr (hollow point)
    Winchester 20gr (power point / hollow point)

    The distance was 50 meters. Conditions were windy. Shooting method was only a front rest which was unstable (wobbly) and no rear rest, just my shoulder. I did not sight in for accuracy at this distance - which is to say, I did not shoot a group and make a scope adjustment until the bullets were hitting where I was aiming. I accepted the scope's setting as it was.

    The target's roundel is 50mm diameter (it is an air-rifle target I print on an A4 sheet of paper as needed).

    Now the targets as shot.

    The Hornady 17gr target sheet reveals: Each 5 shot group can be covered with a 50cent piece (ignoring the flier in roundel #5)


    The Federal 17gr target sheet reveals: Each 4 shot group can be covered with a 50cent piece (with the exception of roundel #1)


    The Hornady 20gr target sheet reveals: Each 4 shot group can be covered with a 50 cent piece (ignoring the flier in roundel #4)


    The Winchester 20gr target sheet reveals: Slightly wider spacing within the group. The rifle had a wet patch run through it and several dry patches, followed by two fouling shots of Hornady 17gr after roundel #3. The improvement in group of roundels #4 and #5 is clearly evident.


    Conclusions: In the field, each brand and projectile weight would be adequate for taking rabbits with head shots at 50 meters, once sighted in accordingly. The test as done shows that Hornady performed the better of the 17gr and the 20gr. However, after seeing how the Winchester groups closed up, it would be worth testing each candidate again but this time with a quick "wet patch and several dry patches followed by a couple of fouling shots" before each target sheet is shot. But as for the conditions the test was conducted under, my vote goes to Hornady. As the 20gr dropped by almost 50mm from the POI of the 17gr, it would be wise to keep this in mind if switching between the two for field work.

    Also, I had set up the same size targets at 100m. And sighted the rifle in for accuracy at 50m before shooting the 100m targets. However, the resulting target sheets are so inconsistent nothing much can be learned. Some groups can be covered with a 50cent piece while others are so scattered it's impossible to tell which roundel was being shot at (on the 20gr target sheets). It wasn't until I got home that the reason why dawned on me. The 100m targets were only Just visible over the backstop mound of the 50m targets. The wind was blowing towards me and sometimes slightly across to the right as well. For the projectile to reach the 100m target it needed to fly only a few inches about the top of the 50m mound. A mound which was acting to funnel/direct the wind. The wind would hit the mound and be forced up. As the projectile flew through reasonably consistent air, it then hits a small pocket of turbulent air and its flight path altered. Only marginally, but when aiming at a 50mm roundel at 100m, it doesn't take much to miss. Throw in the swaying target boards with my wobbly front rest and the results are atrocious. The range officer had a look at my sheets and remarked, "I'm surprised you even did that well in this wind".


    As you can see, the 17gr Hornady wins here too - though all brands would have taken a rabbit with a body shot. And also, the barrel heated up faster and got hotter with the 20gr projectiles than the 17gr ones.

    A quick word about 20gr vs 17gr. Ultimately, taking an animal comes down to hitting force. Momentum. In physics there are official units of momentum. But We don't need them. To me, speed (in whatever unit) times weight (in whatever unit) is enough to measure what has more hitting force. So a 17gr projectile traveling at 2550fps (43,350 unofficial units of momentum) vs a 20gr projectile traveling at 2375fps (47,500 unofficial units of momentum). So the 20gr wins, just. What is this in footpounds. Hornady claims 245 for the 17gr and 250 for the 20gr at the muzzle. A 4fpe difference at 100 yards and a 2 fpe difference at 200yards. Here's a Hornady video they made while testing, of the 17gr hitting ballistic gel in slowmo http://www.youtube.com/watch?v=zytdno_DK_M - personally, I think whatever is the cheapest of the two will do what you need. But as always, whatever is most accurate in Your rifle. My tests show the Hornady Vmax 17gr is the most accurate in My rifle. Now to improve my shooting... using a stable front rest even

    Onward...

    Some people (many?) complain about their Marlin 917 rifles Failing To Eject (FTE). So I thought this would be a good time to have a look at the cause of the problem and some fixes.

    In this first pic you can see the ejector spring standing tall. It is this small sticking-up-thing which makes contact with the rear of the shell as the bolt is drawn back, and thus flicks the shell out of the grasp of the extractor claws.


    In this 2nd pic you can see the red plastic top of the magazine and the extractor claws to the left of the ejector spring. Note how close the spring is to the top of the magazine. Not also the small groove/slot in the bolt that allows it to slide over the ejector spring.


    In the third pic you can see one side of the extractor claw. Notice how it starts as wide as the bolt at the rear and then comes in. The claw on the other side of the bolt does this too.


    Ok. So what is happening when people have a FTE is, as the bolt is drawn back, the shell lightly touches the next shell in the magazine, or the red bit of the mag. This pushes up the shell ever so slightly within the extractor claws. That slightly higher position means, as the bolt pulls the shell back, it also slides right over the ejector spring. The result is a FTE because it is not making contact with the ejector spring.

    So the question is, it the ejector too low or is the extractor not gripping strong enough to prevent the slight bumping of the shell?

    Without seeing each individual gun in question, the first thing to do if you're a DIY type is to remove the extractor and the ejector, give them a bit of a clean and put them back. Just doing this has shown to solve the problem (crud can get behind the extractor claws keeping them slightly wider apart than they should be). The other two work arounds if that fails are: bend the extractor claws in to grip more tightly - or - bend the ejector spring up ever so slightly so it sits a fraction higher (it should still slide under the bolt without too much drama). If DIY is not your forte, then any competent gun smith should be able to rectify this issue without a drama for their minimum charge as it's a quick fix.
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