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Bayonet accuracy tests....quite unexpected results

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LMTmonoMan View Drop Down
Grunt
Grunt


Joined: Mar 18 2018
Location: AL
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    Posted: Sep 27 2018 at 5:43pm
Hello gentlemen, hope all are doing well, and many of you gents are getting to regularly shoot these amazingly fun little rifles.


My second USGI Inland 937xxx, a real nice, clean, and to my knowledge non molested specimen in terms of looking the part of a rifle fresh out of an arsenal rebuild. That said, somehow both the front and rear sight were loose when I first bought it a month or so back.

Somehow the front sight key pin channel must have gotten whollared out thus making my front sight move north/south about 1/16th" with finger pressure.   I was most worried about fixing this sight as I thought I was going to have to buy front sight tools, along with a new keyway and roll pin. However, it was recommended to try some red loctite as a solution so I figured might as well try it.   Low and behold, 3 seperate applications of red loctite in a small plunger in order to push the liquid deeper into the sights channel and overall voided areas really did lock the sight up no pun intended. Thus far, it's looking like a excellent solution on the cheap. Amazing how much more effective fresh new red loctite is over just some that is just a few months old. Keep that mind if you guys have to ever use this solution.


Now on to the rear sight, and the reason for this thread. Prior to reinstalling the rear sight with a permanent solution in mind such as new staking, slight mushrooming the edges of the dovetail, and lastly using the now trusty red loctite in the same fashion as above, I figured it might be the only time I have the opportunity to scope a carbine. This is also something I want to do at least once or twice with any new rifle in order to evaluate accuracy in a more scientific manner by shooting groups at 100yds with 9-10x mag vs. irons, however with carbines and generally AKs, etc, it's almost a non starter.


Few weeks back I bought a cheap carbine scope mount, you guys know the ones, they mount via the dovetail inlet, and ultimately yield hardly any usuable rail space, and what it does yield is usually to far to the rear in order to get proper sight relief for powered optics.   Not only does it have that flaw, when mounted, and installed, it only lasted roughly 30rds before it becomes loose requiring the optic to be removed, and then have the mount retightened. If that was not enough evidence to never buy one of these types of scope mounts for your carbine, then the real kicker is that the mount itself will cause roughly a 50% + malfunction rate due to the ejected brass hitting the top of the mounts inside hood and glancing back down into the bolt in motion, thereby not allowing the bolt to fully return home on the next round. The pic below shows dozens of individual strikes on the new mount, and that was just from one range trip with roughly 50rds fired with it:


While I wanted to shoot eight 10rd/100yd group accuracy evaluations on eight types of commerical carbine ammo now that I had a scope to achieve the mission successfully.....wrong! I relied upon something made in China for reliability, and success, nuff said!   

So with the sad news behind us now, and a blown opportunity to gather valuable data accuracy points, I still salvaged the day by completing my other primary objective for the day...which was to perform a bayonet accuracy evaluation @ 100yds using 10rd groups in order to get a sample of enough size to be a relavent data point. I've been wanting to see the effects of this for some time now, and will repeat my test at 25yds with irons sights to confirm my initial test.

The procedure for the test is as followed:

Two 8" targets were placed side by side at identical height at the 100yd line mark.

Test vehicle used was a USGI rearsenal Inland with original Inland 10/43 barrel that had for this single occasion a NC m1 carbine scope mount, and a cheap LW budget 3-9x32 optic with equally cheap budget LW rings. I knew the crappy mount wouldn't support my quality optics and hard use QD mounts that they are mounted in, but the mount wouldn't even support this optic setup due to it's size, and requiring a longer sight releif offered from the mount.


Ammo used was Monarch/PPU brass cased FMJ.


Variables/target test: Absolutely everything was held constant including cadence of shots, and cool down time b/t different groups. The lone variable, or specific testing aspect/component was mounting a bayonet VS. not mounting a bayonet, and how it effects POA/POI, and accuracy. Because only 20rds needed to be fired for this test, the mount never loosed, and thus I was able to confidently use the optic as the measuring or examining tool I had thought it could be.   


Now the results, and the bit of a shocker......the first group fired off a freshly mounted optic that was totally secure, and repeatable for about 30rds as noted above was done so without a bayonet mounted.

The second group fired was WITH THE BAYO mounted, and exhibited dramatic gains in accuracy, and less variation in the group's overall POI.



VS




Group results: (note on the first groups target, it has the intial sight in shot at the very extreme left side. I don't believe in called flyers, or pulls, so anything but initial sight in shots get recorded in my groups statitics.)




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LMTmonoMan View Drop Down
Grunt
Grunt


Joined: Mar 18 2018
Location: AL
Status: Offline
Points: 152
Post Options Post Options   Thanks (0) Thanks(0)   Quote LMTmonoMan Quote  Post ReplyReply Direct Link To This Post Posted: Sep 27 2018 at 5:53pm
In summary, I actually think that these results aren't that strange given the design of the carbine...specifically how it's not free floated, using a longer, pencil profiled type barrel that is even more susceptible to barrel whip/flex, and lastly how the barrel sits inside the stock channel when secured via the type 3 bayo lug band.

Normally hanging heavy things off the end of your barrel is a recipe to worse accuracy, think suppressors on pencil barreled ARs, however in this unique case, and given the rather archaic tech the carbine features with regards to repeatable accuracy, and overall accuracy as well.....I think somehow the added weight of the bayonet mounted seems to act as some form of a "bow vibration dampener", or similar device that uber precision rifle guys sometimes use on their rifles.   

Perhaps the added weight is helping bed the barrel's movement from shot to shot, specifically constricting the group's overall horizontal disbursement, or what would seem like side to side shift of the barrel from shot to shot. Both targets exhibit similar vertical disbursement, but the horizontal disbursement on the non mounted test target is the main observable difference b/t two targets.

Anyways, food for thought, and the results were very unexpected.   
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