Jump to content
Sign in to follow this  
Aod

BOLT M4A1 Internals

Recommended Posts

Evening everyone,

Thanks to FTZ-WildeCard, I have a BOLT M4 gearbox open on my desk at the moment in need of a little fixing. As there's very very little information about these things around, I've put together my thoughts on the internals of this gun.

 

Overall Assembly:

Gear box casing is well screwed together, screws are all correct size, not over or under tightened. Most screws are 2mm Hex-socket, two of the top-rib screws are PH2.

Inside the gearbox, I am presented with an acceptable sight, no huge globs of grease or chunks of metal flying around, however, due to the recoil-system, there is an accumulation of aluminium dust in the piston assembly, and the grease used on the gears is terrible.

 

Piston Assembly:

 

tbgHZi6.jpg

 

3N131SZ.jpg

 

C7Yl7aJ.jpg

 

UMdRLL1.jpg

 

8son8lO.jpg

 

7Y4MK5q.jpg

 

The piston is, a full-steel teeth type, but the second piston tooth is not shaved down for clearance. The piston body is machined Aluminium, type-II black anodizing. The tooth-rack has full-support (completely covered by body from the back) which is beneficial for strength with very stiff springs. The piston is very very well machined. That being said, I'm not convinced that the extra weight of a full-aluminium piston is sensible, but in low RoF setups as necessitated by the recoil-system, probably acceptable considering the weight reducing cutouts.

Inside the piston, there is no bearing, but instead there is a flat aluminium disk that engages the rod for the recoil weight. This disk has a hollow on the front (muzzle) side, and rests on a thick circle of black rubber, presumably to reduce shock on impact. The disk is held in place by the spring, so cannot come free.

The recoil rod itself is a spring-plunger, which accounts for BOLTs claim that the gun is jam resistant.

 

xLwOeMs.jpg

 

t6a4pDy.jpg

 

The piston head is excellent, it seals well and has very well designed ports for good compression. If one changed piston, I would advise keeping the pistonhead.

 

P3ZfFQ8.jpg

 

The Cylinderhead is excellent again, double o-ring sealed with a large, thick rubber buffer that helps offset the mass of the piston assembly. Excellent candidate for Sorbo-modding.

 

Nozzle is well made, hard plastic (personally, I prefer plastic nozzles to aluminium), and sealed with an O-ring at the back. Curiously, this one was shaved/sanded down at the front for some unknown reason. I forgot to take a photo, sorry.

 

q6lgtVf.jpg

 

Tappet Plate is perfect. Standard flexible/twisty black nylon but nice and thick in all the right places, a keeper for sure.

 

Cylinder is a boring standard ported brass unit. Nothing special, but no issues either. No photo, you know what a brass cylinder looks like :P

 

Gears:

Oh dear, quite disappointing. The gears are obviously well made, and would probably be fine in most setups, but with the increased tension of the recoil setup, are looking rather unhappy.

Unfortunately the shimming was poor, though not shocking, but there is evidence of the poor shimming on the gears in the form of telltale scours.

 

E9PTrsU.jpg

 

SPngnrd.jpg

The Gearbox takes 6mm bushings, and is equipped with stainless-steel double-oil-groove bushings. Oil Groove bushings are inadvisable on the best of days, and Stainless steel is not hard enough for use as bushing material. The problems here have been exacerbated by the absolute lack of lubrication in the bushings. As you can see here, the axle hole on this bushing has widened and is loose on the gear axle, while the photo doesn't show, there's more than 0.7mm of side-to-side play, mechanically unacceptable. In the next photo you can see the material crowning around the hole due to deformation. Replace as soon as possible.

 

q2ucJkP.jpg

 

The Sector gear is well made out of good steel, but the gear axle is steel stock, not a hardened pin, and I anticipate it will break as a result. You can see the start of the wear from the "oil groove bushings" on the insufficiently hard axle. Additionally, the lower-section of the gear that interfaces with the spur gear has been beveled to prevent catching the spur gear with poor shimming, but it has been cut too much, removing a substantial amount of load-bearing material. Replace when able.

 

NkKuqPz.jpg

 

The Spur gear is well made, but is made out of stainless steel again. As you can see in the image, there is substantial deformation of the gear teeth from the much harder carbon-steel of the bevel and sector gears. Additionally, the manufacturer has committed a substantial faux-pas and made the axle out of the same piece of metal as the inner/upper section of the gear, so the axle is soft stainless steel. Replace as soon as possible.

 

1Y14JO9.jpg

 

The Bevel gear is moderate. It is sintered steel, but the sintering is good and the steel is a good alloy. Unfortunately, like the Spur gear, the axle was made as part of the gear body. Sintered steel is a little too brittle for use as an Axle, but this shouldn't be too problematic (amusingly, that makes this gear the only contiguous 1-piece bevel gear I've ever seen). complicating matters, is the fact that the gear is the same type as used in the Marui NextGen recoil guns, with no special cams for the cutoff lever, but can be replaced with a regular bevel gear if you change the AR-latch at the same time, though I wouldn't recommend it if possible.

