I've blogged before about Dennis Lindenbaum, one of the top prone small bore shooters in the game. Over at the pronematch.com blog, he recounts a recent tryout from the U.S. Rifle Development Palma team. Palma, to oversimplify, is a 1000 yard prone match (sling, no tripod) with iron sights (actually plastic apertures..), and typically, a .308 round. Head over to pronematch.com and read all about Dennis's adventure!
Tuesday, June 26, 2012
Saturday, June 23, 2012
As I mentioned earlier, using the Mojo sights on the Israeli Mauser creates a problem for me with the target fading and becoming blurry. I believe this has to do with the fact that the rear aperture is a full 14-16" away from my eye. So I needed a (cheap) fix.
I have fairly decent eyesight, although I do need glasses for daily life. My numbers from a year ago:
With shooting glasses to match that prescription, I have no problem shooting Master scores, and I cannot say eyesight is to blame for not shooting High Master more consistently. However, the main difference on my Service rifle or smallbore rifle and the Mauser is that the rear aperture is only an inch or so from my eye.
The solution I found is to use an old trick of creating another pin-hole aperture closer to the eye. I accomplished this by simply punching a small (approx. 1/32"?) hole in a piece of thin cardboard, and then looking through that hole, holding the cardboard in place with a headband I already wear (for sweat, and also to hold another piece of cardboard in place that I use to occlude my non-aiming eye). Worked like a charm! The sight picture immediately cleared up, with the target returning to a clearly defined black ball.
This technique is surprisingly a "secret" many target shooters never learn about. There are a couple of manufacturers that sell adjustable or fixed apertures that are held in place with suction cups on shooting glasses, or thin films:
I must confess I read about the cardboard technique somewhere online, and other folks simply use electrical tape over their shooting glasses. What I like about my approach is that I can adjust the position of the hole easily, because I look out of slightly different positions on my glasses depending on the shooting position. Plus, it's cheap, as in free.
Many rifle and especially pistol shooters who think their eyes are too far gone to shoot with iron sights find they can still do it by using a pinhole aperture. This means they can keep shooting in divisions which do not allow scopes or red dots, or it saves the expense of having to buy those optics and modifying the firearm. Indeed, many shooters who need glasses to see but don't want to buy prescription shooting glasses can try this technique with non-prescription shooting glasses.
I don't claim to fully understand why this technique works, although I'm sure a photographer or optometrist could explain it. My basic understanding is that the aperture causes the "depth of field" to increase, whereby the lens in the eye is able to sharply focus objects at a greater range of distances. As to why this works, as best I understand it, the aperture reduces the angles at which light would otherwise hit the lens, as well as the area of the lens that actually receives light, and thus the "circle of confusion" for each visible object is reduced. The downside is that the image appears darker, so it is advisable to play with different aperture sizes for different light conditions. Basically, this same effect accounts for some of the reason why a person without their glasses can sometimes see by squinting, or making an "ok" sign with their hand and looking through the hole made by their index finger and thumb. The wikipedia articles linked give a better explanation, and really, it is not so critical to understand how it works, just that it does!
Currently on gunbroker.com someone is selling a stripped IDF Israeli Mauser receiver. I know nothing of the seller, but the receiver looks to be in decent shape. Note that from the IDF crest you can tell this was Belgian manufacture on contract for the IDF. I would have a gunsmith check out the receiver for strength and cracks, but most likely that receiver is just as good as any other Mauser receiver if one wanted to put together a custom Mauser-based sporter, target or hunting rifle. Whether that would be economically wise versus just buying a new rifle is another story... If you want an Israeli Mauser that looks as-issued, pass on this and wait for a complete rifle, as it is less expensive to buy a complete rifle than to try and build one from parts. I bought one very similar to this already, and if I didn't already have one, I'd probably buy this one. I still have not decided what I'll do with it yet (maybe someday a target rifle), for now it is just a very cool paper weight!
Again, I have nothing to do with the sale, so as always, buyer beware.
Monday, June 18, 2012
Now that I have a fairly decent 100 yard zero for the Israeli Mauser, it's time to develop a load that will tighten up the groups. One of the first things I want to do is determine the OAL (overall-length) of a bullet seated into the lands, and then back off of that number by about .020 or .015" or so. So what does this mean, and why might it help the Israeli Mauser shoot more consistently?
OAL (overall-length) is the length of a loaded cartridge, measured from the base of the cartridge to the tip of the bullet. Experience has taught rifle shooters that significant accuracy gains can be had by playing with this measurement. Some say best accuracy arrives from seating the bullets so that they just touch the lands (the part of the chamber where the rifling of the barrel begins). Some say say to back off from that distance .020 to .040 through trial and error. Some get accuracy gains by jamming the bullet slightly into the lands. In any case, .020 off the lands is a good place to start. The reasons for this gain in performance are argued and debated, with several competing theories, although nobody argues that it usually works.
