Bolt Gap - Cocking tube gap check for builders and buyers.

**bladeworks123** · 09-13-2011, 12:04 AM

Originally Posted by wrathsworld

I followed the directions on first page of this post. Locked it back, put in dime, pointed down and slap released the cocking handle. Thats it. Sucks because I don't know a good or reasonable gun smith here in phoenix.

You did follow the directions, but that post was concerning a rifle with too much gap that would not unlock the rollers. And the reason it made yours easier to unlock,,,was because on a rifle with no CT gap already, putting the dime in there, as you pointed out, was keeping it from locking into battery. Bolt was not locking, so it naturally makes it pretty easy to unlock. Welcome to the site by the way, and as you read through the posts, you will find information concerning both DRB platforms. For the most part, they function exactly the same, and have the same settings for gap etc. but there are some differences, and the carrier assembly and fire control groups are the most obvious. If you are mechanicly inclined at all and have the patience, you can usually get one running on your own with the help and advice of some of the vets on this site. if you can't, I think I know a guy that could work on it for you....

. Again, welcome aboard!!!

**bladeworks123** · 09-13-2011, 12:11 AM

Originally Posted by wrathsworld

That picture is awesome, I just finished searching the web to compare just that. I guess I will be buying a bolt carrier because century did grind mine. The front the contacts the cocking tube support has no bevel inside or out so they did grind a little off it. I'm going to end up order the complete set from RTG because my bolt has scoring on it. Looks like it was run full auto till the gun seazed up. But I am going to pull the cocking tube support. To tell you how crappy century is the two holes to take out the cocking handle pin, don't line up. Full alignment on one side only shows an 1/8th of the pin on the other side.

No, actually that is the way the rifle was designed. You will also notice that one of the holes is larger than the other, which does allow the pin to be driven out without interference. It should be driven out from bottom to top. And, you can go ahead and order a new bolt carrier if that is what you want to do, but at this point, I would invest in a new bolt head, locking piece and plus size rollers maybe +2 and +4. Those pieces will be the main ingredients to success. If you can get good bolt gap with those parts, then you can spend the money to get the bolt carrier also. No need to buy more than you need and then find out you need to repress the barrel. I would also look at the back of your bolt head to see if it has been ground. Here is the post that will help describe that....

http://www.militaryfirearm.com/Forum...lt+head+length

Read the whole post, to understand the ground bolt head issue, but if you look at the pics in post #11, it will show you the correct length for your bolt head should be 1.847 on your C91, If you can't tell if it has been ground the best way is to measure it. Hk Bolt heads are longer than the CETME, so again, watch for which measurements you are looking for to get the right one.

**wrathsworld** · 09-13-2011, 12:24 AM

Ok, removed the cocking handle, not sure how to make sure it locked all the way. Dropped in 3 times made sure it was all the way forward. " did not tap it with anything other than my hand though" All three times the bolt gap was .009. As far as the carrier, I called RTG and they don't sell the bolts seperate anymore or right now. A used bolt on HKparts is 100 bucks. RTG has the whole assembly starting at 149.

**bladeworks123** · 09-13-2011, 12:41 AM

Originally Posted by wrathsworld

Ok, removed the cocking handle, not sure how to make sure it locked all the way. Dropped in 3 times made sure it was all the way forward. " did not tap it with anything other than my hand though" All three times the bolt gap was .009. As far as the carrier, I called RTG and they don't sell the bolts seperate anymore or right now. A used bolt on HKparts is 100 bucks. RTG has the whole assembly starting at 149.

I panicked, thought you said you dropped in three dimes.....It's been a long day.... Anyway, the best way to check it is to slam the bolt carrier assembly locked into the trunnion....reinstall the stock assembly and the FCG group. Pull the trigger to drop the hammer against the bolt and then check the gap. But, if you are at .009, and your bolt head has not been ground, add some +4 rollers to what you have and then see where your cocking tube gap is. You probably can get by with just rollers and not have to change too much else. Unless you just want to put all new stuff in. You bought the rifle for nearly nothing by todays standards, so if it were me and I could afford it,,,,buy them now and keep your old stuff around for spares.

**wrathsworld** · 09-13-2011, 01:03 AM

Ok you guys have been great. I redid the check and still got .009. I'm going to go ahead and order a whole new carrier and bolt assy.. The only question I have is since I never tore my HK down this far, should I go with +4 or +6? My understanding is it's supposed to be up to .020. Is .015 the sweet spot and will +4 get me there? RTG has up to +6 rollers. And should I buy spares? How long do rollers last?

**bladeworks123** · 09-13-2011, 01:24 AM

+4's will get you close, if you have standard rollers in there now. I think that .014 to .018 is a real good range to be in. Keep in mind that a new locking piece and bolt head that comes with your new bolt carrier assembly will add some bolt gap also, but you will loose a little gap on new parts as they wear in. There is no real way to give an accurate guess when you will be changing out everything but the trunnion. I would get the +4's and the +6's, try them and see where you end up. You will never be "stuck" with new Hk Parts. As far as how long they will last...several thousands of rounds, if the gun is properly maintained. And while you are ordering parts, go ahead and get yourself a new cocking handle spring , and even think about a new cocking handle carrier assembly, since you know yours has been getting hammered on by the carrier. If you are going to go this far you just as well do it up right and go for the full enchilada.

**wrathsworld** · 09-13-2011, 01:27 AM

Ok I will, I prefer to do things right the first time. I will post back after I get the new parts and let you know where I end up. Again thanks for the help.

**97th Signalman** · 09-13-2011, 08:29 AM

Drine, I am a little mystified about locking and unlocking the bolt with no cocking handle place. Do you just push the bolt/carrier assembly forward when assempling the rifle? If it isn't flying forward driven by the spring, will it go fully into battery? If you install the buttstock assembly and pull the trigger to test bolt gap, how do you get the bolt unlocked and open with out the leverage of the cocking handle to unlock the bolt? I am sure that I am missing something here.

**holescreek** · 09-13-2011, 09:14 AM

"how do you get the bolt unlocked and open with out the leverage of the cocking handle to unlock the bolt? "

Remove the butt stock and press a thin bladed screwdriver into the gap to unlock the bolt.

**wrathsworld** · 09-14-2011, 05:24 PM

Ok, finally got batterys for my calipers. My bolt head is perfect for a G3 1.845 in. My rollers however are small. They both measure 7.94, so is that -6 rollers and should I get standard 8's instead of plus 4's? I measured and zero'd my caliper at least 5 times, everytime I got 7.94 mm so that's acurate. And with those I have .009 bolt gap and no ct gap.