What is this? Rollers Question.

[DerMeister]

http://i40.photobucket.com/albums/e248/yugom5966/CETMErollers.jpg

I got some rollers in the mail that I ordered before I knew that I did not need them. I got a new bolt/carrier assembly and discovered that my old carrier and bolt already had +4 rollers. So I put those in the new carrier with standard rollers, and I have a nearly perfect .014 gap.

Problem is that one of the rollers is VERY tight and after 200+ cycles of the action it will not losen up. It takes a lot of effort to charge the weapon.

So I decided to go open the baggy of new +4 rollers I got, and seen that they were different than any pictures I have seen of them. When I went to put them in, they were really lose, and gave me a gap of .010. Sounds like I got +2 rollers instead.

It is a lot easier to cycle the action, but why do these rollers look so weird? They do not look like the pic of them on the site I ordered them from. And they are not +4, I can tell you that.

I would go back to my old rollers, but like I said one is very tight, and the other is frim. These two new ones are just plain lose.

[rustypirate]

+4 rollers will generally be very tight in a brand new bolt head. They were designed to be used in a bolt head that has experienced some wear. As for the size of the rollers in your photo, you really need some calipers to accurately measure the rollers because the size difference is so very small.

There are several different versions of rollers out there, some flat on one side, while others are dimpled on both ends. That is why it is critical to measure them properly to know what you have.

[rifleman]

the one there looks like a standard, one line across, is a +2 and a cross is +4, unless i have it backwards.

[86thecat]

From the photo the roller in the bolt looks like it has a hole through the middle and two grooves (rings) cut in the end. I picked up a pair of them a while back as they were sold as +4. Mine mic out at .316 inch which should be 8.02 mm.
But IIRC one groove should be +2 and two grooves should be +4, are we confused now? Someone else may know for sure.

[richl]

only 200 rounds. its not even starting to seat in my opinion . lube it really good and hammer another 300 through it .....

mine has 1000 + through her and started to loosen up nice after the 400 mark ...

these rifles are designed for abuse , unlike others that seat and loosen up after 100 rounds,,

remember you have the diesel of battle rifles, time , lube and patients will prevail

[DerMeister]

Anyone know for sure?

I wish I could get some calipers and measure these things out, but it is not worth it to spend $36 on $14 worth of parts.

I guess .010 isnt bad, and when my bolt head wears a little, I will put in the +4 when they fit.

[jfowl31]

just take the rollers with you to a hardware store and measure them if you don't want to spend the $36.

Personally though, those calipers will be used more than just right now if you have them. I'd just buy them, they're a good tool to have.

[86thecat]

DerMeister,
Sorry I couldn't give you a better measurement but my calipers (Starrett) and small Mic (Brown and Sharpe) haven't been calibrated for a few years and I don't have a standard block to double check with. Even if you pick up a caliper, it could vary by a half thou or more from true. Heck even temperature differences can throw you off another couple of tenths. My point is if you've got a good gap and proper operation don't sweat what the exact size of the rollers are.

[richl]

think i have the awnser.....

i bet those are hk 33 rollers and not 91 rollers ..


where did you order them from ???

[W.E.G.]

+4 rollers will generally be very tight in a brand new bolt head. They were designed to be used in a bolt head that has experienced some wear.

Interesting.

So, let's suppose you had a new barrel that was not pressed to perfection, new locking piece, new bolt head and new rollers.

But you still have insufficient bolt gap (because the barrel wasn't "pressed to perfection")

Are you saying that you can expect function issues if you put oversize rollers in this gun because the bolt head hasn't worn enough to use the oversize rollers in the manner that oversize rollers are intended?

Not arguing or disputing.

Just wondering.

[MID]

http://i40.photobucket.com/albums/e248/yugom5966/CETMErollers.jpg

I got some rollers in the mail that I ordered before I knew that I did not need them. I got a new bolt/carrier assembly and discovered that my old carrier and bolt already had +4 rollers. So I put those in the new carrier with standard rollers, and I have a nearly perfect .014 gap.

Problem is that one of the rollers is VERY tight and after 200+ cycles of the action it will not losen up. It takes a lot of effort to charge the weapon.

So I decided to go open the baggy of new +4 rollers I got, and seen that they were different than any pictures I have seen of them. When I went to put them in, they were really lose, and gave me a gap of .010. Sounds like I got +2 rollers instead.

It is a lot easier to cycle the action, but why do these rollers look so weird? They do not look like the pic of them on the site I ordered them from. And they are not +4, I can tell you that.

I would go back to my old rollers, but like I said one is very tight, and the other is frim. These two new ones are just plain lose.

The charging issue is caused by the carrier moving too far form the charging handle. The charging handle is cammed in a way that when you pull it up from laying folded down it has leverage to unlock the bolt, . Once the lever is unfolded the bolt is unlocked and you simply have to over power the recoil spring to charge the rilfe. If the gap between the carrier and charging handle is too much you loose the leverage advantage, and are now trying to over power the bolt which see pressures in excess of tens of thousands of psi.

[jfowl31]

That's the basic idea WEG. Its squeezing rollers that were made to fill in for a worn bolt head... with no wear on the bolt head, things will be tight, and many tend to think that you will actually wear the new bolt head faster with these larger rollers because the tolerances/clearances are so much tighter.

[SteelCore]

of rollers that look like that. That's normal.

[DerMeister]

The charging issue is caused by the carrier moving too far form the charging handle. The charging handle is cammed in a way that when you pull it up from laying folded down it has leverage to unlock the bolt, . Once the lever is unfolded the bolt is unlocked and you simply have to over power the recoil spring to charge the rilfe. If the gap between the carrier and charging handle is too much you loose the leverage advantage, and are now trying to over power the bolt which see pressures in excess of tens of thousands of psi.

it charges fine with the rollers show in the picture, and with the old bolt carrier. No problem charging at all.

However since the old rollers are so freakin tight, it is hard to fully overcome the rollers, becuase the cocking lever does not fully unlock the bolt.

I got an email back, and was told that they are the correct rollers. I will see how it shoots, if the recoil is fine, I won't care, and when the head wears enough I will put the old rollers in.

The guy did say that sometime's CAI did put oversized oversized rollers in guns, which could be an example of my rollers.

[MID]

it charges fine with the rollers show in the picture, and with the old bolt carrier. No problem charging at all.

However since the old rollers are so freakin tight, it is hard to fully overcome the rollers, becuase the cocking lever does not fully unlock the bolt.
.

Because the new larger rollers dont allow the carrier to come forward as much as with the old rollers. Increasing the distance from the carrier to cocking handle plunger. Thus not utilizing the leverage advantage.