The trick is to measure the OAL for a bullet touching the lands. Every bullet style is different, and every rifle's chamber is cut a little different, and wears a little different over time. There are a number of techniques for arriving at this measurement, but the easiest is to use the Hornady OAL gauge with a modified case. Essentially, on the end of the gauge is a modified case with a wide mouth so that a bullet can slide in and out. At the other end of the gauge is a rod you push to advance the bullet, and knob to lock the rod once you feel the bullet touch the lands. You put the gauge in your rifle's chamber, push the bullet forward until you feel it touch the lands, lock the rod, then measure. Simple. Use several bullets from your lot for a decent sample size, and use a bullet comparator to measure off the ogive, and you get a very good idea of how long you can seat a particular brand of bullet in your rifle in order to touch the lands. All you need do then is adjust your bullet seating die to back off of that number as appropriate, and experiment from there.
(NOTE: this information is for experienced hand loaders...seating bullets into the lands will significantly raise chamber pressures and powder levels must be adjusted accordingly!)
So in the case of 155gr. (Sierra Match Kings) bullets I'm using in the Israeli Mauser, although the bullet manufacturer suggests 2.775 as the OAL, the bullets actually touch the lands at approximately 2.816+/-.001 based on my measurements (2.232+/-.001 with a comparator). Thus, I will try loading at 2.796 (roughly .021 longer than the manufacturer's recommendation).
Sunday, June 3, 2012
Over the weekend I was able to take my 1940 Israeli Mauser out for a test-drive. I was shooting in reduced course 100 yard High Power Match with the Ar-15, and although I was shooting on pace for a Master score, a poor off-hand score mathematically eliminated the possibility of a High Master score, so I figured I would use the range time I already paid for to shoot the Mauser in the slow prone portion of the Match.
The results were promising, but revealed a number of challenges faced with using this rifle in a target competition. On the plus side, I found the stock extremely comfortable ergonomically. Being a smaller person, I really like the narrow fore end to grip and the relatively short length of pull. The trigger is great. Overall, a much more comfortable and natural experience for me than the AR, despite the hundreds of hours of trigger time I've spent with the AR. As for the challenges, there are a few but I think they can be overcome.
First and foremost, the sights are going to take some getting used to. Although they are aperture sights from Mojo, the rear sight is forward of the feeding/ejection port, directly over the chamber. So unlike traditional target peep sights an inch or two from the eye, these are a good 5-6" or more inches from the shooter's eye. I have not decided yet whether it is better to focus on the front sight, the target, or to simply "look" at the sight. I ordered interchangeable apertures to experiment with, but the set I have in there now produce a sort of double bull (like a Venn diagram) when I look through them. If aperture sizes don't fix that, I may just have to pick one bull or the other to center.
Second, I need to figure out a sling solution. I tried using a nylon strap with sliders, but it didn't stay put as I put weight on the sling. I think the way to go will be to simply create a loop for my standard service rifle sling, and use that, especially because I am so comfortable with it. Third, the steel butt plate does not want to stay put in my shoulder, despite the rubber on my shooting coat. I may solve that by spraying some tacky glue onto it and my jacket. I found that a loose fit in the shoulder resulted in the shots going far right, but a nice snug fit kept the shots centered, as well as making sure I was well positioned behind the rifle.
As you can see from the target above, my random zero started low, and then I guessed how many clicks on the Mojo sights to come up, but came up to high. I'll have to take some measurements to see how many MOA per click on the sights, because although the instructions estimate .75 MOA, I think it is much less, maybe more like .5. I slowly started walking the sights down, but I think the loosening of the sling caused me to raise shots. I only loaded 20 rounds, so that was it for the day. But I think I have a good sight setting to continue tweaking off of. I am pretty happy about the horizontal distribution of the shots, especially given the difficulty I was having with the sights.
All of the shots were made from the prone position with a sling. Some may question this approach, but I prefer it, even if it takes some time to get a zero. As a target shooter, I don't think there is a whole lot to be learned or gained from shooting off of a rest to zero. I am interested in how the entire system performs, which can only be learned by simulating the position, in my opinion. I think I shoot well enough to be able to make some judgments. For example, immediately before I shot with the Mauser, here is the 20 shot group I shot in the prone rapid fire event with the AR (prone rapid is 2 shots, magazine change, then 8 shots for a total of 10 in 70 seconds; this stage is then repeated for a 20 shot total):
The 10 ring is roughly 2". So the point is, I know I'm capable of shooting at least 2MOA prone with the AR-15, so that is my justification for not using a rest to evaluate the Mauser's capabilities. My 2MOA results pretty much match my Scatt traces. Granted, this will never tell me what the rifle is capable of from a rest, but I don't really care.
I started with a very light .308 load, 41gr. of H355 under a 155gr. bullet, seated to 2.775" OAL. I am just trying to use up the H355 I have and then I'll move on to other powders more suitable for .308, I am just to lazy to dump the powder from my powder measure. I hope consistency will benefit from a different powder and greater velocity, as well as seating closer to the lands. I also have some 168 and 175gr. bullets to try, but I'm hoping that I can get 155s to work because they are cheaper.
All in all, if you move the group above the equator of the target down and center it, you have respectable group. I am planning to use the rifle for the entire High Power match next month if I can figure out a sling solution that works well.