 

3mzT6kL.jpg

 

SHS make an affordable Recoil M4 gearset, the bevel from that seen here. Note that it's practically identical, but with a hardened axle-pin and without the chipping on the bevel-teeth. Buy that and sell the otherwise useless spur and sector gears to an impoverished Marui Recoil M4 owner  ;)

 

Gearbox Casing:

The Casing is fine. Well cast out of an acceptable grade of potmetal. It's not too thin up-front, and after you radius the cylinder windows, will probably last a while. If you replace the gearbox casing, you will lose the moving fake bolt carrier as seen through the ejection port (and will thus need a different charging handle). To keep the recoil functionality with a different gearbox casing, one need only enlarge the hole at the back of the piston space (behind the spring-guide) to around 8mm with a drill.

 

Final Impressions:

The concept and design of the mechanism seems fine, the execution somewhat less so. The poor manufacturing design and material source of the geartrain being the main problem. With appropriate replacement gears and bushing, and a happy and careful shimjob, and this gun should be able to run smoothly and effectively without any significant reliability issues, especially at UK power levels.

 

Happily, the hard-to-replace parts, most importantly, the recoil-weight and buffer tube, is excellently made. It's machined aluminium, substantially better than the stock Marui equivalent, but do note that they are completely incompatible with each other.

Edited by Aod
  • Like 1

Share this post


Link to post
Share on other sites

Cylinder compression was good, despite the accumulated aluminium dust in the cylinder. Airseal nozzle works very well.

 

Hop chamber is very nice, it's a rotary-wheel type that looks very similar to a Madbull Ultimate unit but painted dark gunmetal grey. Barrel is black anodized Aluminium and marked "Bolt 6.0mm", no idea of the actual bore diameter. Hop rubber looks acceptable.

 

Motor is a high-torque unit but with ferrous magnets, it works well enough but upgrading to a Neo-magnet Hightorque would improve trigger response and RoF.

Edited by Aod

Share this post


Link to post
Share on other sites

I throw my spoon to this also, I have Bolt Sopmod version and have done some modifications to its internals.

At first it caused me lot of headache, as it was shooting semi only. Well, finally noticed that selector plate was modded so it would not move cut-off arm. I bought the gun from Germany, and due their laws here it was modded by Bolt to fulfill the laws... I was not aware that law, and it took while to find the small mod done to selector plate. I replaced plate with old unknown maker plate and now it rocks happily.

 

My friend did a metal spring guide from old metallic non-bearing, basically it was just drill a hole through it. Before that we tried to drill a bigger hole to spring guide with bearings, only to found that its bearings inner diameter are just 7mm... And we were after that size hole, so guide snapped. :P

I filed down the second teeth from the piston, just to be sure. 

Oh, and I put the Gate PicoSSR 2 mosfet inside the gearbox. That fet is amazing small, and fit to space where wires come inside box. No need to more wires outside the box  :)

Also I changed the wires to better, if I remember right they are now non silicon AVG18.

I the first or maybe second game the fake bolt carriers actuator arm broke. I had assembled it wrong and it stuck when returning back to front position. Next cycle snapped arm clearly and it was later found inside the box. My friend machined new one from steel, and it is again functioning. 

 

Gun shoot a little too powerful with 1,69J (130m/s with 0.2g) so I replaced the original spring with M115 spring. Now it shoots around 120m/s.

 

Lastly I replaced the regular ris with Iron Airsoft URX4 13". Bad pictures here: http://arniesairsoft.co.uk/forums/index.php?/topic/197001-ar15-variants-and-derivitives-picture-thread/?p=2652247

Love how light the URX4 is! 

 

Otherwise really nice gun, blowback is so nice that I doubt I will newer buy any new gun without one. 

I'm running 11.1V lipo in it, and now I think 7,4V would be safer. What you think?

Edited by Mazor

Share this post


Link to post
Share on other sites

Airsoft World (where my brother and I sourced a Bolt SR47 and a B4A1 respectively) just issued a communications warning against the use of 11.1v Lipos in these rifles. If you are running around UK spec levels (approx 320 ish) the weaker spring means a higher rate of fire than the design was rated for and can cause damage. If your spec is closer to the Taiwan version (400fps) then you can use 11.1v lipos.

Share this post


Link to post
Share on other sites

I recently opened a Bolt, bought  a good 1.5 years ago by the first user, I am the third used.

Believe it or not, never opened before, I looked in it and it had LCT gears, black.

 

Also my piston is just a transparent plastic one.

Share this post


Link to post
Share on other sites

I recently opened a Bolt, bought  a good 1.5 years ago by the first user, I am the third used.

Believe it or not, never opened before, I looked in it and it had LCT gears, black.

