All posts by Hount

Holosun micro red dot feature comparison chart

ABCGLUM and all combinations of them. Confusing isn’t it?

What are the differences between Holosun micro red dot models?

Aimpoint compatible base Solar power Side battery housing (Aimpoint micro style) Circle and 2MOA dot Integrated lens covers Ruggerized frame around turrets 30 m and 30 min waterproof
HS403B x
HS403C x x
HS403GL x x
HS503BU x x x
HS503CU x x x x
HS503GU x x x x
HS515BU x x x x
HS515C x x x x
HS515CM x x x x x x
HS515CU x x x x x
HS515GM x x x x x x


  • A base model without Aimpoint compatible mount
  • B base model with Aimpoint compatible mount
  • C Solar powered model
  • G External battery housing
  • U Ruggerized frame around turrets
  • M Extra ruggerized frame + better waterproofing
  • 403 2MOA dot
  • 503 65MOA ring + 2MOA dot
  • 515 Ring + dot + integrated flip-up lens covers

Cleaning brass with ultrasonic cleaner

Brass cleaning science! We’ve tested three different solutions for cleaning fired brass with ultrasonic cleaner.

The  temperature was set to 50 degrees (Celsius of course, that’s probably roughly 56 to 125 inches in US temperature units, stones or is it nails?) Cleaning time was 15 minutes.

Below in the table you can see the different concentrations used. Every solution was mixed to cost 0.10€. I thought that to be the only viable way to measure different solutions. It would not have been fair to just measure the amount of solution if it’s not feasible to use the most expensive solution in long term use. All mixtures were made to a 125 grams of  35 C° water. This naturally threw difference of the total  amount of cleaning solutions by ~10% as C4+water sums only 127 g and soap+acid+water 150 g. But for the nature of cleaning brass outside of synthetic tests I believe this type of difference is acceptable.

Washing solution Price ( €) Package size (grams) Price per gram Amount in solution (grams) Price of solution
Oregon Ultrasonic 15.9 1000 0.0159 6.98 0.110982
Bore Tech C4 29 473.176473 0.06128791615 2 0.1225758323
W5 dishwasher 1.19 500 0.00238 11 0.02618
Citric acid 0.78 40 0.0195 4 0.078
Mix of acid+soap 1.97 in total 15 in total 0.10418

As you can see the Bore Tech C4 Carbon Remover was used only with ~1.6% concentration. W5 dishwasher soap had to be added relatively huge amount in order to reach even close to what Carbon Remover and Ultrasonic cleaning solvent costs. Most likely lower amount of W5 dishwasher soap would have been sufficient. You can purchase citric acid way cheaper in larger containers.

All brass looked pretty much the same before going into the bath.

Brass were sorted from these three rows to three cleaning containers randomly.

Inside the brass looks pretty bad.

Headstamps were mostly S&B but other brass were also in the mix.

After 15 minutes of cleaning the water had turned to a black musk in every cleaning container.

Let the photos be the judge which solvent won:

From top to bottom: W5+citric acid, Oregon, Bore Tech

It’s clear that Bore Tech C4 Carbon Remover was the most effective on cleaning the outside of the brass. Picture may not show the difference as clearly but nearly all dark spots were gone on brass that was bathed in C4 Carbon Remover, all brass were shiny and uniform color.

Next came the mix of dishwasher and citric-acid. Brass is shiny but slightly tinted toward brown compared to Carbon Remover.

Last place in cleaning the outside came Oregon’s Ultrasonic Cleaning Solution. It left dark spots in most of the brass and it’s even visible in the picture how the brass is darker that with other two contenders.

When comparing inside of the brass there was clear difference between all three cleaning solutions.

Dishwasher soap + citric-acid

16 brass out of 20 were cleaned extremely well with W5+citric-acid. Some were left with dark spots, it’s unclear for me why as when comparing the darker brass with super-shiny all were most likely once fired S&B brass and collected from indoor range. So no moisture contamination should have taken in place.

Oregon Ultrasonic Cleaning Solution

11 brass out of 20 were somewhat cleaned, but none of them came even close compared to W5+acid mix. Some of the “clean” brass in this group might be dirtier than the “dirty” in other groups.

