Why is it important?


There has been a lot of discussion about the barrel pivot pin. Some think it has little or nothing to do with accuracy. The following article is an open honest attempt to show with pictures what we are talking about when it comes to proper fit.


The following targets were fired at 25 yards from a rest. The were fired within about 5 minutes of each with the only thing different was the “Frame” and “Barrel Pivot Pin”


The weather was cool, and not a breath of wind. The ammo is reloads with the three shots from both targets coming from the same box of 20. And target #3 was shot a while back with the same load data, but a different box of ammo.


In fairness to this test, I used a new factory pin in my frame, and Richard’s pin in his frame. I will show in my frame what a first-over pin will do to increase the accuracy beyond a factory pin in picture #3.


Picture of target #1 was fired first with a new factory pin in my Old Contender frame. It is a 12 inch 357 Mag rechambered to 357 Max. It is scoped with a 4X32 NcStar Scope. The loads are using 180gr Hornady HP/XTP. Being pushed with 27grains of Accurate 1680.  Being ignited with CCI 450 Small Rifle Mag primer. With new Remington 357 Max brass. With a COL of 2.160  They are in the mid 1900 fps velocity. The group of three shots measures .800 raw. With the bullet deduct it is .443 which will relate to a 1.772 at 100 yards


Picture of target #2 was fired next with the same loads and only about five minutes after target #1 was shot. Just long enough for me to put my barrel on Richard’s frame. Using his Old Contender that has had many thousands of all kinds of different calibers and barrels used through the years and has ended up with a frame that is just worn out. The pin is worn a little but the left and right sides of the frame where the pin goes are very, very worn. The right side is beyond the use of the second oversized pin. Without making a custom pin and reaming the barrel and frame which would only make this frame and barrel a unit, I recommended he return it to Thompson Center Arms for repair or replacement. The data on this is the three shots measure 1.215 raw. With the bullet deduct it is .858 which relates to 3.432 at 100 yards.


I could have shot more than three rounds at these two targets, but with the comparison of these to target #3 that was shot months ago in my frame with a FIRST OVERSIZE PIN, I wanted them to compare to my three shot group. This was shot from the same rest with the same reload data. The only difference is the ammo was from another box or reloads I did earlier and shot up. But can see for yourself what a difference of having a tight fit on the barrel and frame can do to improve your accuracy. The data on target #3 is .550 raw. With the bullet deduct it is .193 which relates to .772 at 100 yards. In my book that is ¾ MOA, and good enough to get the job done, if I do my part.


This may not be useful to all, but if you are going crazy trying to get that tight group, take a good look at your PIN FIT.

To summarize, if you want ¾ MOA you must have a tight pin fit. If you are happy with the ease of pushing the factory pin out with your fingers, and switching barrels, you can still have fewer than 2 MOA. Or if you old frame is getting very worn, and your rounds are not grouping anymore, you might just have one of those 3 and ½ MOA rigs.


Jim L. “Shots” Hendershot Sr.