Bolt hard to close

[Bullmark]

Hey fellas, I think I have a small issue and want to make sure it isn't something to be concerned about.
I have a custom .280ai.....the action is an Alamo proprietary and runs slick as can be. I do not reload, so I did a modified load dev using Copper Creek online using their development packs. The builder communicated the headspace to Copper Creek and we finally settled on Berger 168vld hunters over 57gr of H4350.....he did move it closer to the lands but how close I cannot say. Since then I've ordered from them several times and he uses that same recipe and seating depth.
On my most recent trip to the range I opened a new box of ammo and the bolt was very difficult to close. At first I was sure it was jammed up somehow. All previous rounds required very little effort to close the bolt, but this time it was much much tighter. I got the bolt closed and went ahead and finished the session and kinda got used to it, but the 6 rounds from the new box all required the extra effort to close the bolt.
I did not notice any big difference in accuracy....but I was only shooting 100yds. My last 3 shot group was opening up a bit, but the barrel was also heating up.
I came home and measured the rounds and they appear to be the same overall length as all the others. I used a micrometer and it's so exact the least little movement changes the reading by .001" or two. But they were all right there with the others.
Knowing very little about reloading, my only explanation is the rounds in the new box are a smidge longer and the bullet is jammed into the chamber....?? So help me out here.
I do plan on emailing Cooper Creek, but I wanted to see what you guys had to say before doing so.
One last ??......any tips on measurements with a micrometer? What level of exactness should you expect? More specifically, how many thousandths of an inch is relevant?? Is 2.980" a big difference from 2.985"......that's .005" , which seems awfully minuscule.
Thanks for the replies......if I get any that is.

 

[Bucklowery]

Hey fellas, I think I have a small issue and want to make sure it isn't something to be concerned about.
I have a custom .280ai.....the action is an Alamo proprietary and runs slick as can be. I do not reload, so I did a modified load dev using Copper Creek online using their development packs. The builder communicated the headspace to Copper Creek and we finally settled on Berger 168vld hunters over 57gr of H4350.....he did move it closer to the lands but how close I cannot say. Since then I've ordered from them several times and he uses that same recipe and seating depth.
On my most recent trip to the range I opened a new box of ammo and the bolt was very difficult to close. At first I was sure it was jammed up somehow. All previous rounds required very little effort to close the bolt, but this time it was much much tighter. I got the bolt closed and went ahead and finished the session and kinda got used to it, but the 6 rounds from the new box all required the extra effort to close the bolt.
I did not notice any big difference in accuracy....but I was only shooting 100yds. My last 3 shot group was opening up a bit, but the barrel was also heating up.
I came home and measured the rounds and they appear to be the same overall length as all the others. I used a micrometer and it's so exact the least little movement changes the reading by .001" or two. But they were all right there with the others.
Knowing very little about reloading, my only explanation is the rounds in the new box are a smidge longer and the bullet is jammed into the chamber....?? So help me out here.
I do plan on emailing Cooper Creek, but I wanted to see what you guys had to say before doing so.
One last ??......any tips on measurements with a micrometer? What level of exactness should you expect? More specifically, how many thousandths of an inch is relevant?? Is 2.980" a big difference from 2.985"......that's .005" , which seems awfully minuscule.
Thanks for the replies......if I get any that is.

You need to measure to shoulder for cartridge not total length COAL. The bullet is most likely not touching lands. You will need a guage to measure headspace

 

[Bullmark]

You need to measure to shoulder for cartridge not total length COAL. The bullet is most likely not touching lands. You will need a guage to measure headspace

You need to measure to shoulder for cartridge not total length COAL. The bullet is most likely not touching lands. You will need a guage to measure headspace

I'm sorry but you need to explain further.....do you mean from the top to the beginning of the taper or the lip of the case? I've never dealt with this type of issue...obviously. thank u for trying to help me

 

[Bullmark]

You need to measure to shoulder for cartridge not total length COAL. The bullet is most likely not touching lands. You will need a guage to measure headspace

I would need a guage to measure to the shoulder correct? Is the assumption here that the case is too long and being jammed in the throat?

 

[Rick Richard]

Shoulder spacing is more than likely your issue. Go on YouTube and search for shoulder space measuring. It will give you the info on how to. Good luck.

 

[Rick Richard]

I would need a guage to measure to the shoulder correct? Is the assumption here that the case is too long and being jammed in the throat?

Yes, you will need a tool and calipers.

 

[Bucklowery]

 

[Bravo 4]

To check if it's an issue with the shoulder not sized back enough for your chamber, maybe color the entire shoulder with a marker and chamber. Then look for shiny spots where the marker was rubbed off.
If the OAL (over all length of the loaded cartridge) is too long, you can check it the same way buy using the marker on the bullet ogive/bearing surface junction. If the bullet is being jammed into the lands you will see it.
Or sacrifice one round and pull the bullet and dump the powder, then chamber and see if the problem still exists with just the case.