Tight bolt lifts 300 PRC custom

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Bang A Gong

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Asking for a friend. This is a new rifle so starting the load development . Worked up loads with new brass to less than max load. No issues with any of the loads. Notable was FPS were well above post with similar charges. Probably due to 31" barrel length. Now the ( hard bolt lifts) clickers start when resized brass is used. Even tried a more aggressive shoulder bump. Seems like every thing tried still results in a tight/hard bolt lift. But new unfired brass loaded with the best group provider don't have the tight bolt lift.
ADG brass loaded to book max loads work fine. Just having this issue after full length sizing. Any thoughts?
 
Custom indicates perhaps the chamber is on the tight (short) side.
If this is the case you can shorten the sizing die about 0.020, doing so 0.010 at a time. This may solve the problem.
On inspecting the brass where is it binding?
Enjoy.
 
Not all shell holders are the same size. Easier to take .005"-.010" off the shell holder, and much cheaper than taking it off the die if you happen to screw up.
 
To be clear, the stiff bolt lift happens AFTER the used and sized cases are fired? What is the brass brand?

new brass and ADG brass doesn't have this issue after firing. ADG brass doesnt have this issue even after firing and sizing?

Does your friend have a runout gauge?

Jerry
 
Mysticprecision said:
To be clear, the stiff bolt lift happens AFTER the used and sized cases are fired? What is the brass brand?

new brass and ADG brass doesn't have this issue after firing. ADG brass doesnt have this issue even after firing and sizing?

Does your friend have a runout gauge?

Jerry
Click to expand...
The way I read that, was new virgins were fine, and ADG virgins could be run up to book max with no issue.


Problems occurred after resizing all brass, even with “a more aggressive shoulder bump” during full length resizing…………
 
Most heavy bolt lift are caused by insufficient sizing. Be at the shoulder ( headspace) or at the .200 datum of the case from case head. Some sizing dies are not giving you enough sizing at the .200 datum point without producing excessive headspace. By setting the die for proper headspace - typically .002 on bolt gun - this leave the .200 datum point not sized properly.
Fix is to get a small base die if available for that cartridge - roll size it ot get a custom sizing die. A different brand of sizing die can fix the problem but not really practical to buy a few just to try !
 
I have a few questions.. But I should point out a few basics first.. I don't know your friends loading process and this is not criticism of the technique. A heavy walled case like ADG brass will grow more on the first firing than thinner walled cases. All fired cases should be measured with a case head space gauge and an average should be taken before resize. A once fired and properly bumped for your chamber, case, will have a longer length case that should be trimmed to spec. at this point not before resize. The case capacity has now been changed and your unfired case data is no longer the same resulting in different velocity and pressures. Inspect your second fired cases carefully.. Looking for anything different than the single fired cases. ^ Janeau has some very good points as does everyone who has replied. I suspect your chamber is tighter than most and giving you some grief. But run a new test ladder.. just five quickies working up your load again for the fired case capacity. Now for a few questions..
What is your favorite colour?
Sorry couldn't resist...
Is there any issue loading the once fired and resized cases into the chamber? How does the ejector mark look after the heavy bolt lift? And are there any unusual conditions at the case neck and shoulder after firing?
Cheers
 
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KodiakHntr said:
The way I read that, was new virgins were fine, and ADG virgins could be run up to book max with no issue.


Problems occurred after resizing all brass, even with “a more aggressive shoulder bump” during full length resizing…………
Click to expand...
Why I am asking cause that is how I perceive it as well... and there in lies the problem. Shooter is aligning ease of extraction as a pressure sign... but using 2 forms of the brass.

When brass is new, it has alot of elasticity which is easily lost under HIGH PRESSURE conditions... ie, it gets stretched. If over pressure occurs in that first firing, you can often see a frosty finish on the case body. That brass isn't going to react the same way the next firing even though powder charges have not changed and you size the case 'back to original'. The brass itself, has materially changed and may not size as much as expected. It will not contract the same amount during the firing phase causing it to stick to the chamber walls and stiff bolt lift is the expression of this problem.

Different alloys of brass show this differently and why one brand is often considered "stronger" vs another.

there can also be issues caused by the action and bolt, barrel but let's assume the custom rifle is built well/properly. here a runout gauge is
helpful.

If my assumption is correct, the easiest way to test is to load FL sized, fired brass with 3 to 5gr LOWER and see if the hard to extract problem goes away. If it does, the rifle/brass is telling you "ouch" to the original loads.

Jerry
 
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