Bore Tech C4 Carbon Remover

Even though Carbon Remover won when comparing cleaning results at outside of the brass it’s not as effective cleaning the inside of the brass than home-made mix of W5 dishwasher soap and citric-acid. 12 out of 20 brass was super-shiny but the rest was left unsatisfying dirty. Notice how there is some black residue around the primer hole where dishwasher+acid left that area cleaner on most brass. Again when checking the headstamps there were no clear correlation between clean and dirty brass. 7 out of 8 dirty brass was S&B and most likely only once fired e.g. factory loads.

All brass in the test were handled with nitrile gloves in order to prevent grease-marks from fingers. Brass was not sorted or selected anyway. Most of the headstamps were S&B. Others were TCS (4pc), G.F.L (1pcs), STV (1pcs) and Geco (1pc). Some brass might have been reloaded (at-least two S&B had different primer than others), but majority of the brass was once fired factory loads. All brass was collected from indoor range so no water or moisture contamination could have taken place which could have baked some of the powder residue to the brass. There were no correlation of cleaning results between different brass whether they were reloads,  or factory ammunition between different companies.

The Ultrasonic Cleaner used in the test was cheap Chinese made 9l Stainless steel made tabletop cleaner. Advertised Ultrasonic cleaning power is 200W but no more than 150W is used from the outlet during cleaning cycle with heating turned off. Brass was placed in three identical thin wall plastic containers and adequate amount of water was added to the stainless steel tank so all three plastic containers holding the 125g water, cleaning solution and brass, started floating. Plastic is not optimal container as it has tendency to absorb ultrasonic waves, but in this test the purpose was not to clean brass as effectively as possible, only to compare different cleaning solution consecrations when their calculated cost was identical.

End result of this test was to continue tests with dishwasher soap and citric-acid. Maybe changing the concentration or adding salt and/or dishwasher detergent to the mix might help cleaning even the most stubborn dirty brass. Naturally cleaning 20 empty shells at a time is not the goal. When cleaning solution mixture is complete the purpose is to clean as much brass as it’s possible to load to the 9 liter (5 yards for you imperial folks) cleaner.

Speed Cycling and reliability mod for Baikal MP-153

There is always that one particular brand, type or batch of shotgun ammunition that does not work with semiauto shotguns. Some shotguns are more picky than others and even same shotgun models some individual guns cycle same ammunition that other guns struggle with.

For DIY person it’s tempting to fix this uncertainty. Naturally lapping the bolt carrier rails, polishing all metal-to-metal contacts will help the gun to cycle. With gas operated shotguns drilling gas ports slightly larger might also help.

After doing all above I still found that there exists ammunition that does not cycle reliably with my Baikal MP-153.  Mostly really old 24g skeet and trap ammunition. Some may ask that why bother? Those asking that question don’t get the tickling sensation when fixing something makes things better.

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Phillips head screw mod to roller cam pin

Some time ago I acquired a roller cam pin to my AR-15. Gas key had to be machined to match the new round cam pin, but that was not an issue as I had planned to give my bolt carrier some diet in a form of tender milling from my trusted gunsmith. (Final weight for bolt carrier is 173 g.)

My roller cam pin had one problem though. The screw that was supposed to hold the brass roller in place had a tendency to loosen up and then jamming itself against gas key.

Roller cam pin screw loosen up and hitting gas key. Effectively preventing bolt from opening.

Original screw was completely flat, without any screw drives. I did not had adequate tools and strong enough thread lock to hold the screw in tightly.


I contacted the roller cam pin manufacturer and they offered to fix it for me. They apparently have some adhesive to semi-permanently attach the screw to rest of the cam pin.
I, being more of an DIY-guy, opted to fix the roller cam pin myself.
After two iterations I was finally happy with the solution.

Custom made phillips head screw for roller cam pin.

It may not be the best possible steel strength for this particular application, but the brass roller leans against small bulge in the cam pin, so the screw don’t have to take any force coming from side. It just has to hold the roller in place and avoid any contact with gas key.


