Could someone give me a brief description on how to check the bolt gap on my PTR?

Thanks

mike

--------------------

"Helping others to find the products they need, from sources other than Joeken since 2005"

quote:

---

Originally posted by lxpony:
And the potential pitfalls of having a bolt gap too close is????????

---

The problem with having too small or no bolt gap is that the rollers are extended so far that the chamber pressure may not be enough to retract them and reliably cycle the weapon, leading to ejection failures. Too large of a bolt gap on the ther hand could let the bolt cycle back while the chamber pressure is still dangerously high. This probably wouldn't result in catastrophic failure, but it definitely wouldn't be pleasant, and would most likely cause some significant damage to the rifle.

--------------------

"Helping others to find the products they need, from sources other than Joeken since 2005"

Mine is at .019 and I recently tried some some different flavors of ammo and some were not touching off on the first hit (Port). 2 in 5 needed 2 strikes. They did not look like light hits.

My shooting buddy with another 91 was having no such trouble.

I was shooting SA and Aussie with no issues for over a 1000 rounds.

I haven't seen any problems as a result of it being this high.

The only mishap I have seen was a case head seperation. This was due to a failure to load using the 'HK slap' and instead using thumb pressure to close the bolt.

I think if my bolt gap was about .014" or so....this method of bolt closure might have been OK. But I am suspecting with it already this high....that simply clicking the bolt shut is not providing the necessary headspace....therefore, a case head seperation resulted.

I did not attempt to load the rifle again in this manner....as I suspect the same thing might occur again, and maybe next time, it will do some damage to the weapon.

I am not saying definitely that the higher bolt gap is the culprit, but I suspect that's what it was.

Other than that, it functions flawlessly. And with the BG set that high, it should be a while before I have to change out the barrel, or rollers.

--------------------

" It's better to be hated for who you are....than liked for who you are not. " Van Zant

Semper Vigilo et Paratus

Raven
(designated sniper of worthless trolls)

quote:

---

Originally posted by Rotor:
What other probs could be caused by large Bolt gap.

Mine is at .019 and I recently tried some some different flavors of ammo and some were not touching off on the first hit (Port). 2 in 5 needed 2 strikes. They did not look like light hits.

My shooting buddy with another 91 was having no such trouble.

I was shooting SA and Aussie with no issues for over a 1000 rounds.

JR

---

The larger the gap is, the less firing pin protrusion you'll have, as the pin goes all the way through the bolt carrier and into the bolt head. At .018" though this should not be a problem unless your firing pin is worn down. I'd tend to think that the ammo was the culprit.

Raven, how is the chamber on your 91 cut? If it's short chambered, then it should get zero headspace with just thumb pressure closing the bolt. If it's cut to be at correct headspace with the bolt head against the breach, that might be the problem. You can probably tell by checking bolt gap on an empty and then a loaded chamber. If the loaded chamber measurement is bigger than .018", then it's short chambered. If it's the same (.018"), it's either just right, or too long. Thats a very strange malfunction you gun had. I can't really think of any explanation that makes sense except that maybe it was a deffective case.

--------------------

"Helping others to find the products they need, from sources other than Joeken since 2005"

I did the hot chamber headspace check. It was .019 empty and .019 with a round in the chamber. I distinctly remember the gunsmith telling me he set the gap on the high side to give me more service life.

Thanks again

Since your bolt gap is the same on a loaded and unloaded chamber, it sounds like the chamber is cut to the exact depth required for headspace. I'd check it with a "No Go" or "Field" gauge just to be sure. If you don't see a bolt gap increase using the "Field" gauge, you might have an oversize chamber. If the ammo you are using is slightly shorter than other milsurp ammo, it might be sliding forward in the chamber and away from the firing pin. Check the brass from a new one against one that you have fired, if there is a lot of swelling evident in the shoulder area, or if the case has gained in length by a significant amount, this would indicate an oversize chamber.

Mike

--------------------

"Helping others to find the products they need, from sources other than Joeken since 2005"

These are the Rollers dimensions.

+4 8.04 mm
+2 8.02 mm
Std 8.00 mm
-2 7.98 mm
-4 7.96 mm

I will check check the headspace with a more than one type of ammo.

Do use Nato or 308. gauges for your rifle?

Mike

--------------------

"Helping others to find the products they need, from sources other than Joeken since 2005"