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View Full Version : Bolt gap drop in PTR-91


wanneroo
March 24, 2015, 21:05
I've had my PTR-91 for almost 2 years. Not long after buying it and running a few hundred rounds bolt gap measured about .013. The gap stayed the same every so often when I checked it. The last time I checked was late summer and didn't bother until now because at max I ran 200-300 rounds through it over the winter, maybe less.

Today spent a few hours taking it all apart and doing a thorough deep clean inside and out with all the various brushes, taking the bolt carrier group apart, etc. Put everything back together and bam bolt gap is only .008.

That seems to be a significant drop in a short space of round count. Perhaps the deep clean changed up the tolerances some by removing all the carbon crap. Is it anything to be worried about or just put new rollers in and call it a day?

Colorobo
March 24, 2015, 21:46
Get ahold of Chris in customer service. Send it back.

SAFN49
March 24, 2015, 22:33
Bolt gap in generally decreases by 0.001" per 1000 rounds.

John Crusher
March 24, 2015, 22:35
I had a JLD PTR-91 that was just over a year old and lost the gap. I'd ran a total of 200 rounds through it. The trunnion went south and JLD didn't do crap for me. I spent the money with Ghilliebear to get it right and then dumped it. Good luck.
If I ever get the hankering for an HK style roller-lock it will be an HK or an Old Century Cetme with Vaculock cast receiver.

MACV
March 24, 2015, 23:26
Mine is at .008. I wouldn't worry about it. The way you measure gap on those rifles in pretty subjective. One person might get .008 and another .010. on the same rifle. If it gets around .004 then change out the rollers.

wanneroo
March 24, 2015, 23:38
Bolt gap in generally decreases by 0.001" per 1000 rounds.

Certainly haven't run 5000 rounds through it, so that's a concern. Seeing how it had hung around .013 I expected maybe a slide down to .012 or something but not this.

I guess tomorrow I can break it down again, take the bolt carrier group apart again, put it all back together and check my work again although probably the result will be the same. Funny enough when I went to the check the gap it looked different than before even though it's only 5/1000ths of an inch, so even before getting the feeler gauge in I was suspicious.

Hopefully I don't have to send it back.

Kingtubby
March 25, 2015, 17:58
Oversized rollers from robertrtg.com is the simplest fix. Swap out takes less time than disassembly of the rifle to do the swap out.

The way you measure gap on those rifles in pretty subjective. One person might get .008 and another .010. on the same rifle.

There is a widely accepted way of checking bolt gap. Charge the action, hk slap into battery, pull the trigger, check gap with feeler gauges till you get a snug fit - there's your gap.

Only way youd get a .002" spread is if one guy is really jamming the gauge in the gap and the other is just looking for a bit of resistance and calling it good. The jammers are just fooling themselves into thinking their gap is better than it is. Ive been there. :facepalm:

yellowhand
March 25, 2015, 20:19
I've found some bad rollers with rifles I've worked on, in that they wear far faster than normal HK ones.
Pick up some HK rollers and swap them out, same size, and see if that is the issue.
What size rollers came with the rifles?
Most of us that have these weapons have enough spare parts to build a couple more for a reason.:whistling:
One of my CETME's has roughly three K rounds down the pipe and ZERO loss of gap from day one.

SAFN49
March 25, 2015, 21:05
One of my CETME's has roughly three K rounds down the pipe and ZERO loss of gap from day one.

You must actually clean your rifles :tongue:

The dirt/grit and lack of lube is what causes the wear.

yellowhand
March 25, 2015, 22:13
You must actually clean your rifles :tongue:

The dirt/grit and lack of lube is what causes the wear.

Old school, after every trip to the range before being put away.
Old habits die hard.
:whistling:
Break free is my friend!:tongue:

wanneroo
July 08, 2015, 15:56
More than 3 months later to follow up, the bolt gap drop worsened and it went back to PTR which turned it around in 2 weeks. The bolt head appears to have been the main issue and was replaced with a new one. They also re-welded the cocking tube and refinished the rifle. I'm going to run a couple hundred rounds through it and see how it goes.

seasmoke
July 09, 2015, 05:12
"They also re-welded the cocking tube" Please fill us in on this issue.

wanneroo
July 09, 2015, 08:25
"They also re-welded the cocking tube" Please fill us in on this issue.

When the bolt gap dropped so fast I noticed hairline cracks appear where the cocking tube meets the receiver right where the welds are. Also the cocking tube gap completely disappeared.