Lyman T-mag reloading turret press loose turret

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patriot87

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Hey guys, I'm hoping someone can shed some light on this for me. Reloading .308 with my Lyman T-Mag turret. Using RCBS short base dies.

When I seat my bullets I am having the C.O.L move a few thousandths of an inch, it changes every round from between 2.796 ti 2.811. I have reseated the dies several times, I have even replaced the dies to rule out the die being the issue. Does this seem normal that the C.O.L changes that much? I realize the tolerances for most .308 guns is 2.8-2.810 but this variance seems excessive! I am relatively new to reloading but I can't see how the C.O.L change would be acceptable when shooting past 200 yards.

Also I am reloading hornady brass and 168gr hornady BTHP.

Any advice you can offer would be helpful, thanks!
 
Yes it does have play, there is a screw on the back of it that is supposed to be raised to 1/64 of an inch below the turret. I slipped in a few sheets of paper on top of that so that it is more stable, but i still get the variances in the C.O.L. I don't know if that little bit of play is normal though because Lyman specifies that it is, but if that is the case this seems like it may be excessive...
 
This is one of the weaknesses with cantilever turret presses. Even seating you are exerting a fair amount of pressure. I don't think paper shims will do the trick. Also, how many times has the brass been reloaded? If your neck tension is getting inconsistent you may not be consistently taking the slop out of the press from round-to-round.
 
raise the screw on the back of the press
if the center bolt has slop you can make a shim or 3 out of a pop can ( you can use scissors for this but don't use good ones )
 
cueball, from your experience does that mean my groupings will be out beyond 200 metres? I just don't want this issue to affect accuracy because I want to start shooting out past 300 yard.
 
just having some fun said:
raise the screw on the back of the press
if the center bolt has slop you can make a shim or 3 out of a pop can ( you can use scissors for this but don't use good ones )
Click to expand...

I have raise the back screw to the point touching the turret, with no change in the COL variance. The centre bolt won't tighten at all(at least by hand power) so how would one go about "shimming" that centre bolt?
 
patriot87 said:
I have raise the back screw to the point touching the turret, with no change in the COL variance. The centre bolt won't tighten at all(at least by hand power) so how would one go about "shimming" that centre bolt?
Click to expand...

you have to remove the center bolt and either put the shim between the turret plate and press, likely make it large enough to be the size of the mating faces or on the bolt befor assembly, it will take out the clearance between the bolt and turret plate, have you tried switching the position of the dies
 
patriot87 said:
If this is in fact just the way the press is, how much will a variance of 1-10 thousandths of an inch in C.O.L make in distance shooting. (assuming it is within safety specs)
Click to expand...

A few ten thousandths of an inch in OAL is unlikely to have any measurable effect. I think most of us wouldn't be able to measure variations in OAL that small consistently. Even a few thousandths of an inch is within the range of statistically valid measurement for my loads using an OAL tool and a Starett micrometer good to 0.0005".

Previous posters have made a good point in that if you are not measuring from the base to ogive, that alone will introduce some variation but with decent match bullets should not be above 0.005" max - at least in my experience.

Changes in group due to OAL is a question of debate. My experience is that it matters more with some bullets and some guns and less with others. In one of my guns, Hornady AMAX is quite sensitive to OAL and 0.01" too short can double the group size (poi is consistent however). Berger suggests loading quite far off the lands (e.g. 0.05" off) to start with VLD bullets, then tuning with large changes in OAL.

See link: http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/
 
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Hey all, thanks for the input it is greatly appreciated. I am thinking it was because I wasn't measuring from the ogive. I have since been using a comparator. I measured the Ogive on factory ammo to start(I am shooting it in a semi) so overall case length is important so it can fit in the magazine, and have duplicated that quite successfully within 0.003" For measuring from base to ogive is 0.003" variation to much? Most of the bullets are within 0.002".
 
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