G&P M870 questions...
 

I recently purchased a G&P M870 with a speed stock and illuminated dual color sight and laser combo. I love the feel an usability of the gun; I do have a few questions for anyone who has experience:

1. I frustratedly discovered that the magazines (22 rd) easily loose their end screws and springs when transported in a bandolier; I ordered a few more and they have the end screws are glued in. Was this a manufacturing defect?

2. Accuracy seems to be lacking and the BB travel is not consistent (I use high quality 25's). I have heard that there is a problem with manufacture left excess grease. Is this true?

3. Is there an exploded diagram of these guns? (to disassemble and clean, see #2 above)

4. A fellow player told me that I should replace the barrels (inner and outer) with a mid-length and my accuracy and fps will be assisted greatly. This true?

Thanks all!!

Ok:

1.) I cant comment on the mag problem. No idea why they would backout like that.

2.) What do you mean the accuracy is lacking? Arr you get 20 feet out of the gun? Or are you getting 100 feet. It is a single shot spring shotgun, however it is one of the more usable shotgun platforms. We need to know what you are trying to get out of it. About the grease, have found excess grease?

3.) google g&p m870 diagram. 4 or 5 diagrams popped up immediately.

4.) The m870 already shoots a bit hot. You might want to think about increasing the weight of your bb first. Sometimes it is simply a matter of finding that sweet spot.

I unfortunately cannot help you with some of the model specific questions, however I can definitely try and help with some of the other issues.

2) When you say BB travel is inconsistent, I take it you mean some BB's just veer completely off course? G&P products are generally not known for having excess grease, however it may be possible. You can fix this by cleaning the inner barrel with a barrel cleaning rod and an appropriate cleaning solution. Aside from this there are many possible causes for inaccuracy. The most obvious one is your hop up. Are you applying too much hop? Perhaps not enough hop? Did you buy the gun second hand? If it's a used gun perhaps the hop is worn down, or misaligned. It's possible you may have gotten a bad batch of BBs. What brand BBs exactly are you using?

4) For some reason many players have fallen victim to the belief that replacing your inner barrel will magically improve FPS/accuracy/range. This simply is NOT true. Not all after market barrels will yield you a performance increase, and an increase in FPS does not always mean an increase in effective range. There are many different manufacturers that make varying qualities and types of barrels, and you will need to do some extensive research to figure out which one is right for your applications. I will mention however that many players swear by tightbore barrels, which basically makes the blast of air more efficient thereby causing an increase in FPS. As I mentioned earlier, this does not mean you will get more range or achieve greater accuracy (although you may). Another misconception is that a longer barrel will yield a performance increase in effective range. This stems from the real steel theory of stabilizing the projectile. I will not divulge into the how much truth there is behind this, but simply put, the physics behind a 6mm BB is completely different than real steel projectiles; thus, you can't apply the knowledge and technology of real steel barrels into airsoft effectively.

I am not saying tightbore barrels are bad, nor am I saying all after market barrels are useless. What I am saying is there are many manufacturers and even players that make claims of performance increases that are greatly exaggerated. My advice to any beginner "airsoft tuner" when it comes to barrels is unless you're willing to spend $70-100 on a barrel, don't bother. The investment is much better spent elsewhere in the gun, namely a decent hop-up set up. Any cheap barrel will likely yield a performance decrease and this is due to the manufacturing process. Cheaper barrels tend to not have a consistent bore diameter and bore surface finish which both lead to innacuracy.

As for outer barrel length, you generally replace your outer barrel to the same/similar length as your inner barrel. Alternatively you could buy a silencer attachment to hide the inner barrel. All the outer barrel really does is stabilize the inner barrel. Often times you will need to wrap the inner barrel in teflon tape or electrical tape to really stabilize it.

I have 2 G&P shotguns and they shoot nice and straight for me, so i cant comment on that, Mags do suck balls tho.

I find if u overload them the spring will get stuck and it will not feed. And the screw on the back has popped out on me a few times. I used some clear scotch tape on the end to keep the screw in.

I also have a super hard time getting mags out so tapes a loop on the bottom of the mags to pull them out.

Thanks! Yeah, The shots are not consistent; yep, I've run a small cloth down the barrel and got a glob out. Guess I'll just clean it after a few shots and repeat until it's cleaned out.

I find a bunch of diagrams for actual shotguns and other misc. airsoft guns... but no M870 airsoft gun. Can you hit me with the link if you found one??

Thanks for all the feedback!! Yeah, I'm thinking my accuracy issues are grease related and they should work themselves out. As far as hop-up, it is set from the factory. What can I do if anything with the hop-up; ie. can it be altered? Can/should I look at upgrading it or the gasket between it and the barrel?

Yeah, they do suck in ways. I'll try adding something to assist pulling them out. Also, I ordered some new mags and they all come with the plastic screws are held in by two small spots of glue. Guess that's their recall fix huh?

My apologies, for some reason I thought the G&P M870 had an adjustable hop. I just confirmed it does not. There are however some people who have modified their M870 to have an adjustable hop. If you're a beginner I don't think I would recommend this level of work as your first project.

You mentioned you removed grease from the barrel, it appears that may be the cause of the accuracy issues. I would give the barrel a thorough cleaning and see how it shoots. If it still doesn't shoot the way you want it to then I would start considering modifications. The problem with spring shotguns is that there aren't many available parts, you will definitely have to do some searching.

Do you recall where or who might have info on upgrading the hops, bucking, etc. and what parts fit these guns? I am currently rebuilding and upgrading my SVD with everything save the chassis; I enjoy mechanical deconstruction/construction. I'd love to maximize this gun as far as possible because I really like the platform for tight woodland situations.

Thanks for any direction on this pursuit!

If I recall correctly, G&P M870s are very similar to the Maruzen CA870 (not to be confused with their gas model 870). There was a thread a while back on the topic (If you search, I'm sure you'll find plenty more) that was discussing how to adjust the hop up. Some people just drilled a hole and used a screw to press down on the hop rubber if that makes any sense, so screwing it tighter would yield a greater hop. Here is that thread:

http://www.airsoftcanada.com/showthread.php?t=93415

Thanks, interesting thread. I've disassembled it and I see exactly what you/they were saying. I believe a real good cleaning and lubricant only where it's needed might be a better play; I leave out-of-the-box mods on the shelf for now.

Sorry for relighting the conversation. I too have just ran into the short mag issue were the spring plug as "undone" itself in the gun.
Kin'a ticked but oh well I'm learning, currently looking at replacement magazines for my G&P medium sheriff. you say that the G&P and Maruzen are very similar - that mean magazine compatibility? 'cause right now I'm looking at the Maruzen long mags

I know for fact the G&P mags work in the Maruzen version. It should be compatible the other way around as well.

Awesome, thank you very much

Cheers