k-31 7.5x55 Swiss and WC846 / BL-C(2)

Gregory Gauvin · April 22, 2014, 02:16 AM

I have been working up an accuracy load for one of my K-31 rifles. I am using .284 win brass converted to 7.5x55 Swiss, 150 grain SP flat base bullets (hornady I believe), win LR primers. I am using WC846 powder. I am loading to a max OAL of 2.890".

I would like some input, and possible suggested accurate loads using this combination. I know most k-31 enthusiasts are probably not running 150 grainers, nor using converted brass. I have 7.5 graff brass and the ability to load 168 grains...needless to say I am limited to 100 yards, and am looking to pull the most accuracy out of the rifle cost effectively for plinking sake.

According to the Hodgdon data, minimum load is 40 grains with a max of 42 for BLC-2 for 150 grain bullets. Other sources show listings of powder charges in excess of 50 grains. I began my test loads at a reduced rate.

36 grains - Accurate, low recoil

37 grain charge - Very Accurate - clover leafed the rounds in the center X of a NRA 100 yard official Military target. I was utterly amazed. However, the load was extremely mild and had very low recoil. Cases sealed the chamber fine and no signs of blow back gases. For shooting a competition...I'd probably play around and dial in something at 36 to 37 grains, but, I feel as if I am shooting a .22 and velocities are probably around 2,000 ft/sec. Furthermore, I know it is OK to run reduced loads with this powder, but it is below minimum. As I increased the charge to 38 grains I got fliers.

38 Grains - Poor Accuracy - extreme spread
39 Grains - Poor Accuracy - extreme spread

I have not finished my testing. I have loads at 40 grains, 41, 41.5, 42, 42.5, 43, 43.5, and 44. As I increase the charge, from any experience here on the forum, do you think I may hit another node and regain accuracy with a hotter charge? Has anyone exceeded the 42 grain max charge? Any pet load data or suggestions? It's a PITA getting my data points down as I am shooting a 5 shot string and cease fire is every 30 minutes. I have yet to invest in a spotting scope.

Lastly, 2 or 3 rounds were difficult to chamber. I had to bump the charging handle to get the rifle into battery. I know this has to do with the short throat of the k-31, and I may have had a few rounds seated too long. I do not recall if I trimmed my brass. I intend to fully size my cases and trim them to length, and reuse my OAL. Should this problem occur again, I am thinking of reducing my OAL to 2.875 and/or do the marker dummy round chamber test and find my OAL. Manual calls for 2.790", but I know they are leaving quite a margin for reliability.

lonniemike · April 22, 2014, 06:33 PM

Difficultty chambering can be not only from excess length. It is just as likely to be a not quite right sizing job. Before loading your rounds, try to chamber some unloaded brass to confirm the shoulder isn't in a bind. Then check to make sure your OAL is ok.
By all means finish up your load spreads. Or even go higher if you don't see pressure signs.You will probably find another accurate node. If you go up or down load charges just about any rifle will show more than one accuracy node.
Hodgdon's data is generally conservative for the Swiss rifles. Their data of 42 grains blc2 with a 150 grain bullet is with a 31" test barrel and shows 2541fps for speed. GP11(174grain) in the same rifle would be well over 2600fps. GP11 in a K31 26" barrel is about 2550fps.Best

April 22, 2014, 02:16 AM	#1
Gregory Gauvin Senior Member Join Date: March 6, 2009 Posts: 368	k-31 7.5x55 Swiss and WC846 / BL-C(2) I have been working up an accuracy load for one of my K-31 rifles. I am using .284 win brass converted to 7.5x55 Swiss, 150 grain SP flat base bullets (hornady I believe), win LR primers. I am using WC846 powder. I am loading to a max OAL of 2.890". I would like some input, and possible suggested accurate loads using this combination. I know most k-31 enthusiasts are probably not running 150 grainers, nor using converted brass. I have 7.5 graff brass and the ability to load 168 grains...needless to say I am limited to 100 yards, and am looking to pull the most accuracy out of the rifle cost effectively for plinking sake. According to the Hodgdon data, minimum load is 40 grains with a max of 42 for BLC-2 for 150 grain bullets. Other sources show listings of powder charges in excess of 50 grains. I began my test loads at a reduced rate. 36 grains - Accurate, low recoil 37 grain charge - Very Accurate - clover leafed the rounds in the center X of a NRA 100 yard official Military target. I was utterly amazed. However, the load was extremely mild and had very low recoil. Cases sealed the chamber fine and no signs of blow back gases. For shooting a competition...I'd probably play around and dial in something at 36 to 37 grains, but, I feel as if I am shooting a .22 and velocities are probably around 2,000 ft/sec. Furthermore, I know it is OK to run reduced loads with this powder, but it is below minimum. As I increased the charge to 38 grains I got fliers. 38 Grains - Poor Accuracy - extreme spread 39 Grains - Poor Accuracy - extreme spread I have not finished my testing. I have loads at 40 grains, 41, 41.5, 42, 42.5, 43, 43.5, and 44. As I increase the charge, from any experience here on the forum, do you think I may hit another node and regain accuracy with a hotter charge? Has anyone exceeded the 42 grain max charge? Any pet load data or suggestions? It's a PITA getting my data points down as I am shooting a 5 shot string and cease fire is every 30 minutes. I have yet to invest in a spotting scope. Lastly, 2 or 3 rounds were difficult to chamber. I had to bump the charging handle to get the rifle into battery. I know this has to do with the short throat of the k-31, and I may have had a few rounds seated too long. I do not recall if I trimmed my brass. I intend to fully size my cases and trim them to length, and reuse my OAL. Should this problem occur again, I am thinking of reducing my OAL to 2.875 and/or do the marker dummy round chamber test and find my OAL. Manual calls for 2.790", but I know they are leaving quite a margin for reliability.

April 22, 2014, 06:33 PM	#2
lonniemike Senior Member Join Date: March 16, 2005 Posts: 139	Difficultty chambering can be not only from excess length. It is just as likely to be a not quite right sizing job. Before loading your rounds, try to chamber some unloaded brass to confirm the shoulder isn't in a bind. Then check to make sure your OAL is ok. By all means finish up your load spreads. Or even go higher if you don't see pressure signs.You will probably find another accurate node. If you go up or down load charges just about any rifle will show more than one accuracy node. Hodgdon's data is generally conservative for the Swiss rifles. Their data of 42 grains blc2 with a 150 grain bullet is with a 31" test barrel and shows 2541fps for speed. GP11(174grain) in the same rifle would be well over 2600fps. GP11 in a K31 26" barrel is about 2550fps.Best