For most work, you don't need one like this, but this is my goto dial test indicator. It's a well made very sensitive indicator that can even be reversed (although I have never had to).
For you, one of its many features that you will love is its barrel size. It will fit down inside the chamber of a 308 or 6BR to dial in a throat.
Mitutoyo 513-504-10T Indicator, Pocket Type, .01in, .0001in. Great savings PLUS Free Shipping when you order today on ITM.com.
www.itm.com
I sometimes use mine with a longer needle to reach further down a bore. This reduces the precision of the indicator but they are so sensitive that you can still dial in your work below a tenth by looking for tiny movement between the scale marks. According to Long Island Indicator Repair, the Tip Thread on the Mitutoyo and Interapid is 1.7mm-0.35 (Starrett is 4-48). But I see conflicting info all over the interweb. If anyone has better info, I'd love to hear about it. My tip selection includes:
- 1.7" (43mm) w 1.4 mm ball
- 2.75" w 0.75mm ball
- 1.2" w 2mm ball
- 0.6" w 0.4mm ball
- 0.6" w 2mm ball
- 0.6" w 3mm ball
Contact Points for Dial Test Indicator 2mm Carbide Ball Tips 44.5mm Long M1.6 Thread Mitutoyo 136013
https://a.co/d/5x0Y9Dc
Note the above link says M1.6, not 1.7. But I have one of these and it fits.... Go figure!