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Jon
Jon, Consultant
Category: Firearms Repair
Satisfied Customers: 1351
Experience:  Professional Gunsmith, Certified Police Firearms Instructor, Concealed Carry Instructor, Journeyman Machinist and Firearms Enthusiast.
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I have four Winchester Model 100 semi-auto rifles in .308 Win.

Customer Question

I have four Winchester Model 100 semi-auto rifles in .308 Win. Two are in the rifle configuration and I have never had a problem with either and both will shoot 1 1/4" groups at 100 yds. from a stable rest. The other two are carbines and I have the same problem with both. I use them for whitetail deer in tight areas where the longer rifle barrel could be a brush catcher and the shorter barrel works better for me. However, neither one will cycle the lighter 150 grain factory loads in the semi-auto mode. They will fire the first round in the chamber but the action will not eject and cycle the next round up. The fired casing simply stays in the chamber. This is with both carbines. The rifles were tore down, cleaned, reassembled and tried and the results were the same with both. I even found a new extractor online and had it installed but the problem continued. However, I had a box of PMC 180 gr. .308 Win ammo and I tried it. I only tried it in one carbine and it worked fine, it cycled the action perfectly and maintained acceptable accuracy for hunting purposes. I have no idea why those two carbines will not cycle the 150 gr. ammo but the two rifle versions will fire, eject and recycle the actions just fine. Could it be the heavier weight bullets are slower and maintain the gas pressures longer to ensure the actions will work were as the 150 gr. bullets are slightly faster and leave the shorter barrels too fast.
Thanks,
Ken
***@******.***
Submitted: 7 months ago.
Category: Firearms Repair
Expert:  Jon replied 7 months ago.
Hi KenMy name is Jon. I will do my best to help.Ken, you hit the nail right on the head. You are developing more pressure inside the barrel of the rifles than you are the carbines. I have seen this scenario more than once. This is also why you will normally get a higher muzzle velocity from a rifle than a carbine. If you try some different brands of 150 grain ammo you will probably find that some will work fine in your carbines. This will most likely be the factory brands with the highest velocities. Try some Hornady ammo, they tend to have a little higher velocity than some factory ammo. I hope this helps. If you have any other questions. please let me know. Please remember to use the stars to rate this answer. Have a great day.