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Adjustable gas system & bullet weight question...

1877 Views 4 Replies 5 Participants Last post by  Woodstock
Howdy all,

I just built a 6.8spcII. I used an adjustable gas block on a mid-gas, 1/11 twist, 16" barrel. I used Hornady factory 120sst ammunition.

Here are my questions:

Now that my weapon is functioning and zeroed with the 120's - will other bullet weights shoot different. I mean will this adjustable gas block + bullet weight combo cause other weight bullets to fly off or become less accurate?

Has anyone tuned their gas system/ rifle for one specific bullet weight?

I was wondering if I should re-tune the gas block for another round that I want to use which would be a hand load for a Barnes 95gr TTSX?

All advice welcome.

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When I started loading the 95 TTSX my gun was seriously over gassed when compared to heavier rounds (I do have a carbine gas system). I now have it tuned to eject everything to around 3:00 with the adjustable gas block.
Adjustable gas system & bullet weight question...

Any variation in powder burn rate/charge and bullet weight of course is going to make a difference in the amount of gas that's pushed through the barrel port to the BCG.

You'll have to shoot said ammo to see how it shoots, whether over or under gassed.

An over gassed gun will suffer with accuracy compared to one that has just enough to cycle the action properly.

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aj: Yes, you will need to adjust the gas for lighter bullets. The objective is just enough gas to reliably lock back on an empty mag and eject to approx. the 4 oclock position. If your adjustable gas block is easy to reach, then its a simple matter to record/memorize the settings for each bullet weight you plan to use. In my case, I have a pet load for one 6.8 rifle (a military model) with 110 grain Prohunters, and a different pet load for a second 6.8 rifle (a hunting model) with 100 grain Accubonds. As I recall, the heavier bullets produced more pressure, therefore needed more port restriction than the lighter bullets. I adjusted my gas keys to fit each of these pet loads and left them there. - CW
Basically the whole idea behind an adjustable gas system is so that you can adjust it to each different load and not be stuck with one size fits all. You will also likely have to adjust your optic a little too.:a26: The basic answer to the other question is no, the gas block will not cause other rounds to fly off or be less accurate. You quite often have to adjust optics for each individual load regardless of gas system but with adjustable your gun is likely to be more accurate due to less slamming of the reciprocating mass (milder cycling).
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