 

Also my piston is just a transparent plastic one.

Looks like you have one of the first gen Bolts then.  

Share this post


Link to post
Share on other sites

Not in my experience, so far they've used the same motor, which is pretty decent.  Still ferrite, but the magnets are just as strong as a weaker neodymium.

Share this post


Link to post
Share on other sites

Looks like you have one of the first gen Bolts then.  

yes indeed, it's upgraded to 430FPS with a chimera mosfet now.

 

Besides, believe it or not LCT M4 that is out now is the same as a bolt.

Only cheaper.

http://www.wgcshop.com/wgc2008/main/product_detail1.php?search_From=category&item=LCT-AEG-L4CQB-SE&search=special&rs=Electric%20Airsoft%20Gun%20-%20AEG&catid=1&cat=900&view_choice=c

Share this post


Link to post
Share on other sites

I do remenber reading somewhere that BOLT had some affiliation with a high end maker of AKs. I thought I had tracked it back to LCT but had never been able to confirm that. I ended up getting one of the first runs of the SOPMODs, haven't opened it up yet myself but from the review if I was happy with the preformance out of the box there doesn't look like there is alot of weak points in the part choices. 

Share this post


Link to post
Share on other sites

I don't have any experience with the internals of any LCT products so can't comment on any possible similarities there, but I can confirm that almost all the Taiwan Airsoft manufacturers cooperate very closely with each other (I'll give you one guess which one is excluded from that. Hint; They make terrible M4s)

 

This is evidenced by G&G guns sometimes having LCT Externals, Socomgear getting AEGs from G&G and VFC, Pistols from WETech etc.

Share this post


Link to post
Share on other sites

The quality of the externals is at least as good as any G&G M4 I've come into contact with. Though there are several niggles, which detract from the overall quality of the gun.

 

- Dust cover doesn't close

- Faux bolt deforms itself over time during EBB (wut!!)

- Bolt release switch is not spung or secured, this means it just flaps pointlessly (annoying as even cheap ACM guns I have seen do not suffer this)

- Front RIS system wobbles from stock, will have to try tightening it

 

Aside from that, the rest is very good - I'll try to put together a video review in the new year and will report back here.

Share this post


Link to post
Share on other sites

I have noticed no other problems except that actuator arm broke. But now it is machined from metal so couple shots will set the bolt free and it unstuck. I have tried to straighten the faux bolt, but it keeps deforming again...

Share this post


Link to post
Share on other sites

On FTZ-WildeCard's rifle, the fake bolt plate itself completely separated at the bend between the sleeve at the top and the plate.

Share this post


Link to post
Share on other sites

Alright so its merely a matter of appearence. And if I really need to I could just remove it completely. The bolts not my primary rifle so it doesn't get alot of abuse or use so i don't worry too much.

That's what I did to FTZ-Wildecard's Rifle, yes. I trimmed the nylon piston-hook away so that it wouldn't engage the piston any more, no need to have that mechanism still operating with no visible benefit.

Share this post


Link to post
Share on other sites

I've been running this along with a RM4 with iron sights only due to fear of the recoil messing up some airsoft optics. Have you guys had any issues with the recoil messing with your optics? I know GBBR users get this alot and this is getting close to Gbb recoil.

Share this post


Link to post
Share on other sites

Alright so its merely a matter of appearence. And if I really need to I could just remove it completely. The bolts not my primary rifle so it doesn't get alot of abuse or use so i don't worry too much.

 

 

Neither has mine, nor my brothers BOLT BR47. Mine was skirmished perhaps twice and was already dead before it made it to its first skirmish. My brothers made it to two before dying.

 

I have to upgrade my complaint level on this from "niggle" to "disillusioned"! Really not for the £320++ asking price, as you'll have to spend money reworking the internals (and this is not a matter of if, it is a matter of when AND how soon). 

 

Still the recoil is much heavier than the TM versions - but still, not worth the extra spend at the moment. Very, very poor product for the price.

Share this post


Link to post
Share on other sites

I have to upgrade my complaint level on this from "niggle" to "disillusioned"! Really not for the £320++ asking price, as you'll have to spend money reworking the internals (and this is not a matter of if, it is a matter of when AND how soon). 

 

Still the recoil is much heavier than the TM versions - but still, not worth the extra spend at the moment. Very, very poor product for the price.

 

I have same opinion here. It is really nice and fun gun to shoot, but not worth of it's price tag... I paid 400€ for this gun, for that money I could buy really good gun that works well OTB.

 

Wires and castle nut are giving me bad headache right now. I am going to open the GB, but every time I do this the wires lose their insulation, resulting to shorting. This time I will drill through the receiver end plate and route wires through there and then under to the buffer. It costs me the sling attachment point, but using the stock one anyway.

 

I am keeping this sucker, it is so nice to shoot. Some day it will be perfect, I hope.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use and the use of session cookies.