Time: 1 hour
Tools used: one random M4 screw, hand-file, cordless drill, hacksaw, PH2 head screwdriver and “Extra hard thread lock”

DIY Shell Prepper

Shotgun Slug and Buckshots have nasty tendency to cost much more than most smaller shotsize ammunition. This has driven many shooters to seek cheaper ways to achieve Slugshots by modifying birdshots or using the birdshot cartridge as a base and just changing the shots to slug.

I came up this brilliant idea of a shotgun shell prepper from Youtube user Mountain Storm . All credits to him for the idea.

Shell Prepper will cut the star crimp away leaving a small rim which will act as the crimp to hold the wad and slugshot in place.

Without further ado – DIY Shell Prepper v.1.0

DIY Shell Prepper

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Freefloat for Norinco 56S

Why not? That’s the answer to your obvious question: Why?

Yes, it is an airsoft stock held in place by some aluminium bar and few screws. I borrowed the whole idea from a fellow hobbyist. Thank you!
Not 100% happy with the outcome but had to live with the tools I had in hand. All of this was made in balcony of urban apartment.
Not 100% happy with the outcome but had to cope with the tools I had in hand. All of this was made in balcony of urban apartment.
I also made thinner front sight from M4 bolt with electric drill and file. Old thick sight next to new as comparison.

SRA Legalizer for SLB holster

Since I got my SLB holster I knew that I would not need another holster with my CZ-75 SP-01 Shadow. Only problem with the holster is that it is not suitable for SRA. SRA rules state that the hoster must cover at least front sight, ejection port and trigger. At it’s vanilla state SLB holster covers only trigger, so something had to be done.

Like my SLB holster accessory for CZ-75 Airsoft gun my only “rules” for this next project was that it must not require any modifications to the holster and I must be able to attach and detach the addition easily without tools.

Without further talk, let me introduce the early prototype of SLB SRA Legalizer!



The SRA Legalizer is made from acrylic, polyethylene plastic, M3 screws, M4 threaded bar, plastic glue and ****load of curse words.

The outer side is held in place by M4 threaded bar. This is the first thing to insert when installing the accessory.
Inner side is held in place by pin made from piano wire.
Inner side is held in place by pin made from piano wire.
This is really an early prototype. As you can see from unfinished corners etc.

DIY carbon fiber magazine extension for Baikal MP-153

Contrary what the topic says this is not fully DIY. The steel adapter is made by fellow hobbyist called ferri. And the carbon fibre tube is from Ebay. It took some filing and Dremel’ing to make the follower pass the steel adapter smoothly.

This came to replace my current barrel-length aluminium magazine. This weights approximately 25 g less than the aluminium magazine and total weight without spring is around 150 g. I seem to have forgotten the magazine support from the picture. And I don’t have suitable spring in hand so no clue how many cartridges will it hold.

Steel, carbon fiber, plastic end cap and some 2-component glue to hold it all together. Total costs 30 €.

Carbon Fiber Magazine
DIY Carbon Fiber 12 cal Magazine

CZ-75 Action Air pistol and SLB holster

After I purchased my SLB holster I immediately throw away my crappy kydex holster I had for my KJW KP-09 CZ-75 Action Air pistol. (KJW stands for Kuan-Ju-Works.)

Only problem is that in SLB quick draw holster the pistol is held in place from the front picatinny rail (present CZ-75 SP-01 Shadow) which obviously my Action Air pistol did not have.

One viable solution would have been to purchase older style SLB front support part, but I don’t feel comfortable screwing and unscrewing that part every time I’d change from ActionAir to Shadow.  And I really like the picatinny solution for Shadow so I had to figure out another solution.

After 1 hour of brainstorming and many nearly-cut-myself-with-knife -situations later… meet the DIY Action Air support for  SLB!

Action Air support for SLB Action Air support for SLB

Pardon the grinding marks, but the tools I used to make this out of PE plastic were: knife, sandpaper, file and tears (I have all of my tools elsewhere, so I had to live with what I had in hands) When I have opportunity I will give this part a quick heatgun treatment to melt all plastic lint and scratches away. 

I can attach and detach this part in seconds and because it is sitting tightly between aluminium support and the original picatinny holder it won’t move anywhere.

Action Air support for SLB

And final picture with my trusty Action Air CZ-75

Action Air support for SLB