Question on coal ?

[BigRso]

Hello everyone,

So I took my new setup to the range today, not really overly impressed with the barrel as of yet shot good but nothing I wasn't doing with my stock barrel. Oh and my damn versa pod adapter broke after 3 shots and swfa said call Versa pod. Shitty day at the range.....

Anyway to my question, with my load of 43.7 gr varget seated to 2.760" it was hard to pull the bolt back not lift but pull back with the same load but seated to 2.745" no issue. Why is this happening also groups open up a bit seated longer. I did check my max coal for this bullet and it was 2.785".

The load was 43.7 gr varget
165 gr gk hpbt
Remington primer
2x fired 308 win
Coal 2.760"
Neck turned
Pocket uniformed
Full lengthen sized

Thanks in advance,
Mike

 

[CK_32]

Wait I'm really confused are you using the right terminology?

Max COAL is 2.75 for 308 but it doesn't mean that's what you should shoot at. I always trim to reccomended which is 2.500..

Also your setting your bullets to 2.76 OAL?! 1 how did you get to that did you work your load from 2.800? Also how are you loading your bullet to 2.76 on a 2.45. Kinda close no?

 

[BigRso]

Wait I'm really confused are you using the right terminology?

Max COAL is 2.75 for 308 but it doesn't mean that's what you should shoot at. I always trim to reccomended which is 2.500..

Also your setting your bullets to 2.76 OAL?! 1 how did you get to that did you work your load from 2.800? Also how are you loading your bullet to 2.76 on a 2.45. Kinda close no?

I am using the right terminology my cartridge over all length (coal) is 2.760" now when you say 2.500" that is the case recommended trim length. Once you seat a bullet add a primer and powder it becomes a cartridge. So my coal is 2.760" which is giving me an issue. Sammi spec says 2.800" as you stated as a general guide line for 308 however for this bullet the longest I can seat it in my chamber is 2.785" and that's touching my lands so I sat it 25 thousandth off the lands making it 2.760". Now that I broke it down my question is why is it hard to pull back on the bolt? Usually high pressure signs would be heavy bolt lift. You also stated that 2.745" is close to 2.760" it is but 15 thousandth lends it self to different pressure and a shorter jump to the lands which both will play a big part in how the load will preform. I am hoping someone with more knowledge would lend me some of there experience.

Thanks and be well,
Mike

 

[pell1203]

Mike, I am certainly not an expert and am looking to learn from the replies but I was wondering if this is a fully custom built action as the dimensions and tolerances you provide seem a bit tighter than usual. Have you measured your overall chamber length using an OAL gage? Could your overall chamber be cut a bit too short and it is causing higher pressures when seated longer... just enough to expand the sides of the cartridge and cause an increase in friction making extraction (bolt pullback) more difficult.

I am sure others with more experience will have more definitive suggestions. Good luck!

 

[rduckwor]

We need to know about the free bore on your rifle. Curious as to your chosen COAL. Tell us more about the build and maybe we can come up with some ideas.

 

[BigRso]

Mike, I am certainly not an expert and am looking to learn from the replies but I was wondering if this is a fully custom built action as the dimensions and tolerances you provide seem a bit tighter than usual. Have you measured your overall chamber length using an OAL gage? Could your overall chamber be cut a bit too short and it is causing higher pressures when seated longer... just enough to expand the sides of the cartridge and cause an increase in friction making extraction (bolt pullback) more difficult.

I am sure others with more experience will have more definitive suggestions. Good

The action is a savage with accu trigger taken off a model 16, I had it trued , mcgowen barrel 1:10 twist , SSS recoil lug , bedded in a choate tactical stock, the smith re tapped the action screws to hold thicker screws as well as base screws. I forget the exact tpi of the screws he used. Stock was torqued to 35 front action screw and 30 rear.

I did use an oal guage by hornady , I found it odd as well how tight the chamber was, but I know more about reloading then building / bolt guns new to long range shooting. Is their something the smith could of done to the action while putting it all together to cause this?

Thanks and be well,
Mike

 

[BigRso]

Just want to thank everyone that's respond in trying to help me with this problem.

Also after reading my post CK_32 I didn't mean to come off like a d--k man sorry. Just put a lot of time into this rig and it isn't working out as expected.

Be well,
Mike

 

[hawk_ce]

Take it to smith and have him put the GO/No-Go gauges in front of you......
How do you like your Choate stock??

 

[BigRso]

Take it to smith and have him put the GO/No-Go gauges in front of you......
How do you like your Choate stock??

It is heavy and the bipod swivel stud sticks out to far and causes issue with bi pods. I would rate it a 3 out of 5.
I was hoping it wasn't that this smith takes forever for everything and is in pa a good 3 hrs from me.

Thanks,
Mike

 

[Dacam]

So with this rifle, its not possible to fire factory ammo correct? Since most factory ammo coal is around 2.800? Why is your chamber so small? Maybe Im missing something.

 

[BigRso]

So with this rifle, its not possible. to fire factory ammo correct? Since most factory ammo coal is around 2.800? Why is your chamber so small? Maybe Im missing something.

No I fired factory ammo today no issue. My thinking was with this particular bullet it can't be seated to long. Could that be at this point I am really confused myself. Is there a way I can measure the headspace with out a go guauge any tricks? The smith said its good o go if I want to make appt I can

 

[Herschel34]

Couple of things to try. First, you may want to try to measure your max COAL again. I bet you measure too long. What method are you using to measure your max COAL?

Second, I would darken the ogive to a loaded dummy round loaded to the same specs that you were having problems with. Use a bleck felt tip pen or a match to darken it with the smoke. My bet is you are in the lands and the bullets are sticking which is causing problems pulling the bolt back. You should see marks from the lands in you are seated too deep.

 

[BigRso]

Couple of things to try. First, you may want to try to measure your max COAL again. I bet you measure too long. What method are you using to measure your max COAL?

Second, I would darken the ogive to a loaded dummy round loaded to the same specs that you were having problems with. Use a bleck felt tip pen or a match to darken it with the smoke. My bet is you are in the lands and the bullets are sticking which is causing problems pulling the bolt back. You should see marks from the lands in you are seated too deep.

Thank you very much will be doing this today. I did two methods to measure first used a hornady guage, then I did the old school wooden dowel method. You seat a bullet to long put it in your chamber using a rubber band to hold the bolt handle in place you mark the dowel at the muzzle, then remove the cartridge close the bolt and mark the dowel again at muzzle and measure the length between the two lines and it tells you the max coal for that bullet touching your lands.

 

[BigRso]

We need to know about the free bore on your rifle. Curious as to your chosen COAL. Tell us more about the build and maybe we can come up with some ideas.

The bore is .300

 

[rduckwor]

The bore is .300

What I meant was the actual distance to the lands in the barrel.

There are a couple of ways to measure this. Let us know if you need them.

"165 gr gk hpbt" - I can't tell what bullet you're using aside from the fact that it is a 168Gr HPBT. What is its profile like? That could be the issue.

The standard COAL for a 308 Win is 2.80 inches. It is curious as to why you loaded shorter.

Thanks,

 

[Deleted member 10043]

Is the head of your case expanding creating a sticky case?

 

[BigRso]

It is 165 gr game king hpbt sierra. I would greatly appreciate it if you could tell me how to get that info. I know how to find out how far I can seat a particular bullet to the lands.

 

[BigRso]

Is the head of your case expanding creating a sticky case?

Could be will try neck turning them a little more