POI shift with matrix 380

Crossbow Hunting

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Karl
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POI shift with matrix 380

Post by Karl » Thu Jun 27, 2019 7:45 am

Getting over some health issues, thought I would take it for a twang first time in many months.

Firstly chronographing went well. Diablo+ 150gn field tips which I assume is 400 grains. 364fps average with F-1 Shooting Chrony. I havent done the math but assume that is close to the right energy levels?

First shot was about 6 inches low and 6 inches right. Adjusted it up to the bullseye with a few more shots, using the one arrow for everything.

Then decided to do a 3 shot group with that arrow and 2 other arrows. 2.5" group at 40 yards....however the POI was now 5" low and 4" to the left. :crazy:

I notice the string had lengthened during the shooting, brace height had changed from about 1/2" to 1/4", would that account for it? Scope issues? I had to pack it in due to rain but will take it out on Sunday and try again.

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Deaf jeff
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Re: POI shift with matrix 380

Post by Deaf jeff » Thu Jun 27, 2019 9:13 am

i would start by checking to be sure all screws are tight, i would not think BH alone would cause that much of a change. i'm sure others will voice their input
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W.Miguire
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Re: POI shift with matrix 380

Post by W.Miguire » Thu Jun 27, 2019 10:51 am

Sounds like your scope is loose. take each screw and clean with acetone and clean the hole and then get some BLUE locktite and put a small amount on each screw and you should be good to go. Just don't over do it with the locktite.
W.M.

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IronNoggin
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Re: POI shift with matrix 380

Post by IronNoggin » Thu Jun 27, 2019 3:37 pm

W.Miguire wrote:
Thu Jun 27, 2019 10:51 am
Sounds like your scope is loose. take each screw and clean with acetone and clean the hole and then get some BLUE locktite and put a small amount on each screw and you should be good to go. Just don't over do it with the locktite.
W.M.
Agreed 100%
The ONLY time my 380 has ever lost it's grouping was directly due to a couple of those mounting bolts working loose.
That was in the early days I owned it.
Followed what he said there, and have never encountered another problem.

Cheers,
Nog
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BrotherRon
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Re: POI shift with matrix 380

Post by BrotherRon » Thu Jun 27, 2019 10:32 pm

Don't forget to take the stock off and check the trigger box screws!
I have found this to be the problem a couple times in the past.
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Karl
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Re: POI shift with matrix 380

Post by Karl » Fri Jun 28, 2019 12:33 am

Thanks gents I managed to tighten the screws, just a little. Will find a tutorial on dissassembly to check the trigger box too.

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robertyb
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Re: POI shift with matrix 380

Post by robertyb » Fri Jun 28, 2019 7:50 am

Karl wrote:
Fri Jun 28, 2019 12:33 am
Thanks gents I managed to tighten the screws, just a little. Will find a tutorial on dissassembly to check the trigger box too.
Two screws hold the stock on, When removed you will see the screws holding the trigger box in place. These are probably your problem as they let your trigger box vibrate loose as you shoot. Use blue loctite on them.
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Excalibur Marketing Dude
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Re: POI shift with matrix 380

Post by Excalibur Marketing Dude » Fri Jun 28, 2019 9:22 am

Thanks guys, you're making my job easy! All your comments are 100% correct and exactly how we address accuracy issues and loose fasteners are normally the problem. Good to know we have so many knowledgeable owners out there, keep up the good work! :D

Peter

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Fazan
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Re: POI shift with matrix 380

Post by Fazan » Fri Jun 28, 2019 6:44 pm

"brace height had changed from about 1/2" to 1/4""
Hmmm. Measured from where?

Karl
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Re: POI shift with matrix 380

Post by Karl » Fri Jun 28, 2019 10:15 pm

Pardon my lazy terminology , distance from the pads. Also probably poor use of imperial measurements, will measure exactly and report back.
Last edited by Karl on Sat Jun 29, 2019 3:58 am, edited 2 times in total.

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Fazan
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Re: POI shift with matrix 380

Post by Fazan » Fri Jun 28, 2019 11:12 pm

I am not an expert by any means, but if I understand right your string " streched" quite a bit for just handful of shots you mentioned. Or your limbs relaxed somehow. I would have a close look at those limbs and bolts holding them in place.
There is quite few people here regarded as string experts. Maybe they can chime in with an opinion for that kind of string stretch with few shots.

Cardinalsfanforever
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Re: POI shift with matrix 380

Post by Cardinalsfanforever » Fri Jun 28, 2019 11:28 pm

I have a matrix 380 and after it set a few weeks, the zero was off about 6". Excel replaced the scope.
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Karl
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Re: POI shift with matrix 380

Post by Karl » Sat Jun 29, 2019 3:49 am

I'll re shoot and take more notice of the string this time. Get some before and after photos.

Karl
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Re: POI shift with matrix 380

Post by Karl » Sat Jun 29, 2019 4:16 am

Just checked trigger box screws, they were tight. :thumbup:

Gents if it is the scope ultimately, can I mount a red dot on a crossbow? They are about the only spares I have laying about, also quite a bit lighter than the tactzone, I never needed its ranged reticles anyway

xcaliber
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Re: POI shift with matrix 380

Post by xcaliber » Sat Jun 29, 2019 7:56 am

Yes you can mount your red dot scope, and with some practice you can get your hold over / under down so it’s second nature. I would zero at 30 yards personally.

Good luck,
Dan
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